using System.IdentityModel.Tokens.Jwt;
using System.Security.Claims;
using System.Text;
using MiAssessment.Core.Interfaces;
using MiAssessment.Model.Entities;
using MiAssessment.Model.Models.Auth;
using Microsoft.Extensions.Logging;
using Microsoft.IdentityModel.Tokens;

namespace MiAssessment.Core.Services;

/// <summary>
/// JWT服务实现
/// </summary>
public class JwtService : IJwtService
{
    private readonly JwtSettings _jwtSettings;
    private readonly ILogger<JwtService> _logger;

    public JwtService(JwtSettings jwtSettings, ILogger<JwtService> logger)
    {
        _jwtSettings = jwtSettings ?? throw new ArgumentNullException(nameof(jwtSettings));
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
    }

    /// <summary>
    /// 生成JWT Token
    /// </summary>
    public string GenerateToken(User user)
    {
        if (user == null)
            throw new ArgumentNullException(nameof(user));

        var key = new SymmetricSecurityKey(Encoding.ASCII.GetBytes(_jwtSettings.Secret));
        var credentials = new SigningCredentials(key, SecurityAlgorithms.HmacSha256);

        var claims = new List<Claim>
        {
            new Claim(ClaimTypes.NameIdentifier, user.Id.ToString()),
            new Claim(ClaimTypes.Name, user.Nickname ?? string.Empty),
            new Claim("uid", user.Uid ?? string.Empty)
        };

        var token = new JwtSecurityToken(
            issuer: _jwtSettings.Issuer,
            audience: _jwtSettings.Audience,
            claims: claims,
            expires: DateTime.UtcNow.AddMinutes(_jwtSettings.ExpirationMinutes),
            signingCredentials: credentials
        );

        var tokenHandler = new JwtSecurityTokenHandler();
        var tokenString = tokenHandler.WriteToken(token);

        _logger.LogInformation("Generated JWT token for user {UserId}", user.Id);

        return tokenString;
    }

    /// <summary>
    /// 验证JWT Token
    /// </summary>
    public ClaimsPrincipal? ValidateToken(string token)
    {
        if (string.IsNullOrWhiteSpace(token))
        {
            _logger.LogWarning("Token validation failed: token is null or empty");
            return null;
        }

        try
        {
            var key = new SymmetricSecurityKey(Encoding.ASCII.GetBytes(_jwtSettings.Secret));
            var tokenHandler = new JwtSecurityTokenHandler();

            var principal = tokenHandler.ValidateToken(token, new TokenValidationParameters
            {
                ValidateIssuerSigningKey = true,
                IssuerSigningKey = key,
                ValidateIssuer = true,
                ValidIssuer = _jwtSettings.Issuer,
                ValidateAudience = true,
                ValidAudience = _jwtSettings.Audience,
                ValidateLifetime = true,
                ClockSkew = TimeSpan.Zero
            }, out SecurityToken validatedToken);

            _logger.LogInformation("Token validated successfully");
            return principal;
        }
        catch (SecurityTokenExpiredException ex)
        {
            _logger.LogWarning("Token validation failed: token expired - {Message}", ex.Message);
            return null;
        }
        catch (SecurityTokenInvalidSignatureException ex)
        {
            _logger.LogWarning("Token validation failed: invalid signature - {Message}", ex.Message);
            return null;
        }
        catch (Exception ex)
        {
            _logger.LogWarning("Token validation failed: {Message}", ex.Message);
            return null;
        }
    }

    /// <summary>
    /// 从Token中提取用户ID
    /// </summary>
    public long? GetUserIdFromToken(string token)
    {
        if (string.IsNullOrWhiteSpace(token))
            return null;

        var principal = ValidateToken(token);
        if (principal == null)
            return null;

        var userIdClaim = principal.FindFirst(ClaimTypes.NameIdentifier);
        if (userIdClaim == null || !long.TryParse(userIdClaim.Value, out var userId))
        {
            _logger.LogWarning("Failed to extract user ID from token");
            return null;
        }

        return userId;
    }
}