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;
	}


}