#include "strokecanvasrenderer.hpp"
#include "strokecanvasitem.hpp"
#include <QCanvasPainter>
#include <QQuickWindow>
#include <QVector4D>
#include <qcolor.h>
#include <QSet>

namespace ZShell::internal {

using Qt::StringLiterals::operator""_s;

static const QString kStrokeHoleShader = u":/shaders/strokeholemask.frag.qsb"_s;

namespace {

struct HoleUniforms {
	QVector4D data1; // center.xy, halfSize.xy
	QVector4D data3; // x: radius, y: feather in logical px
	QVector4D data4; // x: hole enabled
};

static HoleUniforms holeUniforms(
	const QRectF& hole, qreal radius, qreal devicePixelRatio) {
	const bool active = hole.isValid() && hole.width() > 0 && hole.height() > 0;

	if (!active) return {QVector4D(), QVector4D(), QVector4D()};

	const QPointF center = hole.center();
	const QPointF half(hole.width() * 0.5, hole.height() * 0.5);
	const qreal maxRadius = qMin(half.x(), half.y());

	return {
		QVector4D(
			static_cast<float>(center.x()),
			static_cast<float>(center.y()),
			static_cast<float>(half.x()),
			static_cast<float>(half.y())),
		QVector4D(
			static_cast<float>(qMin(radius, maxRadius)),
			static_cast<float>(1.0 / devicePixelRatio),
			0.0f,
			0.0f),
		QVector4D(1.0, 0.0, 0.0, 0.0),
	};
}

static void applyHole(QCanvasCustomBrush& brush, const HoleUniforms& u) {
	brush.setData1(u.data1);
	brush.setData3(u.data3);
	brush.setData4(u.data4);
}

}; // namespace

void StrokeCanvasRenderer::updateBrushHole() {
	const HoleUniforms uniforms =
		holeUniforms(m_hole, m_holeRadius, m_devicePixelRatio);

	if (uniforms.data1 == m_lastHoleData1 &&
		uniforms.data3 == m_lastHoleData3 && uniforms.data4 == m_lastHoleData4)
		return;

	m_lastHoleData1 = uniforms.data1;
	m_lastHoleData3 = uniforms.data3;
	m_lastHoleData4 = uniforms.data4;
	++m_holeToken;

	for (auto& entry : m_brushes) {
		if (entry.holeToken == m_holeToken) continue;

		applyHole(entry.brush, uniforms);
		entry.holeToken = m_holeToken;
	}
}

QCanvasCustomBrush& StrokeCanvasRenderer::brushFor(const QColor& color) {
	const QRgb key = color.rgba();

	if (auto it = m_brushes.find(key); it != m_brushes.end()) return it->brush;

	const HoleUniforms uniforms =
		holeUniforms(m_hole, m_holeRadius, m_devicePixelRatio);

	BrushEntry entry;
	entry.brush.setFragmentShader(kStrokeHoleShader);
	applyHole(entry.brush, uniforms);
	entry.brush.setData2(
		QVector4D(color.redF(), color.greenF(), color.blueF(), color.alphaF()));
	entry.holeToken = m_holeToken;

	return m_brushes.insert(key, entry)->brush;
}

void StrokeCanvasRenderer::drawStroke(
	QCanvasPainter* painter,
	const QVector<QPointF>& points,
	const QColor& color,
	qreal width,
	bool polyline) {
	if (points.isEmpty()) return;

	QCanvasCustomBrush& brush = brushFor(color);

	painter->setStrokeStyle(brush);
	painter->setFillStyle(brush);
	painter->setLineWidth(width);
	painter->setLineCap(QCanvasPainter::LineCap::Round);
	painter->setLineJoin(QCanvasPainter::LineJoin::Round);

	if (polyline) {
		painter->beginPath();
		painter->moveTo(points[0]);
		for (int i = 1; i < points.size(); i++)
			painter->lineTo(points[i]);
		painter->stroke();
		return;
	}

	if (points.size() == 1) {
		painter->beginPath();
		painter->circle(points.front(), width * 0.5);
		painter->fill();
		return;
	}

	auto catmullToBezier = [](const QPointF& p0,
							  const QPointF& p1,
							  const QPointF& p2,
							  const QPointF& p3,
							  qreal tension,
							  QPointF& cp1,
							  QPointF& cp2) {
		cp1 = p1 + (p2 - p0) * tension / 3.0;
		cp2 = p2 - (p3 - p1) * tension / 3.0;
	};

	const qreal tension = 0.5; // increase toward 1.0 for tighter curves

	painter->beginPath();
	painter->moveTo(points[0]);

	for (int i = 0; i < points.size() - 1; ++i) {
		const QPointF& p0 = points[qMax(i - 1, 0)];
		const QPointF& p1 = points[i];
		const QPointF& p2 = points[i + 1];
		const QPointF& p3 = points[qMin(i + 2, points.size() - 1)];

		QPointF cp1, cp2;
		catmullToBezier(p0, p1, p2, p3, tension, cp1, cp2);
		painter->bezierCurveTo(cp1, cp2, p2);
	}

	painter->stroke();
}

void StrokeCanvasRenderer::drawHoverCursor(
	QCanvasPainter* painter,
	const QPointF& point,
	qreal penWidth,
	QColor penColor,
	bool isDrawing) {
	const qreal radius = penWidth * 0.5;

	if (isDrawing) {
		painter->setFillStyle(brushFor(penColor));
		painter->beginPath();
		painter->circle(point, radius);
		painter->fill();
	}

	const qreal lineWidth = 1.5;
	const qreal crosshairSize = 6.0;
	const bool useDashes = penWidth > 10.0;

	auto drawOutline = [&](const QColor& color, qreal width) {
		painter->setStrokeStyle(brushFor(color));
		painter->setLineWidth(width);
		painter->setLineCap(QCanvasPainter::LineCap::Round);


		if (useDashes) {
			const int dashCount = 12;
			const qreal fullAngle = 2.0 * M_PI;
			const qreal dashAngle = fullAngle / dashCount * 0.5;
			const qreal gapAngle = fullAngle / dashCount * 0.5;

			qreal angle = 0.0;
			for (int i = 0; i < dashCount; ++i) {
				painter->beginPath();
				painter->arc(
					point,
					radius,
					angle,
					angle + dashAngle,
					QCanvasPainter::PathWinding::ClockWise,
					QCanvasPainter::PathConnection::NotConnected);
				painter->stroke();
				angle += dashAngle + gapAngle;
			}
		} else {
			painter->beginPath();
			painter->circle(point, radius);
			painter->stroke();
		}
	};

	auto drawCrosshair = [&](const QColor& color, qreal width) {
		painter->setStrokeStyle(brushFor(color));
		painter->setLineWidth(width);
		painter->setLineCap(QCanvasPainter::LineCap::Round);

		const qreal inner = radius + 3.0;
		const qreal outer = radius + 3.0 + crosshairSize;

		painter->beginPath();
		painter->moveTo(point + QPointF(0, -outer));
		painter->lineTo(point + QPointF(0, -inner));
		painter->moveTo(point + QPointF(0, outer));
		painter->lineTo(point + QPointF(0, inner));
		painter->moveTo(point + QPointF(-outer, 0));
		painter->lineTo(point + QPointF(-inner, 0));
		painter->moveTo(point + QPointF(outer, 0));
		painter->lineTo(point + QPointF(inner, 0));
		painter->stroke();
	};

	drawOutline(QColor(0, 0, 0, 160), lineWidth + 1.0);
	drawCrosshair(QColor(0, 0, 0, 160), lineWidth + 1.0);

	drawOutline(QColor(255, 255, 255, 220), lineWidth);
	drawCrosshair(QColor(255, 255, 255, 220), lineWidth);
}

void StrokeCanvasRenderer::synchronizeData(QCanvasPainterItem* item) {
	auto* canvas = static_cast<StrokeCanvasItem*>(item);

	m_penColor = canvas->m_penColor;
	m_penWidth = canvas->m_penWidth;
	m_hole = canvas->m_hole;
	m_holeRadius = canvas->m_holeRadius;
	m_devicePixelRatio =
		canvas->window() ? canvas->window()->effectiveDevicePixelRatio() : 1.0;

	QSet<int> canvasGroupIds;
	for (const auto& stroke : canvas->m_strokes)
		canvasGroupIds.insert(stroke.groupId);

	for (int i = static_cast<int>(m_strokes.size()) - 1; i >= 0; --i) {
		if (!canvasGroupIds.contains(m_strokes[i].groupId)) {
			if (m_strokes[i].groupId >= 0)
				m_pendingGroupRemovals.append(m_strokes[i].groupId);
			m_strokes.remove(i);
		}
	}

	QSet<int> rendererGroupIds;
	for (const auto& stroke : m_strokes)
		rendererGroupIds.insert(stroke.groupId);

	for (const auto& stroke : canvas->m_strokes) {
		if (!rendererGroupIds.contains(stroke.groupId))
			m_strokes.append(stroke);
	}

	m_currentStroke = canvas->m_currentStroke;

	m_hoverVisible = canvas->m_hoverVisible;
	m_hoverPoint = canvas->m_hoverPoint;
	m_isDrawing = canvas->m_isDrawing;
}

void StrokeCanvasRenderer::paint(QCanvasPainter* painter) {
	updateBrushHole();

	for (int id : m_pendingGroupRemovals)
		painter->removePathGroup(id);
	m_pendingGroupRemovals.clear();

	painter->clearRect(0, 0, width(), height());

	for (const auto& stroke : m_strokes) {
		painter->setStrokeStyle(brushFor(stroke.color));
		painter->setFillStyle(brushFor(stroke.color));
		painter->setLineWidth(stroke.width);
		painter->setLineCap(QCanvasPainter::LineCap::Round);
		painter->setLineJoin(QCanvasPainter::LineJoin::Round);

		if (stroke.isSinglePoint) {
			painter->fill(stroke.path, stroke.groupId);
		} else {
			painter->stroke(stroke.path, stroke.groupId);
		}
	}

	drawStroke(
		painter,
		m_currentStroke.points,
		m_currentStroke.color,
		m_currentStroke.width,
		m_currentStroke.isPolyline);

	if (m_hoverVisible)
		drawHoverCursor(
			painter, m_hoverPoint, m_penWidth, m_penColor, m_isDrawing);
}

}; // namespace ZShell::internal