#region --- License ---
/* Licensed under the MIT/X11 license.
 * Copyright (c) 2006-2008 the OpenTK Team.
 * This notice may not be removed from any source distribution.
 * See license.txt for licensing details.
 */
#endregion

using System;
using System.Collections.Generic;
using System.Text;
using System.Diagnostics;

using OpenTK.Audio;

namespace OpenTK.Audio
{
    /// <summary>
    /// Provides methods to create and use an audio context.
    /// </summary>
    public sealed class AudioContext : IDisposable
    {
        #region --- Fields ---

        bool disposed;
        bool is_processing, is_synchronized;
        IntPtr device_handle;
        ContextHandle context_handle;
        bool context_exists;

        string device_name;
        static object audio_context_lock = new object();
        static List<string> available_devices = new List<string>();
        static Dictionary<ContextHandle, AudioContext> available_contexts = new Dictionary<ContextHandle, AudioContext>();
        static bool openal_supported = true;
        static Version version;

        private enum Version
        {
            OpenAL10,
            OpenAL11
        }

        #endregion

        #region --- Constructors ---

        #region static AudioContext()

        /// <private />
        /// <static />
        /// <summary>
        /// Runs before the actual class constructor, to load available devices.
        /// </summary>
        static AudioContext()
        {
            LoadAvailableDevices();
        }

        #endregion

        #region public AudioContext()

        /// <summary>Constructs a new AudioContext, using the default audio device.</summary>
        public AudioContext()
            : this(null, 0, 0, false, true) { }

        #endregion

        #region public AudioContext(string device)

        /// <summary>Constructs a new AudioContext, using the specified audio device.</summary>
        /// <param name="device">The name of the audio device to use.</param>
        /// <remarks>
        /// Use AudioContext.AvailableDevices to obtain a list of all available audio devices.
        /// devices.
        /// </remarks>
        public AudioContext(string device) : this(device, 0, 0, false, true) { }

        #endregion

        #region public AudioContext(string device, int freq)

        /// <summary>Constructs a new AudioContext, using the specified audio device and device parameters.</summary>
        /// <param name="device">The name of the audio device to use.</param>
        /// <param name="freq">Frequency for mixing output buffer, in units of Hz. Pass 0 for driver default.</param>
        /// <remarks>
        /// Use AudioContext.AvailableDevices to obtain a list of all available audio devices.
        /// devices.
        /// </remarks>
        public AudioContext(string device, int freq) : this(device, freq, 0, false, true) { }

        #endregion

        #region public AudioContext(string device, int freq, int refresh)

        /// <summary>Constructs a new AudioContext, using the specified audio device and device parameters.</summary>
        /// <param name="device">The name of the audio device to use.</param>
        /// <param name="freq">Frequency for mixing output buffer, in units of Hz. Pass 0 for driver default.</param>
        /// <param name="refresh">Refresh intervals, in units of Hz. Pass 0 for driver default.</param>
        /// <remarks>
        /// Use AudioContext.AvailableDevices to obtain a list of all available audio devices.
        /// devices.
        /// </remarks>
        public AudioContext(string device, int freq, int refresh)
            : this(device, freq, refresh, false, true) { }

        #endregion

        #region public AudioContext(string device)

        /// <summary>Constructs a new AudioContext, using the specified audio device and device parameters.</summary>
        /// <param name="device">The name of the audio device to use.</param>
        /// <param name="freq">Frequency for mixing output buffer, in units of Hz. Pass 0 for driver default.</param>
        /// <param name="refresh">Refresh intervals, in units of Hz. Pass 0 for driver default.</param>
        /// <param name="sync">Flag, indicating a synchronous context.</param>
        /// <remarks>
        /// Use AudioContext.AvailableDevices to obtain a list of all available audio devices.
        /// devices.
        /// </remarks>
        public AudioContext(string device, int freq, int refresh, bool sync)
            : this(available_devices[0], freq, refresh, sync, true) { }

        #endregion

        #region public AudioContext(string device, int freq, int refresh, bool sync, bool enableEfx)

        /// <summary>Creates the audio context using the specified device and device parameters.</summary>
        /// <param name="device">The device descriptor obtained through AudioContext.AvailableDevices.</param>
        /// <param name="freq">Frequency for mixing output buffer, in units of Hz. Pass 0 for driver default.</param>
        /// <param name="refresh">Refresh intervals, in units of Hz. Pass 0 for driver default.</param>
        /// <param name="sync">Flag, indicating a synchronous context.</param>
        /// <param name="enableEfx">Indicates whether the EFX extension should be initialized, if present.</param>
        /// <exception cref="ArgumentNullException">Occurs when the device string is invalid.</exception>
        /// <exception cref="ArgumentOutOfRangeException">Occurs when a specified parameter is invalid.</exception>
        /// <exception cref="AudioDeviceException">
        /// Occurs when the specified device is not available, or is in use by another program.
        /// </exception>
        /// <exception cref="AudioContextException">
        /// Occurs when an audio context could not be created with the specified parameters.
        /// </exception>
        /// <exception cref="NotSupportedException">
        /// Occurs when an AudioContext already exists.</exception>
        /// <remarks>
        /// <para>For maximum compatibility, you are strongly recommended to use the default constructor.</para>
        /// <para>Multiple AudioContexts are not supported at this point.</para>
        /// <para>
        /// The number of auxilliary EFX sends depends on the audio hardware and drivers. Most Realtek devices, as well
        /// as the Creative SB Live!, support 1 auxilliary send. Creative's Audigy and X-Fi series support 4 sends.
        /// Values higher than supported will be clamped by the driver.
        /// </para>
        /// </remarks>
        public AudioContext(string device, int freq, int refresh, bool sync, bool enableEfx)
        {
            CreateContext(device, freq, refresh, sync, enableEfx);
        }

        #endregion

        #endregion

        #region --- Private Methods ---

        #region static void LoadAvailableDevices()

        /// <private />
        /// <static />
        /// <summary>
        /// Loads all available audio devices into the available_devices array.
        /// </summary>
        /// <remarks>
        /// Only called by the static AudioContext constructor.
        /// </remarks>
        static void LoadAvailableDevices()
        {
            lock (audio_context_lock)
            {
                if (available_devices.Count == 0)
                {
                    try
                    {
                        Debug.WriteLine("Enumerating audio devices.");
                        Debug.Indent();

                        if (Alc.IsExtensionPresent(IntPtr.Zero, "ALC_ENUMERATION_EXT"))
                        {
                            version = Version.OpenAL11;
                            available_devices.AddRange(Alc.GetString(IntPtr.Zero, AlcGetStringList.DeviceSpecifier));
                        }
                        else
                        {
                            version = Version.OpenAL10;
                            Debug.Print("Device enumeration extension not available. Failed to enumerate devices.");
                        }

                        foreach (string s in available_devices)
                            Debug.WriteLine(s);
                    }
                    catch (DllNotFoundException e)
                    {
                        Debug.WriteLine(e.ToString());
                        openal_supported = false;
                    }
                    finally
                    {
                        Debug.Unindent();
                    }
                }
            }
        }

        #endregion

        #region CreateContext

        /// <private />
        /// <summary>Creates the audio context using the specified device.</summary>
        /// <param name="device">The device descriptor obtained through AudioContext.AvailableDevices, or null for the default device.</param>
        /// <param name="freq">Frequency for mixing output buffer, in units of Hz. Pass 0 for driver default.</param>
        /// <param name="refresh">Refresh intervals, in units of Hz. Pass 0 for driver default.</param>
        /// <param name="sync">Flag, indicating a synchronous context.</param>
        /// <param name="enableEfx">Indicates whether the EFX extension should be initialized, if present.</param>
        /// /// <exception cref="ArgumentOutOfRangeException">Occurs when a specified parameter is invalid.</exception>
        /// <exception cref="AudioDeviceException">
        /// Occurs when the specified device is not available, or is in use by another program.
        /// </exception>
        /// <exception cref="AudioContextException">
        /// Occurs when an audio context could not be created with the specified parameters.
        /// </exception>
        /// <exception cref="NotSupportedException">
        /// Occurs when an AudioContext already exists.</exception>
        /// <remarks>
        /// <para>For maximum compatibility, you are strongly recommended to use the default constructor.</para>
        /// <para>Multiple AudioContexts are not supported at this point.</para>
        /// <para>
        /// The number of auxilliary EFX sends depends on the audio hardware and drivers. Most Realtek devices, as well
        /// as the Creative SB Live!, support 1 auxilliary send. Creative's Audigy and X-Fi series support 4 sends.
        /// Values higher than supported will be clamped by the driver.
        /// </para>
        /// </remarks>
        void CreateContext(string device, int freq, int refresh, bool sync, bool enableEfx)
        {
            if (!openal_supported)
                throw new DllNotFoundException("openal32.dll");
            
            if (version == Version.OpenAL11 && available_devices.Count == 0)    // Version.OpenAL10 does not support device enumeration.
                throw new NotSupportedException("No audio hardware is available.");
            if (context_exists) throw new NotSupportedException("Multiple AudioContexts are not supported.");
            if (freq < 0) throw new ArgumentOutOfRangeException("freq", freq, "Should be greater than zero.");
            if (refresh < 0) throw new ArgumentOutOfRangeException("refresh", refresh, "Should be greater than zero.");

            if (!String.IsNullOrEmpty(device))
                device_handle = Alc.OpenDevice(device);
            if (device_handle == IntPtr.Zero)
                device_handle = Alc.OpenDevice(null);
            if (device_handle == IntPtr.Zero)
                Alc.OpenDevice(Alc.GetString(IntPtr.Zero, AlcGetString.DefaultDeviceSpecifier));
            if (device_handle == IntPtr.Zero && available_devices.Count > 0)
                device_handle = Alc.OpenDevice(available_devices[0]);
            if (device_handle == IntPtr.Zero)
                throw new AudioDeviceException(String.Format("Audio device '{0}' does not exist or is tied up by another application.",
                                                             String.IsNullOrEmpty(device) ? "default" : device));

            CheckForAlcErrors();

            // Build the attribute list
            List<int> attributes = new List<int>();
            
            if (freq != 0)
            {
                attributes.Add((int)AlcContextAttributes.Frequency);
                attributes.Add(freq);
            }
            
            if (refresh != 0)
            {
                attributes.Add((int)AlcContextAttributes.Refresh);
                attributes.Add(refresh);
            }
            
            attributes.Add((int)AlcContextAttributes.Frequency);
            attributes.Add(sync ? 1 : 0);

            if (enableEfx && Alc.IsExtensionPresent(device_handle, "ALC_EXT_EFX"))
            {
                int num_slots;
                Alc.GetInteger(device_handle, AlcGetInteger.EfxMaxAuxiliarySends, 1, out num_slots);
                attributes.Add((int)AlcContextAttributes.EfxMaxAuxiliarySends);
                attributes.Add(num_slots);
            }
            attributes.Add(0);

            context_handle = Alc.CreateContext(device_handle, attributes.ToArray());

            if (context_handle == ContextHandle.Zero)
            {
                Alc.CloseDevice(device_handle);
                throw new AudioContextException("The audio context could not be created with the specified parameters.");
            }

            CheckForAlcErrors();

            // HACK: OpenAL SI on Linux/ALSA crashes on MakeCurrent. This hack avoids calling MakeCurrent when
            // an old OpenAL version is detect - it may affect outdated OpenAL versions different than OpenAL SI,
            // but it looks like a good compromise for now.
            if (available_devices.Count > 0)
                MakeCurrent();

            CheckForAlcErrors();
            
            device_name = Alc.GetString(device_handle, AlcGetString.DeviceSpecifier);
            int attribute_count;
            Alc.GetInteger(device_handle, AlcGetInteger.AttributesSize, sizeof(int), out attribute_count);
            if (attribute_count > 0)
            {
                int[] device_attributes = new int[attribute_count];
                Alc.GetInteger(device_handle, AlcGetInteger.AllAttributes, device_attributes.Length * sizeof(int), out device_attributes[0]);
                foreach (int attr in device_attributes)
                {
                    switch ((AlcContextAttributes)attr)
                    {
                        case AlcContextAttributes.Sync: IsSynchronized = true; break;
                    }
                }
            }

            lock (audio_context_lock)
            {
                available_contexts.Add(this.context_handle, this);
                context_exists = true;
            }
        }

        #endregion

        #region void CheckForAlcErrors()
        
        void CheckForAlcErrors()
        {
            AlcError err = Alc.GetError(device_handle);
            if (err != AlcError.NoError)
                throw new AudioContextException(err.ToString());
        }

        #endregion

        #region static void MakeCurrent(AudioContext context)

        /// <private />
        /// <summary>Makes the specified AudioContext current in the calling thread.</summary>
        /// <param name="context">The OpenTK.Audio.AudioContext to make current, or null.</param>
        /// <exception cref="ObjectDisposedException">
        /// Occurs if this function is called after the AudioContext has been disposed.
        /// </exception>
        /// <exception cref="AudioContextException">
        /// Occurs when the AudioContext could not be made current.
        /// </exception>
        static void MakeCurrent(AudioContext context)
        {
            lock (audio_context_lock)
            {
                if (!Alc.MakeContextCurrent(context != null ? context.context_handle : ContextHandle.Zero))
                    throw new AudioContextException(String.Format("ALC {0} error detected at {1}.",
                        Alc.GetError(context != null ? (IntPtr)context.context_handle : IntPtr.Zero).ToString(),
                        context != null ? context.ToString() : "null"));
            }
        }

        #endregion

        #region internal bool IsCurrent

        /// <summary>
        /// Gets or sets a System.Boolean indicating whether the AudioContext
        /// is current.
        /// </summary>
        /// <remarks>
        /// Only one AudioContext can be current in the application at any time,
        /// <b>regardless of the number of threads</b>.
        /// </remarks>
        internal bool IsCurrent
        {
            get
            {
                lock (audio_context_lock)
                {
                    if (available_contexts.Count == 0)
                        return false;
                    else
                    {
                        return AudioContext.CurrentContext == this;
                    }
                }
            }
            set
            {
                if (value) AudioContext.MakeCurrent(this);
                else AudioContext.MakeCurrent(null);
            }
        }

        #endregion

        #region IntPtr Device

        IntPtr Device { get { return device_handle; } }

        #endregion

        #endregion

        #region --- Public Members ---

        #region internal void MakeCurrent()

        /// <summary>Makes the AudioContext current in the calling thread.</summary>
        /// <exception cref="ObjectDisposedException">
        /// Occurs if this function is called after the AudioContext has been disposed.
        /// </exception>
        /// <exception cref="AudioContextException">
        /// Occurs when the AudioContext could not be made current.
        /// </exception>
        /// <remarks>
        /// Only one AudioContext can be current in the application at any time,
        /// <b>regardless of the number of threads</b>.
        /// </remarks>
        public void MakeCurrent()
        {
            AudioContext.MakeCurrent(this);
        }

        #endregion

        #region public bool IsProcessing

        /// <summary>
        /// Gets a System.Boolean indicating whether the AudioContext is
        /// currently processing audio events.
        /// </summary>
        /// <seealso cref="Process"/>
        /// <seealso cref="Suspend"/>
        public bool IsProcessing
        {
            get { return is_processing; }
            private set { is_processing = value; }
        }

        #endregion

        #region public bool IsProcessing

        /// <summary>
        /// Gets a System.Boolean indicating whether the AudioContext is
        /// synchronized.
        /// </summary>
        /// <seealso cref="Process"/>
        public bool IsSynchronized
        {
            get { return is_synchronized; }
            private set { is_synchronized = value; }
        }

        #endregion

        #region public void Process

        /// <summary>
        /// Processes queued audio events.
        /// </summary>
        /// <remarks>
        /// <para>
        /// If AudioContext.IsSynchronized is true, this function will resume
        /// the internal audio processing thread. If AudioContext.IsSynchronized is false,
        /// you will need to call this function multiple times per second to process
        /// audio events.
        /// </para>
        /// <para>
        /// In some implementations this function may have no effect.
        /// </para>
        /// </remarks>
        /// <exception cref="ObjectDisposedException">Occurs when this function is called after the AudioContext had been disposed.</exception>
        /// <seealso cref="Suspend"/>
        /// <seealso cref="IsProcessing"/>
        /// <seealso cref="IsSynchronized"/>
        public void Process()
        {
            if (disposed) throw new ObjectDisposedException(this.ToString());
            Alc.ProcessContext(this.context_handle);
            IsProcessing = true;
        }

        #endregion

        #region public void Suspend

        /// <summary>
        /// Suspends processing of audio events.
        /// </summary>
        /// <remarks>
        /// <para>
        /// To avoid audio artifacts when calling this function, set audio gain to zero before
        /// suspending an AudioContext.
        /// </para>
        /// <para>
        /// In some implementations, it can be faster to suspend processing before changing
        /// AudioContext state.
        /// </para>
        /// <para>
        /// In some implementations this function may have no effect.
        /// </para>
        /// </remarks>
        /// <exception cref="ObjectDisposedException">Occurs when this function is called after the AudioContext had been disposed.</exception>
        /// <seealso cref="Process"/>
        /// <seealso cref="IsProcessing"/>
        /// <seealso cref="IsSynchronized"/>
        public void Suspend()
        {
            if (disposed) throw new ObjectDisposedException(this.ToString());
            Alc.SuspendContext(this.context_handle);
            IsProcessing = false;
        }

        #endregion

        #region public bool SupportsExtension(string extension)

        /// <summary>
        /// Checks whether the specified OpenAL extension is supported.
        /// </summary>
        /// <param name="extension">The name of the extension to check (e.g. "ALC_EXT_EFX").</param>
        /// <returns>true if the extension is supported; false otherwise.</returns>
        public bool SupportsExtension(string extension)
        {
            if (disposed) throw new ObjectDisposedException(this.GetType().FullName);
            return Alc.IsExtensionPresent(this.Device, extension);
        }

        #endregion

        #region public static AudioContext CurrentContext

        /// <summary>
        /// Gets the OpenTK.Audio.AudioContext which is current in the application.
        /// </summary>
        /// <remarks>
        /// Only one AudioContext can be current in the application at any time,
        /// <b>regardless of the number of threads</b>.
        /// </remarks>
        public static AudioContext CurrentContext
        {
            get
            {
                lock (audio_context_lock)
                {
                    if (available_contexts.Count == 0)
                        return null;
                    else
                    {
                        AudioContext context;
                        AudioContext.available_contexts.TryGetValue(
                            (ContextHandle)Alc.GetCurrentContext(),
                            out context);
                        return context;
                    }
                }
            }
        }

        #endregion

        #region public static string[] AvailableDevices

        /// <summary>
        /// Gets a System.String array containing all available audio devices.
        /// </summary>
        /// <remarks>This property allocates memory.</remarks>
        public static string[] AvailableDevices
        {
            get
            {
                if (available_devices.Count == 0)
                    LoadAvailableDevices();
                return available_devices.ToArray();
            }
        }

        #endregion

        #endregion

        #region --- IDisposable Members ---

        /// <summary>
        /// Disposes of the AudioContext, cleaning up all resources consumed by it.
        /// </summary>
        public void Dispose()
        {
            this.Dispose(true);
            GC.SuppressFinalize(this);
        }

        void Dispose(bool manual)
        {
            if (!disposed)
            {
                if (this.IsCurrent)
                    this.IsCurrent = false;

                if (context_handle != ContextHandle.Zero)
                {
                    available_contexts.Remove(context_handle);
                    Alc.DestroyContext(context_handle);
                }

                if (device_handle != IntPtr.Zero)
                    Alc.CloseDevice(device_handle);

                if (manual)
                {
                }
                disposed = true;
            }
        }

        ~AudioContext()
        {
            this.Dispose(false);
        }

        #endregion

        #region --- Overrides ---

        public override int GetHashCode()
        {
            return base.GetHashCode();
        }

        public override bool Equals(object obj)
        {
            return base.Equals(obj);
        }

        public override string ToString()
        {
            return String.Format("{0} (handle: {1}, device: {2})",
                                 this.device_name, this.context_handle, this.device_handle);
        }

        #endregion
    }
}