1 files changed, 106 insertions, 0 deletions
diff --git a/src/SMAPI.Web/Framework/Clients/UpdateManifest/UpdateManifestClient.cs b/src/SMAPI.Web/Framework/Clients/UpdateManifest/UpdateManifestClient.cs
new file mode 100644
index 00000000..27072897
--- /dev/null
+++ b/src/SMAPI.Web/Framework/Clients/UpdateManifest/UpdateManifestClient.cs
@@ -0,0 +1,106 @@
+using System;
+using System.Diagnostics.CodeAnalysis;
+using System.Net;
+using System.Net.Http.Headers;
+using System.Threading.Tasks;
+using Pathoschild.Http.Client;
+using StardewModdingAPI.Toolkit;
+using StardewModdingAPI.Toolkit.Framework.UpdateData;
+using StardewModdingAPI.Web.Framework.Clients.UpdateManifest.ResponseModels;
+
+namespace StardewModdingAPI.Web.Framework.Clients.UpdateManifest
+{
+    /// <summary>An API client for fetching update metadata from an arbitrary JSON URL.</summary>
+    internal class UpdateManifestClient : IUpdateManifestClient
+    {
+        /*********
+        ** Fields
+        *********/
+        /// <summary>The underlying HTTP client.</summary>
+        private readonly IClient Client;
+
+
+        /*********
+        ** Accessors
+        *********/
+        /// <summary>The unique key for the mod site.</summary>
+        public ModSiteKey SiteKey => ModSiteKey.UpdateManifest;
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Construct an instance.</summary>
+        /// <param name="userAgent">The user agent for the API client.</param>
+        public UpdateManifestClient(string userAgent)
+        {
+            this.Client = new FluentClient()
+                .SetUserAgent(userAgent);
+
+            this.Client.Formatters.JsonFormatter.SupportedMediaTypes.Add(new MediaTypeHeaderValue("text/plain"));
+        }
+
+        /// <summary>Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.</summary>
+        public void Dispose()
+        {
+            this.Client.Dispose();
+        }
+
+        /// <inheritdoc/>
+        [SuppressMessage("ReSharper", "ConditionIsAlwaysTrueOrFalseAccordingToNullableAPIContract", Justification = "This is the method which ensures the annotations are correct.")]
+        public async Task<IModPage?> GetModData(string id)
+        {
+            // get raw update manifest
+            UpdateManifestModel? manifest;
+            try
+            {
+                manifest = await this.Client.GetAsync(id).As<UpdateManifestModel?>();
+                if (manifest is null)
+                    return this.GetFormatError(id, "manifest can't be empty");
+            }
+            catch (ApiException ex) when (ex.Status == HttpStatusCode.NotFound)
+            {
+                return new GenericModPage(this.SiteKey, id).SetError(RemoteModStatus.DoesNotExist, $"No update manifest found at {id}");
+            }
+            catch (Exception ex)
+            {
+                return this.GetFormatError(id, ex.Message);
+            }
+
+            // validate
+            if (!SemanticVersion.TryParse(manifest.Format, out _))
+                return this.GetFormatError(id, $"invalid format version '{manifest.Format}'");
+            foreach (UpdateManifestModModel mod in manifest.Mods.Values)
+            {
+                if (mod is null)
+                    return this.GetFormatError(id, "a mod record can't be null");
+                if (string.IsNullOrWhiteSpace(mod.ModPageUrl))
+                    return this.GetFormatError(id, $"all mods must have a {nameof(mod.ModPageUrl)} value");
+                foreach (UpdateManifestVersionModel? version in mod.Versions)
+                {
+                    if (version is null)
+                        return this.GetFormatError(id, "a version record can't be null");
+                    if (string.IsNullOrWhiteSpace(version.Version))
+                        return this.GetFormatError(id, $"all version records must have a {nameof(version.Version)} field");
+                    if (!SemanticVersion.TryParse(version.Version, out _))
+                        return this.GetFormatError(id, $"invalid mod version '{version.Version}'");
+                }
+            }
+
+            // build model
+            return new UpdateManifestModPage(id, manifest);
+        }
+
+
+        /*********
+        ** Private methods
+        *********/
+        /// <summary>Get a mod page instance with an error indicating the update manifest is invalid.</summary>
+        /// <param name="url">The full URL to the update manifest.</param>
+        /// <param name="reason">A human-readable reason phrase indicating why it's invalid.</param>
+        private IModPage GetFormatError(string url, string reason)
+        {
+            return new GenericModPage(this.SiteKey, url).SetError(RemoteModStatus.InvalidData, $"The update manifest at {url} is invalid ({reason})");
+        }
+    }
+}