MatrixContentFilter/Services/InfoCacheService.cs


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using ArcaneLibs.Collections;
using LibMatrix;
using LibMatrix.EventTypes.Spec.State.RoomInfo;
using LibMatrix.Homeservers;

namespace MatrixContentFilter.Services;

public class InfoCacheService(AuthenticatedHomeserverGeneric hs) {
    private static readonly ExpiringSemaphoreCache<string> DisplayNameCache = new();
    public static readonly ExpiringSemaphoreCache<string> RoomNameCache = new();

    public async Task<string> GetDisplayNameAsync(string roomId, string userId) =>
        await DisplayNameCache.GetOrAdd($"{roomId}\t{userId}", async () => {
            var room = hs.GetRoom(roomId);
            try {
                var userState = await room.GetStateOrNullAsync<RoomMemberEventContent>(RoomMemberEventContent.EventId, userId);
                if (!string.IsNullOrWhiteSpace(userState?.DisplayName)) return userState.DisplayName;
            }
            catch (MatrixException e) {
                if (e is not { ErrorCode: MatrixException.ErrorCodes.M_NOT_FOUND or MatrixException.ErrorCodes.M_FORBIDDEN }) 
                    throw;
            }

            var user = await hs.GetProfileAsync(userId);
            if (!string.IsNullOrWhiteSpace(user?.DisplayName)) return user.DisplayName;

            return userId;
        }, TimeSpan.FromMinutes(5));

    public async Task<string> GetRoomNameAsync(string roomId) =>
        await RoomNameCache.GetOrAdd(roomId, async () => {
            var room = hs.GetRoom(roomId);
            var name = await room.GetNameOrFallbackAsync();
            return name;
        }, TimeSpan.FromMinutes(30));
}