#include "comic.h"

#include <QPixmap>
#include <QRegExp>
#include <QString>
#include <algorithm>
#include <QDir>
#include <QFileInfoList>
#include <QCoreApplication>

#include "bookmarks.h" //TODO desacoplar la dependencia con bookmarks
#include "qnaturalsorting.h"
#include "compressed_archive.h"
#include "comic_db.h"

#include "QsLog.h"

enum YACReaderPageSortingMode
{
	YACReaderNumericalSorting,
	YACReaderHeuristicSorting,
	YACReaderAlphabeticalSorting
};

void comic_pages_sort(QList<QString> & pageNames, YACReaderPageSortingMode sortingMode);

const QStringList Comic::imageExtensions = QStringList() << "*.jpg" << "*.jpeg" << "*.png" << "*.gif" << "*.tiff" << "*.tif" << "*.bmp" << "*.webp";
const QStringList Comic::literalImageExtensions = QStringList() << "jpg" << "jpeg" << "png" << "gif" << "tiff" << "tif" << "bmp" << "webp";

#ifndef use_unarr
const QStringList ComicArchiveExtensions = QStringList() << "*.cbr" << "*.cbz" << "*.rar" << "*.zip" << "*.tar" << "*.7z" << "*.cb7" << "*.arj" << "*.cbt";
const QStringList LiteralComicArchiveExtensions = QStringList() << "cbr" << "cbz" << "rar" << "zip" << "tar" << "7z" << "cb7" << "arj" << "cbt";
#else
const QStringList ComicArchiveExtensions = QStringList() << "*.cbr" << "*.cbz" << "*.rar" << "*.zip" << "*.tar" << "*.cbt";
const QStringList LiteralComicArchiveExtensions = QStringList() << "cbr" << "cbz" << "rar" << "zip" << "tar" << "cbt";
#endif //use_unarr
#ifndef NO_PDF
const QStringList Comic::comicExtensions = QStringList() << ComicArchiveExtensions << "*.pdf";
const QStringList Comic::literalComicExtensions = QStringList() << LiteralComicArchiveExtensions << "pdf";
#else
const QStringList Comic::comicExtensions = ComicArchiveExtensions;
const QStringList Comic::literalComicExtensions = LiteralComicArchiveExtensions;
#endif //NO_PDF

//-----------------------------------------------------------------------------
Comic::Comic()
:_pages(),_index(0),_path(),_loaded(false),bm(new Bookmarks()),_loadedPages(),_isPDF(false),_invalidated(false),_errorOpening(false)
{
	setup();
}
//-----------------------------------------------------------------------------
Comic::Comic(const QString & pathFile, int atPage )
:_pages(),_index(0),_path(pathFile),_loaded(false),bm(new Bookmarks()),_loadedPages(),_isPDF(false),_firstPage(atPage),_errorOpening(false)
{
	setup();
}
//-----------------------------------------------------------------------------
Comic::~Comic()
{
    emit destroyed();
	delete bm;
}
//-----------------------------------------------------------------------------
void Comic::setup()
{
	connect(this,SIGNAL(pageChanged(int)),this,SLOT(checkIsBookmark(int)));
	connect(this,SIGNAL(imageLoaded(int)),this,SLOT(updateBookmarkImage(int)));
	connect(this,SIGNAL(imageLoaded(int)),this,SLOT(setPageLoaded(int)));

    auto l = [&](){ _errorOpening = true; };

    void (Comic::* errorOpeningPtr)() = &Comic::errorOpening;
    void (Comic::* errorOpeningWithStringPtr)(QString) = &Comic::errorOpening;

    connect(this, errorOpeningPtr, l);
    connect(this, errorOpeningWithStringPtr, l);

    connect(this, &Comic::crcErrorFound, l);
}
//-----------------------------------------------------------------------------
int Comic::nextPage()
{
	if(_index<_pages.size()-1)
	{
		_index++;

		emit pageChanged(_index);
	}
	else
	{
		emit isLast();
	}
	return _index;
}
//---------------------------------------------------------------------------
int Comic::previousPage()
{
	if(_index>0)
	{
		_index--;

		emit pageChanged(_index);
	}
	else
	{
		emit isCover();
	}
	return _index;
}
//-----------------------------------------------------------------------------
void Comic::setIndex(unsigned int index)
{
	int previousIndex = _index;
	if(static_cast<int>(index)<_pages.size()-1)
	{
		_index = index;
	}
	else
	{
		_index = _pages.size()-1;
	}

	if(previousIndex != _index)
	{
		emit pageChanged(_index);
	}
}
//-----------------------------------------------------------------------------
/*QPixmap * Comic::currentPage()
{
	QPixmap * p = new QPixmap();
	p->loadFromData(_pages[_index]);
	return p;
}
//-----------------------------------------------------------------------------
QPixmap * Comic::operator[](unsigned int index)
{
	QPixmap * p = new QPixmap();
	p->loadFromData(_pages[index]);
	return p;
}*/
bool Comic::load(const QString & path, const ComicDB & comic)
{
	Q_UNUSED(path);
	Q_UNUSED(comic);
	return false;
};
//-----------------------------------------------------------------------------
bool Comic::loaded()
{
	return _loaded;
}
//-----------------------------------------------------------------------------
void Comic::loadFinished()
{
	emit imagesLoaded();
}
//-----------------------------------------------------------------------------
void Comic::setBookmark()
{
	QImage p;
	p.loadFromData(_pages[_index]);
	bm->setBookmark(_index,p);
	//emit bookmarksLoaded(*bm);
	emit bookmarksUpdated();
}
//-----------------------------------------------------------------------------
void Comic::removeBookmark()
{
	bm->removeBookmark(_index);
	//emit bookmarksLoaded(*bm);
	emit bookmarksUpdated();
}
//-----------------------------------------------------------------------------
void Comic::saveBookmarks()
{
	QImage p;
	p.loadFromData(_pages[_index]);
	bm->setLastPage(_index,p);
	bm->save();
}
//-----------------------------------------------------------------------------
void Comic::checkIsBookmark(int index)
{
	emit isBookmark(bm->isBookmark(index));
}
//-----------------------------------------------------------------------------
void Comic::updateBookmarkImage(int index)
{
    if (bm == nullptr) {
        return;
    }
    
	if(bm->isBookmark(index))
	{
		QImage p;
		p.loadFromData(_pages[index]);
		bm->setBookmark(index,p);
		emit bookmarksUpdated();
		//emit bookmarksLoaded(*bm);
		
	}
	if(bm->getLastPage() == index)
	{
		QImage p;
		p.loadFromData(_pages[index]);
		bm->setLastPage(index,p);
		emit bookmarksUpdated();
		//emit bookmarksLoaded(*bm);
	}

}
//-----------------------------------------------------------------------------
void Comic::setPageLoaded(int page)
{
    _loadedPages[page] = true;
}

void Comic::invalidate()
{
    _invalidated = true;
    emit invalidated();
}
//-----------------------------------------------------------------------------
QByteArray Comic::getRawPage(int page)
{
	if(page < 0 || page >= _pages.size())
	{
		return QByteArray();
	}
	return _pages[page];
}
//-----------------------------------------------------------------------------
bool Comic::pageIsLoaded(int page)
{
	if(page < 0 || page >= _pages.size())
	{
		return false;
	}
	return _loadedPages[page];
}

bool Comic::hasBeenAnErrorOpening()
{
    return _errorOpening;
}

bool Comic::fileIsComic(const QString &path)
{
	QFileInfo info(path);
	return literalComicExtensions.contains(info.suffix());
}

QList<QString> Comic::findValidComicFiles(const QList<QUrl> &list)
{
	QLOG_DEBUG() << "-findValidComicFiles-";
	QList<QString> validComicFiles;
	QString currentPath;
	foreach (QUrl url, list) 
	{
		currentPath = url.toLocalFile();
		if(Comic::fileIsComic(currentPath))
		{
			validComicFiles << currentPath;
		}
		else if(QFileInfo(currentPath).isDir())
		{
			validComicFiles << findValidComicFilesInFolder(currentPath);
		}
	}
	QLOG_DEBUG() << "-" << validComicFiles << "-";
	return validComicFiles;
}

QList<QString> Comic::findValidComicFilesInFolder(const QString &path)
{
	QLOG_DEBUG() << "-findValidComicFilesInFolder-" << path;

	if(!QFileInfo(path).isDir())
	return QList<QString>();

	QList<QString> validComicFiles;
	QDir folder(path);
	folder.setNameFilters(Comic::comicExtensions);
	folder.setFilter(QDir::AllDirs|QDir::Files|QDir::NoDotAndDotDot);
	QFileInfoList folderContent = folder.entryInfoList();

	QString currentPath;
	foreach (QFileInfo info, folderContent) 
	{
	        currentPath = info.absoluteFilePath();
		if(info.isDir())
		{
			validComicFiles << findValidComicFilesInFolder(currentPath); //find comics recursively
		}
		else if(Comic::fileIsComic(currentPath))
		{
			validComicFiles << currentPath;
		}
	}
	return validComicFiles;
}

////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////

FileComic::FileComic()
	:Comic()
{

}

FileComic::FileComic(const QString & path, int atPage )
	:Comic(path,atPage)
{
	load(path,atPage);
}

FileComic::~FileComic()
{
	_pages.clear();
	_loadedPages.clear();
	_fileNames.clear();
	_newOrder.clear();
	_order.clear();
}

bool FileComic::load(const QString & path, int atPage)
{
	QFileInfo fi(path);

	if(fi.exists())
	{
		if(atPage == -1)
		{
			bm->newComic(path);
			emit bookmarksUpdated();
		}
		_firstPage = atPage;
		//emit bookmarksLoaded(*bm);

		_path = QDir::cleanPath(path);
		//load files size

		return true;
	}
	else
	{
		//QMessageBox::critical(NULL,tr("Not found"),tr("Comic not found")+" : " + path);
		emit errorOpening();
		return false;
	}
}

bool FileComic::load(const QString & path, const ComicDB & comic)
{
	QFileInfo fi(path);

	if(fi.exists())
	{
		QList<int> bookmarkIndexes;
		bookmarkIndexes << comic.info.bookmark1 << comic.info.bookmark2 << comic.info.bookmark3;
		if(bm->load(bookmarkIndexes,comic.info.currentPage-1))
		{
			emit bookmarksUpdated();
		}
		_firstPage = comic.info.currentPage-1;
		_path = QDir::cleanPath(path);
		return true;
	}
	else
	{
		//QMessageBox::critical(NULL,tr("Not found"),tr("Comic not found")+" : " + path);
		moveToThread(QCoreApplication::instance()->thread());
		emit errorOpening();
		return false;
	}
}

QList<QString> FileComic::filter(const QList<QString> & src)
{
	QList<QString> extensions = getSupportedImageLiteralFormats();
	QList<QString> filtered;
	bool fileAccepted = false;

	foreach(QString fileName,src)
	{
		fileAccepted = false;
		if(!fileName.contains("__MACOSX"))
		{
			foreach(QString extension,extensions)
			{
				if(fileName.endsWith(extension,Qt::CaseInsensitive))
				{
					fileAccepted = true;
					break;
				}
			}
		}
		if(fileAccepted)
		{
			filtered.append(fileName);
		}
	}

	return filtered;
}

//DELEGATE methods
void FileComic::fileExtracted(int index, const QByteArray & rawData)
{
	/*QFile f("c:/temp/out2.txt");
	f.open(QIODevice::Append);
	QTextStream out(&f);*/
	int sortedIndex = _fileNames.indexOf(_order.at(index));
	//out << sortedIndex << " , ";
	//f.close();
	if(sortedIndex == -1)
	{
		return;
	}
	_pages[sortedIndex] = rawData;
	emit imageLoaded(sortedIndex);
	emit imageLoaded(sortedIndex,_pages[sortedIndex]);
}

void FileComic::crcError(int index)
{
	emit crcErrorFound(tr("CRC error on page (%1): some of the pages will not be displayed correctly").arg(index+1));
}

//TODO: comprobar que si se produce uno de estos errores, la carga del c�mic es irrecuperable
void FileComic::unknownError(int index)
{
	Q_UNUSED(index)
	emit errorOpening(tr("Unknown error opening the file"));
	//emit errorOpening();
}

bool FileComic::isCancelled()
{
    return _invalidated;
}

//--------------------------------------

QList<QVector<quint32> > FileComic::getSections(int & sectionIndex)
{
	QVector<quint32> sortedIndexes;
	foreach(QString name, _fileNames)
	{
		sortedIndexes.append(_order.indexOf(name));
	}
	QList<QVector <quint32> > sections;
	quint32 previous = 0;
	sectionIndex = -1;
	int sectionCount = 0;
	QVector <quint32> section;
	int idx = 0;
	unsigned int realIdx;
	foreach(quint32 i, sortedIndexes)
	{
		
		if(_firstPage == idx)
		{
			sectionIndex = sectionCount;
			realIdx  = i;
		}
		if(previous <= i)
		{
			//out << "idx : " << i << endl;
			section.append(i);
			previous = i;
		}
		else
		{
			if(sectionIndex == sectionCount) //found
			{
				if(section.indexOf(realIdx)!=0)
				{
					QVector <quint32> section1;
					QVector <quint32> section2;
					foreach(quint32 si,section)
					{
						if(si<realIdx)
						{
							section1.append(si);
						}
						else
						{
							section2.append(si);
						}
					}
					sectionIndex++;
					sections.append(section1);
					sections.append(section2);
					//out << "SPLIT" << endl;
				}
				else
				{
					sections.append(section);
				}
			}
			else
			{
				sections.append(section);
			}
			section = QVector <quint32> ();
			//out << "---------------" << endl;
			section.append(i);
			//out << "idx : " << i << endl;
			previous = i;
			sectionCount++;
		}

		idx++;
	}
	
	if(sectionIndex == sectionCount) //found
	{
		if(section.indexOf(realIdx)!=0)
		{
			QVector <quint32> section1;
			QVector <quint32> section2;
			foreach(quint32 si,section)
			{
				if(si<realIdx)
				{
					section1.append(si);
				}
				else
				{
					section2.append(si);
				}
			}
			sectionIndex++;
			sections.append(section1);
			sections.append(section2);
			//out << "SPLIT" << endl;

		}
		else
		{
			sections.append(section);
		}
	}
	else
	{
		sections.append(section);
	}

	//out << "se han encontrado : " << sections.count() << " sectionIndex : " << sectionIndex << endl;
	return sections;
}

void FileComic::process()
{
	CompressedArchive archive(_path);
	if(!archive.toolsLoaded())
	{
		moveToThread(QCoreApplication::instance()->thread());
		emit errorOpening(tr("7z not found"));
		return;
	}

	if(!archive.isValid())
	{
		moveToThread(QCoreApplication::instance()->thread());
		emit errorOpening(tr("Format not supported"));
		return;
	}

	//se filtran para obtener s�lo los formatos soportados
	_order = archive.getFileNames();
	_fileNames = filter(_order);

	if(_fileNames.size()==0)
	{
		//QMessageBox::critical(NULL,tr("File error"),tr("File not found or not images in file"));
		moveToThread(QCoreApplication::instance()->thread());
		emit errorOpening();
		return;
	}

	//TODO, cambiar por listas
	//_order = _fileNames;

	_pages.resize(_fileNames.size());
	_loadedPages = QVector<bool>(_fileNames.size(),false);

	emit pageChanged(0); // this indicates new comic, index=0
	emit numPages(_pages.size());
	_loaded = true;

	_cfi=0;

	//TODO, add a setting for choosing the type of page sorting used.
	comic_pages_sort(_fileNames, YACReaderHeuristicSorting);

	if(_firstPage == -1)
	{
		_firstPage = bm->getLastPage();
	}

	if(_firstPage >= _pages.length())
	{
		_firstPage = 0;
	}

	_index = _firstPage;
	emit(openAt(_index));

	int sectionIndex;
	QList<QVector <quint32> > sections = getSections(sectionIndex);

	for(int i = sectionIndex; i<sections.count() ; i++)
	{
        if(_invalidated)
        {
            moveToThread(QCoreApplication::instance()->thread());
            return;
        }
		archive.getAllData(sections.at(i),this);
	}
	for(int i = 0; i<sectionIndex; i++)
	{
        if(_invalidated)
        {
            moveToThread(QCoreApplication::instance()->thread());
            return;
        }
		archive.getAllData(sections.at(i),this);
	}
	//archive.getAllData(QVector<quint32>(),this);
	/*
	foreach(QString name,_fileNames)
	{
		index = _order.indexOf(name);
		sortedIndex = _fileNames.indexOf(name);
		_pages[sortedIndex] = allData.at(index);
		emit imageLoaded(sortedIndex);
		emit imageLoaded(sortedIndex,_pages[sortedIndex]);
	}*/
	moveToThread(QCoreApplication::instance()->thread());
	emit imagesLoaded();
}


////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////

FolderComic::FolderComic()
	:Comic()
{

}

FolderComic::FolderComic(const QString & path, int atPage )
	:Comic(path, atPage )
{
	load(path, atPage );
}

FolderComic::~FolderComic()
{

}

bool FolderComic::load(const QString & path, int atPage )
{
	_path = path;
	if(atPage == -1)
	{
		bm->newComic(_path);
		emit bookmarksUpdated();
	}
	_firstPage = atPage;
	//emit bookmarksLoaded(*bm);
	return true;
}

void FolderComic::process()
{
	QDir d(_path);

	d.setNameFilters(getSupportedImageFormats());
	d.setFilter(QDir::Files|QDir::NoDotAndDotDot);
	//d.setSorting(QDir::Name|QDir::IgnoreCase|QDir::LocaleAware);
	QFileInfoList list = d.entryInfoList();

	//don't fix double page files sorting, because the user can see how the SO sorts the files in the folder.
	std::sort(list.begin(),list.end(),naturalSortLessThanCIFileInfo);

	int nPages = list.size();
	_pages.clear();
	_pages.resize(nPages);
	_loadedPages = QVector<bool>(nPages,false);

	if(nPages==0)
	{
		//TODO emitir este mensaje en otro sitio
		//QMessageBox::critical(NULL,QObject::tr("No images found"),QObject::tr("There are not images on the selected folder"));
		moveToThread(QCoreApplication::instance()->thread());
		emit errorOpening();
	}
	else
	{
		if(_firstPage == -1)
		{
			_firstPage = bm->getLastPage();
		}

		if(_firstPage >= _pages.length())
		{
		    _firstPage = 0;
		}

		_index = _firstPage;

		emit(openAt(_index));

		emit pageChanged(0); // this indicates new comic, index=0
		emit numPages(_pages.size());
		_loaded = true;

		int count=0;
		int i=_firstPage;
		while(count<nPages)
		{
            if(_invalidated)
            {
                moveToThread(QCoreApplication::instance()->thread());
                return;
            }

			QFile f(list.at(i).absoluteFilePath());
			f.open(QIODevice::ReadOnly);
			_pages[i]=f.readAll();
			emit imageLoaded(i);
			emit imageLoaded(i,_pages[i]);
			i++;
			if(i==nPages)
			{
				i=0;
			}
			count++;
		}
	}
        moveToThread(QCoreApplication::instance()->thread());
	emit imagesLoaded();
}

////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////

#ifndef NO_PDF

PDFComic::PDFComic()
	:Comic()
{

}

PDFComic::PDFComic(const QString & path, int atPage)
	:Comic(path,atPage)
{
	load(path,atPage);
}

PDFComic::~PDFComic()
{

}

bool PDFComic::load(const QString & path, int atPage)
{	
	QFileInfo fi(path);

	if(fi.exists())
	{
		_path = path;
		if(atPage == -1)
		{
			bm->newComic(_path);
			emit bookmarksUpdated();
		}
		_firstPage = atPage;
		//emit bookmarksLoaded(*bm);
		return true;
	}
	else
	{
		moveToThread(QCoreApplication::instance()->thread());
		emit errorOpening();
		return false;
	}
}

bool PDFComic::load(const QString & path, const ComicDB & comic)
{
	QFileInfo fi(path);

	if(fi.exists())
	{
		QList<int> bookmarkIndexes;
		bookmarkIndexes << comic.info.bookmark1 << comic.info.bookmark2 << comic.info.bookmark3;
		if(bm->load(bookmarkIndexes,comic.info.currentPage-1))
		{
			emit bookmarksUpdated();
		}
		_firstPage = comic.info.currentPage-1;
		_path = QDir::cleanPath(path);
		return true;
	}
	else
	{
		//QMessageBox::critical(NULL,tr("Not found"),tr("Comic not found")+" : " + path);
		moveToThread(QCoreApplication::instance()->thread());
		emit errorOpening();
		return false;
	}
}

void PDFComic::process()
{
#if defined Q_OS_MAC && defined USE_PDFKIT
	pdfComic = new MacOSXPDFComic();
	if(!pdfComic->openComic(_path))
	{
		delete pdfComic;
		emit errorOpening();
		return;
	}
#elif defined USE_PDFIUM
	pdfComic = new PdfiumComic();
	if(!pdfComic->openComic(_path))
	{
		delete pdfComic;
		emit errorOpening();
		return;
	}
#else
	pdfComic = Poppler::Document::load(_path);
	if (!pdfComic)
	{
		//delete pdfComic;
		//pdfComic = 0;
		moveToThread(QCoreApplication::instance()->thread());
		emit errorOpening();
		return;
	}
	if (pdfComic->isLocked())
	{
		moveToThread(QCoreApplication::instance()->thread());
		emit errorOpening();
		return;
	}

	//pdfComic->setRenderHint(Poppler::Document::Antialiasing, true);
	pdfComic->setRenderHint(Poppler::Document::TextAntialiasing, true);
#endif

	int nPages = pdfComic->numPages();
	emit pageChanged(0); // this indicates new comic, index=0
	emit numPages(nPages);
	_loaded = true;
	//QMessageBox::critical(NULL,QString("%1").arg(nPages),tr("Invalid PDF file"));

	_pages.clear();
	_pages.resize(nPages);
	_loadedPages = QVector<bool>(nPages,false);

	if(_firstPage == -1)
	{
		_firstPage = bm->getLastPage();
	}

	if(_firstPage >= _pages.length())
	{
		_firstPage = 0;
	}

	_index = _firstPage;
	emit(openAt(_index));

	//buffer index to avoid race conditions
	int buffered_index = _index;
	for(int i=buffered_index;i<nPages;i++)
	{
        if(_invalidated)
        {
            delete pdfComic;
            moveToThread(QCoreApplication::instance()->thread());
            return;
        }

		renderPage(i);
	}
	for(int i=0;i<buffered_index;i++)
	{
        if(_invalidated)
        {
            delete pdfComic;
            moveToThread(QCoreApplication::instance()->thread());
            return;
        }
		renderPage(i);
	}
	
	delete pdfComic;
        moveToThread(QCoreApplication::instance()->thread());
	emit imagesLoaded();
}

void PDFComic::renderPage(int page)
{
#if defined Q_OS_MAC && defined USE_PDFKIT
	QImage img = pdfComic->getPage(page);
	if(!img.isNull())
	{
#elif defined USE_PDFIUM
	QImage img = pdfComic->getPage(page);
	if(!img.isNull())
	{
#else
	Poppler::Page* pdfpage = pdfComic->page(page);
	if (pdfpage)
	{
		QImage img = pdfpage->renderToImage(150,150);
		delete pdfpage;
#endif
		QByteArray ba;
		QBuffer buf(&ba);
		img.save(&buf, "jpg", 96);
		_pages[page] = ba;
		emit imageLoaded(page);
		emit imageLoaded(page,_pages[page]);
	}
}

#endif //NO_PDF

Comic * FactoryComic::newComic(const QString & path)
{

	QFileInfo fi(path);
	if(fi.exists())
	{
		if(fi.isFile())
		{	
			#ifndef NO_PDF
			if(fi.suffix().compare("pdf",Qt::CaseInsensitive) == 0)
			{
				return new PDFComic();
			}
			else
			{
				return new FileComic();
			}
			#else
			return new FileComic();
			#endif
		}
		else
		{
			if(fi.isDir())
			{
				return new FolderComic();
			}
			else
			{
				return NULL;
			}
		}
	}
	else
		return NULL;

}


bool is_double_page(const QString & pageName, const QString & commonPrefix, const int maxExpectedDoublePagesNumberLenght)
{
	if(pageName.startsWith(commonPrefix))
	{
		QString substringContainingPageNumbers = pageName.mid(commonPrefix.length());
		QString pageNumbersSubString;
		for(int i = 0 ; i < substringContainingPageNumbers.length() && substringContainingPageNumbers.at(i).isDigit(); i++)
		{
			pageNumbersSubString.append(substringContainingPageNumbers.at(i));
		}
		if(pageNumbersSubString.length() < 3 || pageNumbersSubString.length() > maxExpectedDoublePagesNumberLenght || pageNumbersSubString.length() % 2 == 1)
		{
			return false;
		}

		int leftPageNumber = pageNumbersSubString.left(pageNumbersSubString.length() / 2).toInt();
		int rightPageNumber = pageNumbersSubString.mid(pageNumbersSubString.length() / 2).toInt();

		if(leftPageNumber == 0 || rightPageNumber == 0)
		{
			return false;
		}
		if((rightPageNumber - leftPageNumber) == 1)
		{
			return true;
		}
	}
	return false;
}

QString get_most_common_prefix(const QList<QString> & pageNames)
{
	if(pageNames.isEmpty())
	{
		return "";
	}
	QMap<QString, uint> frequency;
	int currentPrefixLenght = pageNames.at(0).split('/').last().length();
	int currentPrefixCount = 1;

	int i;
	QString previous;
	QString current;
	for(i = 1; i < pageNames.length(); i++)
	{
		int pos = 0;
		previous = pageNames.at(i-1).split('/').last();
		current = pageNames.at(i).split('/').last();
		for(; pos < current.length() && previous[pos] == current[pos]; pos++);

		if(pos < currentPrefixLenght && pos > 0)
		{
			frequency.insert(previous.left(currentPrefixLenght), currentPrefixCount);
			currentPrefixLenght = pos;
			currentPrefixCount++;
		}
		/*
        else if(pos > currentPrefixLenght)
        {
		frequency.insert(pageNames.at(i-1).left(currentPrefixLenght), currentPrefixCount - 1);
		currentPrefixLenght = pos;
		currentPrefixCount = 2;
        }*/
		else if(pos == 0)
		{
			frequency.insert(previous.left(currentPrefixLenght), currentPrefixCount);
			currentPrefixLenght = current.length();
			currentPrefixCount = 1;
		}
		else
		{
			currentPrefixCount++;
		}
	}

	frequency.insert(previous.left(currentPrefixLenght), currentPrefixCount);

	uint maxFrequency = 0;
	QString common_prefix = "";
	foreach(QString key, frequency.keys())
	{
		if(maxFrequency < frequency.value(key))
		{
			maxFrequency = frequency.value(key);
			common_prefix = key;
		}
	}

	QRegExp allNumberRegExp("\\d+");
	if (allNumberRegExp.exactMatch(common_prefix))
	{
		return "";
	}

	if(maxFrequency < pageNames.length() * 0.60) //the most common tipe of image file should a proper page, so we can asume that the common_prefix should be in, at least, the 60% of the pages
        {
		return "";
	}

	return common_prefix;
}

void get_double_pages(const QList<QString> & pageNames, QList<QString> & singlePageNames/*out*/, QList<QString> & doublePageNames/*out*/)
{
	uint maxExpectedDoublePagesNumberLenght = (int)(log10(pageNames.length())+1) * 2;

	QString mostCommonPrefix = get_most_common_prefix(pageNames);

	foreach(const QString & pageName, pageNames)
	{
		if(is_double_page(pageName.split('/').last(), mostCommonPrefix, maxExpectedDoublePagesNumberLenght))
		{
			doublePageNames.append(pageName);
		}
		else
		{
			singlePageNames.append(pageName);
		}
	}
}

QList<QString> merge_pages(QList<QString> & singlePageNames, QList<QString> & doublePageNames)
{
	//NOTE: this implementation doesn't differ from std::merge using a custom comparator, but it can be easily tweaked if merging requeries an additional heuristic behaviour
	QList<QString> pageNames;

	int i = 0;
	int j = 0;

	while (i < singlePageNames.length() && j < doublePageNames.length())
	{
		if (singlePageNames.at(i).compare(doublePageNames.at(j), Qt::CaseInsensitive) < 0)
		{
			pageNames.append(singlePageNames.at(i++));
		}
		else
		{
			pageNames.append(doublePageNames.at(j++));
		}
	}

	while (i < singlePageNames.length())
	{
		pageNames.append(singlePageNames.at(i++));
	}

	while (j < doublePageNames.length())
	{
		pageNames.append(doublePageNames.at(j++));
	}
	
	return pageNames;
}


void comic_pages_sort(QList<QString> & pageNames, YACReaderPageSortingMode sortingMode)
{
	switch(sortingMode)
	{
		case YACReaderNumericalSorting:
			std::sort(pageNames.begin(), pageNames.end(), naturalSortLessThanCI);
			break;

		case YACReaderHeuristicSorting:
		{
			std::sort(pageNames.begin(), pageNames.end(), naturalSortLessThanCI);

			QList<QString> singlePageNames;
			QList<QString> doublePageNames;

			get_double_pages(pageNames, singlePageNames, doublePageNames);

			if(doublePageNames.length() > 0)
			{
				pageNames = merge_pages(singlePageNames, doublePageNames);
			}
		}
		break;
		
		case YACReaderAlphabeticalSorting:
			std::sort(pageNames.begin(), pageNames.end());
			break;
	}
}