using CommandLine;

using MultiversalDiplomacy.Script;

namespace MultiversalDiplomacy;

internal class Program
{
    static void Main(string[] args)
    {
        var parser = Parser.Default;
        var parseResult = parser.ParseArguments(args, typeof(ReplOptions));

        parseResult
            .WithParsed<ReplOptions>(ExecuteRepl);
    }

    static void ExecuteRepl(ReplOptions args)
    {
        // Create a writer to the output file, if specified.
        StreamWriter? outputWriter = null;
        if (args.OutputFile is not null)
        {
            string fullPath = Path.GetFullPath(args.OutputFile);
            string outputPath = Directory.Exists(fullPath)
                ? Path.Combine(fullPath, $"{DateTime.UtcNow.ToString("yyyyMMddHHmmss")}.log")
                : fullPath;
            Console.WriteLine($"Echoing to {outputPath}");
            outputWriter = File.AppendText(outputPath);
        }

        // Define an enumerator for live repl commands.
        static IEnumerable<string?> GetReplInputs()
        {
            // Read user input until it stops (i.e. is null).
            string? input = null;
            do
            {
                input = Console.ReadLine();
                yield return input;
            }
            while (input is not null);
            // The last null is returned because an EOF means we should quit the repl.
        }

        // Define an enumerator for input file commands, if specified.
        static IEnumerable<string?> GetFileInputs(string inputFile)
        {
            // Read all lines from the input file.
            var fullPath = Path.GetFullPath(inputFile);
            var fileName = Path.GetFileName(fullPath);
            foreach (string line in File.ReadLines(fullPath))
            {
                var trimmed = line.Trim();
                Console.WriteLine($"{fileName}> {trimmed.TrimEnd()}");
                yield return trimmed;
            }
            // Don't return a null, since this will be followed by GetReplInputs.
        }

        // Set up the input enumerator.
        IEnumerable<string?> inputs;
        if (args.InputFile is not null)
        {
            Console.WriteLine($"Reading from {args.InputFile}");
            inputs = GetFileInputs(args.InputFile).Concat(GetReplInputs());
        }
        else
        {
            inputs = GetReplInputs();
        }

        IScriptHandler? handler = new ReplScriptHandler();

        Console.Write(handler.Prompt);
        foreach (string? nextInput in inputs)
        {
            // Handle quitting directly.
            if (nextInput is null || nextInput == "quit" || nextInput == "exit")
            {
                break;
            }
            string input = nextInput.Trim();
            outputWriter?.WriteLine(input);
            outputWriter?.Flush();

            // Delegate all other command parsing to the handler.
            handler = handler.HandleInput(input);

            // Quit if the handler ends processing, otherwise prompt for the next command.
            if (handler is null)
            {
                break;
            }
            Console.Write(handler.Prompt);
        }

        Console.WriteLine("exiting");
    }
}