using System.Text.Json;
using ProjectQuint.Probes;

var json = new JsonSerializerOptions { WriteIndented = true, PropertyNamingPolicy = JsonNamingPolicy.CamelCase };
try
{
    var action = args.Length == 0 ? "list" : args[0];
    var options = new Dictionary<string, int>(StringComparer.Ordinal);
    string? output = null;
    for (var index = 1; index < args.Length; index += 2)
    {
        if (index + 1 >= args.Length)
            throw new ArgumentException("Every option requires a value.");
        if (args[index] == "--output" && output == null)
            output = args[index + 1];
        else if (args[index] is "--notes" or "--seed" or "--fps" or "--iterations" &&
                 int.TryParse(args[index + 1], out var value) && options.TryAdd(args[index], value))
            continue;
        else
            throw new ArgumentException("Unknown, duplicated or invalid option.");
    }
    var notes = options.GetValueOrDefault("--notes", 10_000);
    var seed = options.GetValueOrDefault("--seed", 42);
    var fps = options.GetValueOrDefault("--fps", 240);
    var iterations = options.GetValueOrDefault("--iterations", 20);
    if (seed < 0)
        throw new ArgumentException("Seed must be nonnegative.");
    object report;
    switch (action)
    {
        case "list":
            if (options.Count != 0 || output != null)
                throw new ArgumentException("The list command accepts no options.");
            report = new
            {
                schemaVersion = 1,
                component = "headless-core",
                commands = new[] { "list", "replay", "benchmark", "test (wrapper)" },
                input = "seeded synthetic four-lane notes; no music or external library",
                options = new[] { "--notes", "--seed", "--fps", "--iterations (benchmark)", "--output" },
            };
            break;
        case "replay":
            if (options.ContainsKey("--iterations"))
                throw new ArgumentException("Iterations applies only to benchmarks.");
            var workload = SyntheticWorkload.Create(notes, (uint)seed);
            report = new
            {
                schemaVersion = 1, complete = true, notes, seed, frameRate = fps,
                eventCount = workload.Events.Length,
                result = ReplayRunner.Run(workload, fps),
            };
            break;
        case "benchmark":
            report = CoreBenchmark.Run(notes, (uint)seed, fps, iterations, checkpoint =>
            {
                Console.Error.WriteLine($"benchmark {checkpoint.Samples.Length}/{iterations}");
                if (output != null)
                    Save(output, checkpoint);
            });
            break;
        default:
            throw new ArgumentException("Unknown command. Use list, replay, benchmark or test.");
    }
    if (output != null)
        Save(output, report);
    Console.WriteLine(JsonSerializer.Serialize(report, json));
    return 0;
}
catch (Exception error)
{
    // Paths in I/O exceptions can identify the local machine; keep structured failures generic.
    Console.Error.WriteLine(JsonSerializer.Serialize(new
    {
        error = error.GetType().Name,
        detail = error is ArgumentException ? error.Message : "The probe failed; no complete result was produced.",
    }));
    return 1;
}

void Save(string path, object report)
{
    var destination = Path.GetFullPath(path);
    Directory.CreateDirectory(Path.GetDirectoryName(destination)!);
    var temporary = destination + ".tmp";
    File.WriteAllText(temporary, JsonSerializer.Serialize(report, json) + "\n");
    File.Move(temporary, destination, overwrite: true);
}