namespace BlueLaminate.Scraper.Proxies;

/// <summary>
/// <see cref="IProxyProvider"/> for IPRoyal's residential gateway. IPRoyal keeps
/// one fixed host/port (geo.iproyal.com:12321) and encodes everything else —
/// country, sticky-session id, session lifetime — as underscore-delimited
/// parameters appended to the account password. Example password:
/// "secret_country-us_session-ab12cd_lifetime-30m". The account username is sent
/// unchanged. Docs: https://docs.iproyal.com/proxies/residential/proxy
/// </summary>
public sealed class IpRoyalProxyProvider : IProxyProvider
{
    public const string GatewayHost = "geo.iproyal.com";
    public const int GatewayPort = 12321;

    // IPRoyal caps sticky sessions; 30 minutes is a safe default that comfortably
    // covers a single scrape pass without forcing an early IP rotation.
    private static readonly TimeSpan DefaultLifetime = TimeSpan.FromMinutes(30);

    private readonly string _username;
    private readonly string _password;

    public IpRoyalProxyProvider(string username, string password)
    {
        if (string.IsNullOrWhiteSpace(username))
        {
            throw new ArgumentException("IPRoyal username is required.", nameof(username));
        }

        if (string.IsNullOrWhiteSpace(password))
        {
            throw new ArgumentException("IPRoyal password is required.", nameof(password));
        }

        _username = username;
        _password = password;
    }

    public string Name => "iproyal";

    public ProxyLease Acquire(ProxyRequest request)
    {
        var password = _password;
        string? sessionId = null;
        DateTimeOffset? expiresAt = null;

        // Country first; the router picks one at random when several are listed.
        if (!string.IsNullOrWhiteSpace(request.Country))
        {
            password += $"_country-{request.Country.Trim().ToLowerInvariant()}";
        }

        if (request.Sticky)
        {
            sessionId = request.SessionId ?? NewSessionId();
            var lifetime = request.Lifetime ?? DefaultLifetime;
            // IPRoyal expresses lifetime as whole minutes (e.g. "_lifetime-30m").
            var minutes = Math.Max(1, (int)Math.Round(lifetime.TotalMinutes));
            password += $"_session-{sessionId}_lifetime-{minutes}m";
            expiresAt = DateTimeOffset.UtcNow.AddMinutes(minutes);
        }

        return new ProxyLease(
            Host: GatewayHost,
            Port: GatewayPort,
            Username: _username,
            Password: password,
            Provider: Name,
            SessionId: sessionId,
            ExpiresAt: expiresAt);
    }

    // Short, URL/param-safe token. IPRoyal treats the session value opaquely;
    // it only needs to be stable for the duration of a sticky lease.
    private static string NewSessionId() =>
        Guid.NewGuid().ToString("N")[..10];
}