using AcDream.Headless.Configuration;

namespace AcDream.Headless;

internal static class HeadlessEntryPoint
{
    private const string HelpText =
        """
        acdream-headless

        Usage:
          acdream-headless --help
          acdream-headless validate --config <path>

        Commands:
          validate   Validate a versioned headless configuration without connecting.

        Secrets are never accepted on the command line.
        """;

    internal static int Run(
        IReadOnlyList<string> arguments,
        TextWriter output,
        TextWriter error)
    {
        ArgumentNullException.ThrowIfNull(arguments);
        ArgumentNullException.ThrowIfNull(output);
        ArgumentNullException.ThrowIfNull(error);

        if (arguments.Count == 0
            || IsHelp(arguments[0]))
        {
            output.WriteLine(HelpText);
            return (int)HeadlessExitCode.Success;
        }

        if (!string.Equals(
                arguments[0],
                "validate",
                StringComparison.Ordinal))
        {
            error.WriteLine("Unknown command. Run --help for usage.");
            return (int)HeadlessExitCode.UsageError;
        }

        if (arguments.Count != 3
            || !string.Equals(
                arguments[1],
                "--config",
                StringComparison.Ordinal))
        {
            error.WriteLine(
                "validate requires exactly: --config <path>");
            return (int)HeadlessExitCode.UsageError;
        }

        try
        {
            HeadlessConfiguration configuration =
                HeadlessConfigurationLoader.Load(arguments[2]);
            output.WriteLine(
                $"Configuration valid: version {configuration.Version}, "
                + $"{configuration.Sessions.Count} session(s).");
            return (int)HeadlessExitCode.Success;
        }
        catch (Exception exception)
            when (exception is IOException
                or UnauthorizedAccessException
                or ArgumentException
                or NotSupportedException
                or System.Text.Json.JsonException
                or HeadlessConfigurationException)
        {
            error.WriteLine($"Configuration invalid: {exception.Message}");
            return (int)HeadlessExitCode.ConfigurationError;
        }
    }

    private static bool IsHelp(string argument) =>
        string.Equals(argument, "--help", StringComparison.Ordinal)
        || string.Equals(argument, "-h", StringComparison.Ordinal);
}