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

namespace Application.Features.Api.Stocks.GetMarketMovers;

/// <summary>
/// 등락 상위 종목(메인) — 최신 거래일 StockDailyPrice × Stock(active) 에서 코스피+코스닥 통합 상승/하락/상한/하한 각 상위 5.
/// 상승/하락은 상한·하한(±29.5% 근사)을 제외해 4개 그룹이 겹치지 않도록 한다. 각 종목에 최근 종가 스파크라인(과거→최신) 포함.
/// </summary>
internal sealed class Handler(IAppDbContext db) : IQueryHandler<Query, Response>
{
    private const int TopN = 5;
    private const int SparkPoints = 30;
    private const decimal LimitThreshold = 29.5m; // 가격제한(±30%) 근사

    public async Task<Response> Handle(Query request, CancellationToken ct)
    {
        var stockDate = await db.StockDailyPrice.AsNoTracking()
            .OrderByDescending(c => c.TradingDate)
            .Select(c => (DateOnly?)c.TradingDate)
            .FirstOrDefaultAsync(ct);

        if (stockDate is not DateOnly d)
        {
            return Empty();
        }

        var rows = await db.StockDailyPrice.AsNoTracking()
            .Where(c => c.TradingDate == d)
            .Join(db.Stock.AsNoTracking().Where(s => s.IsActive), p => p.StockID, s => s.ID, (p, s) => new Mover
            {
                StockID = p.StockID,
                Code = s.Code,
                Name = s.Name,
                Market = (int)s.Market,
                Close = p.Close,
                ChangeVal = p.ChangeAmount,
                ChangeRate = p.ChangeRate
            })
            .ToListAsync(ct);

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

        var advances = rows.Where(c => c.ChangeRate > 0m && c.ChangeRate < LimitThreshold).OrderByDescending(c => c.ChangeRate).Take(TopN).ToList();
        var declines = rows.Where(c => c.ChangeRate < 0m && c.ChangeRate > -LimitThreshold).OrderBy(c => c.ChangeRate).Take(TopN).ToList();
        var limitUp = rows.Where(c => c.ChangeRate >= LimitThreshold).OrderByDescending(c => c.ChangeRate).Take(TopN).ToList();
        var limitDown = rows.Where(c => c.ChangeRate <= -LimitThreshold).OrderBy(c => c.ChangeRate).Take(TopN).ToList();

        // 스파크라인 — 선택된 종목(≤20)의 최근 종가 시계열을 한 번에 조회
        var ids = advances.Concat(declines).Concat(limitUp).Concat(limitDown).Select(c => c.StockID).Distinct().ToList();
        var sparkByStock = await SparkByStockAsync(ids, d, ct);

        return new Response
        {
            TradeDate = d.ToString("yyyy-MM-dd"),
            Advances = BuildGroup(advances, rows.Count(c => c.ChangeRate > 0m), sparkByStock),
            Declines = BuildGroup(declines, rows.Count(c => c.ChangeRate < 0m), sparkByStock),
            LimitUp = BuildGroup(limitUp, rows.Count(c => c.ChangeRate >= LimitThreshold), sparkByStock),
            LimitDown = BuildGroup(limitDown, rows.Count(c => c.ChangeRate <= -LimitThreshold), sparkByStock)
        };
    }

    /// <summary>선택 종목들의 최근 종가 시계열(과거→최신) — StockID → 종가 리스트.</summary>
    private async Task<Dictionary<int, IReadOnlyList<int>>> SparkByStockAsync(List<int> ids, DateOnly asOf, CancellationToken ct)
    {
        if (ids.Count == 0)
        {
            return [];
        }

        // 최근 ~60일 창으로 스캔 하한 고정 (SparkPoints 거래일 ≈ 6주 → 60캘린더일이면 충분). 히스토리 누적에도 요청당 조회량 상한 유지.
        var floor = asOf.AddDays(-60);
        var raw = await db.StockDailyPrice.AsNoTracking()
            .Where(c => ids.Contains(c.StockID) && c.TradingDate <= asOf && c.TradingDate > floor)
            .Select(c => new { c.StockID, c.TradingDate, c.Close })
            .ToListAsync(ct);

        return raw
            .GroupBy(c => c.StockID)
            .ToDictionary(
                g => g.Key,
                g => (IReadOnlyList<int>)g.OrderByDescending(x => x.TradingDate).Take(SparkPoints).OrderBy(x => x.TradingDate).Select(x => x.Close).ToList());
    }

    private static Response.Group BuildGroup(List<Mover> movers, int total, Dictionary<int, IReadOnlyList<int>> sparkByStock)
    {
        var items = movers.Select(c => new Response.Item
        {
            Code = c.Code,
            Name = c.Name,
            Market = c.Market,
            Close = c.Close,
            ChangeVal = c.ChangeVal,
            FlucRateBp = (int)Math.Round(c.ChangeRate * 100m, MidpointRounding.AwayFromZero),
            Spark = sparkByStock.TryGetValue(c.StockID, out var s) ? s : []
        }).ToList();

        return new Response.Group { Total = total, Items = items };
    }

    private static Response Empty()
    {
        var empty = new Response.Group { Total = 0, Items = [] };
        return new Response
        {
            TradeDate = string.Empty,
            Advances = empty,
            Declines = empty,
            LimitUp = empty,
            LimitDown = empty
        };
    }

    private sealed class Mover
    {
        public int StockID { get; init; }
        public string Code { get; init; } = default!;
        public string Name { get; init; } = default!;
        public int Market { get; init; }
        public int Close { get; init; }
        public int ChangeVal { get; init; }
        public decimal ChangeRate { get; init; }
    }
}