using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;

namespace Chessistics.Scripts.Automation;

/// <summary>
/// Tiny helpers for the file-based IPC. All writes are atomic: write .tmp then rename.
/// </summary>
internal static class IpcFiles
{
    public const string InboxDir = "inbox";
    public const string OutboxDir = "outbox";
    public const string ScreensDir = "screens";
    public const string ReadyFile = "ready.json";
    public const string LogFile = "harness.log";

    public static void EnsureDirs(string root)
    {
        Directory.CreateDirectory(root);
        Directory.CreateDirectory(Path.Combine(root, InboxDir));
        Directory.CreateDirectory(Path.Combine(root, OutboxDir));
        Directory.CreateDirectory(Path.Combine(root, ScreensDir));
    }

    public static void AtomicWrite(string path, string contents)
    {
        var tmp = path + ".tmp";
        File.WriteAllText(tmp, contents);
        if (File.Exists(path)) File.Delete(path);
        File.Move(tmp, path);
    }

    /// <summary>
    /// Return the oldest inbox file whose id hasn't been processed yet, or null.
    /// Sorted by filename — agents should name files with a monotonic prefix for ordering.
    /// </summary>
    public static string? NextInbox(string root, HashSet<string> processed)
    {
        var inbox = Path.Combine(root, InboxDir);
        if (!Directory.Exists(inbox)) return null;

        var files = Directory.GetFiles(inbox, "*.json")
            .Where(f => !f.EndsWith(".tmp.json", StringComparison.Ordinal))
            .OrderBy(f => Path.GetFileName(f), StringComparer.Ordinal)
            .ToList();

        foreach (var f in files)
        {
            if (!processed.Contains(f))
                return f;
        }
        return null;
    }

    public static string OutboxPath(string root, string id) => Path.Combine(root, OutboxDir, id + ".json");

    public static string ScreenshotPath(string root, string name)
    {
        var safe = name.Replace('/', '_').Replace('\\', '_').Replace(':', '_');
        if (!safe.EndsWith(".png", StringComparison.OrdinalIgnoreCase)) safe += ".png";
        return Path.Combine(root, ScreensDir, safe);
    }
}