using Application.Abstractions.Data;
using Application.Abstractions.Messaging;
using Domain.Entities.Store.ValueObject;
using Microsoft.EntityFrameworkCore;
using SharedKernel.Results;

namespace Application.Features.Admin.Store.Coupon.ExpireCodes;

public sealed class Handler(IAppDbContext db) : ICommandHandler<Command, Result<Response>>
{
    public async Task<Result<Response>> Handle(Command request, CancellationToken ct)
    {
        if (request.CodeIDs is null || request.CodeIDs.Length == 0)
        {
            return Result.Failure<Response>(Error.Problem("CouponCode.NoIDs", "만료 처리할 코드를 선택해 주세요."));
        }

        var targets = await db.CouponCode
            .Where(c => c.CouponID == request.CouponID && request.CodeIDs.Contains(c.ID))
            .ToListAsync(ct);

        if (targets.Count == 0)
        {
            return Result.Failure<Response>(Error.NotFound("CouponCode.NotFound", "만료 처리할 코드를 찾을 수 없습니다."));
        }

        var blocked = targets.Where(c => c.Status != CouponCodeStatus.Available && c.Status != CouponCodeStatus.Issued).ToList();

        if (blocked.Count > 0)
        {
            var preview = string.Join(", ", blocked.Take(10).Select(c => $"#{c.ID}({StatusText(c.Status)})"));
            var more = blocked.Count > 10 ? $" 외 {blocked.Count - 10}건" : string.Empty;

            return Result.Failure<Response>(Error.Conflict(
                "CouponCode.NotExpirable",
                $"사용 가능(Available) 또는 발급됨(Issued) 상태 코드만 만료 처리할 수 있습니다. 대상 외 코드: {preview}{more}"
            ));
        }

        // Issued 출발 코드에 연결된 MemberInventory 를 같은 트랜잭션에서 즉시 만료
        var issuedCodeIDs = targets.Where(c => c.Status == CouponCodeStatus.Issued).Select(c => c.ID).ToList();

        if (issuedCodeIDs.Count > 0)
        {
            var inventories = await db.MemberInventory
                .Where(i => issuedCodeIDs.Contains(i.CouponCodeID) && i.UsedAt == null)
                .ToListAsync(ct);

            foreach (var inv in inventories)
            {
                inv.ForceExpire();
            }
        }

        foreach (var code in targets)
        {
            code.Expire();
        }

        await db.SaveChangesAsync(ct);

        return Result.Success(new Response(targets.Count));
    }

    private static string StatusText(CouponCodeStatus status) => status switch
    {
        CouponCodeStatus.Available => "사용 가능",
        CouponCodeStatus.Reserved => "결제 진행 중",
        CouponCodeStatus.Issued => "발급됨",
        CouponCodeStatus.Used => "사용됨",
        CouponCodeStatus.Expired => "만료",
        _ => status.ToString()
    };
}