Masuit.Tools/Masuit.Tools.Abstractions/Files/FileDetector/FileSignatureDetector.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Reflection;
using Masuit.Tools.Reflection;
using Masuit.Tools.Systems;

namespace Masuit.Tools.Files.FileDetector;

public static class FileSignatureDetector
{
	private static List<IDetector> Detectors { get; set; } = [];

	public static IReadOnlyList<IDetector> Registered => Detectors;

	public static void AddDetector<T>() where T : IDetector
	{
		var instance = Activator.CreateInstance<T>();
		AddDetector(instance);
	}

	public static void AddDetector(IDetector instance)
	{
		if (!Detectors.Contains(instance))
		{
			Detectors.Add(instance);
		}
	}

	static FileSignatureDetector()
	{
		var type = typeof(IDetector);
		foreach (var item in AppDomain.CurrentDomain.GetAssemblies().Where(a => !a.FullName.StartsWith(["System", "Microsoft"])).SelectMany(a => a.GetLoadableExportedTypes()))
		{
			if (type.IsAssignableFrom(item) && !item.IsAbstract && !item.IsInterface && item.GetTypeInfo().DeclaredConstructors.First().GetParameters().Length == 0)
			{
				AddDetector(Activator.CreateInstance(item) as IDetector);
			}
		}
	}

	public static IDetector DetectFiletype(string filepath)
	{
		using var stream = File.OpenRead(filepath);
		return DetectFiletype(stream);
	}

	public static IDetector DetectFiletype(this FileInfo file)
	{
		using var stream = file.OpenRead();
		return DetectFiletype(stream);
	}

	public static IDetector DetectFiletype(this Stream stream)
	{
		if (stream.CanSeek)
		{
			string pre = null;
			IDetector foundDetector = new NoneDetector();
			while (true)
			{
				bool found = false;
				foreach (var detector in Detectors.Where(d => d.Precondition == pre))
				{
					stream.Position = 0;
					if (detector.Detect(stream))
					{
						found = true;
						foundDetector = detector;
						pre = detector.Extension;
						break;
					}
				}
				if (!found)
				{
					break;
				}
			}

			stream.Position = 0;
			return foundDetector;
		}

		using var ms = new PooledMemoryStream();
		stream.CopyTo(ms);
		return DetectFiletype(ms);
	}
}