feat: add library scanning mechanic

Tools/GeneralUseHelperFunctions.cs

@@ -5,10 +5,10 @@ using System.Text;
 
 namespace Shadow.Tools;
 
-public class GeneralUseHelpers(ApplicationDbContext db, IConfiguration appsettings)
+public class GeneralUseHelpers(ApplicationDbContext? db = null, IConfiguration? appsettings = null)
 {
-	private readonly ApplicationDbContext _db = db;
-	private readonly IConfiguration _appsettings = appsettings;
+	private readonly ApplicationDbContext? _db = db;
+	private readonly IConfiguration? _appsettings = appsettings;
 
 
 	//async public Task<User?> GetUserFromEmail(string email)
@@ -27,4 +27,23 @@ public class GeneralUseHelpers(ApplicationDbContext db, IConfiguration appsettin
 	//	}
 	//}
 
+	/// <summary>
+	/// Quick and dirty Dictionary&lt;string, string&gt; to JSON serializer
+	/// </summary>
+	/// <param name="dict">Dictionary with keypair of two strings</param>
+	/// <returns>Minified JSON</returns>
+	public static string DictAsJson(Dictionary<string, string> dict)
+	{
+		string resultJson = String.Empty;
+
+		foreach (string key in dict.Keys)
+		{
+			string cleanKey   = key.Replace("\"", "\\\"");       // "a"b" -> "a\"b"
+			string cleanValue = dict[key].Replace("\"", "\\\"");
+			resultJson += $"\"{cleanKey}\": \"{cleanValue}\", "  // "key": "val",<space>
+				.Replace(@"\", @"\\");                           // a\b -> a\\b
+		}
+
+		return "{" + resultJson[..^2] + "}";
+	}
 }

Tools/LibraryWatcher.cs

@@ -0,0 +1,91 @@
+using Shadow.Data;
+using Shadow.Entities;
+using System;
+using System.IO;
+
+namespace Shadow.Tools;
+public class LibraryWatcher(string watchPath, string[] excludedPaths, ApplicationDbContext dbContext)
+{
+	private readonly string libraryPath = watchPath;
+	private readonly string[] excludedPaths = excludedPaths;
+	private readonly ApplicationDbContext db = dbContext;
+	private readonly GeneralUseHelpers guhf = new();
+
+	/// <summary>
+	/// Returns a sorted list of paths to all files in a directory, recursively.
+	/// </summary>
+	/// <param name="directory">Path to directory</param>
+	/// <returns>Sorted list of filepaths</returns>
+	public async Task<List<string>> GetFilesRecursivelyAsync(string directory)
+	{
+		string[] allowedExtensions = [".flac", ".m4a", ".mp3", ".ogg", ".wav"];
+		try
+		{
+			List<string> files =
+				Directory.GetFiles(directory, "*", SearchOption.AllDirectories)
+				.Where(file => allowedExtensions.Any(file.ToLower().EndsWith))
+				.ToList();
+
+			files.Sort();
+			return files;
+		}
+		catch (DirectoryNotFoundException)
+		{
+			Console.WriteLine($"[Error] Directory \"{directory}\" does not exist!\n" +
+				"        Please create it manually, or use `Shadow setupWizard`.");
+			throw new DirectoryNotFoundException();
+		}
+
+	}
+
+	/// <summary>
+	/// Return all multimedia content inside of library
+	/// </summary>
+	/// <returns>List of multimedia filepaths</returns>
+	public async Task<List<string>> GetAllMultimediaAsync()
+	{
+
+		// List files in cache
+		// Note: currently, the only excluded path from scanning is the thumbnail cache.
+		// This might change in the future.
+		List<string> cacheFiles = await GetFilesRecursivelyAsync(excludedPaths[0]);
+
+		// List files in library excluding cache
+		List<string> libraryContent = await GetFilesRecursivelyAsync(libraryPath);
+		List<string> libraryMultimedia = libraryContent.Except(cacheFiles).ToList();
+
+		return libraryMultimedia;
+	}
+
+	/// <summary>
+	/// Scan the library in its entirety
+	/// </summary>
+	/// <returns></returns>
+	public async Task<List<string>> PerformFullScanAsync()
+	{
+		Console.WriteLine("Performing full library scan...");
+
+		List<string> multimedia = await GetAllMultimediaAsync();
+		foreach (string filepath in multimedia)
+		{
+			Console.WriteLine(filepath);
+			Dictionary<string, string> fileInfo = await MetadataExtractor.ExtractAsync(filepath);
+
+			// Pretend we are doing parsing here...
+			Console.WriteLine(GeneralUseHelpers.DictAsJson(fileInfo));
+			MediaParser.CreateSong(db, fileInfo);
+		}
+
+		Console.WriteLine($"Full scan complete! Processed {multimedia.Count} files.");
+
+		// Update state inside of DB
+		string currentLibraryState = MetadataExtractor.GetStringMD5(string.Join("\n", multimedia));
+		Global lastLibraryState = db.Globals.FirstOrDefault(g => g.Key == "libraryState")
+			?? new() { Key = "libraryState"};
+		lastLibraryState.Value = currentLibraryState;
+		db.Update(lastLibraryState);
+		await db.SaveChangesAsync();
+
+		return multimedia;
+	}
+}

Tools/MediaParser.cs

@@ -0,0 +1,126 @@
+using Microsoft.VisualBasic.FileIO;
+using Shadow.Data;
+using Shadow.Entities;
+using System.Security.Cryptography;
+
+namespace Shadow.Tools;
+
+public static class MediaParser
+{
+	/// <summary>
+	/// Generate a random hex string (with length 32 by default)
+	/// </summary>
+	/// <param name="length">Optional: hexstring length</param>
+	/// <returns>A hexstring of given length</returns>
+	public static string HexStr(int length = 32)
+	{
+		return RandomNumberGenerator.GetHexString(length).ToLower();
+	}
+
+	/// <summary>
+	/// Get metadata content opportunistically
+	/// </summary>
+	/// <param name="metadata">Dictionary to search in</param>
+	/// <param name="searchStrings">Keywords to search for</param>
+	/// <returns>Retrieved value (string) on success, otherwise null</returns>
+	public static string? GetAny(Dictionary<string, string> metadata, List<string> searchStrings)
+	{
+		foreach (string searchString in searchStrings)
+		{
+			if (metadata.TryGetValue(searchString, out string? value) && !string.IsNullOrEmpty(value))
+				return value;
+		}
+		return null;
+	}
+
+	/// <summary>
+	/// Map exiftool metadata to Song entity.
+	/// </summary>
+	/// <param name="db">Database context</param>
+	/// <param name="exif">ExifTool metadata</param>
+	/// <returns>New Song entity, or null if song already exists in db</returns>
+	public static Song? CreateSong(ApplicationDbContext db, Dictionary<string, string> exif)
+	{
+
+		// First of all, check if song already exists in db
+		string uri = GetAny(exif, ["_shadow:fileHash"])
+			?? throw new Exception("Fatal error: could not get file hash!");
+		if (db.Songs.FirstOrDefault(s => s.Uri == uri) != null) return null;
+
+		// If not, extract exif data
+		string title = GetAny(exif, [
+			"ItemList:Title",    // iTunes m4a
+			"ItemList:SortName", // iTunes m4a
+			"Vorbis:Title",      // Bandcamp ogg
+			"ID3v2_3:Title",     // Generic mp3/wav ID3 v2.3.0
+			])
+			?? Path.Combine(exif["System:Directory"], exif["System:FileName"]);
+		string filepath = Path.GetFullPath(
+			Path.Combine(exif["System:Directory"], exif["System:FileName"])
+			); // TODO: bulletproof this
+		string filetype = exif["File:FileType"].ToLower();
+
+		// Album/artist related
+		string artistName = GetAny(exif, [
+			"ItemList:Artist",        // iTunes m4a
+			"ItemList:AlbumArtist",   // iTunes m4a
+			"Vorbis:Artist",          // Bandcamp m4a
+			"Vorbis:Albumartist",     // Bandcamp m4a
+			"ID3v2_3:Artist",         // Generic mp3/wav ID3 v2.3.0
+			]) ?? "[Unknown Artist]"; // this is a weak line of defense against deliberately crafted 
+
+		string albumName = GetAny(exif, [
+			"ItemList:Album",        // iTunes m4a
+			"Vorbis:Album",          // Bandcamp m4a
+			"ID3v2_3:Album",         // Generic mp3/wav ID3 v2.3.0
+			]) ?? "[Unknown Album]"; // again, weak line of defense
+
+		// Try to find relevant artists and albums
+		Artist artist = db.Artists
+			.FirstOrDefault(a => a.NormalizedName == artistName.ToLower())
+			?? new Artist
+			{
+				Name = artistName,
+				NormalizedName = artistName.ToLower()
+			};
+
+		Album album = db.Albums
+			.FirstOrDefault(a => a.Name == albumName && a.Artist == artist)
+			?? new Album
+			{
+				Name = albumName,
+				Uri = HexStr(),
+				Artist = artist
+			};
+
+		Song song = new()
+		{
+			Title = title,
+			Uri = uri,
+			Filepath = filepath,
+			Filetype = filetype,
+			Album = album,
+			Artist = artist
+		};
+
+		try
+		{
+			// Is Update() safe here?
+			db.Artists.Update(artist);
+			db.Albums.Update(album);
+			db.Songs.Update(song);
+			artist.Albums.Add(album);
+			artist.Songs.Add(song);
+			db.SaveChanges();
+		}
+		catch (Exception e)
+		{
+			Console.WriteLine("[Error: MediaParser] Failed to extract metadata from {filepath}:\n" +
+				$"{e}");
+		}
+
+		return song;
+	}
+
+
+}

Tools/MetadataExtractor.cs

@@ -0,0 +1,67 @@
+using SharpExifTool;
+using System.Security.Cryptography;
+namespace Shadow.Tools;
+
+public static class MetadataExtractor
+{
+	private readonly static ExifTool exifTool = new();
+	private readonly static GeneralUseHelpers guhf = new();
+	public async static Task<Dictionary<string, string>> ExtractAsync(string fullPath)
+	{
+		// Get all relevant metadata
+		Dictionary<string, string> fileMetadata = new(await
+			exifTool.ExtractAllMetadataAsync(fullPath));
+
+		// Add in a MD5 hint
+		string md5sum = await GetFileMD5Async(fullPath);
+		fileMetadata?.Add("_shadow:fileHash", md5sum);
+
+		return fileMetadata ?? [];
+	}
+
+	/// <summary>
+	/// Compute MD5 checksum of a file
+	/// </summary>
+	/// <param name="fullPath">Input file absolute path</param>
+	/// <returns>MD5 hexstring</returns>
+	public static async Task<string> GetFileMD5Async(string fullPath)
+	{
+		string fallbackValue = String.Empty;
+		
+		try
+		{
+			if (File.Exists(fullPath))
+				using (MD5 md5 = MD5.Create())
+				{
+					using (FileStream stream = File.OpenRead(fullPath))
+					{
+						byte[] hashBytes = await md5.ComputeHashAsync(stream);
+						string hashString = Convert.ToHexStringLower(hashBytes);
+						return hashString;
+					}
+				}
+			else return fallbackValue;
+		}
+		catch
+		{
+			return fallbackValue;
+		}
+	}
+
+	/// <summary>
+	/// Compute MD5 checksum of a string
+	/// </summary>
+	/// <param name="input">Input string for the MD5 hash</param>
+	/// <returns>MD5 hexstring</returns>
+	public static string GetStringMD5(string input)
+	{
+		// https://stackoverflow.com/a/24031467
+		byte[] inputBytes = System.Text.Encoding.ASCII.GetBytes(input);
+		byte[] hashBytes = MD5.HashData(inputBytes);
+		string hashString = Convert.ToHexStringLower(hashBytes);
+
+		return hashString;
+	}
+
+
+}

Tools/Seeder.cs

@@ -177,4 +177,41 @@ public class Seeder
 		return migrationSuccess;
 	}
 
+	/// <summary>
+	/// Check if the library needs a full rescan
+	/// </summary>
+	/// <returns>True if full rescan is needed</returns>
+	/// <exception cref="MissingFieldException">Thrown when either last library state, path to music library or cache is unknown</exception>
+	public async Task<bool> ScanPrefetchAsync()
+	{
+		bool scanNecessary = false;
+		Global? lastLibraryState = await db.Globals.FirstOrDefaultAsync(g => g.Key ==       "libraryState");
+		Global?      libraryPath = await db.Globals.FirstOrDefaultAsync(g => g.Key ==   "musicLibraryPath");
+		Global?        cachePath = await db.Globals.FirstOrDefaultAsync(g => g.Key == "musicThumbnailPath");
+
+		if (libraryPath is null || cachePath is null || lastLibraryState is null)
+		{
+			throw new MissingFieldException("[Error] Missing libraryState, musicLibraryPath, musicThumbnailPath. Please rerun the setup wizard with `Shadow setupWizard`.");
+		}
+		LibraryWatcher lw = new(libraryPath.Value!, [cachePath.Value!], db);
+
+		// Get library contents
+		List<string> currentLibraryStateList = await lw.GetAllMultimediaAsync();
+		// Compute their hash
+		string currentLibraryStateString = string.Join("\n", currentLibraryStateList);
+		string currentLibraryState = MetadataExtractor.GetStringMD5(currentLibraryStateString);
+
+		// Compare against last known library state
+		if (currentLibraryState != lastLibraryState.Value)
+			scanNecessary = true;
+
+		// The contents changed? Initiate a full rescan, then call LibraryWatcher.
+		if (scanNecessary)
+			await lw.PerformFullScanAsync();
+		// State seems identical? Launch just the LibraryWatcher.
+		// TODO: lw.Watch()...
+
+		return scanNecessary;
+
+	}
 }