// -*- C++ -*-
/**
 * \file PreviewLoader.h
 * This file is part of LyX, the document processor.
 * Licence details can be found in the file COPYING.
 *
 * \author Angus Leeming
 *
 * Full author contact details are available in file CREDITS.
 *
 * lyx::graphics::PreviewLoader collects latex snippets together. Then, on a
 * startLoading() call, these are dumped to file and processed, converting
 * each snippet to a separate bitmap image file. Once a bitmap file is ready
 * to be loaded back into LyX, the PreviewLoader emits a signal to inform
 * the initiating process.
 */

#ifndef PREVIEWLOADER_H
#define PREVIEWLOADER_H

#include <boost/utility.hpp>
#include <boost/scoped_ptr.hpp>
#include <boost/signal.hpp>

class Buffer;

namespace lyx {
namespace graphics {

class PreviewImage;

class PreviewLoader : boost::noncopyable {
public:
	/** We need buffer because we require the preamble to the
	 *  LaTeX file.
	 */
	PreviewLoader(Buffer const & buffer);
	///
	~PreviewLoader();

	/** Is there an image already associated with this snippet of LaTeX?
	 *  If so, returns a pointer to it, else returns 0.
	 */
	PreviewImage const * preview(std::string const & latex_snippet) const;

	///
	enum Status {
		///
		NotFound,
		///
		InQueue,
		///
		Processing,
		///
		Ready
	};

	/// How far have we got in loading the image?
	Status status(std::string const & latex_snippet) const;

	/// Add a snippet of LaTeX to the queue for processing.
	void add(std::string const & latex_snippet) const;

	/// Remove this snippet of LaTeX from the PreviewLoader.
	void remove(std::string const & latex_snippet) const;

	/** We have accumulated several latex snippets with status "InQueue".
	 *  Initiate their transformation into bitmap images.
	 */
	void startLoading() const;

	/** Connect and you'll be informed when the bitmap image file
	 *  has been created and is ready for loading through
	 *  lyx::graphics::PreviewImage::image().
	 */
	typedef boost::signal<void(PreviewImage const &)> sig_type;
	typedef sig_type::slot_type slot_type;
	///
	boost::signals::connection connect(slot_type const &) const;

	/** When PreviewImage has finished loading the image file into memory,
	 *  it tells the PreviewLoader to tell the outside world
	 */
	void emitSignal(PreviewImage const &) const;

	/// Which buffer owns this loader.
	Buffer const & buffer() const;

private:
	/// Use the Pimpl idiom to hide the internals.
	class Impl;
	/// The pointer never changes although *pimpl_'s contents may.
	boost::scoped_ptr<Impl> const pimpl_;
};

} // namespace graphics
} // namespace lyx

#endif // PREVIEWLOADER_H
