/*
    This file is part of Mitsuba, a physically based rendering system.

    Copyright (c) 2007-2014 by Wenzel Jakob and others.

    Mitsuba is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License Version 3
    as published by the Free Software Foundation.

    Mitsuba 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 General Public License for more details.

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

#include "upgrade.h"
#include "save.h"
#include <mitsuba/core/fresolver.h>
#include <boost/algorithm/string.hpp>
#include <QtXmlPatterns/QtXmlPatterns>

struct VersionComparator {
    inline bool operator()(const std::pair<Version, fs::path> &s1,
        const std::pair<Version, fs::path> &s2) const {
        return s1.first < s2.first;
    }
};

class XSLTMessageHandler : public QAbstractMessageHandler {
public:
    XSLTMessageHandler() : m_fatalError(false) { }

    void handleMessage(QtMsgType type, const QString &_descr, const QUrl &id, const QSourceLocation &loc) {
        QString descr(_descr);
        int paragraphStart = descr.indexOf("<p>");
        int paragraphEnd = descr.indexOf("</p>");
        if (paragraphStart != -1 && paragraphEnd != -1)
            descr = descr.mid(paragraphStart+3, paragraphEnd-paragraphStart-3);

        if (loc.isNull())
            SLog(EWarn, "%s", qPrintable(descr));
        else
            SLog(EWarn, "%s (line %i, column %i, url=%s)", qPrintable(descr),
                loc.line(), loc.column(), qPrintable(id.toString()));

        if (type == QtFatalMsg)
            m_fatalError = true;
    }

    inline bool fatalError() const { return m_fatalError; }
private:
    bool m_fatalError;
};

UpgradeManager::UpgradeManager(const FileResolver *resolver) : m_resolver(resolver) {
    fs::path transformationPath =
        resolver->resolveAbsolute("data/schema/scene.xsd").parent_path();

    fs::directory_iterator it(transformationPath), end;
    SLog(EInfo, "Searching for transformations..");

    for (; it != end; ++it) {
        fs::path file = *it;
        std::string extension = file.extension().string(),
            filename = file.filename().string();
        if (boost::to_lower_copy(extension) != ".xsl" ||
           !boost::starts_with(filename, "upgrade_"))
            continue;
        Version version(filename.substr(8, filename.length()-12));
        m_transformations.push_back(std::make_pair(version, file));
    }

    std::sort(m_transformations.begin(), m_transformations.end(), VersionComparator());

    for (size_t i=0; i<m_transformations.size(); ++i)
        SLog(EInfo, "  - registered transformation \"%s\", which updates to version %s",
            m_transformations[i].second.filename().string().c_str(),
            m_transformations[i].first.toString().c_str());
}

void UpgradeManager::performUpgrade(const QString &filename, const Version &version) {
    QString backupFilename = filename;
    if (backupFilename.endsWith(".xml", Qt::CaseInsensitive))
        backupFilename.replace(backupFilename.length()-4, 4, ".bak");
    SLog(EInfo, "Saving a backup copy of \"%s\" as \"%s\"",
        QStringToUTF8(filename), QStringToUTF8(backupFilename));

    QFile file(filename), backupFile(backupFilename);
    if (backupFile.exists())
        backupFile.remove();
    if (!file.copy(backupFilename))
        SLog(EError, "Could not create a backup copy -- "
            "stopping the upgrade operation!");

    if (!file.open(QIODevice::ReadOnly))
        SLog(EError, "Unable to open \"%s\" with read access -- stopping "
            "the upgrade operation.", QStringToUTF8(filename));
    QByteArray inputArray = file.readAll(), outputArray;
    file.close();

    QBuffer inputBuffer(&inputArray);
    QBuffer outputBuffer(&outputArray);

    XSLTMessageHandler handler;

    int nTransformations=0;
    for (size_t i=0; i<m_transformations.size(); ++i) {
        if (m_transformations[i].first <= version)
            continue;
        inputBuffer.open(QIODevice::ReadOnly);
        outputBuffer.open(QIODevice::WriteOnly | QIODevice::Truncate);

        SLog(EInfo, "Applying transformation \"%s\" ..",
            m_transformations[i].second.filename().string().c_str());
        QString trafoFilename = fromFsPath(m_transformations[i].second);
        QFile trafoFile(trafoFilename);
        if (!trafoFile.open(QIODevice::ReadOnly | QIODevice::Text))
            SLog(EError, "Unable to open the stylesheet \"%s\" -- stopping "
                "the upgrade operation.", QStringToUTF8(trafoFilename));

        QXmlQuery query(QXmlQuery::XSLT20);
        query.setMessageHandler(&handler);
        query.setFocus(&inputBuffer);
        query.setQuery(&trafoFile);
        if (!query.isValid())
            SLog(EError, "Unable to parse the stylesheet \"%s\" -- stopping "
                "the upgrade operation.", QStringToUTF8(trafoFilename));

        SLog(EInfo, "Transformation is ready, running it now..");
        QXmlFormatter formatter(query, &outputBuffer);
        formatter.setIndentationDepth(1);
        query.evaluateTo(&formatter);

        if (handler.fatalError())
            SLog(EError, "A fatal error was encountered -- stopping "
                "the upgrade operation.");

        /* Swap the outputs */
        inputBuffer.close();
        outputBuffer.close();
        inputArray = outputArray;
        ++nTransformations;
    }

    if (nTransformations == 0) {
        SLog(EError, "Strange -- no transformations were applied? "
            "Stopping the upgrade operation.");
    }

    /* Done, write back to disk */
    SLog(EInfo, "Successfully applied %i transformations, writing the result "
        "to \"%s\" ..", nTransformations, QStringToUTF8(filename));

    if (!file.open(QIODevice::WriteOnly | QIODevice::Truncate)) {
        SLog(EError, "Unable to open \"%s\" with write access -- stopping "
            "the upgrade operation.", QStringToUTF8(filename));
    }

    int line, column;
    QString errorMsg;
    QDomDocument doc;
    if (!doc.setContent(inputArray, &errorMsg, &line, &column))
        SLog(EError, "Unable to parse file: error %s at line %i, colum %i",
            QStringToUTF8(errorMsg), line, column);
    QDomElement root = doc.documentElement();

    /* Search for include nodes */
    QDomNode n = root.firstChild();
    while (!n.isNull()) {
        QDomElement e = n.toElement();
        if (!e.isNull()) {
            if (e.tagName() == "include") {
                fs::path path = m_resolver->resolve(toFsPath(e.attribute("filename")));
                SLog(EInfo, "Recursively upgrading include file \"%s\" ..",
                        path.string().c_str());
                performUpgrade(fromFsPath(path), version);
            }
        }
        n = n.nextSibling();
    }

    QTextStream input(inputArray);
    QTextStream output(&file);
    output << "<?xml version=\"1.0\" encoding=\"utf-8\"?>"
        << endl << endl;
    cleanupXML(input, output);
    file.close();

    QDomDocument tooltipDoc;

}