# -*- coding: utf-8 -*-
from PyQt5.QtGui import *
from PyQt5.QtCore import *
from PyQt5.QtWidgets import *

from libs.shape import Shape
from libs.lib import distance

CURSOR_DEFAULT = Qt.ArrowCursor
CURSOR_POINT = Qt.PointingHandCursor
CURSOR_DRAW = Qt.CrossCursor
CURSOR_MOVE = Qt.ClosedHandCursor
CURSOR_GRAB = Qt.OpenHandCursor

class Canvas(QWidget):
    zoomRequest = pyqtSignal(int)
    scrollRequest = pyqtSignal(int, int)
    newShape = pyqtSignal()
    selectionChanged = pyqtSignal(bool)
    shapeMoved = pyqtSignal()
    drawingPolygon = pyqtSignal(bool)

    updateData = pyqtSignal(int)

    CREATE, EDIT = list(range(2))

    epsilon = 11.0
    
    def __init__(self, *args, **kwargs):
        super(Canvas, self).__init__(*args, **kwargs)
        # Initialise local state
        self.mode = self.EDIT
        self.shapes = []
        self.line_number = None
        self.current = None
        self.selectedShape = None  # save the selected shape here
        self.drawingLineColor = QColor(0, 0, 255)
        self.line = Shape(line_color=self.drawingLineColor)
        self.prevPoint = QPointF()
        self.scale = 1.0
        self.pixmap = QPixmap()
        self.hShape = None
        self.hVertex = None

        self._painter = QPainter()
        self._cursor = CURSOR_DEFAULT

        # Set widget options.
        self.setMouseTracking(True)
        self.drawSquare = False

    def setDrawingColor(self, qColor):
        self.drawingLineColor = qColor

    def drawing(self):
        return self.mode == self.CREATE

    def editing(self):
        return self.mode == self.EDIT

    def setEditing(self, value=True):
        self.mode = self.EDIT if value else self.CREATE
        if not value:
            self.unHighlight()
            self.deSelectShape()
        self.repaint()

    def unHighlight(self):
        if self.hShape:
            self.hShape.higlightClear()
        self.hShape = self.hVertex = None

    def selectedVertex(self):
        return self.hVertex is not None

    def mousePressEvent(self, ev):
        pos = self.transformPos(ev.pos())

        if ev.button() == Qt.LeftButton:
            if self.drawing():
                self.handleDrawing(pos)
            else:
                self.selectedShapePoint(pos)
                self.prevPoint = pos
                self.repaint()


    def mouseMoveEvent(self, ev):
        """Update line with last point and current coordinates."""
        pos = self.transformPos(ev.pos())

        # Polygon drawing.
        if self.drawing():
            self.overrideCursor(CURSOR_DRAW)
            if self.current:
                color = self.drawingLineColor
                if self.outOfPixmap(pos):
                    # Don't allow the user to draw outside the pixmap.
                    # Project the point to the pixmap's edges.
                    pos = self.intersectionPoint(self.current[-1], pos)
                elif len(self.current) > 1 and self.closeEnough(pos, self.current[0]):
                    # Attract line to starting point and colorise to alert the
                    # user:
                    pos = self.current[0]
                    color = self.current.line_color
                    self.overrideCursor(CURSOR_POINT)
                    self.current.highlightVertex(0)

                if self.drawSquare:
                    pass
                else:
                    self.line[1] = pos

                self.line.line_color = color
                self.prevPoint = QPointF()
                self.current.highlightClear()
            else:
                self.prevPoint = pos
            self.repaint()
            return

        # Polygon/Vertex moving.
        if Qt.LeftButton & ev.buttons():
            if self.selectedVertex():
                self.boundedMoveVertex(pos)
                self.shapeMoved.emit()
                self.repaint()
            elif self.selectedShape and self.prevPoint:
                self.overrideCursor(CURSOR_MOVE)
                self.boundedMoveShape(self.selectedShape, pos)
                self.shapeMoved.emit()
                self.repaint()
            return

        # Just hovering over the canvas, 2 posibilities:
        # - Highlight shapes
        # - Highlight vertex
        # Update shape/vertex fill and tooltip value accordingly.
        self.setToolTip("Image")
        for shape in reversed([s for s in self.shapes]):
            # Look for a nearby vertex to highlight. If that fails,
            # check if we happen to be inside a shape.
            index = shape.nearestVertex(pos, self.epsilon)
            if index is not None:
                if self.selectedVertex():
                    self.hShape.highlightClear()
                self.hVertex, self.hShape = index, shape
                shape.highlightVertex(index)
                self.overrideCursor(CURSOR_POINT)
                self.setToolTip("Click & drag to move point")
                self.setStatusTip(self.toolTip())
                self.update()
                break
            elif shape.containsPoint(pos):
                if self.selectedVertex():
                    self.hShape.highlightClear()
                self.hVertex, self.hShape = None, shape
                self.setToolTip("Click & drag to move shape '%s'" % shape.label)
                self.setStatusTip(self.toolTip())
                self.overrideCursor(CURSOR_GRAB)
                self.update()
                break
            else:
                # Nothing found, clear highlights, reset state.
                if self.hShape:
                    self.hShape.highlightClear()
                    self.update()
                self.hVertex, self.hShape = None, None
                self.overrideCursor(CURSOR_DEFAULT)

    def mouseReleaseEvent(self, ev):
        if ev.button() == Qt.LeftButton and self.selectedShape:
            if self.selectedVertex():
                self.overrideCursor(CURSOR_POINT)
            else:
                self.overrideCursor(CURSOR_GRAB)
            self.updateData.emit(len(self.shapes))
        elif ev.button() == Qt.LeftButton:
            pos = self.transformPos(ev.pos())
            if self.drawing():
                self.handleDrawing(pos)
            self.updateData.emit(len(self.shapes))



    def resetAllLines(self):
        assert self.shapes
        self.current = self.shapes.pop()
        self.line.points = [self.current[-1], self.current[0]]
        self.drawingPolygon.emit(True)
        self.current = None
        self.drawingPolygon.emit(False)
        self.update()


    def boundedMoveVertex(self, pos):
        index, shape = self.hVertex, self.hShape
        point = shape[index]
        if self.outOfPixmap(pos):
            pos = self.intersectionPoint(point, pos)

        if self.drawSquare:
            opposite_point_index = (index + 2) % 4
            opposite_point = shape[opposite_point_index]

            min_size = min(abs(pos.x() - opposite_point.x()), abs(pos.y() - opposite_point.y()))
            directionX = -1 if pos.x() - opposite_point.x() < 0 else 1
            directionY = -1 if pos.y() - opposite_point.y() < 0 else 1
            shiftPos = QPointF(opposite_point.x() + directionX * min_size - point.x(),
                               opposite_point.y() + directionY * min_size - point.y())
        else:
            shiftPos = pos - point

        shape.moveVertexBy(index, shiftPos)

        # lindex = (index + 1) % 4
        # rindex = (index + 3) % 4
        # lshift = None
        # rshift = None
        # if index % 2 == 0:
        #     rshift = QPointF(shiftPos.x(), 0)
        #     lshift = QPointF(0, shiftPos.y())
        # else:
        #     lshift = QPointF(shiftPos.x(), 0)
        #     rshift = QPointF(0, shiftPos.y())
        # shape.moveVertexBy(rindex, rshift)
        # shape.moveVertexBy(lindex, lshift)

    def paintEvent(self, event):
        if not self.pixmap:
            return super(Canvas, self).paintEvent(event)

        p = self._painter
        p.begin(self)
        p.setRenderHint(QPainter.Antialiasing)
        p.setRenderHint(QPainter.HighQualityAntialiasing)
        p.setRenderHint(QPainter.SmoothPixmapTransform)

        p.scale(self.scale, self.scale)
        p.translate(self.offsetToCenter())

        p.drawPixmap(0, 0, self.pixmap)
        Shape.scale = self.scale
        for shape in self.shapes:
            shape.fill = shape.selected or shape == self.hShape
            shape.paint(p)
        if self.current:
            self.current.paint(p)
            self.line.paint(p)

        # Paint line
        if self.current is not None and len(self.line) == 2:
            leftTop = self.line[0]
            rightBottom = self.line[1]
            p.setPen(self.drawingLineColor)
            brush = QBrush(Qt.BDiagPattern)
            p.setBrush(brush)
            p.drawLine(leftTop, rightBottom)

        if self.drawing() and not self.prevPoint.isNull() and not self.outOfPixmap(self.prevPoint):
            p.setPen(QColor(0, 0, 0))
            p.drawLine(self.prevPoint.x(), 0, self.prevPoint.x(), self.pixmap.height())
            p.drawLine(0, self.prevPoint.y(), self.pixmap.width(), self.prevPoint.y())

        self.setAutoFillBackground(True)

        pal = self.palette()
        pal.setColor(self.backgroundRole(), QColor(232, 232, 232, 255))
        self.setPalette(pal)

        p.end()


    def boundedMoveShape(self, shape, pos):
        if self.outOfPixmap(pos):
            return False  # No need to move
        o1 = pos + self.offsets[0]
        if self.outOfPixmap(o1):
            pos -= QPointF(min(0, o1.x()), min(0, o1.y()))
        o2 = pos + self.offsets[1]
        if self.outOfPixmap(o2):
            pos += QPointF(min(0, self.pixmap.width() - o2.x()),
                           min(0, self.pixmap.height() - o2.y()))
        # The next line tracks the new position of the cursor
        # relative to the shape, but also results in making it
        # a bit "shaky" when nearing the border and allows it to
        # go outside of the shape's area for some reason. XXX
        #self.calculateOffsets(self.selectedShape, pos)
        dp = pos - self.prevPoint
        if dp:
            shape.moveBy(dp)
            self.prevPoint = pos
            return True
        return False


    def closeEnough(self, p1, p2):
        return distance(p1 - p2) < self.epsilon


    def intersectionPoint(self, p1, p2):
        # Cycle through each image edge in clockwise fashion,
        # and find the one intersecting the current line segment.
        # http://paulbourke.net/geometry/lineline2d/
        size = self.pixmap.size()
        points = [(0, 0),
                  (size.width(), 0),
                  (size.width(), size.height()),
                  (0, size.height())]
        x1, y1 = p1.x(), p1.y()
        x2, y2 = p2.x(), p2.y()
        d, i, (x, y) = min(self.intersectingEdges((x1, y1), (x2, y2), points))
        x3, y3 = points[i]
        x4, y4 = points[(i + 1) % 4]
        if (x, y) == (x1, y1):
            # Handle cases where previous point is on one of the edges.
            if x3 == x4:
                return QPointF(x3, min(max(0, y2), max(y3, y4)))
            else:  # y3 == y4
                return QPointF(min(max(0, x2), max(x3, x4)), y3)
        return QPointF(x, y)



    def intersectingEdges(self, x1y1, x2y2, points):
        """For each edge formed by `points', yield the intersection
        with the line segment `(x1,y1) - (x2,y2)`, if it exists.
        Also return the distance of `(x2,y2)' to the middle of the
        edge along with its index, so that the one closest can be chosen."""
        x1, y1 = x1y1
        x2, y2 = x2y2
        for i in range(4):
            x3, y3 = points[i]
            x4, y4 = points[(i+1) % 4]
            denom = (y4 - y3) * (x2 - x1) - (x4 - x3) * (y2 - y1)
            nua = (x4 - x3) * (y1 - y3) - (y4 - y3) * (x1 - x3)
            nub = (x2 - x1) * (y1 - y3) - (y2 - y1) * (x1 - x3)
            if denom == 0:
                # This covers two cases:
                #   nua == nub == 0: Coincident
                #   otherwise: Parallel
                continue
            ua, ub = nua / denom, nub / denom
            if 0 <= ua <= 1 and 0 <= ub <= 1:
                x = x1 + ua * (x2 - x1)
                y = y1 + ua * (y2 - y1)
                m = QPointF((x3 + x4) / 2, (y3 + y4) / 2)
                d = distance(m - QPointF(x2, y2))
                yield d, i, (x, y)


    def currentCursor(self):
        cursor = QApplication.overrideCursor()
        if cursor is not None:
            cursor = cursor.shape()
        return cursor

    def overrideCursor(self, cursor):
        self._cursor = cursor
        if self.currentCursor() is None:
            QApplication.setOverrideCursor(cursor)
        else:
            QApplication.changeOverrideCursor(cursor)


    def selectedShapePoint(self, point):
        """Select the first shape created which contains this point."""
        self.deSelectShape()
        if self.selectedVertex():
            index, shape = self.hVertex, self.hShape
            shape.highlightVertex(index)
            self.selectShape(shape)
            return
        for shape in reversed(self.shapes):
            if shape.containsPoint(point):
                self.selectShape(shape)
                self.calculateOffsets(shape, point)
                return

    def selectShape(self, shape):
        self.deSelectShape()
        shape.selected = True
        self.selectedShape = shape
        self.selectionChanged.emit(True)
        self.update()

    def calculateOffsets(self, shape, point):
        rect = shape.boundingRect()
        x1 = rect.x() - point.x()
        y1 = rect.y() - point.y()
        x2 = (rect.x() + rect.width()) - point.x()
        y2 = (rect.y() + rect.height()) - point.y()
        self.offsets = QPointF(x1, y1), QPointF(x2, y2)

    def deSelectShape(self):
        if self.selectedShape:
            self.selectedShape.selected = False
            self.selectedShape = None
            self.selectionChanged.emit(False)
            self.update()


    def deleteSelected(self):
        if self.selectedShape:
            shape = self.selectedShape
            self.shapes.remove(self.selectedShape)
            self.selectedShape = None
            self.update()
            return shape


    def handleDrawing(self, pos):
        if self.current and self.current.reachMaxPoints() is False:
            initPos = self.current[0]
            minX = initPos.x()
            minY = initPos.y()
            targetPos = self.line[1]
            maxX = targetPos.x()
            maxY = targetPos.y()
            self.current.addPoint(targetPos)
            self.finalise()
        elif not self.outOfPixmap(pos):
            self.current = Shape()
            self.current.addPoint(pos)
            self.line.points = [pos, pos]
            self.drawingPolygon.emit(True)
            self.update()


    def finalise(self):
        assert self.current
        if self.current.points[0] == self.current.points[-1]:
            self.current = None
            self.drawingPolygon.emit(False)
            self.update()
            return

        self.shapes.append(self.current)
        self.current.label = self.line_number
        self.current = None
        self.newShape.emit()
        self.update()


    def outOfPixmap(self, p):
        w, h = self.pixmap.width(), self.pixmap.height()
        return not (0 <= p.x() <= w and 0 <= p.y() <= h)


    def transformPos(self, point):
        """Convert from widget-logical coordinates to painter-logical coordinates."""
        return point / self.scale - self.offsetToCenter()


    def offsetToCenter(self):
        s = self.scale
        area = super(Canvas, self).size()
        w, h = self.pixmap.width() * s, self.pixmap.height() * s
        aw, ah = area.width(), area.height()
        x = (aw - w) / (2 * s) if aw > w else 0
        y = (ah - h) / (2 * s) if ah > h else 0
        return QPointF(x, y)

    def restoreCursor(self):
        QApplication.restoreOverrideCursor()

    def resetState(self):
        self.restoreCursor()
        self.pixmap = None
        self.update()

    def loadPixmap(self, pixmap):
        self.pixmap = pixmap
        self.shapes = []
        self.repaint()

    # These two, along with a call to adjustSize are required for the
    # scroll area.
    def sizeHint(self):
        return self.minimumSizeHint()

    def minimumSizeHint(self):
        if self.pixmap:
            return self.scale * self.pixmap.size()
        return super(Canvas, self).minimumSizeHint()

    def wheelEvent(self, ev):
        qt_version = 4 if hasattr(ev, "delta") else 5
        if qt_version == 4:
            if ev.orientation() == Qt.Vertical:
                v_delta = ev.delta()
                h_delta = 0
            else:
                h_delta = ev.delta()
                v_delta = 0
        else:
            delta = ev.angleDelta()
            h_delta = delta.x()
            v_delta = delta.y()

        mods = ev.modifiers()
        if Qt.ControlModifier == int(mods) and v_delta:
            self.zoomRequest.emit(v_delta)
        else:
            v_delta and self.scrollRequest.emit(v_delta, Qt.Vertical)
            h_delta and self.scrollRequest.emit(h_delta, Qt.Horizontal)
        ev.accept()