using Application.Abstractions.Data;
using Application.Abstractions.Messaging;
using Microsoft.EntityFrameworkCore;

namespace Application.Features.Admin.Donation.Rank.Search;

public sealed class Handler(IAppDbContext db) : IQueryHandler<Query, Response>
{
    public async Task<Response> Handle(Query request, CancellationToken ct)
    {
        // 탭 → 기간 범위 (롤링 윈도우)
        var now = DateTime.UtcNow;
        var periodStart = request.Tab switch
        {
            0 => now.AddHours(-24),   // 오늘
            1 => now.AddHours(-72),   // 3일
            2 => now.AddDays(-7),     // 1주일
            3 => now.AddDays(-30),    // 1개월
            4 => now.AddDays(-90),    // 3개월
            5 => now.AddDays(-180),   // 6개월
            6 => now.AddDays(-365),   // 1년
            _ => now.AddHours(-24)
        };

        var donations = db.Donation.AsNoTracking().Where(d => d.CreatedAt >= periodStart && d.CreatedAt <= now);

        // 키워드 검색 (검색 창은 후원 내역과 동일)
        if (!string.IsNullOrWhiteSpace(request.Keyword))
        {
            donations = request.Search switch
            {
                1 => donations.Where(x => x.Sponsor != null && x.Sponsor.ID.ToString().Contains(request.Keyword)),
                2 => donations.Where(x => x.Sponsor != null && x.Sponsor.SID.Contains(request.Keyword)),
                3 => donations.Where(x => x.Sponsor != null && x.Sponsor.Name != null && x.Sponsor.Name.Contains(request.Keyword)),
                4 => donations.Where(x => x.Receiver != null && x.Receiver.ID.ToString().Contains(request.Keyword)),
                5 => donations.Where(x => x.Receiver != null && x.Receiver.SID.Contains(request.Keyword)),
                6 => donations.Where(x => x.Receiver != null && x.Receiver.Name != null && x.Receiver.Name.Contains(request.Keyword)),
                7 => donations.Where(x => x.SendName.Contains(request.Keyword)),
                _ => donations
            };
        }

        // 기간 추가 필터 (StartAt/EndAt) — 탭 기간 내에서 추가로 좁히기
        if (!string.IsNullOrWhiteSpace(request.StartAt) && DateTime.TryParse(request.StartAt, out var startAt))
        {
            donations = donations.Where(x => x.CreatedAt >= startAt);
        }

        if (!string.IsNullOrWhiteSpace(request.EndAt) && DateTime.TryParse(request.EndAt, out var endAt))
        {
            donations = donations.Where(x => x.CreatedAt <= endAt);
        }

        // 후원자별 집계
        var grouped = donations.GroupBy(d => d.SponsorMemberID).Select(g => new
        {
            SponsorMemberID = g.Key,
            TotalAmount = g.Sum(x => (long)x.Amount),
            DonationCount = g.Count(),
            LastDonatedAt = g.Max(x => (DateTime?)x.CreatedAt)
        });

        // 정렬 + 순위
        grouped = request.Sort switch
        {
            1 => grouped.OrderByDescending(x => x.TotalAmount).ThenByDescending(x => x.DonationCount),
            2 => grouped.OrderBy(x => x.TotalAmount).ThenBy(x => x.DonationCount),
            3 => grouped.OrderByDescending(x => x.DonationCount).ThenByDescending(x => x.TotalAmount),
            4 => grouped.OrderBy(x => x.DonationCount).ThenBy(x => x.TotalAmount),
            _ => grouped.OrderByDescending(x => x.TotalAmount).ThenByDescending(x => x.DonationCount)
        };

        var total = await grouped.CountAsync(ct);
        var skip = (request.Page - 1) * request.PerPage;

        var paged = await grouped.Skip(skip).Take(request.PerPage).ToListAsync(ct);

        // 마지막 피후원자 lookup — 후원자별 마지막 Donation의 Receiver
        var sponsorIDs = paged.Select(p => p.SponsorMemberID).ToArray();

        var lastReceivers = await donations
            .Where(d => sponsorIDs.Contains(d.SponsorMemberID))
            .GroupBy(d => d.SponsorMemberID)
            .Select(g => new
            {
                SponsorMemberID = g.Key,
                LastDonationID = g.OrderByDescending(x => x.CreatedAt).ThenByDescending(x => x.ID).First().ID
            })
            .ToListAsync(ct);

        var lastDonationIDs = lastReceivers.Select(r => r.LastDonationID).ToArray();

        var lastDonations = await db.Donation.AsNoTracking()
            .Where(d => lastDonationIDs.Contains(d.ID))
            .Include(d => d.Receiver)
            .Select(d => new
            {
                d.ID,
                d.SponsorMemberID,
                ReceiverID = d.Receiver != null ? d.Receiver.ID : (int?)null,
                ReceiverEmail = d.Receiver != null ? d.Receiver.Email : null,
                ReceiverName = d.Receiver != null ? d.Receiver.Name : null
            })
            .ToListAsync(ct);

        var lastBySponsor = lastDonations.ToDictionary(x => x.SponsorMemberID);

        // Sponsor 정보 lookup
        var sponsors = await db.Member.AsNoTracking()
            .Where(m => sponsorIDs.Contains(m.ID))
            .Select(m => new { m.ID, m.Email, m.Name })
            .ToListAsync(ct);

        var sponsorByID = sponsors.ToDictionary(x => x.ID);

        // Rank 번호 — 현재 페이지에서 skip+1 부터 순서대로
        var rows = paged.Select((x, idx) =>
        {
            sponsorByID.TryGetValue(x.SponsorMemberID, out var sponsor);
            lastBySponsor.TryGetValue(x.SponsorMemberID, out var last);

            return new Response.Row
            {
                Num = total - skip - idx,
                Rank = skip + idx + 1,
                SponsorMemberID = x.SponsorMemberID,
                SponsorEmail = sponsor?.Email ?? string.Empty,
                SponsorName = sponsor?.Name,
                TotalAmount = x.TotalAmount,
                DonationCount = x.DonationCount,
                LastReceiverID = last?.ReceiverID,
                LastReceiverEmail = last?.ReceiverEmail,
                LastReceiverName = last?.ReceiverName,
                LastDonatedAt = x.LastDonatedAt
            };
        }).ToList();

        return new Response
        {
            Total = total,
            List = rows
        };
    }
}