# Copyright (C) 2013 Riverbank Computing Limited.
# Copyright (C) 2022 The Qt Company Ltd.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
from __future__ import annotations

import math
import sys

from PySide6.QtCore import QPointF, QTimer, Qt
from PySide6.QtGui import (QBrush, QColor, QLinearGradient, QPainter, QPen,
                           QPixmap, QRadialGradient)
from PySide6.QtWidgets import (QApplication, QFrame, QGraphicsDropShadowEffect,
                               QGraphicsEllipseItem, QGraphicsRectItem,
                               QGraphicsScene, QGraphicsView)


class Lighting(QGraphicsView):
    def __init__(self, parent=None):
        super().__init__(parent)

        self.angle = 0.0
        self.m_scene = QGraphicsScene()
        self.m_lightSource = None
        self.m_items = []

        self.setScene(self.m_scene)

        self.setup_scene()

        timer = QTimer(self)
        timer.timeout.connect(self.animate)
        timer.setInterval(30)
        timer.start()

        self.setRenderHint(QPainter.RenderHint.Antialiasing)
        self.setFrameStyle(QFrame.NoFrame)

    def setup_scene(self):
        self.m_scene.setSceneRect(-300, -200, 600, 460)

        linear_grad = QLinearGradient(QPointF(-100, -100), QPointF(100, 100))
        linear_grad.setColorAt(0, QColor(255, 255, 255))
        linear_grad.setColorAt(1, QColor(192, 192, 255))
        self.setBackgroundBrush(linear_grad)

        radial_grad = QRadialGradient(30, 30, 30)
        radial_grad.setColorAt(0, Qt.yellow)
        radial_grad.setColorAt(0.2, Qt.yellow)
        radial_grad.setColorAt(1, Qt.transparent)

        pixmap = QPixmap(60, 60)
        pixmap.fill(Qt.transparent)

        with QPainter(pixmap) as painter:
            painter.setPen(Qt.NoPen)
            painter.setBrush(radial_grad)
            painter.drawEllipse(0, 0, 60, 60)

        self.m_lightSource = self.m_scene.addPixmap(pixmap)
        self.m_lightSource.setZValue(2)

        for i in range(-2, 3):
            for j in range(-2, 3):
                if (i + j) & 1:
                    item = QGraphicsEllipseItem(0, 0, 50, 50)
                else:
                    item = QGraphicsRectItem(0, 0, 50, 50)

                item.setPen(QPen(Qt.black, 1))
                item.setBrush(QBrush(Qt.white))

                effect = QGraphicsDropShadowEffect(self)
                effect.setBlurRadius(8)
                item.setGraphicsEffect(effect)
                item.setZValue(1)
                item.setPos(i * 80, j * 80)
                self.m_scene.addItem(item)
                self.m_items.append(item)

    def animate(self):
        self.angle += (math.pi / 30)
        xs = 200 * math.sin(self.angle) - 40 + 25
        ys = 200 * math.cos(self.angle) - 40 + 25
        self.m_lightSource.setPos(xs, ys)

        for item in self.m_items:
            effect = item.graphicsEffect()

            delta = QPointF(item.x() - xs, item.y() - ys)
            effect.setOffset(QPointF(delta.toPoint() / 30))

            dd = math.hypot(delta.x(), delta.y())
            color = effect.color()
            color.setAlphaF(max(0.4, min(1 - dd / 200.0, 0.7)))
            effect.setColor(color)

        self.m_scene.update()


if __name__ == '__main__':
    app = QApplication(sys.argv)

    lighting = Lighting()
    lighting.setWindowTitle("Lighting and Shadows")
    lighting.resize(640, 480)
    lighting.show()

    sys.exit(app.exec())
