using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Text.RegularExpressions;
using Dinah.Core;
using System.Threading.Tasks;
using System.Threading;
using FileManager;

namespace LibationFileManager
{
    public abstract class AudibleFileStorage
    {
        protected abstract LongPath GetFilePathCustom(string productId);
        protected abstract List<LongPath> GetFilePathsCustom(string productId);

        #region static
        public static LongPath DownloadsInProgressDirectory => Directory.CreateDirectory(Path.Combine(Configuration.Instance.InProgress, "DownloadsInProgress")).FullName;
        public static LongPath DecryptInProgressDirectory => Directory.CreateDirectory(Path.Combine(Configuration.Instance.InProgress, "DecryptInProgress")).FullName;

        static AudibleFileStorage()
		{
			//Clean up any partially-decrypted files from previous Libation instances.
			//Do no clean DownloadsInProgressDirectory because those files are resumable
			foreach (var tempFile in Directory.EnumerateFiles(DecryptInProgressDirectory))
				FileUtility.SaferDelete(tempFile);
		}


		private static AaxcFileStorage AAXC { get; } = new AaxcFileStorage();
        public static bool AaxcExists(string productId) => AAXC.Exists(productId);

        public static AudioFileStorage Audio { get; } = new AudioFileStorage();

        public static LongPath BooksDirectory
        {
            get
            {
                if (string.IsNullOrWhiteSpace(Configuration.Instance.Books))
                    Configuration.Instance.Books = Path.Combine(Configuration.UserProfile, "Books");
                return Directory.CreateDirectory(Configuration.Instance.Books).FullName;
            }
        }
        #endregion

        #region instance
        private FileType FileType { get; }
        private string regexTemplate { get; }

        protected AudibleFileStorage(FileType fileType)
        {
            FileType = fileType;

            var extAggr = FileTypes.GetExtensions(FileType).Aggregate((a, b) => $"{a}|{b}");
            regexTemplate = $@"{{0}}.*?\.({extAggr})$";
        }

        protected LongPath GetFilePath(string productId)
        {
            // primary lookup
            var cachedFile = FilePathCache.GetFirstPath(productId, FileType);
            if (cachedFile is not null && File.Exists(cachedFile))
                return cachedFile;

            // secondary lookup attempt
            var firstOrNull = GetFilePathCustom(productId);
            if (firstOrNull is not null)
                FilePathCache.Insert(productId, firstOrNull);

            return firstOrNull;
        }

        public List<LongPath> GetPaths(string productId)
            => GetFilePathsCustom(productId);

        protected Regex GetBookSearchRegex(string productId)
        {
            var pattern = string.Format(regexTemplate, productId);
            return new Regex(pattern, RegexOptions.IgnoreCase);
        }
        #endregion
    }

    internal class AaxcFileStorage : AudibleFileStorage
    {
        internal AaxcFileStorage() : base(FileType.AAXC) { }

        protected override LongPath GetFilePathCustom(string productId)
            => GetFilePathsCustom(productId).FirstOrDefault();

        protected override List<LongPath> GetFilePathsCustom(string productId)
        {
            var regex = GetBookSearchRegex(productId);
            return FileUtility
                .SaferEnumerateFiles(DownloadsInProgressDirectory, "*.*", SearchOption.AllDirectories)
                .Where(s => regex.IsMatch(s)).ToList();
        }

        public bool Exists(string productId) => GetFilePath(productId) is not null;
    }

    public class AudioFileStorage : AudibleFileStorage
    {
        internal AudioFileStorage() : base(FileType.Audio)
            => BookDirectoryFiles ??= new BackgroundFileSystem(BooksDirectory, "*.*", SearchOption.AllDirectories);

        private static BackgroundFileSystem BookDirectoryFiles { get; set; }
        private static object bookDirectoryFilesLocker { get; } = new();
		private static EnumerationOptions enumerationOptions { get; } = new()
		{
			RecurseSubdirectories = true,
			IgnoreInaccessible = true,
			MatchCasing = MatchCasing.CaseInsensitive
		};

		protected override LongPath GetFilePathCustom(string productId)
            => GetFilePathsCustom(productId).FirstOrDefault();

        protected override List<LongPath> GetFilePathsCustom(string productId)
        {
            // If user changed the BooksDirectory: reinitialize
            lock (bookDirectoryFilesLocker)
                if (BooksDirectory != BookDirectoryFiles.RootDirectory)
                    BookDirectoryFiles = new BackgroundFileSystem(BooksDirectory, "*.*", SearchOption.AllDirectories);

            var regex = GetBookSearchRegex(productId);
            return BookDirectoryFiles.FindFiles(regex);
        }

        public void Refresh() => BookDirectoryFiles.RefreshFiles();

        public LongPath GetPath(string productId) => GetFilePath(productId);

		public static async IAsyncEnumerable<FilePathCache.CacheEntry> FindAudiobooksAsync(LongPath searchDirectory, [EnumeratorCancellation] CancellationToken cancellationToken)
		{
			ArgumentValidator.EnsureNotNull(searchDirectory, nameof(searchDirectory));

			foreach (LongPath path in Directory.EnumerateFiles(searchDirectory, "*.M4B", enumerationOptions))
			{
				if (cancellationToken.IsCancellationRequested)
					yield break;

				int generation = 0;
				FilePathCache.CacheEntry audioFile = default;

				try
				{
					using var fileStream = File.OpenRead(path);

					var mp4File = await Task.Run(() => new AAXClean.Mp4File(fileStream), cancellationToken);

					generation = GC.GetGeneration(mp4File);

					if (mp4File?.AppleTags?.Asin is not null)
						audioFile = new FilePathCache.CacheEntry(mp4File.AppleTags.Asin, FileType.Audio, path);

				}
				catch (Exception ex)
				{
					Serilog.Log.Error(ex, "Error checking for asin in {@file}", path);
				}
				finally
				{
					GC.Collect(generation);
				}

				if (audioFile is not null)
					yield return audioFile;
			}
		}
	}
}