using System.IdentityModel.Tokens.Jwt;
using System.Security.Claims;
using System.Security.Cryptography;
using System.Text;
using Microsoft.Extensions.Options;
using Microsoft.IdentityModel.Tokens;
using QMax.Api.Configuration;
using QMax.Api.Data.Entities;

namespace QMax.Api.Infrastructure.Auth;

public interface ITokenService
{
    string CreateAccessToken(User user, UserSession session, DateTimeOffset expiresAt);
    string CreateRefreshToken();
    string HashRefreshToken(string refreshToken);
}

public sealed class TokenService(IOptions<QMaxOptions> options) : ITokenService
{
    private readonly QMaxOptions _options = options.Value;

    public string CreateAccessToken(User user, UserSession session, DateTimeOffset expiresAt)
    {
        var key = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(GetJwtSecret()));
        var credentials = new SigningCredentials(key, SecurityAlgorithms.HmacSha256);
        var claims = new[]
        {
            new Claim(JwtRegisteredClaimNames.Sub, user.Id.ToString()),
            new Claim(JwtRegisteredClaimNames.Jti, Guid.NewGuid().ToString()),
            new Claim("sid", session.Id.ToString()),
            new Claim(ClaimTypes.NameIdentifier, user.Id.ToString()),
            new Claim(ClaimTypes.Name, user.DisplayName)
        };

        var token = new JwtSecurityToken(
            issuer: _options.JwtIssuer,
            audience: _options.JwtAudience,
            claims: claims,
            notBefore: DateTime.UtcNow,
            expires: expiresAt.UtcDateTime,
            signingCredentials: credentials);

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

    public string CreateRefreshToken()
    {
        Span<byte> bytes = stackalloc byte[48];
        RandomNumberGenerator.Fill(bytes);
        return Convert.ToBase64String(bytes);
    }

    public string HashRefreshToken(string refreshToken)
    {
        var bytes = SHA256.HashData(Encoding.UTF8.GetBytes(refreshToken));
        return Convert.ToHexString(bytes);
    }

    private string GetJwtSecret()
    {
        if (!string.IsNullOrWhiteSpace(_options.JwtSecret) && _options.JwtSecret.Length >= 32)
        {
            return _options.JwtSecret;
        }

        if (Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT") == "Development")
        {
            return "development-only-qmax-secret-change-before-production";
        }

        throw new InvalidOperationException("QMax:JwtSecret must be set to at least 32 characters in production.");
    }
}