using GreenHome.Application;
using GreenHome.Infrastructure.Data;
using GreenHome.Infrastructure.Services.Usage;
using GreenHome.Sms.Ippanel;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Logging;
using System.Security.Cryptography;
using System.Text;

namespace GreenHome.Infrastructure.Services.Auth;

public sealed class AuthService : IAuthService
{
    private readonly GreenHomeDbContext _dbContext;
    private readonly ISmsService _smsService;
    private readonly UsageTracker _usageTracker;
    private readonly ILogger<AuthService> _logger;
    private readonly string _tokenSecret;
    private const int CodeExpirationMinutes = 5;
    private const int ResendCooldownSeconds = 120;

    public AuthService(
        GreenHomeDbContext dbContext,
        ISmsService smsService,
        UsageTracker usageTracker,
        IConfiguration configuration,
        ILogger<AuthService> logger)
    {
        _dbContext = dbContext;
        _smsService = smsService;
        _usageTracker = usageTracker;
        _logger = logger;
        _tokenSecret = configuration["Auth:TokenSecret"] ?? "greenhome-dev-secret-change-me";
    }

    public async Task<SendCodeResponse> SendVerificationCodeAsync(
        SendCodeRequest request,
        CancellationToken cancellationToken)
    {
        var mobile = Domain.MobileNormalizer.Normalize(request.Mobile);

        if (mobile.Length == 0)
        {
            return new SendCodeResponse
            {
                Success = false,
                Message = "شماره موبایل معتبر نیست"
            };
        }

        var existingUser = await _dbContext.Users
            .AsNoTracking()
            .FirstOrDefaultAsync(u => u.Mobile == mobile, cancellationToken);

        if (existingUser != null && existingUser.IsDisabled)
        {
            return new SendCodeResponse
            {
                Success = false,
                Message = "حساب شما غیرفعال شده است. لطفاً با پشتیبانی تماس بگیرید."
            };
        }

        var canResend = await CanResendCodeAsync(mobile, cancellationToken);
        if (!canResend)
        {
            var lastCode = await _dbContext.VerificationCodes
                .Where(v => v.Mobile == mobile && !v.IsUsed)
                .OrderByDescending(v => v.CreatedAt)
                .FirstOrDefaultAsync(cancellationToken);

            if (lastCode != null)
            {
                var secondsRemaining = (int)(ResendCooldownSeconds - (DateTime.UtcNow - lastCode.CreatedAt).TotalSeconds);
                return new SendCodeResponse
                {
                    Success = false,
                    Message = $"لطفاً {secondsRemaining} ثانیه دیگر دوباره تلاش کنید",
                    ResendAfterSeconds = secondsRemaining > 0 ? secondsRemaining : 0
                };
            }
        }

        var code = GenerateCode();

        var previousCodes = await _dbContext.VerificationCodes
            .Where(v => v.Mobile == mobile && !v.IsUsed)
            .ToListAsync(cancellationToken);

        foreach (var prevCode in previousCodes)
        {
            prevCode.IsUsed = true;
            prevCode.UsedAt = DateTime.UtcNow;
        }

        var verificationCode = new Domain.VerificationCode
        {
            Mobile = mobile,
            Code = code,
            CreatedAt = DateTime.UtcNow,
            ExpiresAt = DateTime.UtcNow.AddMinutes(CodeExpirationMinutes),
            IsUsed = false
        };

        _dbContext.VerificationCodes.Add(verificationCode);
        await _dbContext.SaveChangesAsync(cancellationToken);

        try
        {
            await _smsService.SendPatternSmsAsync(new PatternSmsRequest
            {
                Recipients = [mobile],
                PatternCode = "ruvpjx7lajne1dx",
                Variables = new Dictionary<string, string> { { "code", code } }
            }, cancellationToken);

            if (existingUser != null)
                await _usageTracker.RecordAsync(existingUser.Id, UsageKind.Sms, cancellationToken: cancellationToken);

            _logger.LogInformation("Verification code sent to {Mobile}", mobile);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Failed to send SMS to {Mobile}", mobile);
        }

        return new SendCodeResponse
        {
            Success = true,
            Message = "کد فعال‌سازی ارسال شد",
            ResendAfterSeconds = ResendCooldownSeconds
        };
    }

    public async Task<VerifyCodeResponse> VerifyCodeAsync(
        VerifyCodeRequest request,
        CancellationToken cancellationToken)
    {
        var mobile = Domain.MobileNormalizer.Normalize(request.Mobile);
        var code = request.Code.Trim();

        if (string.IsNullOrWhiteSpace(mobile) || string.IsNullOrWhiteSpace(code) || code.Length != 4)
        {
            return new VerifyCodeResponse
            {
                Success = false,
                Message = "اطلاعات وارد شده معتبر نیست"
            };
        }

        var verificationCode = await _dbContext.VerificationCodes
            .Where(v => v.Mobile == mobile && v.Code == code && !v.IsUsed && v.ExpiresAt > DateTime.UtcNow)
            .OrderByDescending(v => v.CreatedAt)
            .FirstOrDefaultAsync(cancellationToken);

        if (verificationCode == null)
        {
            return new VerifyCodeResponse
            {
                Success = false,
                Message = "کد وارد شده معتبر نیست یا منقضی شده است"
            };
        }

        verificationCode.IsUsed = true;
        verificationCode.UsedAt = DateTime.UtcNow;

        var user = await _dbContext.Users
            .FirstOrDefaultAsync(u => u.Mobile == mobile, cancellationToken);

        if (user != null && user.IsDisabled)
        {
            return new VerifyCodeResponse
            {
                Success = false,
                Message = "حساب شما غیرفعال شده است. لطفاً با پشتیبانی تماس بگیرید."
            };
        }

        if (user == null)
        {
            user = new Domain.User
            {
                Mobile = mobile,
                CreatedAt = DateTime.UtcNow,
                LastLoginAt = DateTime.UtcNow
            };
            _dbContext.Users.Add(user);
        }
        else
        {
            user.LastLoginAt = DateTime.UtcNow;
        }

        await _dbContext.SaveChangesAsync(cancellationToken);

        var token = GenerateToken(user.Id);

        return new VerifyCodeResponse
        {
            Success = true,
            Message = "ورود موفقیت‌آمیز بود",
            Token = token,
            User = new UserDto
            {
                Id = user.Id,
                Mobile = user.Mobile,
                Name = user.Name,
                Family = user.Family,
                Role = user.Role,
                IsDisabled = user.IsDisabled
            }
        };
    }

    public async Task<bool> CanResendCodeAsync(string mobile, CancellationToken cancellationToken)
    {
        var normalizedMobile = Domain.MobileNormalizer.Normalize(mobile);
        var lastCode = await _dbContext.VerificationCodes
            .Where(v => v.Mobile == normalizedMobile && !v.IsUsed)
            .OrderByDescending(v => v.CreatedAt)
            .FirstOrDefaultAsync(cancellationToken);

        if (lastCode == null)
            return true;

        var elapsed = (DateTime.UtcNow - lastCode.CreatedAt).TotalSeconds;
        return elapsed >= ResendCooldownSeconds;
    }

    private static string GenerateCode()
    {
        var random = new Random();
        return random.Next(1000, 9999).ToString();
    }

    public async Task<UserDto?> GetUserByTokenAsync(string token, CancellationToken cancellationToken)
    {
        if (string.IsNullOrWhiteSpace(token))
            return null;

        var parts = token.Split('.');
        if (parts.Length != 3)
            return null;

        if (!int.TryParse(parts[0], out var userId) || !long.TryParse(parts[1], out var expiresAt))
            return null;

        if (expiresAt < DateTimeOffset.UtcNow.ToUnixTimeSeconds())
            return null;

        var payload = $"{parts[0]}.{parts[1]}";
        var expectedSignature = Convert.ToBase64String(
            HMACSHA256.HashData(Encoding.UTF8.GetBytes(_tokenSecret), Encoding.UTF8.GetBytes(payload)));

        if (!CryptographicOperations.FixedTimeEquals(
                Encoding.UTF8.GetBytes(expectedSignature),
                Encoding.UTF8.GetBytes(parts[2])))
            return null;

        var user = await _dbContext.Users.FirstOrDefaultAsync(u => u.Id == userId, cancellationToken);
        if (user == null)
            return null;

        if (user.IsDisabled)
            return null;

        return new UserDto
        {
            Id = user.Id,
            Mobile = user.Mobile,
            Name = user.Name,
            Family = user.Family,
            Role = user.Role,
            IsDisabled = user.IsDisabled
        };
    }

    private string GenerateToken(int userId)
    {
        var expiresAt = DateTimeOffset.UtcNow.AddDays(30).ToUnixTimeSeconds();
        var payload = $"{userId}.{expiresAt}";
        var signature = Convert.ToBase64String(
            HMACSHA256.HashData(Encoding.UTF8.GetBytes(_tokenSecret), Encoding.UTF8.GetBytes(payload)));
        return $"{payload}.{signature}";
    }

}