refactor update check API

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

37 files changed, 685 insertions, 834 deletions

diff --git a/docs/release-notes.md b/docs/release-notes.md
index f3f2efa4..894fd562 100644
--- a/docs/release-notes.md
+++ b/docs/release-notes.md
@@ -24,6 +24,7 @@
 
 * For SMAPI developers:
   * Eliminated MongoDB storage in the web services, which complicated the code unnecessarily. The app still uses an abstract interface for storage, so we can wrap a distributed cache in the future if needed.
+  * Overhauled update checks to simplify individual clients, centralize common logic, and enable upcoming features.
   * Merged the separate legacy redirects app on AWS into the main app on Azure.
 
 ## 3.5
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/C