//
// Copyright (c) 2019-2021 Ryujinx
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.
//

using Ryujinx.Audio.Integration;
using Ryujinx.Audio.Renderer.Dsp;
using Ryujinx.Audio.Renderer.Parameter;
using Ryujinx.Common.Logging;
using Ryujinx.Memory;
using System;
using System.Diagnostics;
using System.Linq;
using System.Threading;

namespace Ryujinx.Audio.Renderer.Server
{
    /// <summary>
    /// The audio renderer manager.
    /// </summary>
    public class AudioRendererManager : IDisposable
    {
        /// <summary>
        /// Lock used for session allocation.
        /// </summary>
        private object _sessionLock = new object();

        /// <summary>
        /// Lock used to control the <see cref="AudioProcessor"/> running state.
        /// </summary>
        private object _audioProcessorLock = new object();

        /// <summary>
        /// The session ids allocation table.
        /// </summary>
        private int[] _sessionIds;

        /// <summary>
        /// The events linked to each session.
        /// </summary>
        private IWritableEvent[] _sessionsSystemEvent;

        /// <summary>
        /// The <see cref="AudioRenderSystem"/> sessions instances.
        /// </summary>
        private AudioRenderSystem[] _sessions;

        /// <summary>
        /// The count of active sessions.
        /// </summary>
        private int _activeSessionCount;

        /// <summary>
        /// The worker thread used to run <see cref="SendCommands"/>.
        /// </summary>
        private Thread _workerThread;

        /// <summary>
        /// Indicate if the worker thread and <see cref="AudioProcessor"/> are running.
        /// </summary>
        private bool _isRunning;

        /// <summary>
        /// The audio device driver to create audio outputs.
        /// </summary>
        private IHardwareDeviceDriver _deviceDriver;

        /// <summary>
        /// The <see cref="AudioProcessor"/> instance associated to this manager.
        /// </summary>
        public AudioProcessor Processor { get; }

        /// <summary>
        /// The dispose state.
        /// </summary>
        private int _disposeState;

        /// <summary>
        /// Create a new <see cref="AudioRendererManager"/>.
        /// </summary>
        public AudioRendererManager()
        {
            Processor = new AudioProcessor();
            _sessionIds = new int[Constants.AudioRendererSessionCountMax];
            _sessions = new AudioRenderSystem[Constants.AudioRendererSessionCountMax];
            _activeSessionCount = 0;

            for (int i = 0; i < _sessionIds.Length; i++)
            {
                _sessionIds[i] = i;
            }
        }

        /// <summary>
        /// Initialize the <see cref="AudioRendererManager"/>.
        /// </summary>
        /// <param name="sessionSystemEvents">The events associated to each session.</param>
        /// <param name="deviceDriver">The device driver to use to create audio outputs.</param>
        public void Initialize(IWritableEvent[] sessionSystemEvents, IHardwareDeviceDriver deviceDriver)
        {
            _sessionsSystemEvent = sessionSystemEvents;
            _deviceDriver = deviceDriver;
        }

        /// <summary>
        /// Get the work buffer size required by a session.
        /// </summary>
        /// <param name="parameter">The user configuration</param>
        /// <returns>The work buffer size required by a session.</returns>
        public static ulong GetWorkBufferSize(ref AudioRendererConfiguration parameter)
        {
            return AudioRenderSystem.GetWorkBufferSize(ref parameter);
        }

        /// <summary>
        /// Acquire a new session id.
        /// </summary>
        /// <returns>A new session id.</returns>
        private int AcquireSessionId()
        {
            lock (_sessionLock)
            {
                int index = _activeSessionCount;

                Debug.Assert(index < _sessionIds.Length);

                int sessionId = _sessionIds[index];

                _sessionIds[index] = -1;

                _activeSessionCount++;

                Logger.Info?.Print(LogClass.AudioRenderer, $"Registered new renderer ({sessionId})");

                return sessionId;
            }
        }

        /// <summary>
        /// Release a given <paramref name="sessionId"/>.
        /// </summary>
        /// <param name="sessionId">The session id to release.</param>
        private void ReleaseSessionId(int sessionId)
        {
            lock (_sessionLock)
            {
                Debug.Assert(_activeSessionCount > 0);

                int newIndex = --_activeSessionCount;

                _sessionIds[newIndex] = sessionId;
            }

            Logger.Info?.Print(LogClass.AudioRenderer, $"Unregistered renderer ({sessionId})");
        }

        /// <summary>
        /// Check if there is any audio renderer active.
        /// </summary>
        /// <returns>Returns true if there is any audio renderer active.</returns>
        private bool HasAnyActiveRendererLocked()
        {
            foreach (AudioRenderSystem renderer in _sessions)
            {
                if (renderer != null)
                {
                    return true;
                }
            }

            return false;
        }

        /// <summary>
        /// Start the <see cref="AudioProcessor"/> and worker thread.
        /// </summary>
        private void StartLocked()
        {
            _isRunning = true;

            // TODO: virtual device mapping (IAudioDevice)
            Processor.Start(_deviceDriver);

            _workerThread = new Thread(SendCommands)
            {
                Name = "AudioRendererManager.Worker"
            };

            _workerThread.Start();
        }

        /// <summary>
        /// Stop the <see cref="AudioProcessor"/> and worker thread.
        /// </summary>
        private void StopLocked()
        {
            _isRunning = false;

            _workerThread.Join();
            Processor.Stop();

            Logger.Info?.Print(LogClass.AudioRenderer, "Stopped audio renderer");
        }

        /// <summary>
        /// Stop sending commands to the <see cref="AudioProcessor"/> without stopping the worker thread.
        /// </summary>
        public void StopSendingCommands()
        {
            _isRunning = false;
        }

        /// <summary>
        /// Worker main function. This is used to dispatch audio renderer commands to the <see cref="AudioProcessor"/>.
        /// </summary>
        private void SendCommands()
        {
            Logger.Info?.Print(LogClass.AudioRenderer, "Starting audio renderer");
            Processor.Wait();

            while (_isRunning)
            {
                lock (_sessionLock)
                {
                    foreach(AudioRenderSystem renderer in _sessions)
                    {
                        renderer?.SendCommands();
                    }
                }

                Processor.Signal();
                Processor.Wait();
            }
        }

        /// <summary>
        /// Register a new <see cref="AudioRenderSystem"/>.
        /// </summary>
        /// <param name="renderer">The <see cref="AudioRenderSystem"/> to register.</param>
        private void Register(AudioRenderSystem renderer)
        {
            lock (_sessionLock)
            {
                _sessions[renderer.GetSessionId()] = renderer;
            }

            lock (_audioProcessorLock)
            {
                if (!_isRunning)
                {
                    StartLocked();
                }
            }
        }

        /// <summary>
        /// Unregister a new <see cref="AudioRenderSystem"/>.
        /// </summary>
        /// <param name="renderer">The <see cref="AudioRenderSystem"/> to unregister.</param>
        internal void Unregister(AudioRenderSystem renderer)
        {
            lock (_sessionLock)
            {
                int sessionId = renderer.GetSessionId();

                _sessions[renderer.GetSessionId()] = null;

                ReleaseSessionId(sessionId);
            }

            lock (_audioProcessorLock)
            {
                if (_isRunning && !HasAnyActiveRendererLocked())
                {
                    StopLocked();
                }
            }
        }

        /// <summary>
        /// Open a new <see cref="AudioRenderSystem"/>
        /// </summary>
        /// <param name="renderer">The new <see cref="AudioRenderSystem"/></param>
        /// <param name="memoryManager">The memory manager that will be used for all guest memory operations.</param>
        /// <param name="parameter">The user configuration</param>
        /// <param name="appletResourceUserId">The applet resource user id of the application.</param>
        /// <param name="workBufferAddress">The guest work buffer address.</param>
        /// <param name="workBufferSize">The guest work buffer size.</param>
        /// <param name="processHandle">The process handle of the application.</param>
        /// <returns>A <see cref="ResultCode"/> reporting an error or a success.</returns>
        public ResultCode OpenAudioRenderer(out AudioRenderSystem renderer, IVirtualMemoryManager memoryManager, ref AudioRendererConfiguration parameter, ulong appletResourceUserId, ulong workBufferAddress, ulong workBufferSize, uint processHandle)
        {
            int sessionId = AcquireSessionId();

            AudioRenderSystem audioRenderer = new AudioRenderSystem(this, _sessionsSystemEvent[sessionId]);

            ResultCode result = audioRenderer.Initialize(ref parameter, processHandle, workBufferAddress, workBufferSize, sessionId, appletResourceUserId, memoryManager);

            if (result == ResultCode.Success)
            {
                renderer = audioRenderer;

                Register(renderer);
            }
            else
            {
                ReleaseSessionId(sessionId);

                renderer = null;
            }

            return result;
        }

        public void Dispose()
        {
            if (Interlocked.CompareExchange(ref _disposeState, 1, 0) == 0)
            {
                Dispose(true);
            }
        }

        protected virtual void Dispose(bool disposing)
        {
            if (disposing)
            {
                // Clone the sessions array to dispose them outside the lock.
                AudioRenderSystem[] sessions;

                lock (_sessionLock)
                {
                    sessions = _sessions.ToArray();
                }

                foreach (AudioRenderSystem renderer in sessions)
                {
                    renderer?.Dispose();
                }

                lock (_audioProcessorLock)
                {
                    if (_isRunning)
                    {
                        StopLocked();
                    }
                }

                Processor.Dispose();
            }
        }
    }
}