// Copyright 2020-2021 The Mumble Developers. All rights reserved.
// Use of this source code is governed by a BSD-style license
// that can be found in the LICENSE file at the root of the
// Mumble source tree or at <https://www.mumble.info/LICENSE>.

#ifndef MUMBLE_CHANNEL_LISTENER_H_
#define MUMBLE_CHANNEL_LISTENER_H_

#include <QtCore/QHash>
#include <QtCore/QObject>
#include <QtCore/QReadWriteLock>
#include <QtCore/QSet>

#include <atomic>

class User;
class Channel;

/// This class serves as a namespace for storing information about ChannelListeners. This is a feature
/// that allows a user to listen to a channel without being in it. Kinda similar to linked channels
/// except that this is something each user can do individually.
class ChannelListener : public QObject {
private:
	Q_OBJECT
	Q_DISABLE_COPY(ChannelListener)

protected:
	/// A lock for guarding m_listeningUsers as well as m_listenedChannels
	mutable QReadWriteLock m_listenerLock;
	/// A map between a user's session and a list of IDs of all channels the user is listening to
	QHash< unsigned int, QSet< int > > m_listeningUsers;
	/// A map between a channel's ID and a list of all user-sessions of users listening to that channel
	QHash< int, QSet< unsigned int > > m_listenedChannels;
#ifdef MUMBLE
	/// A lock for guarding m_listenerVolumeAdjustments
	mutable QReadWriteLock m_volumeLock;
	/// A map between channel IDs and local volume adjustments to be made for ChannelListeners
	/// in that channel
	QHash< int, float > m_listenerVolumeAdjustments;

	/// A flag indicating whether the initial synchronization with the server has finished yet
	std::atomic< bool > m_initialSyncDone;
#endif

	/// The static ChannelListener instance returned by ChannelListener::get()
	static ChannelListener s_instance;

	/// Constructor
	ChannelListener();

	/// Adds a listener to the channel.
	///
	/// @param userSession The session ID of the user
	/// @param channelID The ID of the channel
	void addListenerImpl(unsigned int userSession, int channelID);

	/// Removes a listener from the channel.
	///
	/// @param userSession The session ID of the user
	/// @param channelID The ID of the channel
	void removeListenerImpl(unsigned int userSession, int channelID);

	/// @param userSession The session ID of the user
	/// @param channelID The ID of the channel
	/// @returns Whether the given user is listening to the given channel
	bool isListeningImpl(unsigned int userSession, int channelID) const;

	/// @param userSession The session ID of the user
	/// @returns Whether this user is listening to any channel via the ChannelListener feature
	bool isListeningToAnyImpl(unsigned int userSession) const;

	/// @param channelID The ID of the channel
	/// @returns Whether any user listens to this channel via the ChannelListener feature
	bool isListenedByAnyImpl(int channelID) const;

	/// @param channelID The ID of the channel
	/// @returns A set of user sessions of users listening to the given channel
	const QSet< unsigned int > getListenersForChannelImpl(int channelID) const;

	/// @param userSession The session ID of the user
	/// @returns A set of channel IDs of channels the given user is listening to
	const QSet< int > getListenedChannelsForUserImpl(unsigned int userSession) const;

	/// @param channelID The ID of the channel
	/// @returns The amount of users that are listening to the given channel
	int getListenerCountForChannelImpl(int channelID) const;

	/// @param userSession The session ID of the user
	/// @returns The amount of channels the given user is listening to
	int getListenedChannelCountForUserImpl(unsigned int userSession) const;

#ifdef MUMBLE
	/// Sets the local volume adjustment for any channelListener in the given channel.
	///
	/// @param channelID The ID of the channel
	/// @param volumeAdjustment The volume adjustment to apply
	void setListenerLocalVolumeAdjustmentImpl(int channelID, float volumeAdjustment);

	/// @param channelID The ID of the channel
	/// @param The local volume adjustment for the given channel. If none has been set,
	/// 	1.0f is being returned.
	float getListenerLocalVolumeAdjustmentImpl(int channelID) const;

	/// @param filter Whether to filter out adjustments of 1 (which have no effect)
	/// @returns A map between channel IDs and the currently set volume adjustment
	QHash< int, float > getAllListenerLocalVolumeAdjustmentsImpl(bool filter = false) const;

	/// @done Whether the initial synchronization with the server is done yet
	void setInitialServerSyncDoneImpl(bool done);
#endif

	/// Clears all ChannelListeners and volume adjustments
	void clearImpl();

public:
	/// @returns The static ChannelListener instance
	static ChannelListener &get();

	/// Adds a listener to the channel.
	///
	/// @param userSession The session ID of the user
	/// @param channelID The ID of the channel
	static void addListener(unsigned int userSession, int channelID);

	/// Adds a listener to the channel.
	///
	/// @param userSession The session ID of the user
	/// @param channelID The ID of the channel
	static void addListener(const User *user, const Channel *channel);


	/// Removes a listener from the channel.
	///
	/// @param userSession The session ID of the user
	/// @param channelID The ID of the channel
	static void removeListener(unsigned int userSession, int channelID);

	/// Removes a listener from the channel.
	///
	/// @param userSession The session ID of the user
	/// @param channelID The ID of the channel
	static void removeListener(const User *user, const Channel *channel);


	/// @param userSession The session ID of the user
	/// @param channelID The ID of the channel
	/// @returns Whether the given user is listening to the given channel
	static bool isListening(unsigned int userSession, int channelID);

	/// @param channel A pointer to the channel object
	/// @param user A pointer to the user object
	/// @returns Whether the given user is listening to the given channel
	static bool isListening(const User *user, const Channel *channel);


	/// @param userSession The session ID of the user
	/// @returns Whether this user is listening to any channel via the ChannelListener feature
	static bool isListeningToAny(unsigned int userSession);

	/// @param user A pointer to the user object
	/// @returns Whether this user is listening to any channel via the ChannelListener feature
	static bool isListeningToAny(const User *user);


	/// @param channelID The ID of the channel
	/// @returns Whether any user listens to this channel via the ChannelListener feature
	static bool isListenedByAny(int channelID);

	/// @param channel A pointer to the channel object
	/// @returns Whether any user listens to this channel via the ChannelListener feature
	static bool isListenedByAny(const Channel *channel);


	/// @param channelID The ID of the channel
	/// @returns A set of user sessions of users listening to the given channel
	static const QSet< unsigned int > getListenersForChannel(int channelID);

	/// @param channel A pointer to the channel object
	/// @returns A set of user sessions of users listening to the given channel
	static const QSet< unsigned int > getListenersForChannel(const Channel *channel);


	/// @param userSession The session ID of the user
	/// @returns A set of channel IDs of channels the given user is listening to
	static const QSet< int > getListenedChannelsForUser(unsigned int userSession);

	/// @param user A pointer to the user object
	/// @returns A set of channel IDs of channels the given user is listening to
	static const QSet< int > getListenedChannelsForUser(const User *user);


	/// @param channelID The ID of the channel
	/// @returns The amount of users that are listening to the given channel
	static int getListenerCountForChannel(int channelID);

	/// @param channel A pointer to the channel object
	/// @returns The amount of users that are listening to the given channel
	static int getListenerCountForChannel(const Channel *channel);


	/// @param userSession The session ID of the user
	/// @returns The amount of channels the given user is listening to
	static int getListenedChannelCountForUser(unsigned int userSession);

	/// @param user A pointer to the user object
	/// @returns The amount of channels the given user is listening to
	static int getListenedChannelCountForUser(const User *user);


#ifdef MUMBLE
	/// Sets the local volume adjustment for any channelListener in the given channel.
	///
	/// @param channelID The ID of the channel
	/// @param volumeAdjustment The volume adjustment to apply
	static void setListenerLocalVolumeAdjustment(int channelID, float volumeAdjustment);

	/// Sets the local volume adjustment for any channelListener in the given channel.
	///
	/// @param channel A pointer to the channel object
	/// @param volumeAdjustment The volume adjustment to apply
	static void setListenerLocalVolumeAdjustment(const Channel *channel, float volumeAdjustment);


	/// @param channelID The ID of the channel
	/// @param The local volume adjustment for the given channel. If none has been set,
	/// 	1.0f is being returned.
	static float getListenerLocalVolumeAdjustment(int channelID);

	/// @param channel A pointer to the channel object
	/// @param The local volume adjustment for the given channel. If none has been set,
	/// 	1.0f is being returned.
	static float getListenerLocalVolumeAdjustment(const Channel *channel);

	/// @param filter Whether to filter out adjustments of 1 (which have no effect)
	/// @returns A map between channel IDs and the currently set volume adjustment
	static QHash< int, float > getAllListenerLocalVolumeAdjustments(bool filter = false);

	/// @done Whether the initial synchronization with the server is done yet
	static void setInitialServerSyncDone(bool done);

	/// Saves the current ChannelListener state to the database.
	/// NOTE: This function may only be called from the main thread!
	static void saveToDB();
#endif

	/// Clears all ChannelListeners and volume adjustments
	static void clear();

signals:
#ifdef MUMBLE
	void localVolumeAdjustmentsChanged(int channelID, float newAdjustment, float oldAdjustment);
#endif
};

#endif // MUMBLE_CHANNEL_LISTENER_H_