[OneBot] Implemented get_group_file_url

Lagrange.OneBot/Core/Entity/Action/Response/OneBotGetFileUrl.cs

@@ -0,0 +1,13 @@
+using System.Text.Json.Serialization;
+
+namespace Lagrange.OneBot.Core.Entity.Action.Response;
+
+[Serializable]
+public class OneBotGetFileUrl
+{
+    [JsonPropertyName("group_id")] public uint GroupId { get; set; }
+
+    [JsonPropertyName("file_id")] public string FileId { get; set; } = string.Empty;
+
+    [JsonPropertyName("busid")] public uint BusId { get; set; }
+}

Lagrange.OneBot/Core/Operation/Group/GroupFSOperations.cs

@@ -0,0 +1,23 @@
+using System.Text.Json;
+using System.Text.Json.Nodes;
+using Lagrange.Core;
+using Lagrange.Core.Common.Interface.Api;
+using Lagrange.OneBot.Core.Entity.Action;
+using Lagrange.OneBot.Core.Entity.Action.Response;
+
+namespace Lagrange.OneBot.Core.Operation.Group;
+
+[Operation("get_group_file_url")]
+public class GetGroupFileUrlOperation : IOperation
+{
+    public async Task<OneBotResult> HandleOperation(BotContext context, JsonNode? payload)
+    {
+        if (payload.Deserialize<OneBotGetFileUrl>() is { } url)
+        {
+            string raw = await context.FetchGroupFSDownload(url.GroupId, url.FileId);
+            return new OneBotResult(raw, 0, "ok");
+        }
+
+        throw new Exception();
+    }
+}