Use channel icon instead of guild icon, when available

Closes #987

DiscordChatExporter.Core/Discord/Data/Channel.cs

@@ -1,4 +1,5 @@
-using System.Linq;
+using System;
+using System.Linq;
 using System.Text.Json;
 using DiscordChatExporter.Core.Discord.Data.Common;
 using DiscordChatExporter.Core.Utils.Extensions;
@@ -14,6 +15,7 @@ public partial record Channel(
     ChannelCategory Category,
     string Name,
     int? Position,
+    string? IconUrl,
     string? Topic,
     Snowflake? LastMessageId) : IHasId
 {
@@ -35,6 +37,15 @@ public partial record Channel
         null
     );
 
+    private static string GetIconUrl(Snowflake id, string iconHash)
+    {
+        var extension = iconHash.StartsWith("a_", StringComparison.Ordinal)
+            ? "gif"
+            : "png";
+
+        return $"https://cdn.discordapp.com/icons/{id}/{iconHash}.{extension}";
+    }
+
     public static Channel Parse(JsonElement json, ChannelCategory? category = null, int? positionHint = null)
     {
         var id = json.GetProperty("id").GetNonWhiteSpaceString().Pipe(Snowflake.Parse);
@@ -59,6 +70,9 @@ public partial record Channel
             positionHint ??
             json.GetPropertyOrNull("position")?.GetInt32OrNull();
 
+        // Only available on group DMs
+        var iconUrl = json.GetPropertyOrNull("icon")?.GetNonWhiteSpaceStringOrNull()?.Pipe(h => GetIconUrl(id, h));
+
         var topic = json.GetPropertyOrNull("topic")?.GetStringOrNull();
 
         var lastMessageId = json
@@ -73,6 +87,7 @@ public partial record Channel
             category ?? GetFallbackCategory(kind),
             name,
             position,
+            iconUrl,
             topic,
             lastMessageId
         );

DiscordChatExporter.Core/Discord/Data/Guild.cs

@@ -32,10 +32,9 @@ public record Guild(Snowflake Id, string Name, string IconUrl) : IHasId
         var id = json.GetProperty("id").GetNonWhiteSpaceString().Pipe(Snowflake.Parse);
         var name = json.GetProperty("name").GetNonNullString();
 
-        var iconHash = json.GetPropertyOrNull("icon")?.GetNonWhiteSpaceStringOrNull();
-        var iconUrl = !string.IsNullOrWhiteSpace(iconHash)
-            ? GetIconUrl(id, iconHash)
-            : GetDefaultIconUrl();
+        var iconUrl =
+            json.GetPropertyOrNull("icon")?.GetNonWhiteSpaceStringOrNull()?.Pipe(h => GetIconUrl(id, h)) ??
+            GetDefaultIconUrl();
 
         return new Guild(id, name, iconUrl);
     }

DiscordChatExporter.Core/Exporting/JsonMessageWriter.cs

@@ -244,7 +244,12 @@ internal class JsonMessageWriter : MessageWriter
         _writer.WriteStartObject("guild");
         _writer.WriteString("id", Context.Request.Guild.Id.ToString());
         _writer.WriteString("name", Context.Request.Guild.Name);
-        _writer.WriteString("iconUrl", await Context.ResolveAssetUrlAsync(Context.Request.Guild.IconUrl, cancellationToken));
+
+        _writer.WriteString(
+            "iconUrl",
+            await Context.ResolveAssetUrlAsync(Context.Request.Guild.IconUrl, cancellationToken)
+        );
+
         _writer.WriteEndObject();
 
         // Channel
@@ -255,6 +260,15 @@ internal class JsonMessageWriter : MessageWriter
         _writer.WriteString("category", Context.Request.Channel.Category.Name);
         _writer.WriteString("name", Context.Request.Channel.Name);
         _writer.WriteString("topic", Context.Request.Channel.Topic);
+
+        if (!string.IsNullOrWhiteSpace(Context.Request.Channel.IconUrl))
+        {
+            _writer.WriteString(
+                "iconUrl",
+                await Context.ResolveAssetUrlAsync(Context.Request.Channel.IconUrl, cancellationToken)
+            );
+        }
+
         _writer.WriteEndObject();
 
         // Date range
@@ -295,7 +309,12 @@ internal class JsonMessageWriter : MessageWriter
         _writer.WriteString("nickname", Context.TryGetMember(message.Author.Id)?.Nick ?? message.Author.Name);
         _writer.WriteString("color", Context.TryGetUserColor(message.Author.Id)?.ToHex());
         _writer.WriteBoolean("isBot", message.Author.IsBot);
-        _writer.WriteString("avatarUrl", await Context.ResolveAssetUrlAsync(message.Author.AvatarUrl, cancellationToken));
+
+        _writer.WriteString(
+            "avatarUrl",
+            await Context.ResolveAssetUrlAsync(message.Author.AvatarUrl, cancellationToken)
+        );
+
         _writer.WriteEndObject();
 
         // Attachments

DiscordChatExporter.Core/Exporting/PreambleTemplate.cshtml

@@ -851,7 +851,7 @@
 
 <div class="preamble">
     <div class="preamble__guild-icon-container">
-        <img class="preamble__guild-icon" src="@await ResolveAssetUrlAsync(ExportContext.Request.Guild.IconUrl)" alt="Guild icon" loading="lazy">
+        <img class="preamble__guild-icon" src="@await ResolveAssetUrlAsync(ExportContext.Request.Channel.IconUrl ?? ExportContext.Request.Guild.IconUrl)" alt="Guild icon" loading="lazy">
     </div>
     <div class="preamble__entries-container">
         <div class="preamble__entry">@ExportContext.Request.Guild.Name</div>