using Application.Abstractions.Cache;
using Application.Abstractions.Chat;
using StackExchange.Redis;
using System.Text.Json;

namespace Infrastructure.Chat;

public class RedisChatConnectionTracker(IConnectionMultiplexer redis) : IChatConnectionTracker
{
    private readonly IDatabase _db = redis.GetDatabase();

    private static readonly JsonSerializerOptions _jsonOptions = new()
    {
        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
        WriteIndented = false
    };

    public async Task AddAsync(string channelSID, ConnectedUser user)
    {
        var json = JsonSerializer.Serialize(user, _jsonOptions);
        await _db.HashSetAsync(CacheKeys.ChatChannelConnections(channelSID), user.ConnectionId, json);
    }

    public async Task RemoveAsync(string channelSID, string connectionId)
    {
        await _db.HashDeleteAsync(CacheKeys.ChatChannelConnections(channelSID), connectionId);
    }

    public async Task<IReadOnlyList<ConnectedUser>> GetByChannelAsync(string channelSID)
    {
        var entries = await _db.HashGetAllAsync(CacheKeys.ChatChannelConnections(channelSID));
        if (entries.Length <= 0)
        {
            return [];
        }

        var list = new List<ConnectedUser>(entries.Length);
        foreach (var entry in entries)
        {
            if (!entry.Value.IsNullOrEmpty)
            {
                var user = JsonSerializer.Deserialize<ConnectedUser>((string)entry.Value!, _jsonOptions);
                if (user is not null)
                {
                    list.Add(user);
                }
            }
        }

        return list.AsReadOnly();
    }

    public async Task<int> GetCountByChannelAsync(string channelSID)
    {
        return (int)await _db.HashLengthAsync(CacheKeys.ChatChannelConnections(channelSID));
    }

    public async Task<IReadOnlyList<(
        string ChannelSID,
        ConnectedUser User
    )>> GetAllAsync()
    {
        // 모든 채널 키를 스캔 후 병합 (관리자 집계용)
        var server = _db.Multiplexer.GetServer(_db.Multiplexer.GetEndPoints().First());
        var list = new List<(
            string ChannelSID,
            ConnectedUser User
        )>();

        await foreach (var key in server.KeysAsync(pattern: "chat:channel:*:connections"))
        {
            // 키에서 channelSID 추출 — chat:channel:{sid}:connections
            var keyStr = (string)key!;
            var channelSID = keyStr["chat:channel:".Length..^":connections".Length];

            var entries = await _db.HashGetAllAsync(key);

            foreach (var entry in entries)
            {
                if (!entry.Value.IsNullOrEmpty)
                {
                    var user = JsonSerializer.Deserialize<ConnectedUser>((string)entry.Value!, _jsonOptions);
                    if (user is not null)
                    {
                        list.Add((channelSID, user));
                    }
                }
            }
        }

        return list.AsReadOnly();
    }

    public async Task ClearAllAsync()
    {
        // 서버 시작 시 모든 채널 연결 초기화 (stale 제거)
        var server = _db.Multiplexer.GetServer(_db.Multiplexer.GetEndPoints().First());
        await foreach (var key in server.KeysAsync(pattern: "chat:channel:*:connections"))
        {
            await _db.KeyDeleteAsync(key);
        }
    }
}