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

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

public sealed class Handler(IAppDbContext db) : ICommandHandler<Command, Result<int>>
{
    public async Task<Result<int>> Handle(Command request, CancellationToken ct)
    {
        var exists = await db.Channel.AnyAsync(c => c.SID == request.SID, ct);
        if (exists)
        {
            return Result.Failure<int>(Error.Conflict("Channel.DuplicateSID", "이미 등록된 채널 SID입니다."));
        }

        // 후원 코드 사전 검증: 형식 + 중복 (도메인 안전망 외 사용자 친화적 에러)
        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<int>(Error.Problem("DonationCode.InvalidFormat", "후원 코드는 4~7자 영문/숫자만 가능합니다."));
            }

            normalizedDonationCode = trimmed.ToUpperInvariant();

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

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

        var channel = Domain.Entities.Members.Channel.Create(
            request.MemberID,
            request.SID,
            request.Name,
            request.YouTubeUrl
        );

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

        channel.SetDonationCodeByAdmin(normalizedDonationCode);

        await db.Channel.AddAsync(channel, ct);

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

        return Result.Success(channel.ID);
    }
}