/*
  This file is part of Ingen.
  Copyright 2007-2012 David Robillard <http://drobilla.net/>

  Ingen is free software: you can redistribute it and/or modify it under the
  terms of the GNU Affero General Public License as published by the Free
  Software Foundation, either version 3 of the License, or any later version.

  Ingen 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 Affero General Public License for details.

  You should have received a copy of the GNU Affero General Public License
  along with Ingen.  If not, see <http://www.gnu.org/licenses/>.
*/

#ifndef INGEN_ENGINEBASE_HPP
#define INGEN_ENGINEBASE_HPP

#include <stdint.h>

#include "raul/URI.hpp"

#include "ingen/types.hpp"

namespace Ingen {

class Interface;

/**
   The engine which executes the process graph.

   @ingroup Ingen
*/
class EngineBase
{
public:
	virtual ~EngineBase() {}

	/**
	   Initialise the engine for local use (e.g. without a Jack driver).
	   @param sample_rate Audio sampling rate in Hz.
	   @param block_length Audio block length (i.e. buffer size) in frames.
	*/
	virtual void init(double sample_rate, uint32_t block_length) = 0;

	/**
	   Activate the engine.
	*/
	virtual bool activate() = 0;

	/**
	   Deactivate the engine.
	*/
	virtual void deactivate() = 0;

	/**
	   Return true iff events are waiting to be processed.
	*/
	virtual bool pending_events() = 0;

	/**
	   Process audio for @p sample_count frames.

	   If the return value is non-zero, events have been processed and are
	   awaiting to be finalised (including responding and announcing any changes
	   to clients) via a call to main_iteration().

	   @return The number of events processed.
	*/
	virtual unsigned run(uint32_t sample_count) = 0;

	/**
	   Indicate that a quit is desired.

	   This function simply sets a flag which affects the return value of
	   main_iteration, it does not actually force the engine to stop running or
	   block.  The code driving the engine is responsible for stopping and
	   cleaning up when main_iteration returns false.
	*/
	virtual void quit() = 0;

	/**
	   Run a single iteration of the main context.

	   The main context post-processes events and performs housekeeping duties
	   like collecting garbage.  This should be called regularly, e.g. a few
	   times per second.  The return value indicates whether execution should
	   continue; i.e. if false is returned, a quit has been requested and the
	   caller should cease calling main_iteration() and stop the engine.
	*/
	virtual bool main_iteration() = 0;

	/**
	   Register a client to receive updates about engine changes.
	*/
	virtual void register_client(const Raul::URI& uri,
	                             SPtr<Interface>  client) = 0;

	/**
	   Unregister a client.
	*/
	virtual bool unregister_client(const Raul::URI& uri) = 0;

};

} // namespace Ingen

#endif // INGEN_ENGINEBASE_HPP