/**
 * \file GraphicsCacheItem.C
 * This file is part of LyX, the document processor.
 * Licence details can be found in the file COPYING.
 *
 * \author Baruch Even
 * \author Herbert Voß
 * \author Angus Leeming
 *
 * Full author contact details are available in file CREDITS.
 */

#include <config.h>

#include "GraphicsCacheItem.h"
#include "GraphicsConverter.h"
#include "GraphicsImage.h"

#include "debug.h"

#include "support/filetools.h"
#include "support/FileMonitor.h"
#include "support/lyxlib.h"

#include <boost/bind.hpp>


namespace support = lyx::support;

using support::ChangeExtension;
using support::FileMonitor;
using support::IsFileReadable;
using support::MakeDisplayPath;
using support::OnlyFilename;
using support::getExtFromContents;
using support::tempName;
using support::unlink;
using support::unzipFile;
using support::zippedFile;

using std::endl;
using std::string;


namespace lyx {
namespace graphics {

struct CacheItem::Impl : public boost::signals::trackable {

	///
	Impl(string const & file);

	/** Start the image conversion process, checking first that it is
	 *  necessary. If it is necessary, then a conversion task is started.
	 *  CacheItem asumes that the conversion is asynchronous and so
	 *  passes a Signal to the converting routine. When the conversion
	 *  is finished, this Signal is emitted, returning the converted
	 *  file to this->imageConverted.
	 *
	 *  If no file conversion is needed, then convertToDisplayFormat() calls
	 *  loadImage() directly.
	 *
	 *  convertToDisplayFormat() will set the loading status flag as
	 *  approriate through calls to setStatus().
	 */
	void convertToDisplayFormat();

	/** Load the image into memory. This is called either from
	 *  convertToDisplayFormat() direct or from imageConverted().
	 */
	void loadImage();

	/** Get a notification when the image conversion is done.
	 *  Connected to a signal on_finish_ which is passed to
	 *  Converter::convert.
	 */
	void imageConverted(bool);

	/** Get a notification when the image loading is done.
	 *  Connected to a signal on_finish_ which is passed to
	 *  lyx::graphics::Image::loadImage.
	 */
	void imageLoaded(bool);

	/** Sets the status of the loading process. Also notifies
	 *  listeners that the status has changed.
	 */
	void setStatus(ImageStatus new_status);

	/** Can be invoked directly by the user, but is also connected to the
	 *  FileMonitor and so is invoked when the file is changed
	 *  (if monitoring is taking place).
	 */
	void startLoading();

	/** If we are asked to load the file for a second or further time,
	 *  (because the file has changed), then we'll have to first reset
	 *  many of the variables below.
	 */
	void reset();

	/// The filename we refer too.
	string const filename_;
	///
	FileMonitor const monitor_;

	/// Is the file compressed?
	bool zipped_;
	/// If so, store the uncompressed file in this temporary file.
	string unzipped_filename_;
	/// What file are we trying to load?
	string file_to_load_;
	/** Should we delete the file after loading? True if the file is
	 *  the result of a conversion process.
	 */
	bool remove_loaded_file_;

	/// The image and its loading status.
	boost::shared_ptr<Image> image_;
	///
	ImageStatus status_;

	/// This signal is emitted when the image loading status changes.
	boost::signal0<void> statusChanged;

	/// The connection to the signal Image::finishedLoading
	boost::signals::connection cl_;

	/// The connection of the signal ConvProcess::finishedConversion,
	boost::signals::connection cc_;

	///
	boost::scoped_ptr<Converter> converter_;
};


CacheItem::CacheItem(string const & file)
	: pimpl_(new Impl(file))
{}


CacheItem::~CacheItem()
{}


string const & CacheItem::filename() const
{
	return pimpl_->filename_;
}


void CacheItem::startLoading() const
{
	pimpl_->startLoading();
}


void CacheItem::startMonitoring() const
{
	if (!pimpl_->monitor_.monitoring())
		pimpl_->monitor_.start();
}


bool CacheItem::monitoring() const
{
	return pimpl_->monitor_.monitoring();
}


unsigned long CacheItem::checksum() const
{
	return pimpl_->monitor_.checksum();
}


Image const * CacheItem::image() const
{
	return pimpl_->image_.get();
}


ImageStatus CacheItem::status() const
{
	return pimpl_->status_;
}


boost::signals::connection CacheItem::connect(slot_type const & slot) const
{
	return pimpl_->statusChanged.connect(slot);
}


//------------------------------
// Implementation details follow
//------------------------------


CacheItem::Impl::Impl(string const & file)
	: filename_(file),
	  monitor_(file, 2000),
	  zipped_(false),
	  remove_loaded_file_(false),
	  status_(WaitingToLoad)
{
	monitor_.connect(boost::bind(&Impl::startLoading, this));
}


void CacheItem::Impl::startLoading()
{
	if (status_ != WaitingToLoad)
		reset();

	convertToDisplayFormat();
}


void CacheItem::Impl::reset()
{
	zipped_ = false;
	if (!unzipped_filename_.empty())
		unlink(unzipped_filename_);
	unzipped_filename_.erase();

	if (remove_loaded_file_ && !file_to_load_.empty())
		unlink(file_to_load_);
	remove_loaded_file_ = false;
	file_to_load_.erase();

	if (image_.get())
		image_.reset();

	status_ = WaitingToLoad;

	if (cl_.connected())
		cl_.disconnect();

	if (cc_.connected())
		cc_.disconnect();

	if (converter_.get())
		converter_.reset();
}


void CacheItem::Impl::setStatus(ImageStatus new_status)
{
	if (status_ == new_status)
		return;

	status_ = new_status;
	statusChanged();
}


void CacheItem::Impl::imageConverted(bool success)
{
	string const text = success ? "succeeded" : "failed";
	lyxerr[Debug::GRAPHICS] << "Image conversion " << text << '.' << endl;

	file_to_load_ = converter_.get() ?
		converter_->convertedFile() : string();
	converter_.reset();
	cc_.disconnect();

	success = !file_to_load_.empty() && IsFileReadable(file_to_load_);

	if (!success) {
		lyxerr[Debug::GRAPHICS] << "Unable to find converted file!"
					<< endl;
		setStatus(ErrorConverting);

		if (zipped_)
			unlink(unzipped_filename_);

		return;
	}

	loadImage();
}


// This function gets called from the callback after the image has been
// converted successfully.
void CacheItem::Impl::loadImage()
{
	setStatus(Loading);
	lyxerr[Debug::GRAPHICS] << "Loading image." << endl;

	image_ = Image::newImage();

	cl_.disconnect();
	cl_ = image_->finishedLoading.connect(
		boost::bind(&Impl::imageLoaded, this, _1));
	image_->load(file_to_load_);
}


void CacheItem::Impl::imageLoaded(bool success)
{
	string const text = success ? "succeeded" : "failed";
	lyxerr[Debug::GRAPHICS] << "Image loading " << text << '.' << endl;

	// Clean up after loading.
	if (zipped_)
		unlink(unzipped_filename_);

	if (remove_loaded_file_ && unzipped_filename_ != file_to_load_)
		unlink(file_to_load_);

	cl_.disconnect();

	if (!success) {
		setStatus(ErrorLoading);
		return;
	}

	// Inform the outside world.
	setStatus(Loaded);
}


} // namespace graphics
} // namespace lyx


namespace {

string const findTargetFormat(string const & from)
{
	typedef lyx::graphics::Image::FormatList FormatList;
	FormatList const formats = lyx::graphics::Image::loadableFormats();

	// There must be a format to load from.
	BOOST_ASSERT(!formats.empty());

	// First ascertain if we can load directly with no conversion
	FormatList::const_iterator it  = formats.begin();
	FormatList::const_iterator end = formats.end();
	for (; it != end; ++it) {
		if (from == *it)
			return *it;
	}

	// So, we have to convert to a loadable format. Can we?
	it = formats.begin();
	for (; it != end; ++it) {
		if (lyx::graphics::Converter::isReachable(from, *it))
			return *it;
		else
			lyxerr[Debug::GRAPHICS]
				<< "Unable to convert from " << from
				<< " to " << *it << std::endl;
	}

	// Failed! so we have to try to convert it to PPM format
	// with the standard converter
	return string("ppm");
}

} // anon namespace


namespace lyx {
namespace graphics {

void CacheItem::Impl::convertToDisplayFormat()
{
	setStatus(Converting);

	// First, check that the file exists!
	if (!IsFileReadable(filename_)) {
		if (status_ != ErrorNoFile) {
			setStatus(ErrorNoFile);
			lyxerr[Debug::GRAPHICS]
				<< "\tThe file is not readable" << endl;
		}
		return;
	}

	// Make a local copy in case we unzip it
	string const filename = zippedFile(filename_) ?
		unzipFile(filename_) : filename_;
	string const displayed_filename = MakeDisplayPath(filename_);
	lyxerr[Debug::GRAPHICS] << "[GrahicsCacheItem::convertToDisplayFormat]\n"
		<< "\tAttempting to convert image file: " << filename
		<< "\n\twith displayed filename: " << displayed_filename
		<< endl;

	string from = getExtFromContents(filename);
	lyxerr[Debug::GRAPHICS]
		<< "\n\tThe file contains " << from << " format data." << endl;
	string const to = findTargetFormat(from);

	if (from == to) {
		// No conversion needed!
		lyxerr[Debug::GRAPHICS] << "\tNo conversion needed (from == to)!" << endl;
		file_to_load_ = filename;
		loadImage();
		return;
	}

	lyxerr[Debug::GRAPHICS] << "\tConverting it to " << to << " format." << endl;
	// Take only the filename part of the file, without path or extension.
	string const temp = ChangeExtension(OnlyFilename(filename), string());

	// Add some stuff to create a uniquely named temporary file.
	// This file is deleted in loadImage after it is loaded into memory.
	string const to_file_base = tempName(string(), temp);
	remove_loaded_file_ = true;

	// Remove the temp file, we only want the name...
	unlink(to_file_base);

	// Connect a signal to this->imageConverted and pass this signal to
	// the graphics converter so that we can load the modified file
	// on completion of the conversion process.
	converter_.reset(new Converter(filename, to_file_base, from, to));
	converter_->connect(boost::bind(&Impl::imageConverted, this, _1));
	converter_->startConversion();
}

} // namespace graphics
} // namespace lyx