#ifndef PEGPARSER_H
#define PEGPARSER_H

#include <QObject>

#include <QSharedPointer>
#include <QThread>
#include <QAtomicInt>
#include <QVector>

#include "vconstants.h"
#include "markdownhighlighterdata.h"

struct PegParseConfig
{
    PegParseConfig()
        : m_timeStamp(0),
          m_numOfBlocks(0),
          m_offset(0),
          m_extensions(pmh_EXT_NONE),
          m_fast(false)
    {
    }

    TimeStamp m_timeStamp;

    QByteArray m_data;

    int m_numOfBlocks;

    // Offset of m_data in the document.
    int m_offset;

    int m_extensions;

    // Fast parse.
    bool m_fast;

    QString toString() const
    {
        return QString("PegParseConfig ts %1 data %2 blocks %3").arg(m_timeStamp)
                                                                .arg(m_data.size())
                                                                .arg(m_numOfBlocks);
    }
};

struct PegParseResult
{
    PegParseResult(const QSharedPointer<PegParseConfig> &p_config)
        : m_timeStamp(p_config->m_timeStamp),
          m_numOfBlocks(p_config->m_numOfBlocks),
          m_offset(p_config->m_offset),
          m_pmhElements(NULL)
    {
    }

    ~PegParseResult()
    {
        clearPmhElements();
    }

    void clearPmhElements()
    {
        if (m_pmhElements) {
            pmh_free_elements(m_pmhElements);
            m_pmhElements = NULL;
        }
    }

    bool operator<(const PegParseResult &p_other) const
    {
        return m_timeStamp < p_other.m_timeStamp;
    }

    QString toString() const
    {
        return QString("PegParseResult ts %1").arg(m_timeStamp);
    }

    bool isEmpty() const
    {
        return !m_pmhElements;
    }

    // Parse m_pmhElements.
    void parse(QAtomicInt &p_stop, bool p_fast);

    TimeStamp m_timeStamp;

    int m_numOfBlocks;

    int m_offset;

    pmh_element **m_pmhElements;

    // All image link regions.
    QVector<VElementRegion> m_imageRegions;

    // All header regions.
    // Sorted by start position.
    QVector<VElementRegion> m_headerRegions;

    // Fenced code block regions.
    // Ordered by start position in ascending order.
    QMap<int, VElementRegion>  m_codeBlockRegions;

    // All $ $ inline equation regions.
    QVector<VElementRegion> m_inlineEquationRegions;

    // All $$ $$ display formula regions.
    // Sorted by start position.
    QVector<VElementRegion> m_displayFormulaRegions;

    // HRule regions.
    QVector<VElementRegion> m_hruleRegions;

private:
    void parseImageRegions(QAtomicInt &p_stop);

    void parseHeaderRegions(QAtomicInt &p_stop);

    void parseFencedCodeBlockRegions(QAtomicInt &p_stop);

    void parseInlineEquationRegions(QAtomicInt &p_stop);

    void parseDisplayFormulaRegions(QAtomicInt &p_stop);

    void parseHRuleRegions(QAtomicInt &p_stop);
};

class PegParserWorker : public QThread
{
    Q_OBJECT
public:
    explicit PegParserWorker(QObject *p_parent = nullptr);

    void prepareParse(const QSharedPointer<PegParseConfig> &p_config);

    void reset();

    int state() const
    {
        return m_state;
    }

    TimeStamp workTimeStamp() const
    {
        if (m_parseConfig.isNull()) {
            return 0;
        }

        return m_parseConfig->m_timeStamp;
    }

    const QSharedPointer<PegParseConfig> &parseConfig() const
    {
        return m_parseConfig;
    }

    const QSharedPointer<PegParseResult> &parseResult() const
    {
        return m_parseResult;
    }

public slots:
    void stop();

protected:
    void run() Q_DECL_OVERRIDE;

private:
    QSharedPointer<PegParseResult> parseMarkdown(const QSharedPointer<PegParseConfig> &p_config,
                                                 QAtomicInt &p_stop);

    bool isAskedToStop() const
    {
        return m_stop.load() == 1;
    }

    QAtomicInt m_stop;

    int m_state;

    QSharedPointer<PegParseConfig> m_parseConfig;

    QSharedPointer<PegParseResult> m_parseResult;
};

class PegParser : public QObject
{
    Q_OBJECT
public:
    explicit PegParser(QObject *p_parent = nullptr);

    ~PegParser();

    QSharedPointer<PegParseResult> parse(const QSharedPointer<PegParseConfig> &p_config);

    void parseAsync(const QSharedPointer<PegParseConfig> &p_config);

    static QVector<VElementRegion> parseImageRegions(const QSharedPointer<PegParseConfig> &p_config);

    // MUST pmh_free_elements() the result.
    static pmh_element **parseMarkdownToElements(const QSharedPointer<PegParseConfig> &p_config);

signals:
    void parseResultReady(const QSharedPointer<PegParseResult> &p_result);

private slots:
    void handleWorkerFinished(PegParserWorker *p_worker);

private:
    void init();

    void clear();

    void pickWorker();

    void scheduleWork(PegParserWorker *p_worker, const QSharedPointer<PegParseConfig> &p_config);

    // Maintain a fixed number of workers to pick work.
    QVector<PegParserWorker *> m_workers;

    QSharedPointer<PegParseConfig> m_pendingWork;
};

#endif // PEGPARSER_H