'''
    Copyright (C) 2019 Tusooa Zhu <tusooa@vista.aero>

    This file is part of Krita-docker-color-slider.

    Krita-docker-color-slider 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.

    Krita-docker-color-slider 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 Krita-docker-color-slider.  If not, see <https://www.gnu.org/licenses/>.
'''
from PyQt5.QtWidgets import QWidget
from PyQt5.QtGui import QPixmap, QPainter, QColor, QBrush, QPolygon
from PyQt5.QtCore import QPoint
from krita import ManagedColor


class ColorSlider(QWidget):
    default_color = ManagedColor("", "", "")

    def __init__(self, docker, left_color=default_color, right_color=default_color, parent=None):
        super(ColorSlider, self).__init__(parent)
        self.docker = docker
        self.left_color = left_color
        self.right_color = right_color
        self.slider_pixmap = None
        self.value_x = None
        self.cursor_fill_color = QColor.fromRgbF(1, 1, 1, 1)
        self.cursor_outline_color = QColor.fromRgbF(0, 0, 0, 1)
        self.need_redraw = True

    def set_color(self, pos, color):
        if pos == 'left':
            if self.left_color is not color:
                self.left_color = color
                self.need_redraw = True
        else:
            if self.right_color is not color:
                self.right_color = color
                self.need_redraw = True

    def update_slider(self):
        '''
        Update the slider to a gradient between the two colors.

        The painting of the slider comes from the program Krita. The original code can be accessed
        at the following URL.
        https://github.com/KDE/krita/blob/master/plugins/dockers/advancedcolorselector/kis_shade_selector_line.cpp
        '''
        if self.need_redraw:
            patch_count = self.width()
            base_hsva = list(self.docker.managedcolor_to_qcolor(self.left_color).getHsvF())
            dest_hsva = list(self.docker.managedcolor_to_qcolor(self.right_color).getHsvF())
            diff_hsva = [(dest_hsva[i] - base_hsva[i]) for i in range(4)]
            if dest_hsva[0] == -1.0:
                diff_hsva[0] = 0
            elif base_hsva[0] == -1.0:
                diff_hsva[0] = 0
                base_hsva[0] = dest_hsva[0]
            elif diff_hsva[0] > 0.5:  # make sure the sliding goes through a minor arc
                diff_hsva[0] = diff_hsva[0] - 1.0
            elif diff_hsva[0] < -0.5:
                diff_hsva[0] = diff_hsva[0] + 1.0

            step_hsva = [x / patch_count for x in diff_hsva]

            self.slider_pixmap = QPixmap(self.width(), self.height())
            painter = QPainter(self.slider_pixmap)

            for i in range(patch_count):
                hue = base_hsva[0] + i * step_hsva[0]
                while hue < 0.0:
                    hue += 1.0

                while hue > 1.0:
                    hue -= 1.0

                saturation = base_hsva[1] + i * step_hsva[1]
                value = base_hsva[2] + i * step_hsva[2]
                cur_color = QColor.fromHsvF(hue, saturation, value)
                painter.fillRect(i, 0, 1, self.height(), cur_color)

            painter.end()

            self.need_redraw = False

        widget_painter = QPainter(self)
        self.rendered_image = self.slider_pixmap.toImage()

        widget_painter.drawImage(0, 0, self.rendered_image)
        if self.value_x is not None:
            start_x = self.value_x
            start_y = self.height() / 2
            delta_x = self.height() / 3
            delta_y = self.height() / 3
            points = [QPoint(start_x, start_y),
                      QPoint(start_x - delta_x, start_y + delta_y),
                      QPoint(start_x + delta_x, start_y + delta_y)]
            widget_painter.setBrush(QBrush(self.cursor_fill_color))
            widget_painter.setPen(self.cursor_outline_color)
            widget_painter.drawPolygon(QPolygon(points))

    def paintEvent(self, event):
        self.update_slider()

    def resizeEvent(self, event):  # after resizing the widget, force-redraw the underlying slider
        self.need_redraw = True

    def adjust_pos_x(self, x):  # adjust the x to make it in the range of [0, width - 1]
        if x < 0:
            return 0
        if x >= self.width():
            return self.width() - 1
        return x

    def mouseMoveEvent(self, event):
        pos = event.pos()
        self.value_x = self.adjust_pos_x(pos.x())
        self.update()

    def mouseReleaseEvent(self, event):
        pos = event.pos()
        self.value_x = self.adjust_pos_x(pos.x())
        y = int(self.height() / 2)
        fixed_pos = QPoint(self.value_x, y)
        color = self.rendered_image.pixelColor(fixed_pos)
        mc = self.docker.qcolor_to_managedcolor(color)
        if self.docker.canvas() is not None:
            if self.docker.canvas().view() is not None:
                self.docker.canvas().view().setForeGroundColor(mc)
        self.update()
