1 files changed, 225 insertions, 0 deletions
diff --git a/src/SMAPI.Web/Framework/Clients/Nexus/NexusClient.cs b/src/SMAPI.Web/Framework/Clients/Nexus/NexusClient.cs
new file mode 100644
index 00000000..753d3b4f
--- /dev/null
+++ b/src/SMAPI.Web/Framework/Clients/Nexus/NexusClient.cs
@@ -0,0 +1,225 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Net;
+using System.Threading.Tasks;
+using HtmlAgilityPack;
+using Pathoschild.FluentNexus.Models;
+using Pathoschild.Http.Client;
+using StardewModdingAPI.Toolkit;
+using FluentNexusClient = Pathoschild.FluentNexus.NexusClient;
+
+namespace StardewModdingAPI.Web.Framework.Clients.Nexus
+{
+    /// <summary>An HTTP client for fetching mod metadata from the Nexus website.</summary>
+    internal class NexusClient : INexusClient
+    {
+        /*********
+        ** Fields
+        *********/
+        /// <summary>The URL for a Nexus mod page for the user, excluding the base URL, where {0} is the mod ID.</summary>
+        private readonly string WebModUrlFormat;
+
+        /// <summary>The URL for a Nexus mod page to scrape for versions, excluding the base URL, where {0} is the mod ID.</summary>
+        public string WebModScrapeUrlFormat { get; set; }
+
+        /// <summary>The underlying HTTP client for the Nexus Mods website.</summary>
+        private readonly IClient WebClient;
+
+        /// <summary>The underlying HTTP client for the Nexus API.</summary>
+        private readonly FluentNexusClient ApiClient;
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Construct an instance.</summary>
+        /// <param name="webUserAgent">The user agent for the Nexus Mods web client.</param>
+        /// <param name="webBaseUrl">The base URL for the Nexus Mods site.</param>
+        /// <param name="webModUrlFormat">The URL for a Nexus Mods mod page for the user, excluding the <paramref name="webBaseUrl"/>, where {0} is the mod ID.</param>
+        /// <param name="webModScrapeUrlFormat">The URL for a Nexus mod page to scrape for versions, excluding the base URL, where {0} is the mod ID.</param>
+        /// <param name="apiAppVersion">The app version to show in API user agents.</param>
+        /// <param name="apiKey">The Nexus API authentication key.</param>
+        public NexusClient(string webUserAgent, string webBaseUrl, string webModUrlFormat, string webModScrapeUrlFormat, string apiAppVersion, string apiKey)
+        {
+            this.WebModUrlFormat = webModUrlFormat;
+            this.WebModScrapeUrlFormat = webModScrapeUrlFormat;
+            this.WebClient = new FluentClient(webBaseUrl).SetUserAgent(webUserAgent);
+            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)
+        {
+            // 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);
+            if (mod?.Status == NexusModStatus.AdultContentForbidden)
+                mod = await this.GetModFromApiAsync(id);
+
+            return mod;
+        }
+
+        /// <summary>Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.</summary>
+        public void Dispose()
+        {
+            this.WebClient?.Dispose();
+        }
+
+
+        /*********
+        ** Private methods
+        *********/
+        /// <summary>Get metadata about a mod by scraping the Nexus website.</summary>
+        /// <param name="id">The Nexus mod ID.</param>
+        /// <returns>Returns the mod info if found, else <c>null</c>.</returns>
+        private async Task<NexusMod> GetModFromWebsiteAsync(uint id)
+        {
+            // fetch HTML
+            string html;
+            try
+            {
+                html = await this.WebClient
+                    .GetAsync(string.Format(this.WebModScrapeUrlFormat, id))
+                    .AsString();
+            }
+            catch (ApiException ex) when (ex.Status == HttpStatusCode.NotFound)
+            {
+                return null;
+            }
+
+            // parse HTML
+            var doc = new HtmlDocument();
+            doc.LoadHtml(html);
+
+            // handle Nexus error message
+            HtmlNode node = doc.DocumentNode.SelectSingleNode("//div[contains(@class, 'site-notice')][contains(@class, 'warning')]");
+            if (node != null)
+            {
+                string[] errorParts = node.InnerText.Trim().Split(new[] { '\n' }, 2, System.StringSplitOptions.RemoveEmptyEntries);
+                string errorCode = errorParts[0];
+                string errorText = errorParts.Length > 1 ? errorParts[1] : null;
+                switch (errorCode.Trim().ToLower())
+                {
+                    case "not found":
+                        return null;
+
+                    default:
+                        return new NexusMod { Error = $"Nexus error: {errorCode} ({errorText}).", Status = this.GetWebStatus(errorCode) };
+                }
+            }
+
+            // extract mod info
+            string url = this.GetModUrl(id);
+            string name = doc.DocumentNode.SelectSingleNode("//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>();
+            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;
+
+                latestFileVersion = cur;
+            }
+
+            // yield info
+            return new NexusMod
+            {
+                Name = name,
+                Version = parsedVersion?.ToString() ?? version,
+                LatestFileVersion = latestFileVersion,
+                Url = url
+            };
+        }
+
+        /// <summary>Get metadata about a mod from the Nexus API.</summary>
+        /// <param name="id">The Nexus mod ID.</param>
+        /// <returns>Returns the mod info if found, else <c>null</c>.</returns>
+        private async Task<NexusMod> GetModFromApiAsync(uint id)
+        {
+            // fetch mod
+            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)
+            };
+        }
+
+        /// <summary>Get the full mod page URL for a given ID.</summary>
+        /// <param name="id">The mod ID.</param>
+        private string GetModUrl(uint id)
+        {
+            UriBuilder builder = new UriBuilder(this.WebClient.BaseClient.BaseAddress);
+            builder.Path += string.Format(this.WebModUrlFormat, id);
+            return builder.Uri.ToString();
+        }
+
+        /// <summary>Get the mod status for a web error code.</summary>
+        /// <param name="errorCode">The Nexus error code.</param>
+        private NexusModStatus GetWebStatus(string errorCode)
+        {
+            switch (errorCode.Trim().ToLower())
+            {
+                case "adult content":
+                    return NexusModStatus.AdultContentForbidden;
+
+                case "hidden mod":
+                    return NexusModStatus.Hidden;
+
+                case "not published":
+                    return NexusModStatus.NotPublished;
+
+                default:
+                    return NexusModStatus.Other;
+            }
+        }
+    }
+}