using Application.Abstractions.Data;
using Domain.Entities.Donations;
using Domain.Entities.Donations.ValueObject;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;

namespace Infrastructure.Ranking;

/// <summary>
/// 매일 자정 00:30(KST) 1회 실행 — 랭킹 스냅샷 집계.
/// - YouTubeDailyAggregator 완료 후 실행 (00:00 + 30분 버퍼)
/// - 3가지 랭킹 × 6가지 기간 × (전체 + 카테고리) = N개의 스냅샷 생성
/// - 기존 스냅샷은 삭제 후 재생성 (upsert 대신 단순 truncate+insert)
///
/// 종합 점수 가중치 (Comprehensive):
///   머니 × 0.55 + 후원자수(×10000 환산) × 0.15 + 방송시간(초 / 3600) × 0.15
///   + 조회수 × 0.1 + 좋아요 × 0.05
/// </summary>
internal sealed class RankingDailyAggregatorService(
    IServiceScopeFactory scopeFactory,
    ILogger<RankingDailyAggregatorService> logger
) : BackgroundService
{
    private static readonly TimeSpan InitialDelay = TimeSpan.FromMinutes(3);
    private static readonly TimeZoneInfo Kst = TimeZoneInfo.FindSystemTimeZoneById("Korea Standard Time");
    private const int OffsetMinutesAfterMidnight = 30;

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        await Task.Delay(InitialDelay, stoppingToken);
        logger.LogInformation("[RankingAggregator] 서비스 시작 — 매일 KST 00:{Offset} 실행", OffsetMinutesAfterMidnight.ToString("D2"));

        while (!stoppingToken.IsCancellationRequested)
        {
            var delay = CalculateDelayUntilNextRun();
            logger.LogInformation("[RankingAggregator] 다음 실행까지 대기: {Hours}시간 {Minutes}분", delay.Hours, delay.Minutes);

            try
            {
                await Task.Delay(delay, stoppingToken);
            }
            catch (TaskCanceledException)
            {
                break;
            }

            try
            {
                await AggregateAllAsync(stoppingToken);
            }
            catch (Exception ex)
            {
                logger.LogError(ex, "[RankingAggregator] 집계 실행 중 오류");
            }
        }
    }

    private static TimeSpan CalculateDelayUntilNextRun()
    {
        var nowKst = TimeZoneInfo.ConvertTimeFromUtc(DateTime.UtcNow, Kst);
        var nextRunKst = nowKst.Date.AddDays(1).AddMinutes(OffsetMinutesAfterMidnight);
        var delay = nextRunKst - nowKst;

        if (delay <= TimeSpan.Zero)
        {
            delay = TimeSpan.FromMinutes(1);
        }

        return delay;
    }

    private async Task AggregateAllAsync(CancellationToken ct)
    {
        logger.LogInformation("[RankingAggregator] 스냅샷 집계 시작");
        var periods = Enum.GetValues<RankingPeriod>();
        var types = Enum.GetValues<RankingType>();

        foreach (var period in periods)
        {
            foreach (var type in types)
            {
                try
                {
                    await AggregateOneAsync(type, period, null, ct);
                }
                catch (Exception ex)
                {
                    logger.LogError(ex, "[RankingAggregator] {Type}/{Period} 집계 실패", type, period);
                }
            }
        }

        logger.LogInformation("[RankingAggregator] 스냅샷 집계 완료");
    }

    private async Task AggregateOneAsync(RankingType type, RankingPeriod period, string? category, CancellationToken ct)
    {
        using var scope = scopeFactory.CreateScope();
        var db = scope.ServiceProvider.GetRequiredService<IAppDbContext>();

        var (periodStart, periodEnd) = ResolvePeriodRange(period);

        // 기존 스냅샷 삭제 (동일 type/period/category)
        var existing = await db.RankingSnapshot
            .Where(r => r.Type == type && r.Period == period && r.Category == category)
            .ToListAsync(ct);

        if (existing.Count > 0)
        {
            db.RankingSnapshot.RemoveRange(existing);
            await db.SaveChangesAsync(ct);
        }

        // 전일 스냅샷 (PreviousRank 계산용)
        var previousRanks = existing
            .GroupBy(r => r.MemberID)
            .ToDictionary(g => g.Key, g => g.First().Rank);

        List<AggregatedRow> rows = type switch
        {
            RankingType.Comprehensive => await AggregateComprehensiveAsync(db, periodStart, periodEnd, ct),
            RankingType.Creator => await AggregateCreatorAsync(db, periodStart, periodEnd, ct),
            RankingType.Donor => await AggregateDonorAsync(db, periodStart, periodEnd, ct),
            _ => []
        };

        if (rows.Count == 0)
        {
            return;
        }

        var ranked = rows
            .OrderByDescending(r => r.Score)
            .ThenByDescending(r => r.MoneyAmount)
            .ToList();

        var now = DateTime.UtcNow;
        var snapshots = new List<RankingSnapshot>(ranked.Count);

        for (var i = 0; i < ranked.Count; i++)
        {
            var row = ranked[i];
            var rank = i + 1;
            int? previousRank = previousRanks.GetValueOrDefault(row.MemberID) is var p && p > 0 ? p : null;

            snapshots.Add(RankingSnapshot.Create(
                type,
                period,
                periodStart,
                periodEnd,
                category,
                row.MemberID,
                rank,
                row.Score,
                row.MoneyAmount,
                row.DonorCount,
                row.BroadcastSec,
                row.ViewCount,
                row.LikeCount,
                previousRank
            ));
        }

        await db.RankingSnapshot.AddRangeAsync(snapshots, ct);
        await db.SaveChangesAsync(ct);
        logger.LogInformation("[RankingAggregator] {Type}/{Period} — {Count}개 스냅샷 생성", type, period, snapshots.Count);
    }

    private static (DateTime Start, DateTime End) ResolvePeriodRange(RankingPeriod period)
    {
        var nowKst = TimeZoneInfo.ConvertTimeFromUtc(DateTime.UtcNow, Kst);
        var today = nowKst.Date;

        return period switch
        {
            RankingPeriod.Today => (ToUtc(today), ToUtc(today.AddDays(1))),
            RankingPeriod.Yesterday => (ToUtc(today.AddDays(-1)), ToUtc(today)),
            RankingPeriod.Week => (ToUtc(today.AddDays(-(int)today.DayOfWeek)), ToUtc(today.AddDays(1))),
            RankingPeriod.Month => (ToUtc(new DateTime(today.Year, today.Month, 1)), ToUtc(today.AddDays(1))),
            RankingPeriod.LastMonth => (
                ToUtc(new DateTime(today.Year, today.Month, 1).AddMonths(-1)),
                ToUtc(new DateTime(today.Year, today.Month, 1))
            ),
            RankingPeriod.All => (DateTime.MinValue.ToUniversalTime(), ToUtc(today.AddDays(1))),
            _ => (ToUtc(new DateTime(today.Year, today.Month, 1)), ToUtc(today.AddDays(1)))
        };
    }

    private static DateTime ToUtc(DateTime kstDate)
    {
        var kstUnspecified = DateTime.SpecifyKind(kstDate, DateTimeKind.Unspecified);
        return TimeZoneInfo.ConvertTimeToUtc(kstUnspecified, Kst);
    }

    private static async Task<List<AggregatedRow>> AggregateCreatorAsync(IAppDbContext db, DateTime start, DateTime end, CancellationToken ct)
    {
        var grouped = await db.Donation.AsNoTracking()
            .Where(d => d.CreatedAt >= start && d.CreatedAt < end && !d.IsTest)
            .GroupBy(d => d.ReceiverMemberID)
            .Select(g => new
            {
                MemberID = g.Key,
                MoneyAmount = g.Sum(d => (long)d.NetAmount),
                DonorCount = g.Select(d => d.SponsorMemberID).Distinct().Count()
            })
            .ToListAsync(ct);

        return grouped.Select(g => new AggregatedRow
        {
            MemberID = g.MemberID,
            MoneyAmount = g.MoneyAmount,
            DonorCount = g.DonorCount,
            BroadcastSec = 0,
            ViewCount = 0,
            LikeCount = 0,
            Score = g.MoneyAmount
        }).ToList();
    }

    private static async Task<List<AggregatedRow>> AggregateDonorAsync(IAppDbContext db, DateTime start, DateTime end, CancellationToken ct)
    {
        var grouped = await db.Donation.AsNoTracking()
            .Where(d => d.CreatedAt >= start && d.CreatedAt < end && !d.IsTest)
            .GroupBy(d => d.SponsorMemberID)
            .Select(g => new
            {
                MemberID = g.Key,
                MoneyAmount = g.Sum(d => (long)d.Amount),
                DonorCount = g.Count()
            })
            .ToListAsync(ct);

        return grouped.Select(g => new AggregatedRow
        {
            MemberID = g.MemberID,
            MoneyAmount = g.MoneyAmount,
            DonorCount = g.DonorCount,
            BroadcastSec = 0,
            ViewCount = 0,
            LikeCount = 0,
            Score = g.MoneyAmount
        }).ToList();
    }

    private static async Task<List<AggregatedRow>> AggregateComprehensiveAsync(IAppDbContext db, DateTime start, DateTime end, CancellationToken ct)
    {
        var creatorRows = await AggregateCreatorAsync(db, start, end, ct);
        var creatorMap = creatorRows.ToDictionary(r => r.MemberID, r => r);

        // Member ID 목록 수집 (후원 받은 회원 + 방송 활동 회원)
        var broadcastStats = await db.ChannelBroadcastStats.AsNoTracking()
            .Join(db.Channel.AsNoTracking(), s => s.ChannelID, c => c.ID, (s, c) => new
            {
                c.MemberID,
                s.TotalDurationSec,
                s.CumulativeViews,
                s.TotalLikes
            })
            .ToListAsync(ct);

        foreach (var stat in broadcastStats)
        {
            if (creatorMap.TryGetValue(stat.MemberID, out var row))
            {
                row.BroadcastSec = stat.TotalDurationSec;
                row.ViewCount = stat.CumulativeViews;
                row.LikeCount = stat.TotalLikes;
            }
            else
            {
                creatorMap[stat.MemberID] = new AggregatedRow
                {
                    MemberID = stat.MemberID,
                    MoneyAmount = 0,
                    DonorCount = 0,
                    BroadcastSec = stat.TotalDurationSec,
                    ViewCount = stat.CumulativeViews,
                    LikeCount = stat.TotalLikes
                };
            }
        }

        foreach (var row in creatorMap.Values)
        {
            row.Score = CalculateComprehensiveScore(row);
        }

        return creatorMap.Values.ToList();
    }

    private static long CalculateComprehensiveScore(AggregatedRow row)
    {
        // 머니 × 0.55 + 후원자수 × 10000 × 0.15 + 방송시간/3600(시) × 10000 × 0.15 + 조회수 × 0.1 + 좋아요 × 0.05
        var moneyScore = row.MoneyAmount * 0.55;
        var donorScore = row.DonorCount * 10000.0 * 0.15;
        var broadcastScore = (row.BroadcastSec / 3600.0) * 10000.0 * 0.15;
        var viewScore = row.ViewCount * 0.1;
        var likeScore = row.LikeCount * 0.05;

        return (long)(moneyScore + donorScore + broadcastScore + viewScore + likeScore);
    }

    private sealed class AggregatedRow
    {
        public int MemberID { get; set; }
        public long Score { get; set; }
        public long MoneyAmount { get; set; }
        public int DonorCount { get; set; }
        public long BroadcastSec { get; set; }
        public long ViewCount { get; set; }
        public long LikeCount { get; set; }
    }
}