/***

  Olive - Non-Linear Video Editor
  Copyright (C) 2022 Olive Team

  This program is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  This program 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 General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program.  If not, see <http://www.gnu.org/licenses/>.

***/

#include "scrollinglabel.h"

#include <QPainter>

#include "common/qtutils.h"

namespace olive
{

const int ScrollingLabel::kMinLineHeight = 10;

ScrollingLabel::ScrollingLabel(QWidget *parent)
	: QWidget(parent)
	, animate_(0)
{
	timer_.setInterval(50);
	connect(&timer_, &QTimer::timeout, this, &ScrollingLabel::AnimationUpdate);
}

ScrollingLabel::ScrollingLabel(const QStringList &text, QWidget *parent)
	: ScrollingLabel(parent)
{
	SetText(text);
}

void ScrollingLabel::SetText(const QStringList &text)
{
	text_ = text;

	QFontMetrics fm = fontMetrics();
	text_height_ = fm.height();

	int width = 0;
	foreach (const QString &s, text_) {
		width = qMax(width, QtUtils::QFontMetricsWidth(fm, s));
	}

	setMinimumSize(width, text_height_ * kMinLineHeight);
}

void ScrollingLabel::paintEvent(QPaintEvent *e)
{
	QImage map(width(), height(), QImage::Format_RGBA8888_Premultiplied);
	map.fill(Qt::transparent);

	{
		QPainter p(&map);
		p.setPen(palette().text().color());

		QFontMetrics fm = p.fontMetrics();
		int half_width = width();

		for (int i = 0; i < text_.size(); i++) {
			int text_y = fm.ascent() + height() - animate_ + (fm.height() * i);
			int text_bottom = text_y + fm.descent();
			int text_top = text_y - fm.ascent();

			if (text_bottom < 0 || text_top >= height()) {
				continue;
			}

			const QString &s = text_.at(i);

			int width = QtUtils::QFontMetricsWidth(fm, s);
			p.drawText(half_width / 2 - width / 2, text_y, s);
		}

		for (int y = 0; y < text_height_; y++) {
			double mul = double(y) / double(text_height_);

			SetOpacityOfScanLine(map.scanLine(y), map.width(), 4, mul);
			SetOpacityOfScanLine(map.scanLine(map.height() - 1 - y),
								 map.width(), 4, mul);
		}
	}

	QPainter wp(this);
	wp.drawImage(0, 0, map);
}

void ScrollingLabel::SetOpacityOfScanLine(uchar *scan_line, int width,
										  int channels, double mul)
{
	for (int x = 0; x < width; x++) {
		uchar *pixel = &scan_line[x * 4];

		for (int c = 0; c < channels; c++) {
			pixel[c] *= mul;
		}
	}
}

void ScrollingLabel::AnimationUpdate()
{
	animate_++;

	if (animate_ >= height() + text_.size() * text_height_) {
		animate_ = 0;
	}

	update();
}

}