using System.Text.RegularExpressions;
using Application.Abstractions.Data;
using Application.Abstractions.Messaging;
using SharedKernel.Results;
using Microsoft.EntityFrameworkCore;

namespace Application.Features.Admin.Channel.List.Update;

public sealed class Handler(IAppDbContext db) : ICommandHandler<Command, Result>
{
    public async Task<Result> Handle(Command request, CancellationToken ct)
    {
        var channel = await db.Channel.FirstOrDefaultAsync(c => c.ID == request.ID, ct);
        if (channel is null)
        {
            return Result.Failure(Error.NotFound("Channel.NotFound", "채널을 찾을 수 없습니다."));
        }

        // 후원 코드 사전 검증 (자기 자신은 중복에서 제외)
        string? normalizedDonationCode = null;

        if (!string.IsNullOrWhiteSpace(request.DonationCode))
        {
            var trimmed = request.DonationCode.Trim();

            if (!Regex.IsMatch(trimmed, "^[A-Za-z0-9]{4,7}$"))
            {
                return Result.Failure(Error.Problem("DonationCode.InvalidFormat", "후원 코드는 4~7자 영문/숫자만 가능합니다."));
            }

            normalizedDonationCode = trimmed.ToUpperInvariant();

            var codeTaken = await db.Channel.AnyAsync(c => c.DonationCode == normalizedDonationCode && c.ID != request.ID, ct);

            if (codeTaken)
            {
                return Result.Failure(Error.Conflict("DonationCode.Duplicate", "이미 사용 중인 후원 코드입니다."));
            }
        }

        channel.Update(
            request.Name,
            request.Handle,
            request.YouTubeUrl,
            request.PlatformFeeRate,
            request.StoreCommissionRate,
            request.IsVerified,
            request.IsActive
        );

        channel.SetDonationCodeByAdmin(normalizedDonationCode);

        try
        {
            await db.SaveChangesAsync(ct);
        }
        catch (DbUpdateException)
        {
            return Result.Failure(Error.Conflict("DonationCode.Duplicate", "이미 사용 중인 후원 코드입니다."));
        }

        return Result.Success();
    }
}