using Api.Models;
using Api.Models.DTOs;
using Microsoft.IdentityModel.Tokens;
using System.IdentityModel.Tokens.Jwt;
using System.Security.Claims;
using System.Text;

namespace Api.Services
{
    public interface IJwtService
    {
        string GenerateToken(User user);
        ClaimsPrincipal? ValidateToken(string token);
        DateTime GetTokenExpiration(string token);
    }
    
    public class JwtService : IJwtService
    {
        private readonly JwtSettings _jwtSettings;
        private readonly ILogger<JwtService> _logger;
        private readonly SymmetricSecurityKey _key;
        
        public JwtService(IConfiguration configuration, ILogger<JwtService> logger)
        {
            _jwtSettings = configuration.GetSection("Jwt").Get<JwtSettings>() 
                ?? throw new InvalidOperationException("JWT settings not configured");
            _logger = logger;
            _key = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(_jwtSettings.SecretKey));
        }
        
        public string GenerateToken(User user)
        {
            try
            {
                var tokenHandler = new JwtSecurityTokenHandler();
                var credentials = new SigningCredentials(_key, SecurityAlgorithms.HmacSha256);
                
                var claims = new List<Claim>
                {
                    new Claim(ClaimTypes.NameIdentifier, user.Id.ToString()),
                    new Claim(ClaimTypes.Email, user.Email),
                    new Claim("jti", Guid.NewGuid().ToString()),
                    new Claim("iat", DateTimeOffset.UtcNow.ToUnixTimeSeconds().ToString(), ClaimValueTypes.Integer64)
                };
                
                // Add optional claims if available
                if (!string.IsNullOrEmpty(user.FirstName))
                {
                    claims.Add(new Claim(ClaimTypes.GivenName, user.FirstName));
                }
                
                if (!string.IsNullOrEmpty(user.LastName))
                {
                    claims.Add(new Claim(ClaimTypes.Surname, user.LastName));
                }
                
                // Add provider information
                var providers = user.OAuthProviders.Select(p => p.Provider.ToString()).ToList();
                if (providers.Any())
                {
                    claims.Add(new Claim("providers", string.Join(",", providers)));
                }
                
                var tokenDescriptor = new SecurityTokenDescriptor
                {
                    Subject = new ClaimsIdentity(claims),
                    Expires = DateTime.UtcNow.AddMinutes(_jwtSettings.ExpirationMinutes),
                    SigningCredentials = credentials,
                    Issuer = _jwtSettings.Issuer,
                    Audience = _jwtSettings.Audience
                };
                
                var token = tokenHandler.CreateToken(tokenDescriptor);
                return tokenHandler.WriteToken(token);
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "Error generating JWT token for user {UserId}", user.Id);
                throw new InvalidOperationException("Failed to generate access token", ex);
            }
        }
        
        public ClaimsPrincipal? ValidateToken(string token)
        {
            try
            {
                var tokenHandler = new JwtSecurityTokenHandler();
                
                var validationParameters = new TokenValidationParameters
                {
                    ValidateIssuerSigningKey = true,
                    IssuerSigningKey = _key,
                    ValidateIssuer = true,
                    ValidIssuer = _jwtSettings.Issuer,
                    ValidateAudience = true,
                    ValidAudience = _jwtSettings.Audience,
                    ValidateLifetime = true,
                    ClockSkew = TimeSpan.FromMinutes(5) // Allow 5 minutes clock skew
                };
                
                var principal = tokenHandler.ValidateToken(token, validationParameters, out var validatedToken);
                
                // Ensure the token is a JWT token with the correct algorithm
                if (validatedToken is not JwtSecurityToken jwtToken || 
                    !jwtToken.Header.Alg.Equals(SecurityAlgorithms.HmacSha256, StringComparison.InvariantCultureIgnoreCase))
                {
                    return null;
                }
                
                return principal;
            }
            catch (SecurityTokenException ex)
            {
                _logger.LogWarning(ex, "Invalid token validation attempt");
                return null;
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "Error validating JWT token");
                return null;
            }
        }
        
        public DateTime GetTokenExpiration(string token)
        {
            try
            {
                var tokenHandler = new JwtSecurityTokenHandler();
                var jsonToken = tokenHandler.ReadJwtToken(token);
                return jsonToken.ValidTo;
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "Error reading token expiration");
                throw new InvalidOperationException("Invalid token format", ex);
            }
        }
    }
}