using Application.Abstractions.Cache;
using Application.Abstractions.Chat;
using Application.Abstractions.Data;
using Application.Helpers;
using Domain.Entities.Members.Logs;
using SharedKernel.Extensions;
using Microsoft.AspNetCore.SignalR;
using Microsoft.EntityFrameworkCore;
using Microsoft.IdentityModel.JsonWebTokens;
using System.Collections.Concurrent;

namespace Web.Api.Hubs;

public sealed class ChatHub(IChatMessageStore messageStore, IChatConnectionTracker tracker, IServiceScopeFactory scopeFactory, IChatLeaderboard leaderboard) : Hub<IChatHubClient>
{
    private static readonly ConcurrentDictionary<string, DateTime> _lastMessageTime = new();

    public override async Task OnConnectedAsync()
    {
        // 접속 직후에는 어느 채널에 속할지 모름 → 클라이언트가 JoinChannel 명시 호출 대기
        // 사용자 메타 정보만 Context.Items 에 준비
        var ip = Context.GetHttpContext()?.GetClientIP() ?? "Unknown";
        var ua = Context.GetHttpContext()?.GetUserAgent() ?? "Unknown";

        ConnectedUser user;

        if (Context.User?.Identity?.IsAuthenticated == true)
        {
            var memberID = GetMemberID();
            var memberName = GetMemberName();

            string? email = null;
            if (memberID.HasValue)
            {
                using (var scope = scopeFactory.CreateScope())
                {
                    var db = scope.ServiceProvider.GetRequiredService<IAppDbContext>();
                    email = await db.Member.AsNoTracking().Where(x => x.ID == memberID.Value).Select(x => x.Email).FirstOrDefaultAsync();
                }
            }

            user = new ConnectedUser(Context.ConnectionId, memberID, email, memberName, ip, ua, false, DateTime.UtcNow);
        }
        else
        {
            user = new ConnectedUser(Context.ConnectionId, null, null, null, ip, ua, true, DateTime.UtcNow);
        }

        Context.Items["user"] = user;
        await base.OnConnectedAsync();
    }

    public override async Task OnDisconnectedAsync(Exception? exception)
    {
        _lastMessageTime.TryRemove(Context.ConnectionId, out _);

        if (Context.Items["channelSID"] is string channelSID && !string.IsNullOrEmpty(channelSID))
        {
            await tracker.RemoveAsync(channelSID, Context.ConnectionId);

            if (Context.Items["user"] is ConnectedUser user && !user.IsGuest)
            {
                await Clients.OthersInGroup(ChannelGroup(channelSID)).ReceiveSystemMessage($"{user.MemberName}님이 퇴장했습니다.");
            }

            await BroadcastParticipantCountAsync(channelSID);
        }

        await base.OnDisconnectedAsync(exception);
    }

    /// <summary>
    /// 채널 방 참가 — watch 페이지 진입 시 호출
    /// </summary>
    public async Task JoinChannel(string channelSID)
    {
        if (string.IsNullOrWhiteSpace(channelSID))
        {
            return;
        }

        // 이미 다른 채널에 속해있다면 정리
        if (Context.Items["channelSID"] is string previous && !string.IsNullOrEmpty(previous) && previous != channelSID)
        {
            await LeaveChannelInternal(previous);
        }

        Context.Items["channelSID"] = channelSID;
        await Groups.AddToGroupAsync(Context.ConnectionId, ChannelGroup(channelSID));

        if (Context.Items["user"] is ConnectedUser user)
        {
            await tracker.AddAsync(channelSID, user);

            if (!user.IsGuest && !string.IsNullOrEmpty(user.MemberName))
            {
                await Clients.Caller.Connected($"{user.MemberName}님, 환영합니다.");
                await Clients.OthersInGroup(ChannelGroup(channelSID)).ReceiveSystemMessage($"{user.MemberName}님이 입장했습니다.");
            }
        }

        // 히스토리 + 참여자 수 초기 전송
        var messages = await messageStore.GetRecentMessagesAsync(channelSID, ChatSettings.MaxMessages);
        await Clients.Caller.ReceiveHistory(messages);
        await BroadcastParticipantCountAsync(channelSID);
    }

    /// <summary>
    /// 채널 방 퇴장 — 페이지 이탈 시 호출
    /// </summary>
    public async Task LeaveChannel()
    {
        if (Context.Items["channelSID"] is string channelSID && !string.IsNullOrEmpty(channelSID))
        {
            await LeaveChannelInternal(channelSID);
        }
    }

    private async Task LeaveChannelInternal(string channelSID)
    {
        await Groups.RemoveFromGroupAsync(Context.ConnectionId, ChannelGroup(channelSID));
        await tracker.RemoveAsync(channelSID, Context.ConnectionId);

        if (Context.Items["user"] is ConnectedUser user && !user.IsGuest)
        {
            await Clients.OthersInGroup(ChannelGroup(channelSID)).ReceiveSystemMessage($"{user.MemberName}님이 퇴장했습니다.");
        }

        await BroadcastParticipantCountAsync(channelSID);
        Context.Items["channelSID"] = null;
    }

    /// <summary>
    /// 로그아웃 시 호출 (invoke('Logout'))
    /// </summary>
    public async Task Logout()
    {
        await LeaveChannel();
        await Clients.Caller.Logout("로그아웃 되었습니다.");
    }

    /// <summary>
    /// 채팅 메시지 전송
    /// </summary>
    public async Task SendMessage(string content)
    {
        if (Context.Items["channelSID"] is not string channelSID || string.IsNullOrEmpty(channelSID))
        {
            return;
        }

        if (string.IsNullOrWhiteSpace(content))
        {
            return;
        }

        content = content.Trim();

        if (content.Length > ChatSettings.MaxContentLength)
        {
            return;
        }

        var now = DateTime.UtcNow;
        if (_lastMessageTime.TryGetValue(Context.ConnectionId, out var lastTime))
        {
            if ((now - lastTime).TotalSeconds < ChatSettings.RateLimitSeconds)
            {
                return;
            }
        }
        _lastMessageTime[Context.ConnectionId] = now;

        var memberID = GetMemberID();
        if (memberID is null)
        {
            return;
        }

        ChatMessage message;

        using (var scope = scopeFactory.CreateScope())
        {
            var db = scope.ServiceProvider.GetRequiredService<IAppDbContext>();
            var cache = scope.ServiceProvider.GetRequiredService<ICacheService>();
            var cfg = await ChatExpConfigLoader.GetAsync(cache, db, default);

            var channelID = await db.Channel.AsNoTracking().Where(c => c.SID == channelSID).Select(c => (int?)c.ID).FirstOrDefaultAsync();
            if (channelID is null)
            {
                return;
            }

            // 멤버 표시 정보 — Redis 캐시 5분 TTL. 운영자 변경 후 최대 5분 stale 허용
            var memberCacheKey = $"member:{memberID.Value}:displayInfo";
            var memberData = await cache.GetAsync<MemberDisplayInfo>(memberCacheKey);
            if (memberData is null)
            {
                memberData = await db.Member.AsNoTracking()
                    .Where(x => x.ID == memberID.Value)
                    .Select(x => new MemberDisplayInfo(
                        x.SID,
                        x.Name,
                        x.Icon,
                        x.MemberGrade != null ? x.MemberGrade.Image : null,
                        x.MemberGrade != null ? x.MemberGrade.TextColor : null))
                    .FirstOrDefaultAsync();

                if (memberData is null)
                {
                    return;
                }

                await cache.SetAsync(memberCacheKey, memberData, TimeSpan.FromMinutes(5));
            }

            // 채널 문맥 칭호 (이 채널에서 선택한 대표 칭호, Active 일 때만) — 5분 캐시
            // 칭호 미선택은 모든 필드 null 인 sentinel 로 캐시 (DB 재조회 회피)
            var titleCacheKey = $"member:{memberID.Value}:title:{channelID.Value}";
            var titleData = await cache.GetAsync<TitleDisplayInfo>(titleCacheKey);
            if (titleData is null)
            {
                var queried = await db.DonorTitleSelection.AsNoTracking()
                    .Where(d => d.DonorMemberID == memberID.Value
                             && d.ChannelID == channelID.Value
                             && d.SelectedTitleID != null
                             && d.SelectedTitle!.IsActive)
                    .Select(d => new TitleDisplayInfo(
                        d.SelectedTitle!.IconUrl,
                        d.SelectedTitle.Name,
                        d.SelectedTitle.Color))
                    .FirstOrDefaultAsync();

                titleData = queried ?? new TitleDisplayInfo(null, null, null);
                await cache.SetAsync(titleCacheKey, titleData, TimeSpan.FromMinutes(5));
            }

            // ── XP 적립 (방송 세션 활성 + 최소 글자수 + 세션 상한 미초과) ──
            int? leaderboardRank = null;
            int? leaderboardXp = null;

            if (cfg.ChatXpPerMessage > 0 && content.Length >= cfg.MinContentLength)
            {
                var session = await db.BroadcastSession.Where(s => s.ChannelID == channelID.Value && !s.IsFinalized).OrderByDescending(s => s.CreatedAt).Select(s => new { s.ID }).FirstOrDefaultAsync();
                if (session is not null)
                {
                    // 본인 세션 누적 XP — 채팅 reason 합 + 전체 합을 한 쿼리로 동시 계산 (이전 두 SUM → 한 GROUP BY)
                    var sums = await db.MemberExpLog.AsNoTracking()
                        .Where(e => e.MemberID == memberID.Value && e.BroadcastSessionID == session.ID)
                        .GroupBy(e => e.Reason == "채팅(라이브)")
                        .Select(g => new { IsChat = g.Key, Sum = g.Sum(x => x.Amount) })
                        .ToListAsync();

                    var sessionChatXp = sums.Where(x => x.IsChat).Sum(x => x.Sum);
                    var myXp = sums.Sum(x => x.Sum);

                    if (sessionChatXp < cfg.ChatXpSessionLimit)
                    {
                        var grant = Math.Min(cfg.ChatXpPerMessage, cfg.ChatXpSessionLimit - sessionChatXp);

                        var stats = await db.MemberStats.FirstOrDefaultAsync(s => s.MemberID == memberID.Value);
                        if (stats is not null)
                        {
                            stats.Exp += grant;
                            var logEntry = MemberExpLog.CreateForBroadcast(
                                memberID.Value,
                                "채팅(라이브)",
                                grant,
                                stats.Exp,
                                session.ID,
                                channelID.Value
                            );
                            db.MemberExpLog.Add(logEntry);
                            await db.SaveChangesAsync();

                            // grant 반영 후 메모리상 합 갱신 (DB 재조회 회피)
                            myXp += grant;
                        }
                    }

                    // 본인 랭크 계산 (Top N 크라운 여부) — Redis sorted set 캐시 기반 (TTL 5초)
                    // myXp 는 grant 반영된 메모리 값, higherCount 는 캐시 기준 (최대 5초 stale 가능)
                    if (myXp > 0)
                    {
                        var rankResult = await leaderboard.GetRankAsync(session.ID, memberID.Value, db);
                        var higherCount = rankResult?.HigherCount ?? 0;
                        var rank = higherCount + 1;
                        leaderboardXp = myXp;
                        if (rank <= cfg.CrownTopN)
                        {
                            leaderboardRank = rank;
                        }
                    }
                }
            }

            message = new ChatMessage(
                MemberID: memberID.Value,
                MemberSID: memberData.SID,
                MemberName: memberData.Name ?? "익명",
                Content: content,
                SentAt: now,
                TitleIconUrl: titleData.IconUrl,
                TitleName: titleData.Name,
                TitleColor: titleData.Color,
                GradeImageUrl: memberData.GradeImage,
                GradeTextColor: memberData.GradeTextColor,
                MemberIcon: memberData.Icon,
                LeaderboardRank: leaderboardRank,
                LeaderboardXp: leaderboardXp
            );
        }

        // 채널별 기록 저장
        await messageStore.AddMessageAsync(channelSID, message);

        // 해당 채널 그룹에만 전송
        await Clients.Group(ChannelGroup(channelSID)).ReceiveMessage(message);
    }

    /// <summary>
    /// 채팅 기록 요청
    /// </summary>
    public async Task RequestHistory()
    {
        if (Context.Items["channelSID"] is not string channelSID || string.IsNullOrEmpty(channelSID))
        {
            await Clients.Caller.ReceiveHistory([]);
            return;
        }

        var messages = await messageStore.GetRecentMessagesAsync(channelSID, ChatSettings.MaxMessages);
        await Clients.Caller.ReceiveHistory(messages);
    }

    /// <summary>
    /// 접속자 수 요청 — 현재 참여 중인 채널 기준
    /// </summary>
    public async Task RequestParticipantCount()
    {
        if (Context.Items["channelSID"] is not string channelSID || string.IsNullOrEmpty(channelSID))
        {
            await Clients.Caller.ReceiveParticipantCount(0);
            return;
        }

        var count = await tracker.GetCountByChannelAsync(channelSID);
        await Clients.Caller.ReceiveParticipantCount(count);
    }

    /// <summary>
    /// 참여자 목록 요청 — 현재 참여 중인 채널 기준
    /// </summary>
    public async Task RequestParticipants()
    {
        if (Context.Items["channelSID"] is not string channelSID || string.IsNullOrEmpty(channelSID))
        {
            await Clients.Caller.ReceiveParticipants([]);
            return;
        }

        var users = await tracker.GetByChannelAsync(channelSID);
        var participants = users
            .Where(u => !u.IsGuest && !string.IsNullOrEmpty(u.MemberName))
            .Select(u => new ChatParticipant(u.MemberName!, u.IsGuest))
            .DistinctBy(p => p.MemberName)
            .OrderBy(p => p.MemberName)
            .ToList();
        await Clients.Caller.ReceiveParticipants(participants);
    }

    // 채널 내부 접속자 수 브로드캐스트
    private async Task BroadcastParticipantCountAsync(string channelSID)
    {
        var count = await tracker.GetCountByChannelAsync(channelSID);
        await Clients.Group(ChannelGroup(channelSID)).ReceiveParticipantCount(count);
    }

    private static string ChannelGroup(string channelSID) => $"chat:channel:{channelSID}";

    // 회원 ID 조회
    private int? GetMemberID()
    {
        var sub = Context.User?.FindFirst(JwtRegisteredClaimNames.Sub)?.Value;

        if (int.TryParse(sub, out var memberID))
        {
            return memberID;
        }

        return null;
    }

    // 회원 이름 조회
    private string? GetMemberName()
    {
        return Context.User?.FindFirst(JwtRegisteredClaimNames.Name)?.Value;
    }
}

// 채팅 메시지 표시용 캐시 DTO — 파일 한정 (file-scoped)
file sealed record MemberDisplayInfo(string SID, string? Name, string? Icon, string? GradeImage, string? GradeTextColor);

file sealed record TitleDisplayInfo(string? IconUrl, string? Name, string? Color);