move classes around, name caches more consistently, add more caches

Catalogger.Backend/Cache/InMemoryCache/ChannelCache.cs

@@ -0,0 +1,59 @@
+using System.Collections.Concurrent;
+using System.Diagnostics.CodeAnalysis;
+using Remora.Discord.API.Abstractions.Objects;
+using Remora.Rest.Core;
+
+namespace Catalogger.Backend.Cache.InMemoryCache;
+
+public class ChannelCache
+{
+    private readonly ConcurrentDictionary<Snowflake, IChannel> _channels = new();
+    private readonly ConcurrentDictionary<Snowflake, HashSet<Snowflake>> _guildChannels = new();
+
+    public int Size => _channels.Count;
+
+    public void Set(IChannel channel, Snowflake? guildId = null)
+    {
+        _channels[channel.ID] = channel;
+        if (guildId == null)
+        {
+            if (!channel.GuildID.TryGet(out var snowflake)) return;
+            guildId = snowflake;
+        }
+
+        // Add to set of guild channels
+        _guildChannels.AddOrUpdate(guildId.Value,
+            _ => [channel.ID],
+            (_, l) =>
+            {
+                l.Add(channel.ID);
+                return l;
+            });
+    }
+
+    public bool TryGet(Snowflake id, [NotNullWhen(true)] out IChannel? channel) =>
+        _channels.TryGetValue(id, out channel);
+
+    public void Remove(Snowflake? guildId, Snowflake id, out IChannel? channel)
+    {
+        _channels.Remove(id, out channel);
+        if (guildId == null) return;
+        // Remove from set of guild channels
+        _guildChannels.AddOrUpdate(guildId.Value, _ => [], (_, s) =>
+        {
+            s.Remove(id);
+            return s;
+        });
+    }
+
+    /// <summary>
+    /// Gets all of a guild's cached channels.
+    /// </summary>
+    /// <param name="guildId">The guild to get the channels of</param>
+    /// <returns>A list of cached channels</returns>
+    public IEnumerable<IChannel> GuildChannels(Snowflake guildId) =>
+        !_guildChannels.TryGetValue(guildId, out var channelIds)
+            ? []
+            : channelIds.Select(id => _channels.GetValueOrDefault(id))
+                .Where(c => c != null).Select(c => c!);
+}