refactor update check API

This simplifies the logic for individual clients, centralises common logic, and prepares for upcoming features.

36 files changed, 684 insertions, 834 deletions

diff --git a/src/SMAPI.Toolkit/Framework/UpdateData/ModRepositoryKey.cs b/src/SMAPI.Toolkit/Framework/UpdateData/ModSiteKey.cs
index 765ca334..47cd3f7e 100644
--- a/src/SMAPI.Toolkit/Framework/UpdateData/ModRepositoryKey.cs
+++ b/src/SMAPI.Toolkit/Framework/UpdateData/ModSiteKey.cs
@@ -1,7 +1,7 @@
 namespace StardewModdingAPI.Toolkit.Framework.UpdateData
 {
-    /// <summary>A mod repository which SMAPI can check for updates.</summary>
-    public enum ModRepositoryKey
+    /// <summary>A mod site which SMAPI can check for updates.</summary>
+    public enum ModSiteKey
     {
         /// <summary>An unknown or invalid mod repository.</summary>
         Unknown,
diff --git a/src/SMAPI.Toolkit/Framework/UpdateData/UpdateKey.cs b/src/SMAPI.Toolkit/Framework/UpdateData/UpdateKey.cs
index 3fc1759e..f6044148 100644
--- a/src/SMAPI.Toolkit/Framework/UpdateData/UpdateKey.cs
+++ b/src/SMAPI.Toolkit/Framework/UpdateData/UpdateKey.cs
@@ -11,8 +11,8 @@ namespace StardewModdingAPI.Toolkit.Framework.UpdateData
         /// <summary>The raw update key text.</summary>
         public string RawText { get; }
 
-        /// <summary>The mod repository containing the mod.</summary>
-        public ModRepositoryKey Repository { get; }
+        /// <summary>The mod site containing the mod.</summary>
+        public ModSiteKey Site { get; }
 
         /// <summary>The mod ID within the repository.</summary>
         public string ID { get; }
@@ -26,53 +26,56 @@ namespace StardewModdingAPI.Toolkit.Framework.UpdateData
         *********/
         /// <summary>Construct an instance.</summary>
         /// <param name="rawText">The raw update key text.</param>
-        /// <param name="repository">The mod repository containing the mod.</param>
-        /// <param name="id">The mod ID within the repository.</param>
-        public UpdateKey(string rawText, ModRepositoryKey repository, string id)
+        /// <param name="site">The mod site containing the mod.</param>
+        /// <param name="id">The mod ID within the site.</param>
+        public UpdateKey(string rawText, ModSiteKey site, string id)
         {
-            this.RawText = rawText;
-            this.Repository = repository;
-            this.ID = id;
+            this.RawText = rawText?.Trim();
+            this.Site = site;
+            this.ID = id?.Trim();
             this.LooksValid =
-                repository != ModRepositoryKey.Unknown
+                site != ModSiteKey.Unknown
                 && !string.IsNullOrWhiteSpace(id);
         }
 
         /// <summary>Construct an instance.</summary>
-        /// <param name="repository">The mod repository containing the mod.</param>
-        /// <param name="id">The mod ID within the repository.</param>
-        public UpdateKey(ModRepositoryKey repository, string id)
-            : this($"{repository}:{id}", repository, id) { }
+        /// <param name="site">The mod site containing the mod.</param>
+        /// <param name="id">The mod ID within the site.</param>
+        public UpdateKey(ModSiteKey site, string id)
+            : this(UpdateKey.GetString(site, id), site, id) { }
 
         /// <summary>Parse a raw update key.</summary>
         /// <param name="raw">The raw update key to parse.</param>
         public static UpdateKey Parse(string raw)
         {
-            // split parts
-            string[] parts = raw?.Split(':');
-            if (parts == null || parts.Length != 2)
-                return new UpdateKey(raw, ModRepositoryKey.Unknown, null);
-
-            // extract parts
-            string repositoryKey = parts[0].Trim();
-            string id = parts[1].Trim();
+            // extract site + ID
+            string rawSite;
+            string id;
+            {
+                string[] parts = raw?.Trim().Split(':');
+                if (parts == null || parts.Length != 2)
+                    return new UpdateKey(raw, ModSiteKey.Unknown, null);
+
+                rawSite = parts[0].Trim();
+                id = parts[1].Trim();
+            }
             if (string.IsNullOrWhiteSpace(id))
                 id = null;
 
             // parse
-            if (!Enum.TryParse(repositoryKey, true, out ModRepositoryKey repository))
-                return new UpdateKey(raw, ModRepositoryKey.Unknown, id);
+            if (!Enum.TryParse(rawSite, true, out ModSiteKey site))
+                return new UpdateKey(raw, ModSiteKey.Unknown, id);
             if (id == null)
-                return new UpdateKey(raw, repository, null);
+                return new UpdateKey(raw, site, null);
 
-            return new UpdateKey(raw, repository, id);
+            return new UpdateKey(raw, site, id);
         }
 
         /// <summary>Get a string that represents the current object.</summary>
         public override string ToString()
         {
             return this.LooksValid
-                ? $"{this.Repository}:{this.ID}"
+                ? UpdateKey.GetString(this.Site, this.ID)
                 : this.RawText;
         }
 
@@ -82,7 +85,7 @@ namespace StardewModdingAPI.Toolkit.Framework.UpdateData
         {
             return
                 other != null
-                && this.Repository == other.Repository
+                && this.Site == other.Site
                 && string.Equals(this.ID, other.ID, StringComparison.InvariantCultureIgnoreCase);
         }
 
@@ -97,7 +100,15 @@ namespace StardewModdingAPI.Toolkit.Framework.UpdateData
         /// <returns>A hash code for the current object.</returns>
         public override int GetHashCode()
         {
-            return $"{this.Repository}:{this.ID}".ToLower().GetHashCode();
+            return $"{this.Site}:{this.ID}".ToLower().GetHashCode();
+        }
+
+        /// <summary>Get the string representation of an update key.</summary>
+        /// <param name="site">The mod site containing the mod.</param>
+        /// <param name="id">The mod ID within the repository.</param>
+        public static string GetString(ModSiteKey site, string id)
+        {
+            return $"{site}:{id}".Trim();
         }
     }
 }
diff --git a/src/SMAPI.Web/Controllers/ModsApiController.cs b/src/SMAPI.Web/Controllers/ModsApiController.cs
index b9d7c32d..14be520d 100644
--- a/src/SMAPI.Web/Controllers/ModsApiController.cs
+++ b/src/SMAPI.Web/Controllers/ModsApiController.cs
@@ -15,13 +15,13 @@ using StardewModdingAPI.Web.Framework;
 using StardewModdingAPI.Web.Framework.Caching;
 using StardewModdingAPI.Web.Framework.Caching.Mods;
 using StardewModdingAPI.Web.Framework.Caching.Wiki;
+using StardewModdingAPI.Web.Framework.Clients;
 using StardewModdingAPI.Web.Framework.Clients.Chucklefish;
 using StardewModdingAPI.Web.Framework.Clients.CurseForge;
 using StardewModdingAPI.Web.Framework.Clients.GitHub;
 using StardewModdingAPI.Web.Framework.Clients.ModDrop;
 using StardewModdingAPI.Web.Framework.Clients.Nexus;
 using StardewModdingAPI.Web.Framework.ConfigModels;
-using StardewModdingAPI.Web.Framework.ModRepositories;
 
 namespace StardewModdingAPI.Web.Controllers
 {
@@ -33,8 +33,8 @@ namespace StardewModdingAPI.Web.Controllers
         /*********
         ** Fields
         *********/
-        /// <summary>The mod repositories which provide mod metadata.</summary>
-        private readonly IDictionary<ModRepositoryKey, IModRepository> Repositories;
+        /// <summary>The mod sites which provide mod metadata.</summary>
+        private readonly ModSiteManager ModSites;
 
         /// <summary>The cache in which to store wiki data.</summary>
         private readonly IWikiCacheRepository WikiCache;
@@ -69,16 +69,7 @@ namespace StardewModdingAPI.Web.Controllers
             this.WikiCache = wikiCache;
             this.ModCache = modCache;
             this.Config = config;
-            this.Repositories =
-                new IModRepository[]
-                {
-                    new ChucklefishRepository(chucklefish),
-                    new CurseForgeRepository(curseForge),
-                    new GitHubRepository(github),
-                    new ModDropRepository(modDrop),
-                    new NexusRepository(nexus)
-                }
-                .ToDictionary(p => p.VendorKey);
+            this.ModSites = new ModSiteManager(new IModSiteClient[] { chucklefish, curseForge, github, modDrop, nexus });
         }
 
         /// <summary>Fetch version metadata for the given mods.</summary>
@@ -149,40 +140,18 @@ namespace StardewModdingAPI.Web.Controllers
                 }
 
                 // fetch data
-                ModInfoModel data = await this.GetInfoForUpdateKeyAsync(updateKey, allowNonStandardVersions);
-                if (data.Error != null)
+                ModInfoModel data = await this.GetInfoForUpdateKeyAsync(updateKey, allowNonStandardVersions, wikiEntry?.MapRemoteVersions);
+                if (data.Status != RemoteModStatus.Ok)
                 {
-                    errors.Add(data.Error);
+                    errors.Add(data.Error ?? data.Status.ToString());
                     continue;
                 }
 
-                // handle main version
-                if (data.Version != null)
-                {
-                    ISemanticVersion version = this.GetMappedVersion(data.Version, wikiEntry?.MapRemoteVersions, allowNonStandardVersions);
-                    if (version == null)
-                    {
-                        errors.Add($"The update key '{updateKey}' matches a mod with invalid semantic version '{data.Version}'.");
-                        continue;
-                    }
-
-                    if (this.IsNewer(version, main?.Version))
-                        main = new ModEntryVersionModel(version, data.Url);
-                }
-
-                // handle optional version
-                if (data.PreviewVersion != null)
-                {
-                    ISemanticVersion version = this.GetMappedVersion(data.PreviewVersion, wikiEntry?.MapRemoteVersions, allowNonStandardVersions);
-                    if (version == null)
-                    {
-                        errors.Add($"The update key '{updateKey}' matches a mod with invalid optional semantic version '{data.PreviewVersion}'.");
-                        continue;
-                    }
-
-                    if (this.IsNewer(version, optional?.Version))
-                        optional = new ModEntryVersionModel(version, data.Url);
-                }
+                // handle versions
+                if (this.IsNewer(data.Version, main?.Version))
+                    main = new ModEntryVersionModel(data.Version, data.Url);
+                if (this.IsNewer(data.PreviewVersion, optional?.Version))
+                    optional = new ModEntryVersionModel(data.PreviewVersion, data.Url);
             }
 
             // get unofficial version
@@ -222,7 +191,7 @@ namespace StardewModdingAPI.Web.Controllers
             }
 
             // get recommended update (if any)
-            ISemanticVersion installedVersion = this.GetMappedVersion(search.InstalledVersion?.ToString(), wikiEntry?.MapLocalVersions, allowNonStandard: allowNonStandardVersions);
+            ISemanticVersion installedVersion = this.ModSites.GetMappedVersion(search.InstalledVersion?.ToString(), wikiEntry?.MapLocalVersions, allowNonStandard: allowNonStandardVersions);
             if (apiVersion != null && installedVersion != null)
             {
                 // get newer versions
@@ -282,32 +251,27 @@ namespace StardewModdingAPI.Web.Controllers
         /// <summary>Get the mod info for an update key.</summary>
         /// <param name="updateKey">The namespaced update key.</param>
         /// <param name="allowNonStandardVersions">Whether to allow non-standard versions.</param>
-        private async Task<ModInfoModel> GetInfoForUpdateKeyAsync(UpdateKey updateKey, bool allowNonStandardVersions)
+        /// <param name="mapRemoteVersions">Maps remote versions to a semantic version for update checks.</param>
+        private async Task<ModInfoModel> GetInfoForUpdateKeyAsync(UpdateKey updateKey, bool allowNonStandardVersions, IDictionary<string, string> mapRemoteVersions)
         {
-            // get from cache
-            if (this.ModCache.TryGetMod(updateKey.Repository, updateKey.ID, out Cached<ModInfoModel> cachedMod) && !this.ModCache.IsStale(cachedMod.LastUpdated, cachedMod.Data.Status == RemoteModStatus.TemporaryError ? this.Config.Value.ErrorCacheMinutes : this.Config.Value.SuccessCacheMinutes))
-                return cachedMod.Data;
-
-            // fetch from mod site
+            // get mod page
+            IModPage page;
             {
-                // get site
-                if (!this.Repositories.TryGetValue(updateKey.Repository, out IModRepository repository))
-                    return new ModInfoModel().SetError(RemoteModStatus.DoesNotExist, $"There's no mod site with key '{updateKey.Repository}'. Expected one of [{string.Join(", ", this.Repositories.Keys)}].");
+                bool isCached =
+                    this.ModCache.TryGetMod(updateKey.Site, updateKey.ID, out Cached<IModPage> cachedMod)
+                    && !this.ModCache.IsStale(cachedMod.LastUpdated, cachedMod.Data.Status == RemoteModStatus.TemporaryError ? this.Config.Value.ErrorCacheMinutes : this.Config.Value.SuccessCacheMinutes);
 
-                // fetch mod
-                ModInfoModel mod = await repository.GetModInfoAsync(updateKey.ID);
-                if (mod.Error == null)
+                if (isCached)
+                    page = cachedMod.Data;
+                else
                 {
-                    if (mod.Version == null)
-                        mod.SetError(RemoteModStatus.InvalidData, $"The update key '{updateKey}' matches a mod with no version number.");
-                    else if (!SemanticVersion.TryParse(mod.Version, allowNonStandardVersions, out _))
-                        mod.SetError(RemoteModStatus.InvalidData, $"The update key '{updateKey}' matches a mod with invalid semantic version '{mod.Version}'.");
+                    page = await this.ModSites.GetModPageAsync(updateKey);
+                    this.ModCache.SaveMod(updateKey.Site, updateKey.ID, page);
                 }
-
-                // cache mod
-                this.ModCache.SaveMod(repository.VendorKey, updateKey.ID, mod);
-                return mod;
             }
+
+            // get version info
+            return this.ModSites.GetPageVersions(page, allowNonStandardVersions, mapRemoteVersions);
         }
 
         /// <summary>Get update keys based on the available mod metadata, while maintaining the precedence order.</summary>
@@ -334,13 +298,13 @@ namespace StardewModdingAPI.Web.Controllers
                 if (entry != null)
                 {
                     if (entry.NexusID.HasValue)
-                        yield return $"{ModRepositoryKey.Nexus}:{entry.NexusID}";
+                        yield return UpdateKey.GetString(ModSiteKey.Nexus, entry.NexusID?.ToString());
                     if (entry.ModDropID.HasValue)
-                        yield return $"{ModRepositoryKey.ModDrop}:{entry.ModDropID}";
+                        yield return UpdateKey.GetString(ModSiteKey.ModDrop, entry.ModDropID?.ToString());
                     if (entry.CurseForgeID.HasValue)
-                        yield return $"{ModRepositoryKey.CurseForge}:{entry.CurseForgeID}";
+                        yield return UpdateKey.GetString(ModSiteKey.CurseForge, entry.CurseForgeID?.ToString());
                     if (entry.ChucklefishID.HasValue)
-                        yield return $"{ModRepositoryKey.Chucklefish}:{entry.ChucklefishID}";
+                        yield return UpdateKey.GetString(ModSiteKey.Chucklefish, entry.ChucklefishID?.ToString());
                 }
             }
 
@@ -355,51 +319,5 @@ namespace StardewModdingAPI.Web.Controllers
                     yield return key;
             }
         }
-
-        /// <summary>Get a semantic local version for update checks.</summary>
-        /// <param name="version">The version to parse.</param>
-        /// <param name="map">A map of version replacements.</param>
-        /// <param name="allowNonStandard">Whether to allow non-standard versions.</param>
-        private ISemanticVersion GetMappedVersion(string version, IDictionary<string, string> map, bool allowNonStandard)
-        {
-            // try mapped version
-            string rawNewVersion = this.GetRawMappedVersion(version, map, allowNonStandard);
-            if (SemanticVersion.TryParse(rawNewVersion, allowNonStandard, out ISemanticVersion parsedNew))
-                return parsedNew;
-
-            // return original version
-            return SemanticVersion.TryParse(version, allowNonStandard, out ISemanticVersion parsedOld)
-                ? parsedOld
-                : null;
-        }
-
-        /// <summary>Get a semantic local version for update checks.</summary>
-        /// <param name="version">The version to map.</param>
-        /// <param name="map">A map of version replacements.</param>
-        /// <param name="allowNonStandard">Whether to allow non-standard versions.</param>
-        private string GetRawMappedVersion(string version, IDictionary<string, string> map, bool allowNonStandard)
-        {
-            if (version == null || map == null || !map.Any())
-                return version;
-
-            // match exact raw version
-            if (map.ContainsKey(version))
-                return map[version];
-
-            // match parsed version
-            if (SemanticVersion.TryParse(version, allowNonStandard, out ISemanticVersion parsed))
-            {
-                if (map.ContainsKey(parsed.ToString()))
-                    return map[parsed.ToString()];
-
-                foreach ((string fromRaw, string toRaw) in map)
-                {
-                    if (SemanticVersion.TryParse(fromRaw, allowNonStandard, out ISemanticVersion target) && parsed.Equals(target) && SemanticVersion.TryParse(toRaw, allowNonStandard, out ISemanticVersion newVersion))
-                        return newVersion.ToString();
-                }
-            }
-
-            return version;
-        }
     }
 }
diff --git a/src/SMAPI.Web/Framework/Caching/Mods/IModCacheRepository.cs b/src/SMAPI.Web/Framework/Caching/Mods/IModCacheRepository.cs
index 004202f9..0d912c7b 100644
--- a/src/SMAPI.Web/Framework/Caching/Mods/IModCacheRepository.cs
+++ b/src/SMAPI.Web/Framework/Caching/Mods/IModCacheRepository.cs
@@ -1,6 +1,6 @@
 using System;
 using StardewModdingAPI.Toolkit.Framework.UpdateData;
-using StardewModdingAPI.Web.Framework.ModRepositories;
+using StardewModdingAPI.Web.Framework.Clients;
 
 namespace StardewModdingAPI.Web.Framework.Caching.Mods
 {
@@ -15,13 +15,13 @@ namespace StardewModdingAPI.Web.Framework.Caching.Mods
         /// <param name="id">The mod's unique ID within the <paramref name="site"/>.</param>
         /// <param name="mod">The fetched mod.</param>
         /// <param name="markRequested">Whether to update the mod's 'last requested' date.</param>
-        bool TryGetMod(ModRepositoryKey site, string id, out Cached<ModInfoModel> mod, bool markRequested = true);
+        bool TryGetMod(ModSiteKey site, string id, out Cached<IModPage> mod, bool markRequested = true);
 
         /// <summary>Save data fetched for a mod.</summary>
         /// <param name="site">The mod site on which the mod is found.</param>
         /// <param name="id">The mod's unique ID within the <paramref name="site"/>.</param>
         /// <param name="mod">The mod data.</param>
-        void SaveMod(ModRepositoryKey site, string id, ModInfoModel mod);
+        void SaveMod(ModSiteKey site, string id, IModPage mod);
 
         /// <summary>Delete data for mods which haven't been requested within a given time limit.</summary>
         /// <param name="age">The minimum age for which to remove mods.</param>
diff --git a/src/SMAPI.Web/Framework/Caching/Mods/ModCacheMemoryRepository.cs b/src/SMAPI.Web/Framework/Caching/Mods/ModCacheMemoryRepository.cs
index 62461116..6b0ec1ec 100644
--- a/src/SMAPI.Web/Framework/Caching/Mods/ModCacheMemoryRepository.cs
+++ b/src/SMAPI.Web/Framework/Caching/Mods/ModCacheMemoryRepository.cs
@@ -2,7 +2,7 @@ using System;
 using System.Collections.Generic;
 using System.Linq;
 using StardewModdingAPI.Toolkit.Framework.UpdateData;
-using StardewModdingAPI.Web.Framework.ModRepositories;
+using StardewModdingAPI.Web.Framework.Clients;
 
 namespace StardewModdingAPI.Web.Framework.Caching.Mods
 {
@@ -13,7 +13,7 @@ namespace StardewModdingAPI.Web.Framework.Caching.Mods
         ** Fields
         *********/
         /// <summary>The cached mod data indexed by <c>{site key}:{ID}</c>.</summary>
-        private readonly IDictionary<string, Cached<ModInfoModel>> Mods = new Dictionary<string, Cached<ModInfoModel>>(StringComparer.InvariantCultureIgnoreCase);
+        private readonly IDictionary<string, Cached<IModPage>> Mods = new Dictionary<string, Cached<IModPage>>(StringComparer.InvariantCultureIgnoreCase);
 
 
         /*********
@@ -24,7 +24,7 @@ namespace StardewModdingAPI.Web.Framework.Caching.Mods
         /// <param name="id">The mod's unique ID within the <paramref name="site"/>.</param>
         /// <param name="mod">The fetched mod.</param>
         /// <param name="markRequested">Whether to update the mod's 'last requested' date.</param>
-        public bool TryGetMod(ModRepositoryKey site, string id, out Cached<ModInfoModel> mod, bool markRequested = true)
+        public bool TryGetMod(ModSiteKey site, string id, out Cached<IModPage> mod, bool markRequested = true)
         {
             // get mod
             if (!this.Mods.TryGetValue(this.GetKey(site, id), out var cachedMod))
@@ -45,10 +45,10 @@ namespace StardewModdingAPI.Web.Framework.Caching.Mods
         /// <param name="site">The mod site on which the mod is found.</param>
         /// <param name="id">The mod's unique ID within the <paramref name="site"/>.</param>
         /// <param name="mod">The mod data.</param>
-        public void SaveMod(ModRepositoryKey site, string id, ModInfoModel mod)
+        public void SaveMod(ModSiteKey site, string id, IModPage mod)
         {
             string key = this.GetKey(site, id);
-            this.Mods[key] = new Cached<ModInfoModel>(mod);
+            this.Mods[key] = new Cached<IModPage>(mod);
         }
 
         /// <summary>Delete data for mods which haven't been requested within a given time limit.</summary>
@@ -73,7 +73,7 @@ namespace StardewModdingAPI.Web.Framework.Caching.Mods
         /// <summary>Get a cache key.</summary>
         /// <param name="site">The mod site.</param>
         /// <param name="id">The mod ID.</param>
-        private string GetKey(ModRepositoryKey site, string id)
+        private string GetKey(ModSiteKey site, string id)
         {
             return $"{site}:{id.Trim()}".ToLower();
         }
diff --git a/src/SMAPI.Web/Framework/Clients/Chucklefish/ChucklefishClient.cs b/src/SMAPI.Web/Framework/Clients/Chucklefish/ChucklefishClient.cs
index cdb281e2..ca156da4 100644
--- a/src/SMAPI.Web/Framework/Clients/Chucklefish/ChucklefishClient.cs
+++ b/src/SMAPI.Web/Framework/Clients/Chucklefish/ChucklefishClient.cs
@@ -3,6 +3,7 @@ using System.Net;
 using System.Threading.Tasks;
 using HtmlAgilityPack;
 using Pathoschild.Http.Client;
+using StardewModdingAPI.Toolkit.Framework.UpdateData;
 
 namespace StardewModdingAPI.Web.Framework.Clients.Chucklefish
 {
@@ -20,6 +21,13 @@ namespace StardewModdingAPI.Web.Framework.Clients.Chucklefish
 
 
         /*********
+        ** Accessors
+        *********/
+        /// <summary>The unique key for the mod site.</summary>
+        public ModSiteKey SiteKey => ModSiteKey.Chucklefish;
+
+
+        /*********
         ** Public methods
         *********/
         /// <summary>Construct an instance.</summary>
@@ -32,42 +40,40 @@ namespace StardewModdingAPI.Web.Framework.Clients.Chucklefish
             this.Client = new FluentClient(baseUrl).SetUserAgent(userAgent);
         }
 
-        /// <summary>Get metadata about a mod.</summary>
-        /// <param name="id">The Chucklefish mod ID.</param>
-        /// <returns>Returns the mod info if found, else <c>null</c>.</returns>
-        public async Task<ChucklefishMod> GetModAsync(uint id)
+        /// <summary>Get update check info about a mod.</summary>
+        /// <param name="id">The mod ID.</param>
+        public async Task<IModPage> GetModData(string id)
         {
+            IModPage page = new GenericModPage(this.SiteKey, id);
+
+            // get mod ID
+            if (!uint.TryParse(id, out uint parsedId))
+                return page.SetError(RemoteModStatus.DoesNotExist, $"The value '{id}' isn't a valid Chucklefish mod ID, must be an integer ID.");
+
             // fetch HTML
             string html;
             try
             {
                 html = await this.Client
-                    .GetAsync(string.Format(this.ModPageUrlFormat, id))
+                    .GetAsync(string.Format(this.ModPageUrlFormat, parsedId))
                     .AsString();
             }
             catch (ApiException ex) when (ex.Status == HttpStatusCode.NotFound || ex.Status == HttpStatusCode.Forbidden)
             {
-                return null;
+                return page.SetError(RemoteModStatus.DoesNotExist, "Found no Chucklefish mod with this ID.");
             }
-
-            // parse HTML
             var doc = new HtmlDocument();
             doc.LoadHtml(html);
 
             // extract mod info
-            string url = this.GetModUrl(id);
+            string url = this.GetModUrl(parsedId);
             string name = doc.DocumentNode.SelectSingleNode("//meta[@name='twitter:title']").Attributes["content"].Value;
             if (name.StartsWith("[SMAPI] "))
                 name = name.Substring("[SMAPI] ".Length);
             string version = doc.DocumentNode.SelectSingleNode("//h1/span")?.InnerText;
 
-            // create model
-            return new ChucklefishMod
-            {
-                Name = name,
-                Version = version,
-                Url = url
-            };
+            // return info
+            return page.SetInfo(name: name, version: version, url: url, downloads: Array.Empty<IModDownload>());
         }
 
         /// <summary>Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.</summary>
diff --git a/src/SMAPI.Web/Framework/Clients/Chucklefish/ChucklefishMod.cs b/src/SMAPI.Web/Framework/Clients/Chucklefish/ChucklefishMod.cs
deleted file mode 100644
index fd0101d4..00000000
--- a/src/SMAPI.Web/Framework/Clients/Chucklefish/ChucklefishMod.cs
+++ /dev/null
@@ -1,18 +0,0 @@
-namespace StardewModdingAPI.Web.Framework.Clients.Chucklefish
-{
-    /// <summary>Mod metadata from the Chucklefish mod site.</summary>
-    internal class ChucklefishMod
-    {
-        /*********
-        ** Accessors
-        *********/
-        /// <summary>The mod name.</summary>
-        public string Name { get; set; }
-
-        /// <summary>The mod's semantic version number.</summary>
-        public string Version { get; set; }
-
-        /// <summary>The mod's web URL.</summary>
-        public string Url { get; set; }
-    }
-}
diff --git a/src/SMAPI.Web/Framework/Clients/Chucklefish/IChucklefishClient.cs b/src/SMAPI.Web/Framework/Clients/Chucklefish/IChucklefishClient.cs
index 1d8b256e..836d43f7 100644
--- a/src/SMAPI.Web/Framework/Clients/Chucklefish/IChucklefishClient.cs
+++ b/src/SMAPI.Web/Framework/Clients/Chucklefish/IChucklefishClient.cs
@@ -1,17 +1,7 @@
 using System;
-using System.Threading.Tasks;
 
 namespace StardewModdingAPI.Web.Framework.Clients.Chucklefish
 {
     /// <summary>An HTTP client for fetching mod metadata from the Chucklefish mod site.</summary>
-    internal interface IChucklefishClient : IDisposable
-    {
-        /*********
-        ** Methods
-        *********/
-        /// <summary>Get metadata about a mod.</summary>
-        /// <param name="id">The Chucklefish mod ID.</param>
-        /// <returns>Returns the mod info if found, else <c>null</c>.</returns>
-        Task<ChucklefishMod> GetModAsync(uint id);
-    }
+    internal interface IChucklefishClient : IModSiteClient, IDisposable { }
 }
diff --git a/src/SMAPI.Web/Framework/Clients/CurseForge/CurseForgeClient.cs b/src/SMAPI.Web/Framework/Clients/CurseForge/CurseForgeClient.cs
index a6fd21fd..d8008721 100644
--- a/src/SMAPI.Web/Framework/Clients/CurseForge/CurseForgeClient.cs
+++ b/src/SMAPI.Web/Framework/Clients/CurseForge/CurseForgeClient.cs
@@ -1,8 +1,8 @@
-using System.Linq;
+using System.Collections.Generic;
 using System.Text.RegularExpressions;
 using System.Threading.Tasks;
 using Pathoschild.Http.Client;
-using StardewModdingAPI.Toolkit;
+using StardewModdingAPI.Toolkit.Framework.UpdateData;
 using StardewModdingAPI.Web.Framework.Clients.CurseForge.ResponseModels;
 
 namespace StardewModdingAPI.Web.Framework.Clients.CurseForge
@@ -21,6 +21,13 @@ namespace StardewModdingAPI.Web.Framework.Clients.CurseForge
 
 
         /*********
+        ** Accessors
+        *********/
+        /// <summary>The unique key for the mod site.</summary>
+        public ModSiteKey SiteKey => ModSiteKey.CurseForge;
+
+
+        /*********
         ** Public methods
         *********/
         /// <summary>Construct an instance.</summary>
@@ -31,59 +38,34 @@ namespace StardewModdingAPI.Web.Framework.Clients.CurseForge
             this.Client = new FluentClient(apiUrl).SetUserAgent(userAgent);
         }
 
-        /// <summary>Get metadata about a mod.</summary>
-        /// <param name="id">The CurseForge mod ID.</param>
-        /// <returns>Returns the mod info if found, else <c>null</c>.</returns>
-        public async Task<CurseForgeMod> GetModAsync(long id)
+        /// <summary>Get update check info about a mod.</summary>
+        /// <param name="id">The mod ID.</param>
+        public async Task<IModPage> GetModData(string id)
         {
+            IModPage page = new GenericModPage(this.SiteKey, id);
+
+            // get ID
+            if (!uint.TryParse(id, out uint parsedId))
+                return page.SetError(RemoteModStatus.DoesNotExist, $"The value '{id}' isn't a valid CurseForge mod ID, must be an integer ID.");
+
             // get raw data
             ModModel mod = await this.Client
-                .GetAsync($"addon/{id}")
+                .GetAsync($"addon/{parsedId}")
                 .As<ModModel>();
             if (mod == null)
-                return null;
+                return page.SetError(RemoteModStatus.DoesNotExist, "Found no CurseForge mod with this ID.");
 
-            // get latest versions
-            string invalidVersion = null;
-            ISemanticVersion latest = null;
+            // get downloads
+            List<IModDownload> downloads = new List<IModDownload>();
             foreach (ModFileModel file in mod.LatestFiles)
             {
-                // extract version
-                ISemanticVersion version;
-                {
-                    string raw = this.GetRawVersion(file);
-                    if (raw == null)
-                        continue;
-
-                    if (!SemanticVersion.TryParse(raw, out version))
-                    {
-                        invalidVersion ??= raw;
-                        continue;
-                    }
-                }
-
-                // track latest version
-                if (latest == null || version.IsNewerThan(latest))
-                    latest = version;
-            }
-
-            // get error
-            string error = null;
-            if (latest == null && invalidVersion == null)
-            {
-                error = mod.LatestFiles.Any()
-                    ? $"CurseForge mod {id} has no downloads which specify the version in a recognised format."
-                    : $"CurseForge mod {id} has no downloads.";
+                downloads.Add(
+                    new GenericModDownload(name: file.DisplayName ?? file.FileName, description: null, version: this.GetRawVersion(file))
+                );
             }
 
-            // generate result
-            return new CurseForgeMod
-            {
-                Name = mod.Name,
-                LatestVersion = latest?.ToString() ?? invalidVersion,
-                Url = mod.WebsiteUrl,
-                Error = error
-            };
+            // return info
+            return page.SetInfo(name: mod.Name, version: null, url: mod.WebsiteUrl, downloads: downloads);
         }
 
         /// <summary>Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.</summary>
diff --git a/src/SMAPI.Web/Framework/Clients/CurseForge/CurseForgeMod.cs b/src/SMAPI.Web/Framework/Clients/CurseForge/CurseForgeMod.cs
deleted file mode 100644
index e5bb8cf1..00000000
--- a/src/SMAPI.Web/Framework/Clients/CurseForge/CurseForgeMod.cs
+++ /dev/null
@@ -1,23 +0,0 @@
-using Newtonsoft.Json;
-
-namespace StardewModdingAPI.Web.Framework.Clients.CurseForge
-{
-    /// <summary>Mod metadata from the CurseForge API.</summary>
-    internal class CurseForgeMod
-    {
-        /*********
-        ** Accessors
-        *********/
-        /// <summary>The mod name.</summary>
-        public string Name { get; set; }
-
-        /// <summary>The latest file version.</summary>
-        public string LatestVersion { get; set; }
-
-        /// <summary>The mod's web URL.</summary>
-        public string Url { get; set; }
-
-        /// <summary>A user-friendly error which indicates why fetching the mod info failed (if applicable).</summary>
-        public string Error { get; set; }
-    }
-}
diff --git a/src/SMAPI.Web/Framework/Clients/CurseForge/ICurseForgeClient.cs b/src/SMAPI.Web/Framework/Clients/CurseForge/ICurseForgeClient.cs
index 907b4087..2018c230 100644
--- a/src/SMAPI.Web/Framework/Clients/CurseForge/ICurseForgeClient.cs
+++ b/src/SMAPI.Web/Framework/Clients/CurseForge/ICurseForgeClient.cs
@@ -1,17 +1,7 @@
 using System;
-using System.Threading.Tasks;
 
 namespace StardewModdingAPI.Web.Framework.Clients.CurseForge
 {
     /// <summary>An HTTP client for fetching mod metadata from the CurseForge API.</summary>
-    internal interface ICurseForgeClient : IDisposable
-    {
-        /*********
-        ** Methods
-        *********/
-        /// <summary>Get metadata about a mod.</summary>
-        /// <param name="id">The CurseForge mod ID.</param>
-        /// <returns>Returns the mod info if found, else <c>null</c>.</returns>
-        Task<CurseForgeMod> GetModAsync(long id);
-    }
+    internal interface ICurseForgeClient : IModSiteClient, IDisposable { }
 }
diff --git a/src/SMAPI.Web/Framework/Clients/GenericModDownload.cs b/src/SMAPI.Web/Framework/Clients/GenericModDownload.cs
new file mode 100644
index 00000000..f08b471c
--- /dev/null
+++ b/src/SMAPI.Web/Framework/Clients/GenericModDownload.cs
@@ -0,0 +1,36 @@
+namespace StardewModdingAPI.Web.Framework.Clients
+{
+    /// <summary>Generic metadata about a file download on a mod page.</summary>
+    internal class GenericModDownload : IModDownload
+    {
+        /*********
+        ** Accessors
+        *********/
+        /// <summary>The download's display name.</summary>
+        public string Name { get; set; }
+
+        /// <summary>The download's description.</summary>
+        public string Description { get; set; }
+
+        /// <summary>The download's file version.</summary>
+        public string Version { get; set; }
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Construct an empty instance.</summary>
+        public GenericModDownload() { }
+
+        /// <summary>Construct an instance.</summary>
+        /// <param name="name">The download's display name.</param>
+        /// <param name="description">The download's description.</param>
+        /// <param name="version">The download's file version.</param>
+        public GenericModDownload(string name, string description, string version)
+        {
+            this.Name = name;
+            this.Description = description;
+            this.Version = version;
+        }
+    }
+}
diff --git a/src/SMAPI.Web/Framework/Clients/GenericModPage.cs b/src/SMAPI.Web/Framework/Clients/GenericModPage.cs
new file mode 100644
index 00000000..622e6c56
--- /dev/null
+++ b/src/SMAPI.Web/Framework/Clients/GenericModPage.cs
@@ -0,0 +1,79 @@
+using System.Collections.Generic;
+using System.Linq;
+using StardewModdingAPI.Toolkit.Framework.UpdateData;
+
+namespace StardewModdingAPI.Web.Framework.Clients
+{
+    /// <summary>Generic metadata about a mod page.</summary>
+    internal class GenericModPage : IModPage
+    {
+        /*********
+        ** Accessors
+        *********/
+        /// <summary>The mod site containing the mod.</summary>
+        public ModSiteKey Site { get; set; }
+
+        /// <summary>The mod's unique ID within the site.</summary>
+        public string Id { get; set; }
+
+        /// <summary>The mod name.</summary>
+        public string Name { get; set; }
+
+        /// <summary>The mod's semantic version number.</summary>
+        public string Version { get; set; }
+
+        /// <summary>The mod's web URL.</summary>
+        public string Url { get; set; }
+
+        /// <summary>The mod downloads.</summary>
+        public IModDownload[] Downloads { get; set; } = new IModDownload[0];
+
+        /// <summary>The mod availability status on the remote site.</summary>
+        public RemoteModStatus Status { get; set; } = RemoteModStatus.Ok;
+
+        /// <summary>A user-friendly error which indicates why fetching the mod info failed (if applicable).</summary>
+        public string Error { get; set; }
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Construct an empty instance.</summary>
+        public GenericModPage() { }
+
+        /// <summary>Construct an instance.</summary>
+        /// <param name="site">The mod site containing the mod.</param>
+        /// <param name="id">The mod's unique ID within the site.</param>
+        public GenericModPage(ModSiteKey site, string id)
+        {
+            this.Site = site;
+            this.Id = id;
+        }
+
+        /// <summary>Set the fetched mod info.</summary>
+        /// <param name="name">The mod name.</param>
+        /// <param name="version">The mod's semantic version number.</param>
+        /// <param name="url">The mod's web URL.</param>
+        /// <param name="downloads">The mod downloads.</param>
+        public IModPage SetInfo(string name, string version, string url, IEnumerable<IModDownload> downloads)
+        {
+            this.Name = name;
+            this.Version = version;
+            this.Url = url;
+            this.Downloads = downloads.ToArray();
+
+            return this;
+        }
+
+        /// <summary>Set a mod fetch error.</summary>
+        /// <param name="status">The mod availability status on the remote site.</param>
+        /// <param name="error">A user-friendly error which indicates why fetching the mod info failed (if applicable).</param>
+        public IModPage SetError(RemoteModStatus status, string error)
+        {
+            this.Status = status;
+            this.Error = error;
+
+            return this;
+        }
+    }
+}
diff --git a/src/SMAPI.Web/Framework/Clients/GitHub/GitHubClient.cs b/src/SMAPI.Web/Framework/Clients/GitHub/GitHubClient.cs
index 84c20957..2f1eb854 100644
--- a/src/SMAPI.Web/Framework/Clients/GitHub/GitHubClient.cs
+++ b/src/SMAPI.Web/Framework/Clients/GitHub/GitHubClient.cs
@@ -3,6 +3,7 @@ using System.Linq;
 using System.Net;
 using System.Threading.Tasks;
 using Pathoschild.Http.Client;
+using StardewModdingAPI.Toolkit.Framework.UpdateData;
 
 namespace StardewModdingAPI.Web.Framework.Clients.GitHub
 {
@@ -17,6 +18,13 @@ namespace StardewModdingAPI.Web.Framework.Clients.GitHub
 
 
         /*********
+        ** Accessors
+        *********/
+        /// <summary>The unique key for the mod site.</summary>
+        public ModSiteKey SiteKey => ModSiteKey.GitHub;
+
+
+        /*********
         ** Public methods
         *********/
         /// <summary>Construct an instance.</summary>
@@ -79,6 +87,54 @@ namespace StardewModdingAPI.Web.Framework.Clients.GitHub
             }
         }
 
+        /// <summary>Get update check info about a mod.</summary>
+        /// <param name="id">The mod ID.</param>
+        public async Task<IModPage> GetModData(string id)
+        {
+            IModPage page = new GenericModPage(this.SiteKey, id);
+
+            if (!id.Contains("/") || id.IndexOf("/", StringComparison.OrdinalIgnoreCase) != id.LastIndexOf("/", StringComparison.OrdinalIgnoreCase))
+                return page.SetError(RemoteModStatus.DoesNotExist, $"The value '{id}' isn't a valid GitHub mod ID, must be a username and project name like 'Pathoschild/SMAPI'.");
+
+            // fetch repo info
+            GitRepo repository = await this.GetRepositoryAsync(id);
+            if (repository == null)
+                return page.SetError(RemoteModStatus.DoesNotExist, "Found no GitHub repository for this ID.");
+            string name = repository.FullName;
+            string url = $"{repository.WebUrl}/releases";
+
+            // get releases
+            GitRelease latest;
+            GitRelease preview;
+            {
+                // get latest release (whether preview or stable)
+                latest = await this.GetLatestReleaseAsync(id, includePrerelease: true);
+                if (latest == null)
+                    return page.SetError(RemoteModStatus.DoesNotExist, "Found no GitHub release for this ID.");
+
+                // get stable version if different
+                preview = null;
+                if (latest.IsPrerelease)
+                {
+                    GitRelease release = await this.GetLatestReleaseAsync(id, includePrerelease: false);
+                    if (release != null)
+                    {
+                        preview = latest;
+                        latest = release;
+                    }
+                }
+            }
+
+            // get downloads
+            IModDownload[] downloads = new[] { latest, preview }
+                .Where(release => release != null)
+                .Select(release => (IModDownload)new GenericModDownload(release.Name, release.Body, release.Tag))
+                .ToArray();
+
+            // return info
+            return page.SetInfo(name: name, url: url, version: null, downloads: downloads);
+        }
+
         /// <summary>Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.</summary>
         public void Dispose()
         {
diff --git a/src/SMAPI.Web/Framework/Clients/GitHub/IGitHubClient.cs b/src/SMAPI.Web/Framework/Clients/GitHub/IGitHubClient.cs
index a34f03bd..0d6f4643 100644
--- a/src/SMAPI.Web/Framework/Clients/GitHub/IGitHubClient.cs
+++ b/src/SMAPI.Web/Framework/Clients/GitHub/IGitHubClient.cs
@@ -4,7 +4,7 @@ using System.Threading.Tasks;
 namespace StardewModdingAPI.Web.Framework.Clients.GitHub
 {
     /// <summary>An HTTP client for fetching metadata from GitHub.</summary>
-    internal interface IGitHubClient : IDisposable
+    internal interface IGitHubClient : IModSiteClient, IDisposable
     {
         /*********
         ** Methods
diff --git a/src/SMAPI.Web/Framework/Clients/IModSiteClient.cs b/src/SMAPI.Web/Framework/Clients/IModSiteClient.cs
new file mode 100644
index 00000000..33277711
--- /dev/null
+++ b/src/SMAPI.Web/Framework/Clients/IModSiteClient.cs
@@ -0,0 +1,23 @@
+using System.Threading.Tasks;
+using StardewModdingAPI.Toolkit.Framework.UpdateData;
+
+namespace StardewModdingAPI.Web.Framework.Clients
+{
+    /// <summary>A client for fetching update check info from a mod site.</summary>
+    internal interface IModSiteClient
+    {
+        /*********
+        ** Accessors
+        *********/
+        /// <summary>The unique key for the mod site.</summary>
+        public ModSiteKey SiteKey { get; }
+
+
+        /*********
+        ** Methods
+        *********/
+        /// <summary>Get update check info about a mod.</summary>
+        /// <param name="id">The mod ID.</param>
+        Task<IModPage> GetModData(string id);
+    }
+}
diff --git a/src/SMAPI.Web/Framework/Clients/ModDrop/IModDropClient.cs b/src/SMAPI.Web/Framework/Clients/ModDrop/IModDropClient.cs
index 3ede46e2..468b72b1 100644
--- a/src/SMAPI.Web/Framework/Clients/ModDrop/IModDropClient.cs
+++ b/src/SMAPI.Web/Framework/Clients/ModDrop/IModDropClient.cs
@@ -1,17 +1,7 @@
 using System;
-using System.Threading.Tasks;
 
 namespace StardewModdingAPI.Web.Framework.Clients.ModDrop
 {
     /// <summary>An HTTP client for fetching mod metadata from the ModDrop API.</summary>
-    internal interface IModDropClient : IDisposable
-    {
-        /*********
-        ** Methods
-        *********/
-        /// <summary>Get metadata about a mod.</summary>
-        /// <param name="id">The ModDrop mod ID.</param>
-        /// <returns>Returns the mod info if found, else <c>null</c>.</returns>
-        Task<ModDropMod> GetModAsync(long id);
-    }
+    internal interface IModDropClient : IDisposable, IModSiteClient { }
 }
diff --git a/src/SMAPI.Web/Framework/Clients/ModDrop/ModDropClient.cs b/src/SMAPI.Web/Framework/Clients/ModDrop/ModDropClient.cs
index 5ad2d2f8..3a1c5b9d 100644
--- a/src/SMAPI.Web/Framework/Clients/ModDrop/ModDropClient.cs
+++ b/src/SMAPI.Web/Framework/Clients/ModDrop/ModDropClient.cs
@@ -1,6 +1,7 @@
+using System.Collections.Generic;
 using System.Threading.Tasks;
 using Pathoschild.Http.Client;
-using StardewModdingAPI.Toolkit;
+using StardewModdingAPI.Toolkit.Framework.UpdateData;
 using StardewModdingAPI.Web.Framework.Clients.ModDrop.ResponseModels;
 
 namespace StardewModdingAPI.Web.Framework.Clients.ModDrop
@@ -19,6 +20,13 @@ namespace StardewModdingAPI.Web.Framework.Clients.ModDrop
 
 
         /*********
+        ** Accessors
+        *********/
+        /// <summary>The unique key for the mod site.</summary>
+        public ModSiteKey SiteKey => ModSiteKey.ModDrop;
+
+
+        /*********
         ** Public methods
         *********/
         /// <summary>Construct an instance.</summary>
@@ -31,60 +39,45 @@ namespace StardewModdingAPI.Web.Framework.Clients.ModDrop
             this.ModUrlFormat = modUrlFormat;
         }
 
-        /// <summary>Get metadata about a mod.</summary>
-        /// <param name="id">The ModDrop mod ID.</param>
-        /// <returns>Returns the mod info if found, else <c>null</c>.</returns>
-        public async Task<ModDropMod> GetModAsync(long id)
+        /// <summary>Get update check info about a mod.</summary>
+        /// <param name="id">The mod ID.</param>
+        public async Task<IModPage> GetModData(string id)
         {
+            var page = new GenericModPage(this.SiteKey, id);
+
+            if (!long.TryParse(id, out long parsedId))
+                return page.SetError(RemoteModStatus.DoesNotExist, $"The value '{id}' isn't a valid ModDrop mod ID, must be an integer ID.");
+
             // get raw data
             ModListModel response = await this.Client
                 .PostAsync("")
                 .WithBody(new
                 {
-                    ModIDs = new[] { id },
+                    ModIDs = new[] { parsedId },
                     Files = true,
                     Mods = true
                 })
                 .As<ModListModel>();
-            ModModel mod = response.Mods[id];
+            ModModel mod = response.Mods[parsedId];
             if (mod.Mod?.Title == null || mod.Mod.ErrorCode.HasValue)
                 return null;
 
-            // get latest versions
-            ISemanticVersion latest = null;
-            ISemanticVersion optional = null;
+            // get files
+            var downloads = new List<IModDownload>();
             foreach (FileDataModel file in mod.Files)
             {
                 if (file.IsOld || file.IsDeleted || file.IsHidden)
                     continue;
 
-                if (!SemanticVersion.TryParse(file.Version, out ISemanticVersion version))
-                    continue;
-
-                if (file.IsDefault)
-                {
-                    if (latest == null || version.IsNewerThan(latest))
-                        latest = version;
-                }
-                else if (optional == null || version.IsNewerThan(optional))
-                    optional = version;
+                downloads.Add(
+                    new GenericModDownload(file.Name, file.Description, file.Version)
+                );
             }
-            if (latest == null)
-            {
-                latest = optional;
-                optional = null;
-            }
-            if (optional != null && latest.IsNewerThan(optional))
-                optional = null;
 
-            // generate result
-            return new ModDropMod
-            {
-                Name = mod.Mod?.Title,
-                LatestDefaultVersion = latest,
-                LatestOptionalVersion = optional,
-                Url = string.Format(this.ModUrlFormat, id)
-            };
+            // return info
+            string name = mod.Mod?.Title;
+            string url = string.Format(this.ModUrlFormat, id);
+            return page.SetInfo(name: name, version: null, url: url, downloads: downloads);
         }
 
         /// <summary>Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.</summary>
diff --git a/src/SMAPI.Web/Framework/Clients/ModDrop/ModDropMod.cs b/src/SMAPI.Web/Framework/Clients/ModDrop/ModDropMod.cs
deleted file mode 100644
index def79106..00000000
--- a/src/SMAPI.Web/Framework/Clients/ModDrop/ModDropMod.cs
+++ /dev/null
@@ -1,21 +0,0 @@
-namespace StardewModdingAPI.Web.Framework.Clients.ModDrop
-{
-    /// <summary>Mod metadata from the ModDrop API.</summary>
-    internal class ModDropMod
-    {
-        /*********
-        ** Accessors
-        *********/
-        /// <summary>The mod name.</summary>
-        public string Name { get; set; }
-
-        /// <summary>The latest default file version.</summary>
-        public ISemanticVersion LatestDefaultVersion { get; set; }
-
-        /// <summary>The latest optional file version.</summary>
-        public ISemanticVersion LatestOptionalVersion { get; set; }
-
-        /// <summary>The mod's web URL.</summary>
-        public string Url { get; set; }
-    }
-}
diff --git a/src/SMAPI.Web/Framework/Clients/ModDrop/ResponseModels/FileDataModel.cs b/src/SMAPI.Web/Framework/Clients/ModDrop/ResponseModels/FileDataModel.cs
index fa84b287..b01196f4 100644
--- a/src/SMAPI.Web/Framework/Clients/ModDrop/ResponseModels/FileDataModel.cs
+++ b/src/SMAPI.Web/Framework/Clients/ModDrop/ResponseModels/FileDataModel.cs
@@ -1,8 +1,21 @@
+using Newtonsoft.Json;
+
 namespace StardewModdingAPI.Web.Framework.Clients.ModDrop.ResponseModels
 {
     /// <summary>Metadata from the ModDrop API about a mod file.</summary>
     public class FileDataModel
     {
+        /// <summary>The file title.</summary>
+        [JsonProperty("title")]
+        public string Name { get; set; }
+
+        /// <summary>The file description.</summary>
+        [JsonProperty("desc")]
+        public string Description { get; set; }
+
+        /// <summary>The file version.</summary>
+        public string Version { get; set; }
+
         /// <summary>Whether the file is deleted.</summary>
         public bool IsDeleted { get; set; }
 
@@ -14,8 +27,5 @@ namespace StardewModdingAPI.Web.Framework.Clients.ModDrop.ResponseModels
 
         /// <summary>Whether this is an archived file.</summary>
         public bool IsOld { get; set; }
-
-        /// <summary>The file version.</summary>
-        public string Version { get; set; }
     }
 }
diff --git a/src/SMAPI.Web/Framework/Clients/Nexus/INexusClient.cs b/src/SMAPI.Web/Framework/Clients/Nexus/INexusClient.cs
index e56e7af4..a44b8c66 100644
--- a/src/SMAPI.Web/Framework/Clients/Nexus/INexusClient.cs
+++ b/src/SMAPI.Web/Framework/Clients/Nexus/INexusClient.cs
@@ -1,17 +1,7 @@
 using System;
-using System.Threading.Tasks;
 
 namespace StardewModdingAPI.Web.Framework.Clients.Nexus
 {
     /// <summary>An HTTP client for fetching mod metadata from Nexus Mods.</summary>
-    internal interface INexusClient : IDisposable
-    {
-        /*********
-        ** Methods
-        *********/
-        /// <summary>Get metadata about a mod.</summary>
-        /// <param name="id">The Nexus mod ID.</param>
-        /// <returns>Returns the mod info if found, else <c>null</c>.</returns>
-        Task<NexusMod> GetModAsync(uint id);
-    }
+    internal interface INexusClient : IModSiteClient, IDisposable { }
 }
diff --git a/src/SMAPI.Web/Framework/Clients/Nexus/NexusClient.cs b/src/SMAPI.Web/Framework/Clients/Nexus/NexusClient.cs
index 753d3b4f..ef3ef22e 100644
--- a/src/SMAPI.Web/Framework/Clients/Nexus/NexusClient.cs
+++ b/src/SMAPI.Web/Framework/Clients/Nexus/NexusClient.cs
@@ -7,6 +7,8 @@ using HtmlAgilityPack;
 using Pathoschild.FluentNexus.Models;
 using Pathoschild.Http.Client;
 using StardewModdingAPI.Toolkit;
+using StardewModdingAPI.Toolkit.Framework.UpdateData;
+using StardewModdingAPI.Web.Framework.Clients.Nexus.ResponseModels;
 using FluentNexusClient = Pathoschild.FluentNexus.NexusClient;
 
 namespace StardewModdingAPI.Web.Framework.Clients.Nexus
@@ -31,6 +33,13 @@ namespace StardewModdingAPI.Web.Framework.Clients.Nexus
 
 
         /*********
+        ** Accessors
+        *********/
+        /// <summary>The unique key for the mod site.</summary>
+        public ModSiteKey SiteKey => ModSiteKey.Nexus;
+
+
+        /*********
         ** Public methods
         *********/
         /// <summary>Construct an instance.</summary>
@@ -48,20 +57,32 @@ namespace StardewModdingAPI.Web.Framework.Clients.Nexus
             this.ApiClient = new FluentNexusClient(apiKey, "SMAPI", apiAppVersion);
         }
 
-        /// <summary>Get metadata about a mod.</summary>
-        /// <param name="id">The Nexus mod ID.</param>
-        /// <returns>Returns the mod info if found, else <c>null</c>.</returns>
-        public async Task<NexusMod> GetModAsync(uint id)
+        /// <summary>Get update check info about a mod.</summary>
+        /// <param name="id">The mod ID.</param>
+        public async Task<IModPage> GetModData(string id)
         {
+            IModPage page = new GenericModPage(this.SiteKey, id);
+
+            if (!uint.TryParse(id, out uint parsedId))
+                return page.SetError(RemoteModStatus.DoesNotExist, $"The value '{id}' isn't a valid Nexus mod ID, must be an integer ID.");
+
             // Fetch from the Nexus website when possible, since it has no rate limits. Mods with
             // adult content are hidden for anonymous users, so fall back to the API in that case.
             // Note that the API has very restrictive rate limits which means we can't just use it
             // for all cases.
-            NexusMod mod = await this.GetModFromWebsiteAsync(id);
+            NexusMod mod = await this.GetModFromWebsiteAsync(parsedId);
             if (mod?.Status == NexusModStatus.AdultContentForbidden)
-                mod = await this.GetModFromApiAsync(id);
+                mod = await this.GetModFromApiAsync(parsedId);
+
+            // page doesn't exist
+            if (mod == null || mod.Status == NexusModStatus.Hidden || mod.Status == NexusModStatus.NotPublished)
+                return page.SetError(RemoteModStatus.DoesNotExist, "Found no Nexus mod with this ID.");
 
-            return mod;
+            // return info
+            page.SetInfo(name: mod.Name, url: mod.Url, version: mod.Version, downloads: mod.Downloads);
+            if (mod.Status != NexusModStatus.Ok)
+                page.SetError(RemoteModStatus.TemporaryError, mod.Error);
+            return page;
         }
 
         /// <summary>Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.</summary>
@@ -115,37 +136,28 @@ namespace StardewModdingAPI.Web.Framework.Clients.Nexus
 
             // extract mod info
             string url = this.GetModUrl(id);
-            string name = doc.DocumentNode.SelectSingleNode("//h1")?.InnerText.Trim();
+            string name = doc.DocumentNode.SelectSingleNode("//div[@id='pagetitle']//h1")?.InnerText.Trim();
             string version = doc.DocumentNode.SelectSingleNode("//ul[contains(@class, 'stats')]//li[@class='stat-version']//div[@class='stat']")?.InnerText.Trim();
             SemanticVersion.TryParse(version, out ISemanticVersion parsedVersion);
 
-            // extract file versions
-            List<string> rawVersions = new List<string>();
+            // extract files
+            var downloads = new List<IModDownload>();
             foreach (var fileSection in doc.DocumentNode.SelectNodes("//div[contains(@class, 'files-tabs')]"))
             {
                 string sectionName = fileSection.Descendants("h2").First().InnerText;
                 if (sectionName != "Main files" && sectionName != "Optional files")
                     continue;
 
-                rawVersions.AddRange(
-                    from statBox in fileSection.Descendants().Where(p => p.HasClass("stat-version"))
-                    from versionStat in statBox.Descendants().Where(p => p.HasClass("stat"))
-                    select versionStat.InnerText.Trim()
-                );
-            }
-
-            // choose latest file version
-            ISemanticVersion latestFileVersion = null;
-            foreach (string rawVersion in rawVersions)
-            {
-                if (!SemanticVersion.TryParse(rawVersion, out ISemanticVersion cur))
-                    continue;
-                if (parsedVersion != null && !cur.IsNewerThan(parsedVersion))
-                    continue;
-                if (latestFileVersion != null && !cur.IsNewerThan(latestFileVersion))
-                    continue;
+                foreach (var container in fileSection.Descendants("dt"))
+                {
+                    string fileName = container.GetDataAttribute("name").Value;
+                    string fileVersion = container.GetDataAttribute("version").Value;
+                    string description = container.SelectSingleNode("following-sibling::*[1][self::dd]//div").InnerText?.Trim(); // get text of next <dd> tag; derived from https://stackoverflow.com/a/25535623/262123
 
-                latestFileVersion = cur;
+                    downloads.Add(
+                        new GenericModDownload(fileName, description, fileVersion)
+                    );
+                }
             }
 
             // yield info
@@ -153,8 +165,8 @@ namespace StardewModdingAPI.Web.Framework.Clients.Nexus
             {
                 Name = name,
                 Version = parsedVersion?.ToString() ?? version,
-                LatestFileVersion = latestFileVersion,
-                Url = url
+                Url = url,
+                Downloads = downloads.ToArray()
             };
         }
 
@@ -167,29 +179,15 @@ namespace StardewModdingAPI.Web.Framework.Clients.Nexus
             Mod mod = await this.ApiClient.Mods.GetMod("stardewvalley", (int)id);
             ModFileList files = await this.ApiClient.ModFiles.GetModFiles("stardewvalley", (int)id, FileCategory.Main, FileCategory.Optional);
 
-            // get versions
-            if (!SemanticVersion.TryParse(mod.Version, out ISemanticVersion mainVersion))
-                mainVersion = null;
-            ISemanticVersion latestFileVersion = null;
-            foreach (string rawVersion in files.Files.Select(p => p.FileVersion))
-            {
-                if (!SemanticVersion.TryParse(rawVersion, out ISemanticVersion cur))
-                    continue;
-                if (mainVersion != null && !cur.IsNewerThan(mainVersion))
-                    continue;
-                if (latestFileVersion != null && !cur.IsNewerThan(latestFileVersion))
-                    continue;
-
-                latestFileVersion = cur;
-            }
-
             // yield info
             return new NexusMod
             {
                 Name = mod.Name,
                 Version = SemanticVersion.TryParse(mod.Version, out ISemanticVersion version) ? version?.ToString() : mod.Version,
-                LatestFileVersion = latestFileVersion,
-                Url = this.GetModUrl(id)
+                Url = this.GetModUrl(id),
+                Downloads = files.Files
+                    .Select(file => (IModDownload)new GenericModDownload(file.Name, null, file.FileVersion))
+                    .ToArray()
             };
         }
 
diff --git a/src/SMAPI.Web/Framework/Clients/Nexus/NexusMod.cs b/src/SMAPI.Web/Framework/Clients/Nexus/ResponseModels/NexusMod.cs
index 0f1b29d5..aef90ede 100644
--- a/src/SMAPI.Web/Framework/Clients/Nexus/NexusMod.cs
+++ b/src/SMAPI.Web/Framework/Clients/Nexus/ResponseModels/NexusMod.cs
@@ -1,6 +1,6 @@
 using Newtonsoft.Json;
 
-namespace StardewModdingAPI.Web.Framework.Clients.Nexus
+namespace StardewModdingAPI.Web.Framework.Clients.Nexus.ResponseModels
 {
     /// <summary>Mod metadata from Nexus Mods.</summary>
     internal class NexusMod
@@ -14,9 +14,6 @@ namespace StardewModdingAPI.Web.Framework.Clients.Nexus
         /// <summary>The mod's semantic version number.</summary>
         public string Version { get; set; }
 
-        /// <summary>The latest file version.</summary>
-        public ISemanticVersion LatestFileVersion { get; set; }
-
         /// <summary>The mod's web URL.</summary>
         [JsonProperty("mod_page_uri")]
         public string Url { get; set; }
@@ -25,7 +22,11 @@ namespace StardewModdingAPI.Web.Framework.Clients.Nexus
         [JsonIgnore]
         public NexusModStatus Status { get; set; } = NexusModStatus.Ok;
 
-        /// <summary>A user-friendly error which indicates why fetching the mod info failed (if applicable).</summary>
+        /// <summary>The files available to download.</summary>
+        [JsonIgnore]
+        public IModDownload[] Downloads { get; set; }
+
+        /// <summary>A custom user-friendly error which indicates why fetching the mod info failed (if applicable).</summary>
         [JsonIgnore]
         public string Error { get; set; }
     }
diff --git a/src/SMAPI.Web/Framework/Extensions.cs b/src/SMAPI.Web/Framework/Extensions.cs
index ad7e645a..3a246245 100644
--- a/src/SMAPI.Web/Framework/Extensions.cs
+++ b/src/SMAPI.Web/Framework/Extensions.cs
@@ -13,6 +13,12 @@ namespace StardewModdingAPI.Web.Framework
     /// <summary>Provides extensions on ASP.NET Core types.</summary>
     public static class Extensions
     {
+        /*********
+        ** Public methods
+        *********/
+        /****
+        ** View helpers
+        ****/
         /// <summary>Get a URL with the absolute path for an action method. Unlike <see cref="IUrlHelper.Action"/>, only the specified <paramref name="values"/> are added to the URL without merging values from the current HTTP request.</summary>
         /// <param name="helper">The URL helper to extend.</param>
         /// <param name="action">The name of the action method.</param>
diff --git a/src/SMAPI.Web/Framework/IModDownload.cs b/src/SMAPI.Web/Framework/IModDownload.cs
new file mode 100644
index 00000000..dc058bcb
--- /dev/null
+++ b/src/SMAPI.Web/Framework/IModDownload.cs
@@ -0,0 +1,15 @@
+namespace StardewModdingAPI.Web.Framework
+{
+    /// <summary>Generic metadata about a file download on a mod page.</summary>
+    internal interface IModDownload
+    {
+        /// <summary>The download's display name.</summary>
+        string Name { get; }
+
+        /// <summary>The download's description.</summary>
+        string Description { get; }
+
+        /// <summary>The download's file version.</summary>
+        string Version { get; }
+    }
+}
diff --git a/src/SMAPI.Web/Framework/IModPage.cs b/src/SMAPI.Web/Framework/IModPage.cs
new file mode 100644
index 00000000..e66d401f
--- /dev/null
+++ b/src/SMAPI.Web/Framework/IModPage.cs
@@ -0,0 +1,52 @@
+using System.Collections.Generic;
+using StardewModdingAPI.Toolkit.Framework.UpdateData;
+
+namespace StardewModdingAPI.Web.Framework
+{
+    /// <summary>Generic metadata about a mod page.</summary>
+    internal interface IModPage
+    {
+        /*********
+        ** Accessors
+        *********/
+        /// <summary>The mod site containing the mod.</summary>
+        ModSiteKey Site { get; }
+
+        /// <summary>The mod's unique ID within the site.</summary>
+        string Id { get; }
+
+        /// <summary>The mod name.</summary>
+        string Name { get; }
+
+        /// <summary>The mod's semantic version number.</summary>
+        string Version { get; }
+
+        /// <summary>The mod's web URL.</summary>
+        string Url { get; }
+
+        /// <summary>The mod downloads.</summary>
+        IModDownload[] Downloads { get; }
+
+        /// <summary>The mod page status.</summary>
+        RemoteModStatus Status { get; }
+
+        /// <summary>A user-friendly error which indicates why fetching the mod info failed (if applicable).</summary>
+        string Error { get; }
+
+
+        /*********
+        ** Methods
+        *********/
+        /// <summary>Set the fetched mod info.</summary>
+        /// <param name="name">The mod name.</param>
+        /// <param name="version">The mod's semantic version number.</param>
+        /// <param name="url">The mod's web URL.</param>
+        /// <param name="downloads">The mod downloads.</param>
+        IModPage SetInfo(string name, string version, string url, IEnumerable<IModDownload> downloads);
+
+        /// <summary>Set a mod fetch error.</summary>
+        /// <param name="status">The mod availability status on the remote site.</param>
+        /// <param name="error">A user-friendly error which indicates why fetching the mod info failed (if applicable).</param>
+        IModPage SetError(RemoteModStatus status, string error);
+    }
+}
diff --git a/src/SMAPI.Web/Framework/ModRepositories/ModInfoModel.cs b/src/SMAPI.Web/Framework/ModInfoModel.cs
index 46b98860..7845b8c5 100644
--- a/src/SMAPI.Web/Framework/ModRepositories/ModInfoModel.cs
+++ b/src/SMAPI.Web/Framework/ModInfoModel.cs
@@ -1,4 +1,6 @@
-namespace StardewModdingAPI.Web.Framework.ModRepositories
+using StardewModdingAPI.Web.Framework.Clients;
+
+namespace StardewModdingAPI.Web.Framework
 {
     /// <summary>Generic metadata about a mod.</summary>
     internal class ModInfoModel
@@ -10,20 +12,14 @@ namespace StardewModdingAPI.Web.Framework.ModRepositories
         public string Name { get; set; }
 
         /// <summary>The mod's latest version.</summary>
-        public string Version { get; set; }
+        public ISemanticVersion Version { get; set; }
 
         /// <summary>The mod's latest optional or prerelease version, if newer than <see cref="Version"/>.</summary>
-        public string PreviewVersion { get; set; }
+        public ISemanticVersion PreviewVersion { get; set; }
 
         /// <summary>The mod's web URL.</summary>
         public string Url { get; set; }
 
-        /// <summary>The license URL, if available.</summary>
-        public string LicenseUrl { get; set; }
-
-        /// <summary>The license name, if available.</summary>
-        public string LicenseName { get; set; }
-
         /// <summary>The mod availability status on the remote site.</summary>
         public RemoteModStatus Status { get; set; } = RemoteModStatus.Ok;
 
@@ -42,7 +38,7 @@ namespace StardewModdingAPI.Web.Framework.ModRepositories
         /// <param name="version">The semantic version for the mod's latest release.</param>
         /// <param name="previewVersion">The semantic version for the mod's latest preview release, if available and different from <see cref="Version"/>.</param>
         /// <param name="url">The mod's web URL.</param>
-        public ModInfoModel(string name, string version, string url, string previewVersion = null)
+        public ModInfoModel(string name, ISemanticVersion version, string url, ISemanticVersion previewVersion = null)
         {
             this
                 .SetBasicInfo(name, url)
@@ -63,7 +59,7 @@ namespace StardewModdingAPI.Web.Framework.ModRepositories
         /// <summary>Set the mod version info.</summary>
         /// <param name="version">The semantic version for the mod's latest release.</param>
         /// <param name="previewVersion">The semantic version for the mod's latest preview release, if available and different from <see cref="Version"/>.</param>
-        public ModInfoModel SetVersions(string version, string previewVersion = null)
+        public ModInfoModel SetVersions(ISemanticVersion version, ISemanticVersion previewVersion = null)
         {
             this.Version = version;
             this.PreviewVersion = previewVersion;
@@ -71,17 +67,6 @@ namespace StardewModdingAPI.Web.Framework.ModRepositories
             return this;
         }
 
-        /// <summary>Set the license info, if available.</summary>
-        /// <param name="url">The license URL.</param>
-        /// <param name="name">The license name.</param>
-        public ModInfoModel SetLicense(string url, string name)
-        {
-            this.LicenseUrl = url;
-            this.LicenseName = name;
-
-            return this;
-        }
-
         /// <summary>Set a mod error.</summary>
         /// <param name="status">The mod availability status on the remote site.</param>
         /// <param name="error">The error message indicating why the mod is invalid (if applicable).</param>
diff --git a/src/SMAPI.Web/Framework/ModRepositories/BaseRepository.cs b/src/SMAPI.Web/Framework/ModRepositories/BaseRepository.cs
deleted file mode 100644
index f9f9f47d..00000000
--- a/src/SMAPI.Web/Framework/ModRepositories/BaseRepository.cs
+++ /dev/null
@@ -1,51 +0,0 @@
-using System.Text.RegularExpressions;
-using System.Threading.Tasks;
-using StardewModdingAPI.Toolkit.Framework.UpdateData;
-
-namespace StardewModdingAPI.Web.Framework.ModRepositories
-{
-    internal abstract class RepositoryBase : IModRepository
-    {
-        /*********
-        ** Accessors
-        *********/
-        /// <summary>The unique key for this vendor.</summary>
-        public ModRepositoryKey VendorKey { get; }
-
-
-        /*********
-        ** Public methods
-        *********/
-        /// <summary>Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.</summary>
-        public abstract void Dispose();
-
-        /// <summary>Get metadata about a mod in the repository.</summary>
-        /// <param name="id">The mod ID in this repository.</param>
-        public abstract Task<ModInfoModel> GetModInfoAsync(string id);
-
-
-        /*********
-        ** Protected methods
-        *********/
-        /// <summary>Construct an instance.</summary>
-        /// <param name="vendorKey">The unique key for this vendor.</param>
-        protected RepositoryBase(ModRepositoryKey vendorKey)
-        {
-            this.VendorKey = vendorKey;
-        }
-
-        /// <summary>Normalize a version string.</summary>
-        /// <param name="version">The version to normalize.</param>
-        protected string NormalizeVersion(string version)
-        {
-            if (string.IsNullOrWhiteSpace(version))
-                return null;
-
-            version = version.Trim();
-            if (Regex.IsMatch(version, @"^v\d", RegexOptions.CultureInvariant | RegexOptions.IgnoreCase)) // common version prefix
-                version = version.Substring(1);
-
-            return version;
-        }
-    }
-}
diff --git a/src/SMAPI.Web/Framework/ModRepositories/ChucklefishRepository.cs b/src/SMAPI.Web/Framework/ModRepositories/ChucklefishRepository.cs
deleted file mode 100644
index 0945735a..00000000
--- a/src/SMAPI.Web/Framework/ModRepositories/ChucklefishRepository.cs
+++ /dev/null
@@ -1,57 +0,0 @@
-using System;
-using System.Threading.Tasks;
-using StardewModdingAPI.Toolkit.Framework.UpdateData;
-using StardewModdingAPI.Web.Framework.Clients.Chucklefish;
-
-namespace StardewModdingAPI.Web.Framework.ModRepositories
-{
-    /// <summary>An HTTP client for fetching mod metadata from the Chucklefish mod site.</summary>
-    internal class ChucklefishRepository : RepositoryBase
-    {
-        /*********
-        ** Fields
-        *********/
-        /// <summary>The underlying HTTP client.</summary>
-        private readonly IChucklefishClient Client;
-
-
-        /*********
-        ** Public methods
-        *********/
-        /// <summary>Construct an instance.</summary>
-        /// <param name="client">The underlying HTTP client.</param>
-        public ChucklefishRepository(IChucklefishClient client)
-            : base(ModRepositoryKey.Chucklefish)
-        {
-            this.Client = client;
-        }
-
-        /// <summary>Get metadata about a mod in the repository.</summary>
-        /// <param name="id">The mod ID in this repository.</param>
-        public override async Task<ModInfoModel> GetModInfoAsync(string id)
-        {
-            // validate ID format
-            if (!uint.TryParse(id, out uint realID))
-                return new ModInfoModel().SetError(RemoteModStatus.DoesNotExist, $"The value '{id}' isn't a valid Chucklefish mod ID, must be an integer ID.");
-
-            // fetch info
-            try
-            {
-                var mod = await this.Client.GetModAsync(realID);
-                return mod != null
-                    ? new ModInfoModel(name: mod.Name, version: this.NormalizeVersion(mod.Version), url: mod.Url)
-                    : new ModInfoModel().SetError(RemoteModStatus.DoesNotExist, "Found no Chucklefish mod with this ID.");
-            }
-            catch (Exception ex)
-            {
-                return new ModInfoModel().SetError(RemoteModStatus.TemporaryError, ex.ToString());
-            }
-        }
-
-        /// <summary>Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.</summary>
-        public override void Dispose()
-        {
-            this.Client.Dispose();
-        }
-    }
-}
diff --git a/src/SMAPI.Web/Framework/ModRepositories/CurseForgeRepository.cs b/src/SMAPI.Web/Framework/ModRepositories/CurseForgeRepository.cs
deleted file mode 100644
index 93ddc1eb..00000000
--- a/src/SMAPI.Web/Framework/ModRepositories/CurseForgeRepository.cs
+++ /dev/null
@@ -1,63 +0,0 @@
-using System;
-using System.Threading.Tasks;
-using StardewModdingAPI.Toolkit.Framework.UpdateData;
-using StardewModdingAPI.Web.Framework.Clients.CurseForge;
-
-namespace StardewModdingAPI.Web.Framework.ModRepositories
-{
-    /// <summary>An HTTP client for fetching mod metadata from CurseForge.</summary>
-    internal class CurseForgeRepository : RepositoryBase
-    {
-        /*********
-        ** Fields
-        *********/
-        /// <summary>The underlying CurseForge API client.</summary>
-        private readonly ICurseForgeClient Client;
-
-
-        /*********
-        ** Public methods
-        *********/
-        /// <summary>Construct an instance.</summary>
-        /// <param name="client">The underlying CurseForge API client.</param>
-        public CurseForgeRepository(ICurseForgeClient client)
-            : base(ModRepositoryKey.CurseForge)
-        {
-            this.Client = client;
-        }
-
-        /// <summary>Get metadata about a mod in the repository.</summary>
-        /// <param name="id">The mod ID in this repository.</param>
-        public override async Task<ModInfoModel> GetModInfoAsync(string id)
-        {
-            // validate ID format
-            if (!uint.TryParse(id, out uint curseID))
-                return new ModInfoModel().SetError(RemoteModStatus.DoesNotExist, $"The value '{id}' isn't a valid CurseForge mod ID, must be an integer ID.");
-
-            // fetch info
-            try
-            {
-                CurseForgeMod mod = await this.Client.GetModAsync(curseID);
-                if (mod == null)
-                    return new ModInfoModel().SetError(RemoteModStatus.DoesNotExist, "Found no CurseForge mod with this ID.");
-                if (mod.Error != null)
-                {
-                    RemoteModStatus remoteStatus = RemoteModStatus.InvalidData;
-                    return new ModInfoModel().SetError(remoteStatus, mod.Error);
-                }
-
-                return new ModInfoModel(name: mod.Name, version: this.NormalizeVersion(mod.LatestVersion), url: mod.Url);
-            }
-            catch (Exception ex)
-            {
-                return new ModInfoModel().SetError(RemoteModStatus.TemporaryError, ex.ToString());
-            }
-        }
-
-        /// <summary>Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.</summary>
-        public override void Dispose()
-        {
-            this.Client.Dispose();
-        }
-    }
-}
diff --git a/src/SMAPI.Web/Framework/ModRepositories/GitHubRepository.cs b/src/SMAPI.Web/Framework/ModRepositories/GitHubRepository.cs
deleted file mode 100644
index c62cb73f..00000000
--- a/src/SMAPI.Web/Framework/ModRepositories/GitHubRepository.cs
+++ /dev/null
@@ -1,82 +0,0 @@
-using System;
-using System.Threading.Tasks;
-using StardewModdingAPI.Toolkit.Framework.UpdateData;
-using StardewModdingAPI.Web.Framework.Clients.GitHub;
-
-namespace StardewModdingAPI.Web.Framework.ModRepositories
-{
-    /// <summary>An HTTP client for fetching mod metadata from GitHub project releases.</summary>
-    internal class GitHubRepository : RepositoryBase
-    {
-        /*********
-        ** Fields
-        *********/
-        /// <summary>The underlying GitHub API client.</summary>
-        private readonly IGitHubClient Client;
-
-
-        /*********
-        ** Public methods
-        *********/
-        /// <summary>Construct an instance.</summary>
-        /// <param name="client">The underlying GitHub API client.</param>
-        public GitHubRepository(IGitHubClient client)
-            : base(ModRepositoryKey.GitHub)
-        {
-            this.Client = client;
-        }
-
-        /// <summary>Get metadata about a mod in the repository.</summary>
-        /// <param name="id">The mod ID in this repository.</param>
-        public override async Task<ModInfoModel> GetModInfoAsync(string id)
-        {
-            ModInfoModel result = new ModInfoModel().SetBasicInfo(id, $"https://github.com/{id}/releases");
-
-            // validate ID format
-            if (!id.Contains("/") || id.IndexOf("/", StringComparison.InvariantCultureIgnoreCase) != id.LastIndexOf("/", StringComparison.InvariantCultureIgnoreCase))
-                return result.SetError(RemoteModStatus.DoesNotExist, $"The value '{id}' isn't a valid GitHub mod ID, must be a username and project name like 'Pathoschild/LookupAnything'.");
-
-            // fetch info
-            try
-            {
-                // fetch repo info
-                GitRepo repository = await this.Client.GetRepositoryAsync(id);
-                if (repository == null)
-                    return result.SetError(RemoteModStatus.DoesNotExist, "Found no GitHub repository for this ID.");
-                result
-                    .SetBasicInfo(repository.FullName, $"{repository.WebUrl}/releases")
-                    .SetLicense(url: repository.License?.Url, name: repository.License?.SpdxId ?? repository.License?.Name);
-
-                // get latest release (whether preview or stable)
-                GitRelease latest = await this.Client.GetLatestReleaseAsync(id, includePrerelease: true);
-                if (latest == null)
-                    return result.SetError(RemoteModStatus.DoesNotExist, "Found no GitHub release for this ID.");
-
-                // split stable/prerelease if applicable
-                GitRelease preview = null;
-                if (latest.IsPrerelease)
-                {
-                    GitRelease release = await this.Client.GetLatestReleaseAsync(id, includePrerelease: false);
-                    if (release != null)
-                    {
-                        preview = latest;
-                        latest = release;
-                    }
-                }
-
-                // return data
-                return result.SetVersions(version: this.NormalizeVersion(latest.Tag), previewVersion: this.NormalizeVersion(preview?.Tag));
-            }
-            catch (Exception ex)
-            {
-                return result.SetError(RemoteModStatus.TemporaryError, ex.ToString());
-            }
-        }
-
-        /// <summary>Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.</summary>
-        public override void Dispose()
-        {
-            this.Client.Dispose();
-        }
-    }
-}
diff --git a/src/SMAPI.Web/Framework/ModRepositories/IModRepository.cs b/src/SMAPI.Web/Framework/ModRepositories/IModRepository.cs
deleted file mode 100644
index 68f754ae..00000000
--- a/src/SMAPI.Web/Framework/ModRepositories/IModRepository.cs
+++ /dev/null
@@ -1,24 +0,0 @@
-using System;
-using System.Threading.Tasks;
-using StardewModdingAPI.Toolkit.Framework.UpdateData;
-
-namespace StardewModdingAPI.Web.Framework.ModRepositories
-{
-    /// <summary>A repository which provides mod metadata.</summary>
-    internal interface IModRepository : IDisposable
-    {
-        /*********
-        ** Accessors
-        *********/
-        /// <summary>The unique key for this vendor.</summary>
-        ModRepositoryKey VendorKey { get; }
-
-
-        /*********
-        ** Public methods
-        *********/
-        /// <summary>Get metadata about a mod in the repository.</summary>
-        /// <param name="id">The mod ID in this repository.</param>
-        Task<ModInfoModel> GetModInfoAsync(string id);
-    }
-}
diff --git a/src/SMAPI.Web/Framework/ModRepositories/ModDropRepository.cs b/src/SMAPI.Web/Framework/ModRepositories/ModDropRepository.cs
deleted file mode 100644
index 62142668..00000000
--- a/src/SMAPI.Web/Framework/ModRepositories/ModDropRepository.cs
+++ /dev/null
@@ -1,57 +0,0 @@
-using System;
-using System.Threading.Tasks;
-using StardewModdingAPI.Toolkit.Framework.UpdateData;
-using StardewModdingAPI.Web.Framework.Clients.ModDrop;
-
-namespace StardewModdingAPI.Web.Framework.ModRepositories
-{
-    /// <summary>An HTTP client for fetching mod metadata from the ModDrop API.</summary>
-    internal class ModDropRepository : RepositoryBase
-    {
-        /*********
-        ** Fields
-        *********/
-        /// <summary>The underlying ModDrop API client.</summary>
-        private readonly IModDropClient Client;
-
-
-        /*********
-        ** Public methods
-        *********/
-        /// <summary>Construct an instance.</summary>
-        /// <param name="client">The underlying Nexus Mods API client.</param>
-        public ModDropRepository(IModDropClient client)
-            : base(ModRepositoryKey.ModDrop)
-        {
-            this.Client = client;
-        }
-
-        /// <summary>Get metadata about a mod in the repository.</summary>
-        /// <param name="id">The mod ID in this repository.</param>
-        public override async Task<ModInfoModel> GetModInfoAsync(string id)
-        {
-            // validate ID format
-            if (!long.TryParse(id, out long modDropID))
-                return new ModInfoModel().SetError(RemoteModStatus.DoesNotExist, $"The value '{id}' isn't a valid ModDrop mod ID, must be an integer ID.");
-
-            // fetch info
-            try
-            {
-                ModDropMod mod = await this.Client.GetModAsync(modDropID);
-                return mod != null
-                    ? new ModInfoModel(name: mod.Name, version: mod.LatestDefaultVersion?.ToString(), previewVersion: mod.LatestOptionalVersion?.ToString(), url: mod.Url)
-                    : new ModInfoModel().SetError(RemoteModStatus.DoesNotExist, "Found no ModDrop mod with this ID.");
-            }
-            catch (Exception ex)
-            {
-                return new ModInfoModel().SetError(RemoteModStatus.TemporaryError, ex.ToString());
-            }
-        }
-
-        /// <summary>Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.</summary>
-        public override void Dispose()
-        {
-            this.Client.Dispose();
-        }
-    }
-}
diff --git a/src/SMAPI.Web/Framework/ModRepositories/NexusRepository.cs b/src/SMAPI.Web/Framework/ModRepositories/NexusRepository.cs
deleted file mode 100644
index 9551258c..00000000
--- a/src/SMAPI.Web/Framework/ModRepositories/NexusRepository.cs
+++ /dev/null
@@ -1,65 +0,0 @@
-using System;
-using System.Threading.Tasks;
-using StardewModdingAPI.Toolkit.Framework.UpdateData;
-using StardewModdingAPI.Web.Framework.Clients.Nexus;
-
-namespace StardewModdingAPI.Web.Framework.ModRepositories
-{
-    /// <summary>An HTTP client for fetching mod metadata from Nexus Mods.</summary>
-    internal class NexusRepository : RepositoryBase
-    {
-        /*********
-        ** Fields
-        *********/
-        /// <summary>The underlying Nexus Mods API client.</summary>
-        private readonly INexusClient Client;
-
-
-        /*********
-        ** Public methods
-        *********/
-        /// <summary>Construct an instance.</summary>
-        /// <param name="client">The underlying Nexus Mods API client.</param>
-        public NexusRepository(INexusClient client)
-            : base(ModRepositoryKey.Nexus)
-        {
-            this.Client = client;
-        }
-
-        /// <summary>Get metadata about a mod in the repository.</summary>
-        /// <param name="id">The mod ID in this repository.</param>
-        public override async Task<ModInfoModel> GetModInfoAsync(string id)
-        {
-            // validate ID format
-            if (!uint.TryParse(id, out uint nexusID))
-                return new ModInfoModel().SetError(RemoteModStatus.DoesNotExist, $"The value '{id}' isn't a valid Nexus mod ID, must be an integer ID.");
-
-            // fetch info
-            try
-            {
-                NexusMod mod = await this.Client.GetModAsync(nexusID);
-                if (mod == null)
-                    return new ModInfoModel().SetError(RemoteModStatus.DoesNotExist, "Found no Nexus mod with this ID.");
-                if (mod.Error != null)
-                {
-                    RemoteModStatus remoteStatus = mod.Status == NexusModStatus.Hidden || mod.Status == NexusModStatus.NotPublished
-                        ? RemoteModStatus.DoesNotExist
-                        : RemoteModStatus.TemporaryError;
-                    return new ModInfoModel().SetError(remoteStatus, mod.Error);
-                }
-
-                return new ModInfoModel(name: mod.Name, version: this.NormalizeVersion(mod.Version), previewVersion: mod.LatestFileVersion?.ToString(), url: mod.Url);
-            }
-            catch (Exception ex)
-            {
-                return new ModInfoModel().SetError(RemoteModStatus.TemporaryError, ex.ToString());
-            }
-        }
-
-        /// <summary>Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.</summary>
-        public override void Dispose()
-        {
-            this.Client.Dispose();
-        }
-    }
-}
diff --git a/src/SMAPI.Web/Framework/ModSiteManager.cs b/src/SMAPI.Web/Framework/ModSiteManager.cs
new file mode 100644
index 00000000..eaae7935
--- /dev/null
+++ b/src/SMAPI.Web/Framework/ModSiteManager.cs
@@ -0,0 +1,180 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text.RegularExpressions;
+using System.Threading.Tasks;
+using StardewModdingAPI.Toolkit;
+using StardewModdingAPI.Toolkit.Framework.UpdateData;
+using StardewModdingAPI.Web.Framework.Clients;
+
+namespace StardewModdingAPI.Web.Framework
+{
+    /// <summary>Handles fetching data from mod sites.</summary>
+    internal class ModSiteManager
+    {
+        /*********
+        ** Fields
+        *********/
+        /// <summary>The mod sites which provide mod metadata.</summary>
+        private readonly IDictionary<ModSiteKey, IModSiteClient> ModSites;
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Construct an instance.</summary>
+        /// <param name="modSites">The mod sites which provide mod metadata.</param>
+        public ModSiteManager(IModSiteClient[] modSites)
+        {
+            this.ModSites = modSites.ToDictionary(p => p.SiteKey);
+        }
+
+        /// <summary>Get the mod info for an update key.</summary>
+        /// <param name="updateKey">The namespaced update key.</param>
+        public async Task<IModPage> GetModPageAsync(UpdateKey updateKey)
+        {
+            // get site
+            if (!this.ModSites.TryGetValue(updateKey.Site, out IModSiteClient client))
+                return new GenericModPage(updateKey.Site, updateKey.ID).SetError(RemoteModStatus.DoesNotExist, $"There's no mod site with key '{updateKey.Site}'. Expected one of [{string.Join(", ", this.ModSites.Keys)}].");
+
+            // fetch mod
+            IModPage mod;
+            try
+            {
+                mod = await client.GetModData(updateKey.ID);
+            }
+            catch (Exception ex)
+            {
+                mod = new GenericModPage(updateKey.Site, updateKey.ID).SetError(RemoteModStatus.TemporaryError, ex.ToString());
+            }
+
+            // handle errors
+            return mod ?? new GenericModPage(updateKey.Site, updateKey.ID).SetError(RemoteModStatus.DoesNotExist, $"Found no {updateKey.Site} mod with ID '{updateKey.ID}'.");
+        }
+
+        /// <summary>Parse version info for the given mod page info.</summary>
+        /// <param name="page">The mod page info.</param>
+        /// <param name="mapRemoteVersions">Maps remote versions to a semantic version for update checks.</param>
+        /// <param name="allowNonStandardVersions">Whether to allow non-standard versions.</param>
+        public ModInfoModel GetPageVersions(IModPage page, bool allowNonStandardVersions, IDictionary<string, string> mapRemoteVersions)
+        {
+            // get base model
+            ModInfoModel model = new ModInfoModel()
+                .SetBasicInfo(page.Name, page.Url)
+                .SetError(page.Status, page.Error);
+            if (page.Status != RemoteModStatus.Ok)
+                return model;
+
+            // fetch versions
+            if (!this.TryGetLatestVersions(page, allowNonStandardVersions, mapRemoteVersions, out ISemanticVersion mainVersion, out ISemanticVersion previewVersion))
+                return model.SetError(RemoteModStatus.InvalidData, $"The {page.Site} mod with ID '{page.Id}' has no valid versions.");
+
+            // return info
+            return model.SetVersions(mainVersion, previewVersion);
+        }
+
+        /// <summary>Get a semantic local version for update checks.</summary>
+        /// <param name="version">The version to parse.</param>
+        /// <param name="map">A map of version replacements.</param>
+        /// <param name="allowNonStandard">Whether to allow non-standard versions.</param>
+        public ISemanticVersion GetMappedVersion(string version, IDictionary<string, string> map, bool allowNonStandard)
+        {
+            // try mapped version
+            string rawNewVersion = this.GetRawMappedVersion(version, map, allowNonStandard);
+            if (SemanticVersion.TryParse(rawNewVersion, allowNonStandard, out ISemanticVersion parsedNew))
+                return parsedNew;
+
+            // return original version
+            return SemanticVersion.TryParse(version, allowNonStandard, out ISemanticVersion parsedOld)
+                ? parsedOld
+                : null;
+        }
+
+
+        /*********
+        ** Private methods
+        *********/
+        /// <summary>Get the mod version numbers for the given mod.</summary>
+        /// <param name="mod">The mod to check.</param>
+        /// <param name="allowNonStandardVersions">Whether to allow non-standard versions.</param>
+        /// <param name="mapRemoteVersions">Maps remote versions to a semantic version for update checks.</param>
+        /// <param name="main">The main mod version.</param>
+        /// <param name="preview">The latest prerelease version, if newer than <paramref name="main"/>.</param>
+        private bool TryGetLatestVersions(IModPage mod, bool allowNonStandardVersions, IDictionary<string, string> mapRemoteVersions, out ISemanticVersion main, out ISemanticVersion preview)
+        {
+            main = null;
+            preview = null;
+
+            ISemanticVersion ParseVersion(string raw)
+            {
+                raw = this.NormalizeVersion(raw);
+                return this.GetMappedVersion(raw, mapRemoteVersions, allowNonStandardVersions);
+            }
+
+            if (mod != null)
+            {
+                // get versions
+                main = ParseVersion(mod.Version);
+                foreach (string rawVersion in mod.Downloads.Select(p => p.Version))
+                {
+                    ISemanticVersion cur = ParseVersion(rawVersion);
+                    if (cur == null)
+                        continue;
+
+                    if (main == null || cur.IsNewerThan(main))
+                        main = cur;
+                    if (cur.IsPrerelease() && (preview == null || cur.IsNewerThan(preview)))
+                        preview = cur;
+                }
+
+                if (preview != null && !preview.IsNewerThan(main))
+                    preview = null;
+            }
+
+            return main != null;
+        }
+
+        /// <summary>Get a semantic local version for update checks.</summary>
+        /// <param name="version">The version to map.</param>
+        /// <param name="map">A map of version replacements.</param>
+        /// <param name="allowNonStandard">Whether to allow non-standard versions.</param>
+        private string GetRawMappedVersion(string version, IDictionary<string, string> map, bool allowNonStandard)
+        {
+            if (version == null || map == null || !map.Any())
+                return version;
+
+            // match exact raw version
+            if (map.ContainsKey(version))
+                return map[version];
+
+            // match parsed version
+            if (SemanticVersion.TryParse(version, allowNonStandard, out ISemanticVersion parsed))
+            {
+                if (map.ContainsKey(parsed.ToString()))
+                    return map[parsed.ToString()];
+
+                foreach ((string fromRaw, string toRaw) in map)
+                {
+                    if (SemanticVersion.TryParse(fromRaw, allowNonStandard, out ISemanticVersion target) && parsed.Equals(target) && SemanticVersion.TryParse(toRaw, allowNonStandard, out ISemanticVersion newVersion))
+                        return newVersion.ToString();
+                }
+            }
+
+            return version;
+        }
+
+        /// <summary>Normalize a version string.</summary>
+        /// <param name="version">The version to normalize.</param>
+        private string NormalizeVersion(string version)
+        {
+            if (string.IsNullOrWhiteSpace(version))
+                return null;
+
+            version = version.Trim();
+            if (Regex.IsMatch(version, @"^v\d", RegexOptions.CultureInvariant | RegexOptions.IgnoreCase)) // common version prefix
+                version = version.Substring(1);
+
+            return version;
+        }
+    }
+}
diff --git a/src/SMAPI.Web/Framework/ModRepositories/RemoteModStatus.cs b/src/SMAPI.Web/Framework/RemoteModStatus.cs
index 02876556..139ecfd3 100644
--- a/src/SMAPI.Web/Framework/ModRepositories/RemoteModStatus.cs
+++ b/src/SMAPI.Web/Framework/RemoteModStatus.cs
@@ -1,4 +1,4 @@
-namespace StardewModdingAPI.Web.Framework.ModRepositories
+namespace StardewModdingAPI.Web.Framework
 {
     /// <summary>The mod availability status on a remote site.</summary>
     internal enum RemoteModStatus