using System.IdentityModel.Tokens.Jwt;
using System.Security.Claims;
using System.Security.Cryptography;
using System.Text;
using EchoHub.Core.Models;
using Microsoft.IdentityModel.Tokens;

namespace EchoHub.Server.Auth;

public class JwtTokenService
{
    private readonly string _secret;
    private readonly string _issuer;
    private readonly string _audience;

    private static readonly TimeSpan AccessTokenLifetime = TimeSpan.FromMinutes(15);
    public static readonly TimeSpan RefreshTokenLifetime = TimeSpan.FromDays(30);

    public JwtTokenService(IConfiguration configuration)
    {
        _secret = configuration["Jwt:Secret"]
            ?? throw new InvalidOperationException("Jwt:Secret is not configured.");
        _issuer = configuration["Jwt:Issuer"]
            ?? throw new InvalidOperationException("Jwt:Issuer is not configured.");
        _audience = configuration["Jwt:Audience"]
            ?? throw new InvalidOperationException("Jwt:Audience is not configured.");
    }

    public (string Token, DateTimeOffset ExpiresAt) GenerateAccessToken(User user)
    {
        var key = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(_secret));
        var credentials = new SigningCredentials(key, SecurityAlgorithms.HmacSha256);
        var expiresAt = DateTimeOffset.UtcNow.Add(AccessTokenLifetime);

        Claim[] claims =
        [
            new(JwtRegisteredClaimNames.Sub, user.Id.ToString()),
            new("username", user.Username),
            new("display_name", user.DisplayName ?? user.Username),
            new(JwtRegisteredClaimNames.Jti, Guid.NewGuid().ToString()),
        ];

        var token = new JwtSecurityToken(
            issuer: _issuer,
            audience: _audience,
            claims: claims,
            expires: expiresAt.UtcDateTime,
            signingCredentials: credentials);

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

    public static string GenerateRefreshToken()
    {
        var randomBytes = new byte[64];
        using var rng = RandomNumberGenerator.Create();
        rng.GetBytes(randomBytes);
        return Convert.ToBase64String(randomBytes);
    }

    public static string HashToken(string token)
    {
        var bytes = SHA256.HashData(Encoding.UTF8.GetBytes(token));
        return Convert.ToBase64String(bytes);
    }
}