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

namespace Application.Features.Api.Crew.SearchMember;

internal sealed class Handler(
    IAppDbContext db,
    IYouTubeChannelCache channelCache
) : IQueryHandler<Query, Response>
{
    public async Task<Response> Handle(Query request, CancellationToken ct)
    {
        if (string.IsNullOrWhiteSpace(request.Keyword) || request.Keyword.Trim().Length < 2)
        {
            return new Response([]);
        }

        var kw = request.Keyword.Trim();

        // 이미 등록된 크루원의 MemberID 목록
        var existingMemberIDs = await db.CrewMember.AsNoTracking()
            .Where(m => m.CrewID == request.CrewID)
            .Select(m => m.MemberID)
            .ToListAsync(ct);

        // 진행 중인 초대의 TargetMemberID 목록 (중복 초대 방지)
        var pendingInviteMemberIDs = await db.CrewInvitation.AsNoTracking()
            .Where(i => i.CrewID == request.CrewID && i.Status == CrewInviteStatus.Pending)
            .Select(i => i.TargetMemberID)
            .ToListAsync(ct);

        var excludeMemberIDs = existingMemberIDs.Concat(pendingInviteMemberIDs).Distinct().ToList();

        var list = await db.Member.AsNoTracking()
            .Where(m => !m.IsWithdraw && !m.IsDenied)
            .Where(m => !excludeMemberIDs.Contains(m.ID))
            .Where(m => db.Channel.Any(c => c.MemberID == m.ID))
            .Where(m =>
                m.Email.Contains(kw) ||
                db.Channel.Any(c => c.MemberID == m.ID && (
                    c.Name.Contains(kw) ||
                    (c.Handle != null && c.Handle.Contains(kw))
                ))
            )
            .Take(20)
            .Select(m => new
            {
                m.ID,
                m.Name,
                m.Email,
                m.Thumb,
                Channel = db.Channel.AsNoTracking()
                    .Where(c => c.MemberID == m.ID)
                    .Select(c => new { c.SID, c.Name, c.Handle, c.ThumbnailUrl })
                    .FirstOrDefault()
            })
            .ToListAsync(ct);

        // YouTube 채널 정보 캐시 일괄 조회 (Redis 우선, 미스 시 DB fallback)
        var channelSIDs = list.Where(x => x.Channel != null).Select(x => x.Channel!.SID).ToList();
        var ytCache = channelSIDs.Count > 0
            ? await channelCache.GetManyAsync(channelSIDs)
            : [];

        var result = list.Select(x =>
        {
            string? channelThumb = null;
            if (x.Channel != null)
            {
                channelThumb = ytCache.TryGetValue(x.Channel.SID, out var ytInfo)
                    ? ytInfo.ThumbnailUrl
                    : x.Channel.ThumbnailUrl;
            }

            return new SearchResultItem(
                x.ID,
                x.Name,
                x.Email,
                x.Thumb,
                x.Channel?.Name,
                channelThumb,
                x.Channel?.Handle
            );
        }).ToList();

        return new Response(result);
    }
}