using LibVLCSharp.Shared.Helpers;
using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices;
using System.Threading;
using System.Threading.Tasks;

namespace LibVLCSharp.Shared
{
    /// <summary>
    /// Media is an abstract representation of a playable media. It can be a network stream or a local video/audio file.
    /// </summary>
    public class Media : Internal
    {
        static readonly ConcurrentDictionary<IntPtr, StreamData> DicStreams = new ConcurrentDictionary<IntPtr, StreamData>();
        static int _streamIndex;
        
        internal struct Native
        {
            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_new_location")]
            internal static extern IntPtr LibVLCMediaNewLocation(IntPtr libVLC, IntPtr mrl);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_new_path")]
            internal static extern IntPtr LibVLCMediaNewPath(IntPtr libVLC, IntPtr path);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_new_as_node")]
            internal static extern IntPtr LibVLCMediaNewAsNode(IntPtr libVLC, IntPtr name);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_new_fd")]
            internal static extern IntPtr LibVLCMediaNewFd(IntPtr libVLC, int fd);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_release")]
            internal static extern void LibVLCMediaRelease(IntPtr media);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_list_media")]
            internal static extern IntPtr LibVLCMediaListMedia(IntPtr mediaList);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_new_callbacks")]
            internal static extern IntPtr LibVLCMediaNewCallbacks(IntPtr libVLC, IntPtr openCb, IntPtr readCb, IntPtr seekCb, IntPtr closeCb, IntPtr opaque);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_add_option")]
            internal static extern void LibVLCMediaAddOption(IntPtr media, [MarshalAs(UnmanagedType.LPStr)] string options);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_add_option_flag")]
            internal static extern void LibVLCMediaAddOptionFlag(IntPtr media, [MarshalAs(UnmanagedType.LPStr)] string options, uint flags);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_get_mrl")]
            internal static extern IntPtr LibVLCMediaGetMrl(IntPtr media);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_duplicate")]
            internal static extern IntPtr LibVLCMediaDuplicate(IntPtr media);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_get_meta")]
            internal static extern IntPtr LibVLCMediaGetMeta(IntPtr media, MetadataType metadataType);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_set_meta")]
            internal static extern void LibVLCMediaSetMeta(IntPtr media, MetadataType metadataType, [MarshalAs(UnmanagedType.LPStr)] string value);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_save_meta")]
            internal static extern int LibVLCMediaSaveMeta(IntPtr media);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_get_state")]
            internal static extern VLCState LibVLCMediaGetState(IntPtr media);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_event_manager")]
            internal static extern IntPtr LibVLCMediaEventManager(IntPtr media);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_get_stats")]
            internal static extern int LibVLCMediaGetStats(IntPtr media, out MediaStats statistics);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_get_duration")]
            internal static extern long LibVLCMediaGetDuration(IntPtr media);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_is_parsed")]
            internal static extern int LibVLCMediaIsParsed(IntPtr media);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_parse_with_options")]
            internal static extern int LibVLCMediaParseWithOptions(IntPtr media, MediaParseOptions mediaParseOptions, int timeout);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_get_parsed_status")]
            internal static extern MediaParsedStatus LibVLCMediaGetParsedStatus(IntPtr media);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_parse_stop")]
            internal static extern void LibVLCMediaParseStop(IntPtr media);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_set_user_data")]
            internal static extern void LibVLCMediaSetUserData(IntPtr media, IntPtr userData);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_get_user_data")]
            internal static extern IntPtr LibVLCMediaGetUserData(IntPtr media);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_tracks_get")]
            internal static extern uint LibVLCMediaTracksGet(IntPtr media, out IntPtr tracksPtr);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_tracks_release")]
            internal static extern void LibVLCMediaTracksRelease(IntPtr tracks, uint count);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_subitems")]
            internal static extern IntPtr LibVLCMediaSubitems(IntPtr media);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_get_type")]
            internal static extern MediaType LibVLCMediaGetType(IntPtr media);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_slaves_add")]
            internal static extern int LibVLCMediaAddSlaves(IntPtr media, MediaSlaveType slaveType, uint priority, [MarshalAs(UnmanagedType.LPStr)] string uri);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_slaves_clear")]
            internal static extern void LibVLCMediaClearSlaves(IntPtr media);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_slaves_get")]
            internal static extern uint LibVLCMediaGetSlaves(IntPtr media, out IntPtr slaves);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_slaves_release")]
            internal static extern void LibVLCMediaReleaseSlaves(IntPtr slaves, uint count);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                EntryPoint = "libvlc_media_retain")]
            internal static extern void LibVLCMediaRetain(IntPtr media);

            [DllImport(Constants.LibraryName, CallingConvention = CallingConvention.Cdecl,
                            EntryPoint = "libvlc_media_get_codec_description")]
            internal static extern string LibvlcMediaGetCodecDescription(TrackType type, uint codec);
        }
        
        /// <summary>
        /// Media Constructs a libvlc Media instance
        /// </summary>
        /// <param name="libVLC">A libvlc instance</param>
        /// <param name="mrl">A path, location, or node name, depending on the 3rd parameter</param>
        /// <param name="type">The type of the 2nd argument.</param>
        public Media(LibVLC libVLC, string mrl, FromType type = FromType.FromPath)
            : base(() => SelectNativeCtor(libVLC, mrl, type), Native.LibVLCMediaRelease)
        {
        }

        static IntPtr SelectNativeCtor(LibVLC libVLC, string mrl, FromType type)
        {
            if (libVLC == null) throw new ArgumentNullException(nameof(libVLC));
            if (string.IsNullOrEmpty(mrl)) throw new ArgumentNullException(nameof(mrl));

            var mrlPtr = Utf8StringMarshaler.GetInstance().MarshalManagedToNative(mrl);
            if (mrlPtr == IntPtr.Zero)
                throw new ArgumentException($"error marshalling {mrl} to UTF-8 for native interop");

            switch (type)
            {
                case FromType.FromLocation:
                    return Native.LibVLCMediaNewLocation(libVLC.NativeReference, mrlPtr);
                case FromType.FromPath:
                    return Native.LibVLCMediaNewPath(libVLC.NativeReference, mrlPtr);
                case FromType.AsNode:
                    return Native.LibVLCMediaNewAsNode(libVLC.NativeReference, mrlPtr);
                default:
                    return IntPtr.Zero;
            }
        }

        /// <summary>
        /// Create a media for an already open file descriptor.
        /// The file descriptor shall be open for reading(or reading and writing).
        ///
        /// Regular file descriptors, pipe read descriptors and character device
        /// descriptors(including TTYs) are supported on all platforms.
        /// Block device descriptors are supported where available.
        /// Directory descriptors are supported on systems that provide fdopendir().
        /// Sockets are supported on all platforms where they are file descriptors,
        /// i.e.all except Windows.
        /// 
        /// \note This library will <b>not</b> automatically close the file descriptor
        /// under any circumstance.Nevertheless, a file descriptor can usually only be
        /// rendered once in a media player.To render it a second time, the file
        /// descriptor should probably be rewound to the beginning with lseek().
        /// </summary>
        /// <param name="libVLC">A libvlc instance</param>
        /// <param name="fd">open file descriptor</param>
        public Media(LibVLC libVLC, int fd)
            : base(() => Native.LibVLCMediaNewFd(libVLC.NativeReference, fd), Native.LibVLCMediaRelease)
        {
        }

        /// <summary>
        /// Create a media from a media list
        /// </summary>
        /// <param name="mediaList">media list to create media from</param>
        public Media(MediaList mediaList)
            : base(() => Native.LibVLCMediaListMedia(mediaList.NativeReference), Native.LibVLCMediaRelease)
        {
        }

        /// <summary>
        /// Create a media from a .NET Stream
        /// requires libvlc 3.0 or higher
        /// </summary>
        /// <param name="libVLC">the libvlc instance</param>
        /// <param name="stream">the .NET Stream to be used by libvlc. LibVLCSharp will NOT dispose or close it.</param>
        /// <param name="options">the libvlc options</param>
        public Media(LibVLC libVLC, Stream stream, params string[] options)
            : base(() => CtorFromCallbacks(libVLC, stream), Native.LibVLCMediaRelease)
        {
            if (options.Any())
                Native.LibVLCMediaAddOption(NativeReference, options.ToString());
        }

        

        static IntPtr CtorFromCallbacks(LibVLC libVLC, Stream stream)
        {
            if (libVLC == null) throw new ArgumentNullException(nameof(libVLC));
            if (stream == null) throw new ArgumentNullException(nameof(stream));

            var openMedia = new OpenMedia(CallbackOpenMedia);
            var readMedia = new ReadMedia(CallbackReadMedia);
            var seekMedia = new SeekMedia(CallbackSeekMedia);
            var closeMedia = new CloseMedia(CallbackCloseMedia);

            var opaque = AddStream(stream, openMedia, readMedia, seekMedia, closeMedia);

            if (opaque == IntPtr.Zero)
                throw new InvalidOperationException("Cannot create opaque parameter");

            return Native.LibVLCMediaNewCallbacks(libVLC.NativeReference,
                Marshal.GetFunctionPointerForDelegate(openMedia),
                Marshal.GetFunctionPointerForDelegate(readMedia),
                Marshal.GetFunctionPointerForDelegate(seekMedia),
                Marshal.GetFunctionPointerForDelegate(closeMedia),
                opaque);
        }

        internal Media(IntPtr mediaPtr)
            : base(() => mediaPtr, Native.LibVLCMediaRelease)
        {
        }

        /// <summary>Add an option to the media.</summary>
        /// <param name="options">the options (as a string)</param>
        /// <remarks>
        /// <para>This option will be used to determine how the media_player will</para>
        /// <para>read the media. This allows to use VLC's advanced</para>
        /// <para>reading/streaming options on a per-media basis.</para>
        /// <para>The options are listed in 'vlc --long-help' from the command line,</para>
        /// <para>e.g. &quot;-sout-all&quot;. Keep in mind that available options and their semantics</para>
        /// <para>vary across LibVLC versions and builds.</para>
        /// <para>Not all options affects libvlc_media_t objects:</para>
        /// <para>Specifically, due to architectural issues most audio and video options,</para>
        /// <para>such as text renderer options, have no effects on an individual media.</para>
        /// <para>These options must be set through libvlc_new() instead.</para>
        /// </remarks>
        public void AddOption(string options)
        {
            if(string.IsNullOrEmpty(options)) throw new ArgumentNullException(nameof(options));

            Native.LibVLCMediaAddOption(NativeReference, options);
        }

        /// <summary>
        /// Convenience method for crossplatform media configuration
        /// </summary>
        /// <param name="mediaConfiguration">mediaConfiguration translate to strings parsed by the vlc engine, some are platform specific</param>
        public void AddOption(MediaConfiguration mediaConfiguration)
        {
            if (mediaConfiguration == null) throw new ArgumentNullException(nameof(mediaConfiguration));

            AddOption(mediaConfiguration.Build());
        }

        /// <summary>Add an option to the media with configurable flags.</summary>
        /// <param name="options">the options (as a string)</param>
        /// <param name="flags">the flags for this option</param>
        /// <remarks>
        /// <para>This option will be used to determine how the media_player will</para>
        /// <para>read the media. This allows to use VLC's advanced</para>
        /// <para>reading/streaming options on a per-media basis.</para>
        /// <para>The options are detailed in vlc --long-help, for instance</para>
        /// <para>&quot;--sout-all&quot;. Note that all options are not usable on medias:</para>
        /// <para>specifically, due to architectural issues, video-related options</para>
        /// <para>such as text renderer options cannot be set on a single media. They</para>
        /// <para>must be set on the whole libvlc instance instead.</para>
        /// </remarks>
        public void AddOptionFlag(string options, uint flags)
        {
            if (string.IsNullOrEmpty(options)) throw new ArgumentNullException(nameof(options));

            Native.LibVLCMediaAddOptionFlag(NativeReference, options, flags);
        }

        string _mrl;
        /// <summary>Get the media resource locator (mrl) from a media descriptor object</summary>
        public string Mrl
        {
            get
            {
                if (string.IsNullOrEmpty(_mrl))
                {
                    var mrlPtr = Native.LibVLCMediaGetMrl(NativeReference);
                    _mrl = Utf8StringMarshaler.GetInstance().MarshalNativeToManaged(mrlPtr) as string;
                }
                return _mrl;
            }
        }

        /// <summary>Duplicate a media descriptor object.</summary>
        public Media Duplicate()
        {
            var duplicatePtr = Native.LibVLCMediaDuplicate(NativeReference);
            if(duplicatePtr == IntPtr.Zero) throw new Exception("Failure to duplicate");
            return new Media(duplicatePtr);
        }

        /// <summary>Read the meta of the media.</summary>
        /// <param name="metadataType">the meta to read</param>
        /// <returns>the media's meta</returns>
        /// <remarks>
        /// If the media has not yet been parsed this will return NULL.
        /// </remarks>
        public string Meta(MetadataType metadataType)
        {
            var metaPtr = Native.LibVLCMediaGetMeta(NativeReference, metadataType);
            if (metaPtr == IntPtr.Zero) return string.Empty;
            return Utf8StringMarshaler.GetInstance().MarshalNativeToManaged(metaPtr) as string;
        }

        /// <summary>
        /// <para>Set the meta of the media (this function will not save the meta, call</para>
        /// <para>libvlc_media_save_meta in order to save the meta)</para>
        /// </summary>
        /// <param name="metadataType">the <see cref="MetadataType"/>  to write</param>
        /// <param name="value">the media's meta</param>
        public void SetMeta(MetadataType metadataType, string value)
        {
            if(string.IsNullOrEmpty(value)) throw new ArgumentNullException(value);

            Native.LibVLCMediaSetMeta(NativeReference, metadataType, value);
        }

        /// <summary>Save the meta previously set</summary>
        /// <returns>true if the write operation was successful</returns>
        public bool SaveMeta() => Native.LibVLCMediaSaveMeta(NativeReference) != 0;

        /// <summary>
        /// Get current <see cref="VLCState"/> of media descriptor object.
        /// </summary>
        public VLCState State => Native.LibVLCMediaGetState(NativeReference);

        /// <summary>Get the current statistics about the media
        /// structure that contain the statistics about the media
        /// </summary>
        public MediaStats Statistics => Native.LibVLCMediaGetStats(NativeReference, out var mediaStats) == 0 
            ? default(MediaStats) : mediaStats;

        MediaEventManager _eventManager;
        /// <summary>
        /// <para>Get event manager from media descriptor object.</para>
        /// <para>NOTE: this function doesn't increment reference counting.</para>
        /// </summary>
        /// <returns>event manager object</returns>
        MediaEventManager EventManager
        {
            get
            {
                if (_eventManager != null) return _eventManager;
                var eventManagerPtr = Native.LibVLCMediaEventManager(NativeReference);
                _eventManager = new MediaEventManager(eventManagerPtr);
                return _eventManager;
            }
        }

        /// <summary>Get duration (in ms) of media descriptor object item.</summary>
        /// <returns>duration of media item or -1 on error</returns>
        public long Duration => Native.LibVLCMediaGetDuration(NativeReference);

        /// <summary>
        /// Parse the media asynchronously with options.      
        /// It uses a flag to specify parse options (see <see cref="MediaParseOptions"/>). All these flags can be combined. By default, media is parsed if it's a local file.
        /// <para/> Note: Parsing can be aborted with ParseStop().
        /// </summary>
        /// <param name="options">parse options</param>
        /// <param name="timeout">maximum time allowed to preparse the media. 
        /// <para/>If -1, the default "preparse-timeout" option will be used as a timeout. 
        /// <para/>If 0, it will wait indefinitely. If > 0, the timeout will be used (in milliseconds). 
        /// </param>
        /// <param name="cancellationToken">token to cancel the operation</param>
        public async Task<bool> Parse(MediaParseOptions options = MediaParseOptions.ParseLocal, int timeout = -1, CancellationToken cancellationToken = default)
        {
            try
            {
                if (cancellationToken.IsCancellationRequested)
                    cancellationToken.ThrowIfCancellationRequested();

                _tcs = new TaskCompletionSource<bool>();
                var timeoutToken = new CancellationTokenSource(timeout);

                ParsedChanged += OnParsedChanged;

                cancellationToken.Register(() =>
                {
                    ParsedChanged -= OnParsedChanged;
                    Native.LibVLCMediaParseStop(NativeReference);
                    _tcs?.TrySetCanceled();
                });

                timeoutToken.Token.Register(() =>
                {
                    ParsedChanged -= OnParsedChanged;
                    Native.LibVLCMediaParseStop(NativeReference);
                    _tcs?.TrySetCanceled();
                });

                var result = Native.LibVLCMediaParseWithOptions(NativeReference, options, timeout);
                if (result == -1)
                {
                    timeoutToken.Cancel();
                    timeoutToken.Dispose();
                    _tcs.TrySetResult(false);
                    return false;
                }

                return await _tcs.Task;
            }
            catch (OperationCanceledException)
            {
                _tcs?.TrySetCanceled();
                return false;
            }
            catch (Exception ex)
            {
                _tcs?.TrySetException(ex);
                return false;
            }
            finally
            {
                ParsedChanged -= OnParsedChanged;
            }
        }

        TaskCompletionSource<bool> _tcs;

        void OnParsedChanged(object sender, MediaParsedChangedEventArgs mediaParsedChangedEventArgs)
        {
            if (ParsedStatus == MediaParsedStatus.Done)
                _tcs?.TrySetResult(true);
            else if (ParsedStatus == MediaParsedStatus.Failed)
                _tcs?.TrySetException(new VLCException($"parsing of {this} failed"));
            else _tcs?.TrySetResult(false);
        }

        /// <summary>Return true is the media descriptor object is parsed</summary>
        /// <returns>true if media object has been parsed otherwise it returns false</returns>
        public bool IsParsed => Native.LibVLCMediaIsParsed(NativeReference) != 0;

        /// <summary>Get Parsed status for media descriptor object.</summary>
        /// <returns>a value of the libvlc_media_parsed_status_t enum</returns>
        /// <remarks>
        /// <para>libvlc_MediaParsedChanged</para>
        /// <para>libvlc_media_parsed_status_t</para>
        /// <para>LibVLC 3.0.0 or later</para>
        /// </remarks>
        public MediaParsedStatus ParsedStatus => Native.LibVLCMediaGetParsedStatus(NativeReference);

        /// <summary>Stop the parsing of the media</summary>
        /// <remarks>
        /// <para>When the media parsing is stopped, the libvlc_MediaParsedChanged event will</para>
        /// <para>be sent with the libvlc_media_parsed_status_timeout status.</para>
        /// <para>libvlc_media_parse_with_options</para>
        /// <para>LibVLC 3.0.0 or later</para>
        /// </remarks>
        public void ParseStop() => Native.LibVLCMediaParseStop(NativeReference);

        /// <summary>Get media descriptor's elementary streams description
        /// <para>address to store an allocated array of Elementary Streams</para>
        /// <para>descriptions (must be freed with libvlc_media_tracks_release</para>
        /// <para>by the caller) [OUT]</para>
        /// <returns>the number of Elementary Streams (zero on error)</returns>
        /// <remarks>
        /// <para>Note, you need to call libvlc_media_parse() or play the media at least once</para>
        /// <para>before calling this function.</para>
        /// <para>Not doing this will result in an empty array.</para>
        /// <para>LibVLC 2.1.0 and later.</para>
        /// </remarks>
        /// </summary>
        public MediaTrack[] Tracks => MarshalUtils.Retrieve(NativeReference, (IntPtr nativeRef, out IntPtr array) => Native.LibVLCMediaTracksGet(nativeRef, out array),
            MarshalUtils.PtrToStructure<MediaTrackStructure>,
            m => m.Build(),
            Native.LibVLCMediaTracksRelease);

        /// <summary>
        /// <para>Get subitems of media descriptor object. This will increment</para>
        /// <para>the reference count of supplied media descriptor object. Use</para>
        /// <para>libvlc_media_list_release() to decrement the reference counting.</para>
        /// </summary>
        /// <returns>list of media descriptor subitems or NULL</returns>
        public MediaList SubItems => new MediaList(Native.LibVLCMediaSubitems(NativeReference));
       
        public MediaType Type => Native.LibVLCMediaGetType(NativeReference);

        /// <summary>Add a slave to the current media.</summary>
        /// <param name="type">subtitle or audio</param>
        /// <param name="priority">from 0 (low priority) to 4 (high priority)</param>
        /// <param name="uri">Uri of the slave (should contain a valid scheme).</param>
        /// <returns>0 on success, -1 on error.</returns>
        /// <remarks>
        /// <para>A slave is an external input source that may contains an additional subtitle</para>
        /// <para>track (like a .srt) or an additional audio track (like a .ac3).</para>
        /// <para>This function must be called before the media is parsed (via</para>
        /// <para>libvlc_media_parse_with_options()) or before the media is played (via</para>
        /// <para>libvlc_media_player_play())</para>
        /// <para>LibVLC 3.0.0 and later.</para>
        /// </remarks>
        public bool AddSlave(MediaSlaveType type, uint priority, string uri) => 
            Native.LibVLCMediaAddSlaves(NativeReference, type, priority, uri) != 0;


        /// <summary>
        /// <para>Clear all slaves previously added by libvlc_media_slaves_add() or</para>
        /// <para>internally.</para>
        /// </summary>
        /// <remarks>LibVLC 3.0.0 and later.</remarks>
        public void ClearSlaves() => Native.LibVLCMediaClearSlaves(NativeReference);

        /// <summary>Get a media descriptor's slave list</summary>
        /// <para>address to store an allocated array of slaves (must be</para>
        /// <para>freed with libvlc_media_slaves_release()) [OUT]</para>
        /// <returns>the number of slaves (zero on error)</returns>
        /// <remarks>
        /// <para>The list will contain slaves parsed by VLC or previously added by</para>
        /// <para>libvlc_media_slaves_add(). The typical use case of this function is to save</para>
        /// <para>a list of slave in a database for a later use.</para>
        /// <para>LibVLC 3.0.0 and later.</para>
        /// <para>libvlc_media_slaves_add</para>
        /// </remarks>
        public MediaSlave[] Slaves => MarshalUtils.Retrieve(NativeReference, (IntPtr nativeRef, out IntPtr array) => Native.LibVLCMediaGetSlaves(nativeRef, out array),
            MarshalUtils.PtrToStructure<MediaSlaveStructure>,
            s => s.Build(),
            Native.LibVLCMediaReleaseSlaves);

        public override bool Equals(object obj)
        {
            return obj is Media media &&
                   EqualityComparer<IntPtr>.Default.Equals(NativeReference, media.NativeReference);
        }

        public override int GetHashCode()
        {
            return this.NativeReference.GetHashCode();
        }

        internal class StreamData
        {
            internal IntPtr Handle { get; set; }
            internal Stream Stream { get; set; }
            internal byte[] Buffer { get; set; }
            internal OpenMedia OpenMedia { get; set; }
            internal ReadMedia ReadMedia { get; set; }
            internal SeekMedia SeekMedia { get; set; }
            internal CloseMedia CloseMedia { get; set; }
        }

        #region private

        [MonoPInvokeCallback(typeof(OpenMedia))]
        static int CallbackOpenMedia(IntPtr opaque, ref IntPtr data, out ulong size)
        {
            data = opaque;

            try
            {
                var streamData = GetStream(opaque);
                try
                {
                    size = (ulong)streamData.Stream.Length;
                }
                catch (Exception)
                {
                    // byte length of the bitstream or UINT64_MAX if unknown
                    size = ulong.MaxValue;
                }

                if (streamData.Stream.CanSeek)
                {
                    streamData.Stream.Seek(0L, SeekOrigin.Begin);
                }

                return 0;
            }
            catch (Exception)
            {
                size = 0UL;
                return -1;
            }
        }

        [MonoPInvokeCallback(typeof(ReadMedia))]
        static int CallbackReadMedia(IntPtr opaque, IntPtr buf, uint len)
        {
            try
            {
                var streamData = GetStream(opaque);
                int read;

                lock (streamData)
                {
                    var canRead = Math.Min((int)len, streamData.Buffer.Length);
                    read = streamData.Stream.Read(streamData.Buffer, 0, canRead);
                    Marshal.Copy(streamData.Buffer, 0, buf, read);
                }

                return read;
            }
            catch (Exception)
            {
                return -1;
            }
        }

        [MonoPInvokeCallback(typeof(SeekMedia))]
        static int CallbackSeekMedia(IntPtr opaque, ulong offset)
        {
            try
            {
                var streamData = GetStream(opaque);
                streamData.Stream.Seek((long)offset, SeekOrigin.Begin);
                return 0;
            }
            catch (Exception)
            {
                return -1;
            }
        }

        [MonoPInvokeCallback(typeof(CloseMedia))]
        static void CallbackCloseMedia(IntPtr opaque)
        {
            try
            {
                var streamData = GetStream(opaque);

                if (streamData.Stream.CanSeek)
                    streamData.Stream.Seek(0, SeekOrigin.Begin);
            }
            catch (Exception)
            {
                // ignored
            }
        }

        static IntPtr AddStream(Stream stream, OpenMedia openMedia, ReadMedia readMedia, SeekMedia seekMedia, CloseMedia closeMedia)
        {
            if (stream == null)
            {
                throw new ArgumentNullException(nameof(stream));
            }

            IntPtr handle;

            lock (DicStreams)
            {
                _streamIndex++;

                handle = new IntPtr(_streamIndex);
                DicStreams[handle] = new StreamData
                {
                    Buffer = new byte[0x4000],
                    Handle = handle,
                    Stream = stream,
                    OpenMedia = openMedia,
                    ReadMedia = readMedia,
                    SeekMedia = seekMedia,
                    CloseMedia = closeMedia
                };
            }
            return handle;
        }

        static StreamData GetStream(IntPtr handle)
        {
            return !DicStreams.TryGetValue(handle, out var result) ? null : result;
        }

        static void RemoveStream(IntPtr handle)
        {
            DicStreams.TryRemove(handle, out var result);
        }

        void Retain()
        {
            if (NativeReference != IntPtr.Zero)
                Native.LibVLCMediaRetain(NativeReference);
        }

        #endregion

        #region Events

        public event EventHandler<MediaMetaChangedEventArgs> MetaChanged
        {
            add => EventManager.AttachEvent(EventType.MediaMetaChanged, value);
            remove => EventManager.DetachEvent(EventType.MediaMetaChanged, value);
        }

        public event EventHandler<MediaParsedChangedEventArgs> ParsedChanged
        {
            add => EventManager.AttachEvent(EventType.MediaParsedChanged, value);
            remove => EventManager.DetachEvent(EventType.MediaParsedChanged, value);
        }

        public event EventHandler<MediaParsedChangedEventArgs> SubItemAdded
        {
            add => EventManager.AttachEvent(EventType.MediaSubItemAdded, value);
            remove => EventManager.DetachEvent(EventType.MediaSubItemAdded, value);
        }

        public event EventHandler<MediaDurationChangedEventArgs> DurationChanged
        {
            add => EventManager.AttachEvent(EventType.MediaDurationChanged, value);
            remove => EventManager.DetachEvent(EventType.MediaDurationChanged, value);
        }

        public event EventHandler<MediaFreedEventArgs> MediaFreed
        {
            add => EventManager.AttachEvent(EventType.MediaFreed, value);
            remove => EventManager.DetachEvent(EventType.MediaFreed, value);
        }

        public event EventHandler<MediaStateChangedEventArgs> StateChanged
        {
            add => EventManager.AttachEvent(EventType.MediaStateChanged, value);
            remove => EventManager.DetachEvent(EventType.MediaStateChanged, value);
        }

        public event EventHandler<MediaSubItemAddedEventArgs> SubItemTreeAdded
        {
            add => EventManager.AttachEvent(EventType.MediaSubItemTreeAdded, value);
            remove => EventManager.DetachEvent(EventType.MediaSubItemTreeAdded, value);
        }

        #endregion

        /// <summary>
        /// Dispose of this media
        /// </summary>
        /// <param name="disposing"></param>
        protected override void Dispose(bool disposing)
        {
            if (IsDisposed || NativeReference == IntPtr.Zero)
                return;

            base.Dispose(disposing);
        }
    }

    #region Callbacks

    /// <summary>
    /// <para>It consists of a media location and various optional meta data.</para>
    /// <para>@{</para>
    /// <para></para>
    /// <para>LibVLC media item/descriptor external API</para>
    /// </summary>
    /// <summary>Callback prototype to open a custom bitstream input media.</summary>
    /// <param name="opaque">private pointer as passed to libvlc_media_new_callbacks()</param>
    /// <param name="data">storage space for a private data pointer [OUT]</param>
    /// <param name="size">byte length of the bitstream or UINT64_MAX if unknown [OUT]</param>
    /// <returns>
    /// <para>0 on success, non-zero on error. In case of failure, the other</para>
    /// <para>callbacks will not be invoked and any value stored in *datap and *sizep is</para>
    /// <para>discarded.</para>
    /// </returns>
    /// <remarks>
    /// <para>The same media item can be opened multiple times. Each time, this callback</para>
    /// <para>is invoked. It should allocate and initialize any instance-specific</para>
    /// <para>resources, then store them in *datap. The instance resources can be freed</para>
    /// <para>in the</para>
    /// <para>For convenience, *datap is initially NULL and *sizep is initially 0.</para>
    /// </remarks>
    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    internal delegate int OpenMedia(IntPtr opaque, ref IntPtr data, out ulong size);

    /// <summary>Callback prototype to read data from a custom bitstream input media.</summary>
    /// <param name="opaque">private pointer as set by the</param>
    /// <param name="buf">start address of the buffer to read data into</param>
    /// <param name="len">bytes length of the buffer</param>
    /// <returns>
    /// <para>strictly positive number of bytes read, 0 on end-of-stream,</para>
    /// <para>or -1 on non-recoverable error</para>
    /// </returns>
    /// <remarks>
    /// <para>callback</para>
    /// <para>If no data is immediately available, then the callback should sleep.</para>
    /// <para>The application is responsible for avoiding deadlock situations.</para>
    /// <para>In particular, the callback should return an error if playback is stopped;</para>
    /// <para>if it does not return, then libvlc_media_player_stop() will never return.</para>
    /// </remarks>
    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    internal delegate int ReadMedia(IntPtr opaque, IntPtr buf, uint len);

    /// <summary>Callback prototype to seek a custom bitstream input media.</summary>
    /// <param name="opaque">private pointer as set by the</param>
    /// <param name="offset">absolute byte offset to seek to</param>
    /// <returns>0 on success, -1 on error.</returns>
    /// <remarks>callback</remarks>
    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    internal delegate int SeekMedia(IntPtr opaque, ulong offset);

    /// <summary>Callback prototype to close a custom bitstream input media.</summary>
    /// <param name="opaque">private pointer as set by the</param>
    /// <remarks>callback</remarks>
    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    internal delegate void CloseMedia(IntPtr opaque);

    #endregion

    #region enums

    /// <summary>Note the order of libvlc_state_t enum must match exactly the order of</summary>
    /// <remarks>
    /// <para>mediacontrol_PlayerStatus,</para>
    /// <para>input_state_e enums,</para>
    /// <para>and VideoLAN.LibVLCSharp.State (at bindings/cil/src/media.cs).</para>
    /// <para>Expected states by web plugins are:</para>
    /// <para>IDLE/CLOSE=0, OPENING=1, PLAYING=3, PAUSED=4,</para>
    /// <para>STOPPING=5, ENDED=6, ERROR=7</para>
    /// </remarks>
    public enum VLCState
    {
        /// <summary>
        /// Nothing special happening
        /// </summary>
        NothingSpecial = 0,

        /// <summary>
        /// Opening media
        /// </summary>
        Opening = 1,

        /// <summary>
        /// Buffering media
        /// </summary>
        Buffering = 2,

        /// <summary>
        /// Playing media
        /// </summary>
        Playing = 3,

        /// <summary>
        /// Paused media
        /// </summary>
        Paused = 4,

        /// <summary>
        /// Stopped media
        /// </summary>
        Stopped = 5,

        /// <summary>
        /// Ended media
        /// </summary>
        Ended = 6,

        /// <summary>
        /// Error media
        /// </summary>
        Error = 7
    }

    /// <summary>
    /// Media track type such as Audio, Video or Text
    /// </summary>
    public enum TrackType
    {
        /// <summary>
        /// Unknown track
        /// </summary>
        Unknown = -1,

        /// <summary>
        /// Audio track
        /// </summary>
        Audio = 0,

        /// <summary>
        /// Video track
        /// </summary>
        Video = 1,

        /// <summary>
        /// Text track
        /// </summary>
        Text = 2
    }

    /// <summary>
    /// Video orientation
    /// </summary>
    public enum VideoOrientation
    {
        /// <summary>Normal. Top line represents top, left column left.</summary>
        TopLeft = 0,
        /// <summary>Flipped horizontally</summary>
        TopRight = 1,
        /// <summary>Flipped vertically</summary>
        BottomLeft = 2,
        /// <summary>Rotated 180 degrees</summary>
        BottomRight = 3,
        /// <summary>Transposed</summary>
        LeftTop = 4,
        /// <summary>Rotated 90 degrees clockwise (or 270 anti-clockwise)</summary>
        LeftBottom = 5,
        /// <summary>Rotated 90 degrees anti-clockwise</summary>
        RightTop = 6,
        /// <summary>Anti-transposed</summary>
        RightBottom = 7
    }

    /// <summary>
    /// Video projection
    /// </summary>
    [Flags]
    public enum VideoProjection
    {
        /// <summary>
        /// Rectangular
        /// </summary>
        Rectangular = 0,
        /// <summary>360 spherical</summary>
        Equirectangular = 1,

        /// <summary>
        /// Cubemap layout standard
        /// </summary>
        CubemapLayoutStandard = 256
    }

    /// <summary>Type of a media slave: subtitle or audio.</summary>
    public enum MediaSlaveType
    {
        /// <summary>
        /// Subtitle
        /// </summary>
        Subtitle = 0,
        
        /// <summary>
        /// Audio
        /// </summary>
        Audio = 1
    }

    /// <summary>Meta data types</summary>
    public enum MetadataType
    {
        Title = 0,
        Artist = 1,
        Genre = 2,
        Copyright = 3,
        Album = 4,
        TrackNumber = 5,
        Description = 6,
        Rating = 7,
        Date = 8,
        Setting = 9,
        URL = 10,
        Language = 11,
        NowPlaying = 12,
        Publisher = 13,
        EncodedBy = 14,
        ArtworkURL = 15,
        TrackID = 16,
        TrackTotal = 17,
        Director = 18,
        Season = 19,
        Episode = 20,
        ShowName = 21,
        Actors = 22,
        AlbumArtist = 23,
        DiscNumber = 24,
        DiscTotal = 25
    }

    /// <summary>
    /// The FromType enum is used to drive the media creation.
    /// A media is usually created using a string, which can represent one of 3 things: FromPath, FromLocation, AsNode.
    /// </summary>
    public enum FromType
    {
        /// <summary>
        /// Create a media for a certain file path.
        /// </summary>
        FromPath,
        /// <summary>
        /// Create a media with a certain given media resource location,
        /// for instance a valid URL.
        /// note To refer to a local file with this function,
        /// the file://... URI syntax <b>must</b> be used (see IETF RFC3986).
        /// We recommend using FromPath instead when dealing with
        ///local files.
        /// </summary>
        FromLocation,
        /// <summary>
        /// Create a media as an empty node with a given name.
        /// </summary>
        AsNode
    }

    /// <summary>
    /// Parse flags used by libvlc_media_parse_with_options()
    /// </summary>
    /// <remarks>libvlc_media_parse_with_options</remarks>
    [Flags]
    public enum MediaParseOptions
    {
        /// <summary>Parse media if it's a local file</summary>
        ParseLocal = 0,
        /// <summary>Parse media even if it's a network file</summary>
        ParseNetwork = 1,
        /// <summary>Fetch meta and covert art using local resources</summary>
        FetchLocal = 2,
        /// <summary>Fetch meta and covert art using network resources</summary>
        FetchNetwork = 4,
        /// <summary>
        /// Interact with the user (via libvlc_dialog_cbs) when preparsing this item
        /// (and not its sub items). Set this flag in order to receive a callback
        /// when the input is asking for credentials.
        /// </summary>
        DoInteract = 8
    }

    /// <summary>
    /// Parse status used sent by libvlc_media_parse_with_options() or returned by
    /// libvlc_media_get_parsed_status()
    /// </summary>
    /// <remarks>
    /// libvlc_media_parse_with_options
    /// libvlc_media_get_parsed_status
    /// </remarks>
    public enum MediaParsedStatus
    {
        Skipped = 1,
        Failed = 2,
        Timeout = 3,
        Done = 4
    }

    /// <summary>Media type</summary>
    /// <remarks>libvlc_media_get_type</remarks>
    public enum MediaType
    {
        Unknown = 0,
        File = 1,
        Directory = 2,
        Disc = 3,
        Stream = 4,
        Playlist = 5
    }

    #endregion

    /// <summary>
    /// Small configuration helper
    /// </summary>
    public class MediaConfiguration
    {
        HashSet<string> _options = new HashSet<string>();

        public MediaConfiguration EnableHardwareDecoding()
        {
#if ANDROID
            _options.Add(":codec=mediacodec_ndk");
#endif
            return this;
        }

        public string Build() => string.Join(",", _options);
    }
}