pkNX/pkNX.Containers/FileMitm.cs

using System;
using System.IO;

namespace pkNX.Containers;

/// <summary>
/// Man in the middle redirection of file r/w requests
/// </summary>
public static class FileMitm
{
    public static bool Enabled { get; private set; }

    public static void EnableIfSetup() => Enabled = PathOriginal != null;
    public static void Disable() => Enabled = false;

    private static string? PathOriginal;
    private static string? PathRedirect;

    public static byte[] ReadAllBytes(string path)
    {
        path = GetRedirectedReadPath(path);
        return File.ReadAllBytes(path);
    }

    public static void WriteAllBytes(string path, ReadOnlySpan<byte> data)
    {
        if (string.IsNullOrWhiteSpace(path))
            throw new FileNotFoundException("Invalid filename.");
        path = GetRedirectedWritePath(path);
        File.WriteAllBytes(path, data);
    }

    public static string GetRedirectedReadPath(string path)
    {
        if (!Enabled)
            return path;
        if (PathOriginal is null)
            throw new ArgumentException("No original path specified.");
        var newDest = path.Replace(PathOriginal, PathRedirect);
        if (!File.Exists(newDest))
            return path;
        return newDest;
    }

    public static string GetRedirectedWritePath(string path)
    {
        if (!Enabled)
            return path;
        if (PathOriginal is null)
            throw new ArgumentException("No original path specified.");
        var newDest = path.Replace(PathOriginal, PathRedirect);
        var parent = Path.GetDirectoryName(newDest) ?? throw new ArgumentException("Invalid path specified.");
        Directory.CreateDirectory(parent);
        return newDest;
    }

    public static void SetRedirect(string original, string dest)
    {
        PathOriginal = original;
        PathRedirect = dest;
        Enabled = true;
    }
}