using Application.Abstractions.Crypto;
using Application.Abstractions.Data;
using Application.Abstractions.Messaging;
using Application.Abstractions.Messaging.Email;
using Application.Abstractions.YouTube;
using Application.Common;
using Domain.Entities.EmailVerification.ValueObject;
using Microsoft.Extensions.Logging;
using SharedKernel.Results;
using Microsoft.EntityFrameworkCore;

namespace Application.Features.Api.MyPage.Withdraw;

internal sealed class Handler(
    IAppDbContext db,
    IMailService mailService,
    IGoogleOAuthService oauthService,
    IYouTubeChannelCache youTubeChannelCache,
    IFieldEncryptor fieldEncryptor,
    ILogger<Handler> logger
) : ICommandHandler<Command, Result>
{
    public async Task<Result> Handle(Command request, CancellationToken ct)
    {
        if (string.IsNullOrWhiteSpace(request.Code))
        {
            return Result.Failure(Error.Problem("MyPage.CodeRequired", "인증번호를 입력해주세요."));
        }

        var member = await db.Member.FirstOrDefaultAsync(m => m.ID == request.MemberID, ct);
        if (member is null)
        {
            return Result.Failure(Error.NotFound("MyPage.MemberNotFound", "회원 정보를 찾을 수 없습니다."));
        }

        if (member.IsWithdraw)
        {
            return Result.Failure(Error.Problem("MyPage.AlreadyWithdrawn", "이미 탈퇴한 회원입니다."));
        }

        // 유효한 인증번호 조회 (미인증, 만료 전, 가장 최근)
        var verifyNumber = await db.EmailVerifyNumber
            .Where(e => e.Email == member.Email
                && e.Type == VerificationType.Withdraw
                && !e.IsVerified
                && e.Expiration > DateTime.UtcNow)
            .OrderByDescending(e => e.CreatedAt)
            .FirstOrDefaultAsync(ct);

        if (verifyNumber is null)
        {
            return Result.Failure(Error.NotFound("MyPage.CodeNotFound", "인증번호가 올바르지 않거나 만료되었습니다."));
        }

        if (verifyNumber.Code != request.Code.Trim())
        {
            return Result.Failure(Error.Problem("MyPage.CodeMismatch", "인증번호가 일치하지 않습니다."));
        }

        // 인증 완료 처리
        verifyNumber.MarkVerified();

        // RefreshToken 무효화
        var refreshTokens = await db.RefreshToken.Where(t => t.MemberID == request.MemberID && !t.IsRevoked).ToListAsync(ct);
        foreach (var token in refreshTokens)
        {
            token.Revoke();
        }

        // 발송용 이메일 확보 (탈퇴 처리 전)
        var memberEmail = member.Email;

        // YouTube API Services ToS 준수 — 탈퇴 시 YouTube 출처 데이터 즉시 삭제
        //  1) OAuth refresh/access token revoke (Google /revoke 엔드포인트)
        //  2) MemberOAuthToken 행 삭제
        //  3) Channel.WipeYouTubeData() 로 채널 측 YT 필드 wipe
        //  4) Redis YouTubeChannel:{channelID} 캐시 invalidate
        var oauthTokens = await db.MemberOAuthToken.Where(t => t.MemberID == request.MemberID).ToListAsync(ct);
        var purgedChannelIds = new List<string>();

        foreach (var token in oauthTokens)
        {
            // refresh_token 우선, 없으면 access_token 으로 revoke (둘 다 무효화됨)
            var encrypted = token.RefreshTokenEnc ?? token.AccessTokenEnc;
            if (!string.IsNullOrEmpty(encrypted))
            {
                try
                {
                    var plaintext = fieldEncryptor.Decrypt(encrypted, 1);
                    if (!string.IsNullOrEmpty(plaintext))
                    {
                        await oauthService.RevokeTokenAsync(plaintext, ct);
                    }
                }
                catch (Exception ex)
                {
                    // revoke 실패해도 row 삭제는 진행 (best-effort)
                    logger.LogWarning(ex, "[Withdraw] OAuth revoke 실패 (memberID={MemberID}) — row 삭제는 진행", request.MemberID);
                }
            }

            db.MemberOAuthToken.Remove(token);
        }

        var channels = await db.Channel.Where(c => c.MemberID == request.MemberID).ToListAsync(ct);
        foreach (var channel in channels)
        {
            if (!string.IsNullOrEmpty(channel.YouTubeChannelID))
            {
                purgedChannelIds.Add(channel.YouTubeChannelID);
            }
            channel.WipeYouTubeData();
        }

        // 회원 탈퇴 처리
        member.Withdraw();

        await db.SaveChangesAsync(ct);

        // Redis 캐시 invalidate (DB 커밋 후 — 트랜잭션 rollback 시 stale 방지)
        foreach (var channelID in purgedChannelIds)
        {
            try
            {
                await youTubeChannelCache.RemoveAsync(channelID);
            }
            catch (Exception ex)
            {
                logger.LogWarning(ex, "[Withdraw] Redis YouTube 캐시 제거 실패 (channelID={ChannelID})", channelID);
            }
        }

        // 탈퇴 완료 안내 메일
        var emailTpl = (await db.Config.AsNoTracking().FirstOrDefaultAsync(ct))?.EmailTemplate;
        if (!string.IsNullOrWhiteSpace(emailTpl?.WithdrawEmailFormContent))
        {
            var subject = string.IsNullOrWhiteSpace(emailTpl.WithdrawEmailFormTitle)
                ? "회원탈퇴가 완료되었습니다"
                : emailTpl.WithdrawEmailFormTitle;
            var content = emailTpl.WithdrawEmailFormContent.Render(
                ("Email", memberEmail),
                ("Reason", "회원 본인 요청"),
                ("CreatedAt", DateTime.UtcNow.AddHours(9).ToString("yyyy-MM-dd HH:mm")));
            await mailService.SendAsync(new SendData(memberEmail, subject, content), ct);
        }

        return Result.Success();
    }
}