#include "nglpdfdocument.h"
#include "nglpdfpage.h"

#include <QtCore/QUrl>
#include <QLabel>
#include <QScrollArea>
#include <QScrollBar>
#include <QVBoxLayout>
#include <QTimer>

#include <iostream>
#include <memory>

namespace NGL
{
PDFDocument::PDFDocument(QWidget *parent)
  : QWidget(parent)
  , m_doc(nullptr)
  , m_currentPage(0)
  , m_maxCachedPages(20)
  , m_scaleFactor(1.0)
  , m_widthFactor(1.0)
  , m_rotation(Poppler::Page::Rotate0)
{
  QVBoxLayout *lay = new QVBoxLayout(this);
  lay->setContentsMargins(0,0,0,0);
  lay->setSpacing(0);

  m_pdfLabel = new QWidget(this);
  m_pdfLabel->setSizePolicy(QSizePolicy::Fixed, QSizePolicy::Fixed);
  QVBoxLayout *l = new QVBoxLayout(m_pdfLabel);
  const int innerMargin = 6;
  l->setContentsMargins(innerMargin, innerMargin, innerMargin, innerMargin);
  l->setSpacing(innerMargin);
  l->setSizeConstraint(QLayout::SetFixedSize);

  m_scrollArea = new QScrollArea(this);
  m_scrollArea->setAlignment(Qt::AlignHCenter | Qt::AlignVCenter);

  m_scrollArea->setWidgetResizable(true);
  m_scrollArea->setWidget(m_pdfLabel);

  lay->addWidget(m_scrollArea);
}

PDFDocument::~PDFDocument()
{
  qDeleteAll(m_pages);
  m_pages.clear();
  m_doc.reset();
}

bool PDFDocument::showPDF(const QUrl &url)
{
  return showPDF(url.toLocalFile());
}

bool PDFDocument::showPDF(const QString &path)
{
  if (path.isEmpty())
    return false;

  if (path == m_currentPath)
  {
    m_scaleFactor = 0;
    m_widthFactor = 1;
    setZoomFactor(1.0);
    setRotation(Poppler::Page::Rotate0);
    return true;
  }

  m_doc.reset(Poppler::Document::load(path));
  if (!m_doc)
    return false;
  m_currentPath = path;

  return showPDFInternal();
}

bool PDFDocument::showPDF(const QByteArray &pdf)
{
  m_currentPath.clear();

  m_doc.reset(Poppler::Document::loadFromData(pdf));
  if (!m_doc)
    return false;

  return showPDFInternal();
}

bool PDFDocument::showPDFInternal()
{
  disconnect(m_scrollArea->verticalScrollBar(), &QScrollBar::valueChanged, this, &PDFDocument::onVSliderValueChanged);

  m_doc->setRenderHint(Poppler::Document::Antialiasing);
  m_doc->setRenderHint(Poppler::Document::TextAntialiasing);
  m_doc->setRenderHint(Poppler::Document::TextHinting);
  m_doc->setRenderHint(Poppler::Document::TextSlightHinting);

  m_scrollArea->horizontalScrollBar()->setSliderPosition(0);
  m_scrollArea->verticalScrollBar()->setSliderPosition(0);

  m_renderedPages.clear();
  qDeleteAll(m_pages);
  m_pages.clear();
  m_ranges.clear();

  QVBoxLayout *l = qobject_cast<QVBoxLayout *> (m_pdfLabel->layout());
  const int cnt = m_doc->numPages();
  m_pages.reserve(cnt);
  for (int i = 0; i < cnt; ++i)
  {
    PDFPage *p = new PDFPage(m_pdfLabel);
    p->setZoomFactor(m_scaleFactor);
    p->setRotation(m_rotation);
    auto pagePtr = m_doc->page(i);
    p->setPopplerPage(pagePtr.get());
    // keep ownership via unique_ptr; PDFPage will not delete the Poppler::Page pointer
    connect(p, &PDFPage::pageRendered,
            this, &PDFDocument::onPageRendered);
    connect(p, &PDFPage::externalLinkClicked,
            this, &PDFDocument::linkClicked);
    connect(p, &PDFPage::linkClicked,
            this, &PDFDocument::onLinkClicked);
    m_pages += p;

    l->addWidget(p);
  }
  rebuildRanges();

  m_currentPage = std::min(m_currentPage, static_cast<int>(m_ranges.count() - 1));

  ensureCurPageVisible();
  emit currentPageChanged(m_currentPage + 1, m_ranges.count());
  connect(m_scrollArea->verticalScrollBar(), &QScrollBar::valueChanged, this, &PDFDocument::onVSliderValueChanged);
  return true;
}

void PDFDocument::resizePdfToWidth()
{
  double scale = m_scaleFactor;
  
  m_widthFactor = double(m_pdfLabel->size().width()) / size().width() * 1.03;
  
  m_scaleFactor = 0;  
  setZoomFactor(scale);
}

int PDFDocument::curPage() const
{
  return m_currentPage + 1;
}

int PDFDocument::numPages() const
{
  return m_doc ? m_doc->numPages() : -1;
}

void PDFDocument::setZoomFactor(double zoom)
{
  if (qFuzzyCompare(m_scaleFactor, zoom))
    return;
  m_scaleFactor = zoom;
  
  for (PDFPage *p : qAsConst(m_pages))
    p->setZoomFactor(m_scaleFactor / m_widthFactor);

  rebuildRanges();
}

void PDFDocument::setRotation(Poppler::Page::Rotation rot)
{
  if (m_rotation == rot)
    return;
  m_rotation = rot;
  if (m_pages.isEmpty())  
    return;
  
  for (PDFPage *p : qAsConst(m_pages))
    p->setRotation(m_rotation);

  rebuildRanges();
  emit currentPageChanged(m_currentPage+1, m_ranges.count());
  emit rotationChanged(m_rotation);
}

bool PDFDocument::setPage(int page)
{
  page--;
  if (m_currentPage == page)
  {
    ensureCurPageVisible();
    return true;
  }
  if (m_pages.isEmpty())  
  {
    m_currentPage = page;
    return true;
  }
  if (page < 0 || numPages() < 0 || page >= m_doc->numPages())
    return false;
  
  m_currentPage = page;
  emit currentPageChanged(m_currentPage + 1, m_ranges.count());
  ensureCurPageVisible();
  return true;
}

bool PDFDocument::nextPage()
{
  if (m_doc == nullptr || m_currentPage >= m_doc->numPages() - 1)
    return false;
  m_currentPage++;
  emit currentPageChanged(m_currentPage + 1, m_ranges.count());
  ensureCurPageVisible();
  return true;
}

bool PDFDocument::previousPage()
{
  if (m_doc == nullptr || m_currentPage < 1)
    return false;
  m_currentPage--;
  emit currentPageChanged(m_currentPage + 1, m_ranges.count());
  ensureCurPageVisible();
  return true;
}

void PDFDocument::onVSliderValueChanged(int y)
{
  
  y += m_scrollArea->height() / 2;
  int curPage = m_ranges.count() - 1;
  for (int i = 0; i < m_ranges.count(); ++i)
  {
    if (m_ranges.at(i) > y)
    {
      curPage = i - 1;
      break;
    }
  }
  if (curPage != m_currentPage && curPage >= 0)
  {
    m_currentPage = curPage;
    emit currentPageChanged(m_currentPage + 1, m_ranges.count());
  }
}

void PDFDocument::onPageRendered()
{
  PDFPage *p = qobject_cast<PDFPage *> (sender());
  if (m_renderedPages.contains(p))
    return;

  while (m_renderedPages.count() > m_maxCachedPages - 1)
  {
    p = m_renderedPages.takeFirst();
    if (p)
      p->clearPixmap();
  }
  m_renderedPages.push_back(p);
}

void PDFDocument::onLinkClicked(const Poppler::LinkDestination &dest)
{
  PDFPage *p = qobject_cast<PDFPage *>(sender());
  if (!p)
    return;
  m_currentPage = dest.pageNumber() - 1;
  emit currentPageChanged(m_currentPage + 1, m_ranges.count());
  ensureCurPageVisible(qRound(dest.right() * p->width()),
                       qRound(dest.top() * p->height()));
}

QVector<QImage> PDFDocument::getPrintableImages(int resolution) const
{
  QVector<QImage> imageList;
  imageList.reserve(m_pages.size());
  for (const PDFPage *p : m_pages)
    imageList.append(p->getPrintableImage(resolution));
  return imageList;
}

QImage PDFDocument::getPrintableImage(int pageNum, int resolution) const
{
  if (pageNum < 0 || pageNum >= m_pages.size())
    return QImage();
  return m_pages[pageNum]->getPrintableImage(resolution);
}

void PDFDocument::ensureCurPageVisible(int xOfs, int yOfs)
{
  if (m_currentPage >= m_ranges.size() || m_currentPage < 0)
    return;

  
  
  if (m_scrollArea->verticalScrollBar()->maximum() == 0)
  {
    QTimer::singleShot(50, this, [this, xOfs, yOfs]() { ensureCurPageVisible(xOfs, yOfs); });
    return;
  }
  
  
  
  int y = m_ranges.at(m_currentPage) + yOfs;
  
  y -= m_pdfLabel->layout()->spacing() * 2;

  int x = m_scrollArea->horizontalScrollBar()->value() + xOfs;

  
  m_scrollArea->ensureVisible(x, y, 0, 0);
  y += m_scrollArea->height();
  
  m_scrollArea->ensureVisible(x, y, 0, 0);
}

void PDFDocument::rebuildRanges()
{
  QVBoxLayout *l = qobject_cast<QVBoxLayout *> (m_pdfLabel->layout());
  m_ranges.clear();
  int height = l->contentsMargins().top();
  for (PDFPage *p : qAsConst(m_pages))
  {
    m_ranges += height;
    height += p->height();
    height += l->spacing();
  }
  m_pdfLabel->resize(m_pdfLabel->sizeHint());
  m_pdfLabel->setMinimumSize(m_pdfLabel->sizeHint());
}

}