using System.IdentityModel.Tokens.Jwt;
using System.Security.Claims;
using System.Text;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Options;
using Microsoft.IdentityModel.Tokens;

public class AuthService : IAuthService
{
    private readonly AppDbContext _db;
    private readonly JwtOptions _jwtOptions;

    public AuthService(AppDbContext db, IOptions<JwtOptions> jwtOptions)
    {
        _db = db;
        _jwtOptions = jwtOptions.Value;
    }

    public async Task<LoginResponse> LoginAsync(LoginRequest req)
    {
        var user = await _db.Users.FirstOrDefaultAsync(u => u.Username == req.Username);
        if (user is null || !BCrypt.Net.BCrypt.Verify(req.Password, user.PasswordHash))
            throw new ValidationException("Invalid username or password.", "INVALID_CREDENTIALS");

        if (!user.IsActive)
            throw new ConflictException("Account is disabled.", "ACCOUNT_DISABLED");

        var token = GenerateJwt(user);
        return new LoginResponse(token, user.Id, user.Username, user.FullName, user.Role.ToDbString());
    }

    public async Task<User> GetCurrentUserAsync(Guid userId)
    {
        var user = await _db.Users.FindAsync(userId);
        if (user is null)
            throw new NotFoundException("User not found.", "USER_NOT_FOUND");
        return user;
    }

    private string GenerateJwt(User user)
    {
        var key = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(_jwtOptions.Secret));
        var creds = new SigningCredentials(key, SecurityAlgorithms.HmacSha256);

        var claims = new[]
        {
            new Claim(ClaimTypes.NameIdentifier, user.Id.ToString()),
            new Claim(ClaimTypes.Name, user.Username),
            new Claim(ClaimTypes.Role, user.Role.ToDbString()),
            new Claim("fullName", user.FullName)
        };

        var token = new JwtSecurityToken(
            issuer: _jwtOptions.Issuer,
            audience: _jwtOptions.Audience,
            claims: claims,
            expires: DateTime.UtcNow.AddMinutes(_jwtOptions.ExpiryMinutes),
            signingCredentials: creds);

        return new JwtSecurityTokenHandler().WriteToken(token);
    }
}