using Application.Abstractions.Data;
using Application.Abstractions.Hub;
using Application.Abstractions.Messaging;
using Application.Abstractions.YouTube;
using SharedKernel.Results;
using Domain.Entities.Donations.ValueObject;
using Microsoft.EntityFrameworkCore;

namespace Application.Features.Api.Crew.GetCrewMembers;

internal sealed class Handler(
    IAppDbContext db,
    IPresenceTracker presence,
    IYouTubeChannelCache channelCache
) : IQueryHandler<Query, Result<Response>>
{
    public async Task<Result<Response>> Handle(Query request, CancellationToken ct)
    {
        var crew = await db.Crew.AsNoTracking()
            .FirstOrDefaultAsync(c => c.ID == request.CrewID, ct);

        if (crew is null)
        {
            return Result.Failure<Response>(Error.NotFound("Crew.NotFound", "크루를 찾을 수 없습니다."));
        }

        // 1) 확정 멤버 (Accepted)
        var members = await db.CrewMember.AsNoTracking()
            .Where(m => m.CrewID == request.CrewID)
            .OrderBy(m => m.SortOrder)
            .ThenBy(m => m.JoinedAt)
            .Select(m => new
            {
                m.ID,
                m.MemberID,
                m.ChannelID,
                m.Nickname,
                m.Role,
                m.SortOrder,
                m.IsActive,
                m.JoinedAt,
                Thumb = m.Member != null ? m.Member.Thumb : null,
                ChannelName = m.Channel != null ? m.Channel.Name : null,
                ChannelSID = m.Channel != null ? m.Channel.SID : null,
                ChannelDbThumb = m.Channel != null ? m.Channel.ThumbnailUrl : null
            })
            .ToListAsync(ct);

        // 2) 미응답/거절/만료 초대
        var invitations = await db.CrewInvitation.AsNoTracking()
            .Where(i => i.CrewID == request.CrewID && i.Status != CrewInviteStatus.Accepted)
            .OrderByDescending(i => i.InvitedAt)
            .Select(i => new
            {
                ID = -i.ID, // 음수: CrewMember.ID와 충돌 방지
                MemberID = i.TargetMemberID,
                ChannelID = (int?)null,
                i.Nickname,
                i.Role,
                i.SortOrder,
                IsActive = false,
                JoinedAt = i.InvitedAt,
                Thumb = i.TargetMember != null ? i.TargetMember.Thumb : null,
                ChannelInfo = db.Channel.AsNoTracking()
                    .Where(c => c.MemberID == i.TargetMemberID)
                    .Select(c => new { c.Name, c.SID, c.ThumbnailUrl })
                    .FirstOrDefault(),
                i.Status,
                i.ExpiresAt
            })
            .ToListAsync(ct);

        // 3) 모든 MemberID 일괄 online 체크 (Redis 1회)
        var allMemberIDs = members.Select(m => m.MemberID)
            .Concat(invitations.Select(i => i.MemberID))
            .Distinct()
            .ToList();

        var onlineSet = await presence.GetOnlineMembersAsync(allMemberIDs);

        // 4) 채널 SID 일괄 수집 → YouTube 캐시 조회 (Redis MGET 1회, 미스 시 DB ThumbnailUrl fallback)
        var channelSIDs = members.Where(m => m.ChannelSID != null).Select(m => m.ChannelSID!)
            .Concat(invitations.Where(i => i.ChannelInfo != null).Select(i => i.ChannelInfo!.SID))
            .Distinct()
            .ToList();

        var ytCache = channelSIDs.Count > 0
            ? await channelCache.GetManyAsync(channelSIDs)
            : [];

        string? ResolveChannelThumb(string? sid, string? dbThumb)
        {
            if (sid == null) { return null; }
            return ytCache.TryGetValue(sid, out var info) ? info.ThumbnailUrl : dbThumb;
        }

        // 5) 통합 응답
        var combined = new List<CrewMemberItem>(members.Count + invitations.Count);

        foreach (var m in members)
        {
            combined.Add(new CrewMemberItem(
                m.ID, m.MemberID, m.ChannelID, m.Nickname, m.Role,
                m.SortOrder, m.IsActive, m.JoinedAt,
                m.Thumb, m.ChannelName,
                ResolveChannelThumb(m.ChannelSID, m.ChannelDbThumb),
                "Accepted", null,
                onlineSet.Contains(m.MemberID)
            ));
        }

        var now = DateTime.UtcNow;
        foreach (var i in invitations)
        {
            // lazy expiration: Pending인데 ExpiresAt 지난 것은 Expired 처리
            var isExpired = i.Status == CrewInviteStatus.Pending && i.ExpiresAt < now;
            var statusLabel = i.Status == CrewInviteStatus.Declined ? "Declined"
                : isExpired || i.Status == CrewInviteStatus.Expired ? "Expired"
                : "Pending";

            combined.Add(new CrewMemberItem(
                i.ID, i.MemberID, i.ChannelID, i.Nickname, i.Role,
                i.SortOrder, i.IsActive, i.JoinedAt,
                i.Thumb, i.ChannelInfo?.Name,
                ResolveChannelThumb(i.ChannelInfo?.SID, i.ChannelInfo?.ThumbnailUrl),
                statusLabel,
                statusLabel == "Pending" ? i.ExpiresAt : null,
                onlineSet.Contains(i.MemberID)
            ));
        }

        return Result.Success(new Response(combined));
    }
}