using System.Globalization;

namespace FakeGameServer;

internal enum FakeMode
{
    Normal,
    NoReady,
    FailOnStart,
    CrashAfterReady,
    IgnoreStop,
    IgnoreAll,
}

internal sealed record FakeSettings(
    FakeMode Mode,
    int StartupMs,
    int StopMs,
    int CrashAfterMs,
    int CrashExitCode,
    bool StdinEofStopsServer)
{
    public static FakeSettings FromEnvironment()
    {
        var mode = Enum.TryParse<FakeMode>(Env("FAKE_MODE"), true, out var parsed) ? parsed : FakeMode.Normal;
        return new FakeSettings(
            mode,
            EnvInt("FAKE_STARTUP_MS", 500),
            EnvInt("FAKE_STOP_MS", 200),
            EnvInt("FAKE_CRASH_AFTER_MS", 300),
            EnvInt("FAKE_CRASH_EXIT_CODE", 0),
            string.Equals(Env("FAKE_STDIN_EOF"), "stop", StringComparison.OrdinalIgnoreCase));
    }

    private static string? Env(string name) => Environment.GetEnvironmentVariable(name);

    private static int EnvInt(string name, int fallback) =>
        int.TryParse(Env(name), NumberStyles.Integer, CultureInfo.InvariantCulture, out var value)
            ? value
            : fallback;
}

internal sealed record CommandLine(string? DataPath, int? Port, string? SetConfig)
{
    // Flags that take a value. Like the real game, the next token is taken as the value
    // when there is no "=", even if that token is another flag.
    private static readonly HashSet<string> ValueOptions = new(StringComparer.OrdinalIgnoreCase)
    {
        "dataPath", "port", "setconfig", "withconfig", "logPath", "ip", "maxclients",
    };

    public static CommandLine Parse(string[] args)
    {
        var values = new Dictionary<string, string?>(StringComparer.OrdinalIgnoreCase);
        for (var i = 0; i < args.Length; i++)
        {
            var arg = args[i];
            if (!arg.StartsWith("--", StringComparison.Ordinal))
            {
                continue;
            }

            var body = arg[2..];
            var eq = body.IndexOf('=', StringComparison.Ordinal);
            if (eq >= 0)
            {
                values[body[..eq]] = body[(eq + 1)..];
            }
            else if (ValueOptions.Contains(body) && i + 1 < args.Length)
            {
                values[body] = args[++i];
            }
            else
            {
                values[body] = null;
            }
        }

        values.TryGetValue("dataPath", out var dataPath);
        values.TryGetValue("setconfig", out var setConfig);
        values.TryGetValue("port", out var portText);
        int? port = int.TryParse(portText, NumberStyles.None, CultureInfo.InvariantCulture, out var n) ? n : null;
        return new CommandLine(dataPath, port, setConfig);
    }
}