//    Copyright (C) 2019-2020 Jakub Melka
//
//    This file is part of PdfForQt.
//
//    PdfForQt is free software: you can redistribute it and/or modify
//    it under the terms of the GNU Lesser General Public License as published by
//    the Free Software Foundation, either version 3 of the License, or
//    (at your option) any later version.
//
//    PdfForQt 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 Lesser General Public License for more details.
//
//    You should have received a copy of the GNU Lesser General Public License
//    along with PDFForQt.  If not, see <https://www.gnu.org/licenses/>.

#include "pdfcompiler.h"
#include "pdfcms.h"
#include "pdfdrawspacecontroller.h"
#include "pdfprogress.h"
#include "pdfexecutionpolicy.h"

#include <QtConcurrent/QtConcurrent>

#include <execution>

namespace pdf
{

PDFAsynchronousPageCompiler::PDFAsynchronousPageCompiler(PDFDrawWidgetProxy* proxy) :
    BaseClass(proxy),
    m_proxy(proxy)
{
    m_cache.setMaxCost(128 * 1024 * 1024);
}

void PDFAsynchronousPageCompiler::start()
{
    switch (m_state)
    {
        case State::Inactive:
        {
            m_state = State::Active;
            break;
        }

        case State::Active:
            break; // We have nothing to do...

        case State::Stopping:
        {
            // We shouldn't call this function while stopping!
            Q_ASSERT(false);
            break;
        }
    }
}

void PDFAsynchronousPageCompiler::stop(bool clearCache)
{
    switch (m_state)
    {
        case State::Inactive:
            break; // We have nothing to do...

        case State::Active:
        {
            // Stop the engine
            m_state = State::Stopping;

            for (const auto& taskItem : m_tasks)
            {
                disconnect(taskItem.second.taskWatcher, &QFutureWatcher<PDFPrecompiledPage>::finished, this, &PDFAsynchronousPageCompiler::onPageCompiled);
                taskItem.second.taskWatcher->waitForFinished();
            }
            m_tasks.clear();

            if (clearCache)
            {
                m_cache.clear();
            }

            m_state = State::Inactive;
            break;
        }

        case State::Stopping:
        {
            // We shouldn't call this function while stopping!
            Q_ASSERT(false);
            break;
        }
    }
}

void PDFAsynchronousPageCompiler::reset()
{
    stop(true);
    start();
}

void PDFAsynchronousPageCompiler::setCacheLimit(int limit)
{
    m_cache.setMaxCost(limit);
}

const PDFPrecompiledPage* PDFAsynchronousPageCompiler::getCompiledPage(PDFInteger pageIndex, bool compile)
{
    if (m_state != State::Active || !m_proxy->getDocument())
    {
        // Engine is not active, always return nullptr
        return nullptr;
    }

    const PDFPrecompiledPage* page = m_cache.object(pageIndex);
    if (!page && compile && !m_tasks.count(pageIndex))
    {
        // Compile the page
        auto compilePage = [this, pageIndex]() -> PDFPrecompiledPage
        {
            PDFPrecompiledPage compiledPage;
            PDFCMSPointer cms = m_proxy->getCMSManager()->getCurrentCMS();
            PDFRenderer renderer(m_proxy->getDocument(), m_proxy->getFontCache(), cms.data(), m_proxy->getOptionalContentActivity(), m_proxy->getFeatures(), m_proxy->getMeshQualitySettings());
            renderer.compile(&compiledPage, pageIndex);
            return compiledPage;
        };

        m_proxy->getFontCache()->setCacheShrinkEnabled(this, false);
        CompileTask& task = m_tasks[pageIndex];
        task.taskFuture = QtConcurrent::run(compilePage);
        task.taskWatcher = new QFutureWatcher<PDFPrecompiledPage>(this);
        connect(task.taskWatcher, &QFutureWatcher<PDFPrecompiledPage>::finished, this, &PDFAsynchronousPageCompiler::onPageCompiled);
        task.taskWatcher->setFuture(task.taskFuture);
    }

    return page;
}

void PDFAsynchronousPageCompiler::onPageCompiled()
{
    std::vector<PDFInteger> compiledPages;

    // Search all tasks for finished tasks
    for (auto it = m_tasks.begin(); it != m_tasks.end();)
    {
        CompileTask& task = it->second;
        if (task.taskWatcher->isFinished())
        {
            if (m_state == State::Active)
            {
                // If we are in active state, try to store precompiled page
                PDFPrecompiledPage* page = new PDFPrecompiledPage(task.taskWatcher->result());
                qint64 memoryConsumptionEstimate = page->getMemoryConsumptionEstimate();
                if (m_cache.insert(it->first, page, memoryConsumptionEstimate))
                {
                    compiledPages.push_back(it->first);
                }
                else
                {
                    // We can't insert page to the cache, because cache size is too small. We will
                    // emit error string to inform the user, that cache is too small.
                    QString message = PDFTranslationContext::tr("Precompiled page size is too high (%1 kB). Cache size is %2 kB. Increase the cache size!").arg(memoryConsumptionEstimate / 1024).arg(m_cache.maxCost() / 1024);
                    emit renderingError(it->first, { PDFRenderError(RenderErrorType::Error, message) });
                }
            }

            task.taskWatcher->deleteLater();
            it = m_tasks.erase(it);
        }
        else
        {
            // Just increment the counter
            ++it;
        }
    }

    // We allow font cache shrinking, when we aren't doing something in parallel.
    m_proxy->getFontCache()->setCacheShrinkEnabled(this, m_tasks.empty());

    if (!compiledPages.empty())
    {
        Q_ASSERT(std::is_sorted(compiledPages.cbegin(), compiledPages.cend()));
        emit pageImageChanged(false, compiledPages);
    }
}

class PDFTextLayoutGenerator : public PDFPageContentProcessor
{
    using BaseClass = PDFPageContentProcessor;

public:
    explicit PDFTextLayoutGenerator(PDFRenderer::Features features,
                                    const PDFPage* page,
                                    const PDFDocument* document,
                                    const PDFFontCache* fontCache,
                                    const PDFCMS* cms,
                                    const PDFOptionalContentActivity* optionalContentActivity,
                                    QMatrix pagePointToDevicePointMatrix,
                                    const PDFMeshQualitySettings& meshQualitySettings) :
        BaseClass(page, document, fontCache, cms, optionalContentActivity, pagePointToDevicePointMatrix, meshQualitySettings),
        m_features(features)
    {

    }

    /// Creates text layout from the text
    PDFTextLayout createTextLayout();

protected:
    virtual bool isContentSuppressedByOC(PDFObjectReference ocgOrOcmd) override;
    virtual bool isContentKindSuppressed(ContentKind kind) const override;
    virtual void performOutputCharacter(const PDFTextCharacterInfo& info) override;

private:
    PDFRenderer::Features m_features;
    PDFTextLayout m_textLayout;
};

PDFTextLayout PDFTextLayoutGenerator::createTextLayout()
{
    m_textLayout.perform();
    m_textLayout.optimize();
    return qMove(m_textLayout);
}

bool PDFTextLayoutGenerator::isContentSuppressedByOC(PDFObjectReference ocgOrOcmd)
{
    if (m_features.testFlag(PDFRenderer::IgnoreOptionalContent))
    {
        return false;
    }

    return PDFPageContentProcessor::isContentSuppressedByOC(ocgOrOcmd);
}

bool PDFTextLayoutGenerator::isContentKindSuppressed(ContentKind kind) const
{
    switch (kind)
    {
        case ContentKind::Shapes:
        case ContentKind::Text:
        case ContentKind::Images:
        case ContentKind::Shading:
            return true;

        case ContentKind::Tiling:
            return false; // Tiling can have text

        default:
        {
            Q_ASSERT(false);
            break;
        }
    }

    return false;
}

void PDFTextLayoutGenerator::performOutputCharacter(const PDFTextCharacterInfo& info)
{
    if (!isContentSuppressed())
    {
        m_textLayout.addCharacter(info);
    }
}

PDFAsynchronousTextLayoutCompiler::PDFAsynchronousTextLayoutCompiler(PDFDrawWidgetProxy* proxy) :
    BaseClass(proxy),
    m_proxy(proxy),
    m_isRunning(false)
{
    connect(&m_textLayoutCompileFutureWatcher, &QFutureWatcher<PDFTextLayoutStorage>::finished, this, &PDFAsynchronousTextLayoutCompiler::onTextLayoutCreated);
}

void PDFAsynchronousTextLayoutCompiler::start()
{
    switch (m_state)
    {
        case State::Inactive:
        {
            m_state = State::Active;
            break;
        }

        case State::Active:
            break; // We have nothing to do...

        case State::Stopping:
        {
            // We shouldn't call this function while stopping!
            Q_ASSERT(false);
            break;
        }
    }
}

void PDFAsynchronousTextLayoutCompiler::stop(bool clearCache)
{
    switch (m_state)
    {
        case State::Inactive:
            break; // We have nothing to do...

        case State::Active:
        {
            // Stop the engine
            m_state = State::Stopping;
            m_textLayoutCompileFutureWatcher.waitForFinished();

            if (clearCache)
            {
                m_textLayouts = std::nullopt;
            }

            m_state = State::Inactive;
            break;
        }

        case State::Stopping:
        {
            // We shouldn't call this function while stopping!
            Q_ASSERT(false);
            break;
        }
    }
}

void PDFAsynchronousTextLayoutCompiler::reset()
{
    stop(true);
    start();
}

PDFTextLayout PDFAsynchronousTextLayoutCompiler::getTextLayout(PDFInteger pageIndex)
{
    if (m_state != State::Active || !m_proxy->getDocument())
    {
        // Engine is not active, always return empty layout
        return PDFTextLayout();
    }

    if (m_textLayouts)
    {
        return m_textLayouts->getTextLayout(pageIndex);
    }

    return PDFTextLayout();
}

PDFTextLayoutGetter PDFAsynchronousTextLayoutCompiler::getTextLayoutLazy(PDFInteger pageIndex)
{
    if (m_state != State::Active || !m_proxy->getDocument())
    {
        // Engine is not active, always return empty layout
        return PDFTextLayoutGetter(nullptr, pageIndex);
    }

    if (m_textLayouts)
    {
        return m_textLayouts->getTextLayoutLazy(pageIndex);
    }

    return PDFTextLayoutGetter(nullptr, pageIndex);
}

PDFTextSelection PDFAsynchronousTextLayoutCompiler::getTextSelectionAll(QColor color) const
{
    PDFTextSelection result;

    if (m_textLayouts)
    {
        const PDFTextLayoutStorage& textLayouts = *m_textLayouts;

        QMutex mutex;
        PDFIntegerRange<size_t> pageRange(0, textLayouts.getCount());
        auto selectPageText = [this, &mutex, &textLayouts, &result, color](PDFInteger pageIndex)
        {
            PDFTextLayout textLayout = textLayouts.getTextLayout(pageIndex);
            PDFTextSelectionItems items;

            const PDFTextBlocks& blocks = textLayout.getTextBlocks();
            for (size_t blockId = 0, blockCount = blocks.size(); blockId < blockCount; ++blockId)
            {
                const PDFTextBlock& block = blocks[blockId];
                const PDFTextLines& lines = block.getLines();

                if (!lines.empty())
                {
                    const PDFTextLine& lastLine = lines.back();
                    Q_ASSERT(!lastLine.getCharacters().empty());

                    PDFCharacterPointer ptrStart;
                    ptrStart.pageIndex = pageIndex;
                    ptrStart.blockIndex = blockId;
                    ptrStart.lineIndex = 0;
                    ptrStart.characterIndex = 0;

                    PDFCharacterPointer ptrEnd;
                    ptrEnd.pageIndex = pageIndex;
                    ptrEnd.blockIndex = blockId;
                    ptrEnd.lineIndex = lines.size() - 1;
                    ptrEnd.characterIndex = lastLine.getCharacters().size() - 1;

                    items.emplace_back(ptrStart, ptrEnd);
                }
            }

            QMutexLocker lock(&mutex);
            result.addItems(qMove(items), color);
        };
        PDFExecutionPolicy::execute(PDFExecutionPolicy::Scope::Page, pageRange.begin(), pageRange.end(), selectPageText);
    }

    result.build();
    return result;
}

void PDFAsynchronousTextLayoutCompiler::makeTextLayout()
{
    if (m_state != State::Active || !m_proxy->getDocument())
    {
        // Engine is not active, do not calculate layout
        return;
    }

    if (m_textLayouts.has_value())
    {
        // Value is computed already
        return;
    }

    if (m_isRunning)
    {
        // Text layout is already being processed
        return;
    }

    // Jakub Melka: Mark, that we are running (test for future is not enough,
    // because future can finish before this function exits, for example)
    m_isRunning = true;

    ProgressStartupInfo info;
    info.showDialog = true;
    info.text = tr("Indexing document contents...");

    m_proxy->getFontCache()->setCacheShrinkEnabled(this, false);
    const PDFCatalog* catalog = m_proxy->getDocument()->getCatalog();
    m_proxy->getProgress()->start(catalog->getPageCount(), qMove(info));

    PDFCMSPointer cms = m_proxy->getCMSManager()->getCurrentCMS();

    auto createTextLayout = [this, cms, catalog]() -> PDFTextLayoutStorage
    {
        PDFTextLayoutStorage result(catalog->getPageCount());
        QMutex mutex;
        auto generateTextLayout = [this, &result, &mutex, cms, catalog](PDFInteger pageIndex)
        {
            if (!catalog->getPage(pageIndex))
            {
                // Invalid page index
                result.setTextLayout(pageIndex, PDFTextLayout(), &mutex);
                return;
            }

            const PDFPage* page = catalog->getPage(pageIndex);
            Q_ASSERT(page);

            PDFTextLayoutGenerator generator(m_proxy->getFeatures(), page, m_proxy->getDocument(), m_proxy->getFontCache(), cms.data(), m_proxy->getOptionalContentActivity(), QMatrix(), m_proxy->getMeshQualitySettings());
            generator.processContents();
            result.setTextLayout(pageIndex, generator.createTextLayout(), &mutex);
            m_proxy->getProgress()->step();
        };

        auto pageRange = PDFIntegerRange<PDFInteger>(0, catalog->getPageCount());
        PDFExecutionPolicy::execute(PDFExecutionPolicy::Scope::Page, pageRange.begin(), pageRange.end(), generateTextLayout);
        return result;
    };

    Q_ASSERT(!m_textLayoutCompileFuture.isRunning());
    m_textLayoutCompileFuture = QtConcurrent::run(createTextLayout);
    m_textLayoutCompileFutureWatcher.setFuture(m_textLayoutCompileFuture);
}

void PDFAsynchronousTextLayoutCompiler::onTextLayoutCreated()
{
    m_proxy->getFontCache()->setCacheShrinkEnabled(this, true);
    m_proxy->getProgress()->finish();

    m_textLayouts = m_textLayoutCompileFuture.result();
    m_isRunning = false;
    emit textLayoutChanged();
}

}   // namespace pdf