fetch mod info from Nexus website until we can use their API again (#454)

1 files changed, 93 insertions, 0 deletions

diff --git a/src/SMAPI.Web/Framework/Clients/Nexus/NexusWebScrapeClient.cs b/src/SMAPI.Web/Framework/Clients/Nexus/NexusWebScrapeClient.cs
new file mode 100644
index 00000000..1e941e3d
--- /dev/null
+++ b/src/SMAPI.Web/Framework/Clients/Nexus/NexusWebScrapeClient.cs
@@ -0,0 +1,93 @@
+using System;
+using System.Net;
+using System.Threading.Tasks;
+using HtmlAgilityPack;
+using Pathoschild.Http.Client;
+
+namespace StardewModdingAPI.Web.Framework.Clients.Nexus
+{
+    /// <summary>An HTTP client for fetching mod metadata from the Nexus website.</summary>
+    internal class NexusWebScrapeClient : INexusClient
+    {
+        /*********
+        ** Properties
+        *********/
+        /// <summary>The URL for a Nexus web page excluding the base URL, where {0} is the mod ID.</summary>
+        private readonly string ModUrlFormat;
+
+        /// <summary>The underlying HTTP client.</summary>
+        private readonly IClient Client;
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Construct an instance.</summary>
+        /// <param name="userAgent">The user agent for the Nexus Mods API client.</param>
+        /// <param name="baseUrl">The base URL for the Nexus Mods site.</param>
+        /// <param name="modUrlFormat">The URL for a Nexus Mods web page excluding the <paramref name="baseUrl"/>, where {0} is the mod ID.</param>
+        public NexusWebScrapeClient(string userAgent, string baseUrl, string modUrlFormat)
+        {
+            this.ModUrlFormat = modUrlFormat;
+            this.Client = new FluentClient(baseUrl).SetUserAgent(userAgent);
+        }
+
+        /// <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 HTML
+            string html;
+            try
+            {
+                html = await this.Client
+                    .GetAsync(string.Format(this.ModUrlFormat, 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})." };
+                }
+            }
+
+            // extract mod info
+            string url = new UriBuilder(this.Client.BaseClient.BaseAddress) { Path = string.Format(this.ModUrlFormat, id) }.Uri.ToString();
+            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();
+
+            return new NexusMod
+            {
+                Name = name,
+                Version = version,
+                Url = url
+            };
+        }
+
+        /// <summary>Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.</summary>
+        public void Dispose()
+        {
+            this.Client?.Dispose();
+        }
+    }
+}