#include "ui/ThemeIcons.h"

#include <QDir>
#include <QGuiApplication>
#include <QIcon>
#include <QPainter>
#include <QQmlApplicationEngine>
#include <QScreen>
#include <QStandardPaths>
#include <QStringList>
#include <QUrl>

namespace app {
namespace {

/* What a usable theme has to have; every window in the app needs it. */
const char kProbe[] = "mail-attachment";

/* The desktop's own theme first (whatever the platform theme set), then
 * Breeze: this window is dark, so the dark variant, and Breeze proper as
 * Qt's fallback for the odd name that only lives there. Before any of that
 * the search paths have to be filled in -- Qt only builds them from XDG once
 * a theme name was set, and a shell that was started outside the desktop
 * session (nix-shell) has no XDG_DATA_DIRS pointing at the icon packages,
 * hence the system profile. */
void adoptIconTheme() {
  const QStringList known = QStandardPaths::standardLocations(
      QStandardPaths::GenericDataLocation);
  QStringList paths;
  for (const QString &d : known)
    paths << d + QStringLiteral("/icons");
  paths << QDir::homePath() + QStringLiteral("/.icons");
  const QString system = QStringLiteral("/run/current-system/sw/share/icons");
  if (!paths.contains(system) && QDir(system).exists())
    paths << system;
  paths << QStringLiteral(":/icons");
  QIcon::setThemeSearchPaths(paths);

  QStringList candidates;
  if (!QIcon::themeName().isEmpty())
    candidates << QIcon::themeName();
  candidates << QStringLiteral("breeze-dark") << QStringLiteral("breeze")
             << QStringLiteral("hicolor");
  for (const QString &name : candidates) {
    QIcon::setThemeName(name);
    if (QIcon::hasThemeIcon(QLatin1String(kProbe)))
      return;
  }
}

/* The bundled set: app/icons/*.svg, compiled in as :/cst-icons/<name>.svg by
 * app/CMakeLists.txt. A machine without an icon theme -- Android, where the
 * Qt theme lookup finds nothing and QML was left showing its glyph fallback,
 * which the phone fonts cannot draw -- gets the same icons from here. */
QIcon bundledIcon(const QString &name) {
  return QIcon(QStringLiteral(":/cst-icons/") + name + QStringLiteral(".svg"));
}

QIcon iconForName(const QString &name) {
  const QIcon themed = QIcon::fromTheme(name);
  if (!themed.isNull())
    return themed;
  return bundledIcon(name);
}

/* "?color=%23eff0f1": the tint, and nothing else so far. */
QColor colorOption(const QString &id, QString *name) {
  QColor color;
  *name = id;
  const int q = id.indexOf(QLatin1Char('?'));
  if (q < 0)
    return color;
  *name = id.left(q);
  const QStringList options = id.mid(q + 1).split(QLatin1Char('&'));
  for (const QString &opt : options) {
    if (!opt.startsWith(QLatin1String("color=")))
      continue;
    const QColor c(QUrl::fromPercentEncoding(opt.mid(6).toUtf8()));
    if (c.isValid())
      color = c;
  }
  return color;
}

qreal targetRatio() {
  if (const QScreen *s = QGuiApplication::primaryScreen())
    return qMax<qreal>(1.0, s->devicePixelRatio());
  return 1.0;
}

}  // namespace

ThemeIconProvider::ThemeIconProvider()
    : QQuickImageProvider(QQuickImageProvider::Image) {}

QImage ThemeIconProvider::requestImage(const QString &id, QSize *size,
                                       const QSize &requestedSize) {
  QString name;
  const QColor color = colorOption(id, &name);
  if (name.isEmpty())
    return QImage();

  const QIcon icon = iconForName(name);
  if (icon.isNull())
    return QImage(); /* QML shows its fallback glyph */

  const int px = requestedSize.isValid() && requestedSize.width() > 0
                     ? requestedSize.width()
                     : 22;
  const qreal ratio = targetRatio();
  QPixmap pm = icon.pixmap(QSize(px, px), ratio, QIcon::Normal, QIcon::Off);
  if (pm.isNull())
    return QImage();
  if (color.isValid()) {
    QPainter p(&pm);
    p.setCompositionMode(QPainter::CompositionMode_SourceIn);
    p.fillRect(pm.rect(), color);
  }
  QImage img = pm.toImage();
  img.setDevicePixelRatio(ratio);
  if (size)
    *size = QSize(px, px);
  return img;
}

void installThemeIcons(QQmlApplicationEngine *engine) {
  adoptIconTheme();
  if (engine)
    engine->addImageProvider(QStringLiteral("csttheme"), new ThemeIconProvider);
}

QString iconThemeName() { return QIcon::themeName(); }

bool themeIconAvailable(const QString &name) { return !iconForName(name).isNull(); }

}  // namespace app