#include "ui/SessionImages.h"

#include <QFileInfo>
#include <QImageReader>
#include <QQmlApplicationEngine>

#include "cst_attach.h"

namespace app {
namespace {

/* "img-1a2b3c4d.png?w=160": the stored name, then what the view asked for.
 * The size comes from the QML side as sourceSize, which Qt passes in as
 * requestedSize; the query string is accepted too, so a plain URL can ask. */
QString relOf(const QString &id) {
  const int q = id.indexOf(QLatin1Char('?'));
  return q < 0 ? id : id.left(q);
}

}  // namespace

SessionImages::SessionImages()
    : QQuickImageProvider(QQuickImageProvider::Image) {}

void SessionImages::setDir(const QString &dir) {
  QMutexLocker lock(&m_mu);
  m_dir = dir;
}

QImage SessionImages::requestImage(const QString &id, QSize *size,
                                   const QSize &requestedSize) {
  const QString rel = relOf(id);
  if (!cst_attach_rel_ok(rel.toUtf8().constData()))
    return QImage(); /* QML sees Image.Error and falls back to the name */
  QString dir;
  {
    QMutexLocker lock(&m_mu);
    dir = m_dir;
  }
  if (dir.isEmpty())
    return QImage();
  const QString path = dir + QLatin1Char('/') + rel;
  if (!QFileInfo::exists(path))
    return QImage();

  QImageReader reader(path);
  reader.setAutoTransform(true);
  const QSize full = reader.size();
  if (!full.isValid()) {
    /* No size in the header (or not a picture at all): hand back what Qt
     * makes of it and let the view scale it. */
    const QImage img = reader.read();
    if (size)
      *size = img.size();
    return img;
  }
  /* Shrink to what the view shows, never up: a screenshot is decoded at the
   * size of its thumbnail instead of at 4K. */
  const bool smaller = requestedSize.isValid() && requestedSize.width() > 0 &&
                       requestedSize.height() > 0 &&
                       (full.width() > requestedSize.width() ||
                        full.height() > requestedSize.height());
  if (smaller) {
    const QSize scaled = full.scaled(requestedSize, Qt::KeepAspectRatio);
    reader.setScaledSize(scaled);
    if (size)
      *size = scaled;
  } else if (size) {
    *size = full;
  }
  return reader.read();
}

SessionImages *installSessionImages(QQmlApplicationEngine *engine) {
  SessionImages *images = new SessionImages;
  if (engine)
    engine->addImageProvider(QStringLiteral("cstattach"), images);
  return images;
}

}  // namespace app