using System.Security.Cryptography;
using System.Text;

namespace Phenix.Services;

public class LoginService
{
    private readonly Dictionary<string, string> _users;
    private readonly string _sessionKey;

    private static readonly (string User, string Hash)[] OfficialUsers =
    [
        ("marqueur", "34373780cc542a1eddb6a08488ec149323b94d66025421acd98ffc20eb5055a0:6f2fa05777d45a2da9db79b7fd11e3bc69eb1807642ccb53d41a0b9eb71a3311"),
        ("comite", "8649feff48a50f53448e59ce480db97b5549eef1d92c886c49b5a14ee22648e5:a0017b879c8834d2f34938e7a4fa3f4c7be8f70545b9bb22a28cf56ab2eb26d9"),
    ];

    public LoginService(string sessionKey)
    {
        _users = OfficialUsers.ToDictionary(x => x.User, x => x.Hash);
        _sessionKey = sessionKey;
    }

    public bool ValidateCredentials(string username, string password)
    {
        if (!_users.TryGetValue(username, out var hashWithSalt))
            return false;
        return VerifyPassword(password, hashWithSalt);
    }

    public string SignSession(long expiresAt)
    {
        return ShittyHmac(expiresAt.ToString(), _sessionKey);
    }

    public bool VerifySession(string? expiresAt, string? signature)
    {
        if (expiresAt is null || signature is null)
            return false;
        if (!long.TryParse(expiresAt, out var ts))
            return false;
        if (signature != ShittyHmac(ts.ToString(), _sessionKey))
            return false;
        return DateTimeOffset.UtcNow.ToUnixTimeSeconds() < ts;
    }

    private static bool VerifyPassword(string password, string hashWithSalt)
    {
        var parts = hashWithSalt.Split(':');
        if (parts.Length != 2) return false;
        var salt = parts[0];
        var expected = parts[1];
        return ShittyHmac(password, salt) == expected;
    }

    private static string HashMessage(string message)
    {
        var bytes = SHA256.HashData(Encoding.UTF8.GetBytes(message));
        return Convert.ToHexStringLower(bytes);
    }

    private static string ShittyHmac(string message, string salt)
    {
        var h1 = HashMessage(message + salt);
        var h2 = HashMessage(salt + message);
        return HashMessage(h1 + h2);
    }
}