from pyqtgraph.Qt import QtGui, QtCore  
from pyqtgraph.GraphicsScene import GraphicsScene
from pyqtgraph.Point import Point
import weakref

class GraphicsItem(object):
    """
    **Bases:** :class:`object`

    Abstract class providing useful methods to GraphicsObject and GraphicsWidget.
    (This is required because we cannot have multiple inheritance with QObject subclasses.)
    """
    def __init__(self, register=True):
        self._viewWidget = None
        self._viewBox = None
        self._connectedView = None
        if register:
            GraphicsScene.registerObject(self)  ## workaround for pyqt bug in graphicsscene.items()
    
    def getViewWidget(self):
        """
        Return the view widget for this item. If the scene has multiple views, only the first view is returned.
        The return value is cached; clear the cached value with forgetViewWidget()
        """
        if self._viewWidget is None:
            scene = self.scene()
            if scene is None:
                return None
            views = scene.views()
            if len(views) < 1:
                return None
            self._viewWidget = weakref.ref(self.scene().views()[0])
        return self._viewWidget()
        
    def forgetViewWidget(self):
        self._viewWidget = None
        
    def getViewBox(self):
        """
        Return the first ViewBox or GraphicsView which bounds this item's visible space.
        If this item is not contained within a ViewBox, then the GraphicsView is returned.
        If the item is contained inside nested ViewBoxes, then the inner-most ViewBox is returned.
        The result is cached; clear the cache with forgetViewBox()
        """
        if self._viewBox is None:
            p = self
            while True:
                p = p.parentItem()
                if p is None:
                    vb = self.getViewWidget()
                    if vb is None:
                        return None
                    else:
                        self._viewBox = weakref.ref(vb)
                        break
                if hasattr(p, 'implements') and p.implements('ViewBox'):
                    self._viewBox = weakref.ref(p)
                    break
        return self._viewBox()  ## If we made it this far, _viewBox is definitely not None

    def forgetViewBox(self):
        self._viewBox = None
        
        
    def deviceTransform(self, viewportTransform=None):
        """
        Return the transform that converts local item coordinates to device coordinates (usually pixels).
        Extends deviceTransform to automatically determine the viewportTransform.
        """
        if viewportTransform is None:
            view = self.getViewWidget()
            if view is None:
                return None
            viewportTransform = view.viewportTransform()
        return QtGui.QGraphicsObject.deviceTransform(self, viewportTransform)
        
    def viewTransform(self):
        """Return the transform that maps from local coordinates to the item's ViewBox coordinates
        If there is no ViewBox, return the scene transform.
        Returns None if the item does not have a view."""
        view = self.getViewBox()
        if view is None:
            return None
        if hasattr(view, 'implements') and view.implements('ViewBox'):
            tr = self.itemTransform(view.innerSceneItem())
            if isinstance(tr, tuple):
                tr = tr[0]   ## difference between pyside and pyqt
            return tr
        else:
            return self.sceneTransform()
            #return self.deviceTransform(view.viewportTransform())



    def getBoundingParents(self):
        """Return a list of parents to this item that have child clipping enabled."""
        p = self
        parents = []
        while True:
            p = p.parentItem()
            if p is None:
                break
            if p.flags() & self.ItemClipsChildrenToShape:
                parents.append(p)
        return parents
    
    def viewRect(self):
        """Return the bounds (in item coordinates) of this item's ViewBox or GraphicsWidget"""
        view = self.getViewBox()
        if view is None:
            return None
        bounds = self.mapRectFromView(view.viewRect())
        if bounds is None:
            return None

        bounds = bounds.normalized()
        
        ## nah.
        #for p in self.getBoundingParents():
            #bounds &= self.mapRectFromScene(p.sceneBoundingRect())
            
        return bounds
        
        
        
    def pixelVectors(self):
        """Return vectors in local coordinates representing the width and height of a view pixel."""
        vt = self.deviceTransform()
        if vt is None:
            return None
        vt = vt.inverted()[0]
        orig = vt.map(QtCore.QPointF(0, 0))
        return vt.map(QtCore.QPointF(1, 0))-orig, vt.map(QtCore.QPointF(0, 1))-orig
        
    def pixelLength(self, direction):
        """
        Return the length of one pixel in the direction indicated (in local coordinates)
        If the result would be infinite (this happens if the device transform is not properly configured yet),
        then return None instead.
        """
        dt = self.deviceTransform()
        if dt is None:
            return None
        viewDir = Point(dt.map(direction) - dt.map(Point(0,0)))
        try:
            norm = viewDir.norm()
        except ZeroDivisionError:
            return None
        dti = dt.inverted()[0]
        return Point(dti.map(norm)-dti.map(Point(0,0))).length()
        

    def pixelSize(self):
        v = self.pixelVectors()
        return (v[0].x()**2+v[0].y()**2)**0.5, (v[1].x()**2+v[1].y()**2)**0.5

    def pixelWidth(self):
        vt = self.deviceTransform()
        if vt is None:
            return 0
        vt = vt.inverted()[0]
        return Point(vt.map(QtCore.QPointF(1, 0))-vt.map(QtCore.QPointF(0, 0))).length()
        
    def pixelHeight(self):
        vt = self.deviceTransform()
        if vt is None:
            return 0
        vt = vt.inverted()[0]
        return Point(vt.map(QtCore.QPointF(0, 1))-vt.map(QtCore.QPointF(0, 0))).length()
        
        
    def mapToDevice(self, obj):
        """
        Return *obj* mapped from local coordinates to device coordinates (pixels).
        If there is no device mapping available, return None.
        """
        vt = self.deviceTransform()
        if vt is None:
            return None
        return vt.map(obj)
        
    def mapFromDevice(self, obj):
        """
        Return *obj* mapped from device coordinates (pixels) to local coordinates.
        If there is no device mapping available, return None.
        """
        vt = self.deviceTransform()
        if vt is None:
            return None
        vt = vt.inverted()[0]
        return vt.map(obj)

    def mapRectToDevice(self, rect):
        """
        Return *rect* mapped from local coordinates to device coordinates (pixels).
        If there is no device mapping available, return None.
        """
        vt = self.deviceTransform()
        if vt is None:
            return None
        return vt.mapRect(rect)

    def mapRectFromDevice(self, rect):
        """
        Return *rect* mapped from device coordinates (pixels) to local coordinates.
        If there is no device mapping available, return None.
        """
        vt = self.deviceTransform()
        if vt is None:
            return None
        vt = vt.inverted()[0]
        return vt.mapRect(rect)
    
    def mapToView(self, obj):
        vt = self.viewTransform()
        if vt is None:
            return None
        return vt.map(obj)
        
    def mapRectToView(self, obj):
        vt = self.viewTransform()
        if vt is None:
            return None
        return vt.mapRect(obj)
        
    def mapFromView(self, obj):
        vt = self.viewTransform()
        if vt is None:
            return None
        vt = vt.inverted()[0]
        return vt.map(obj)

    def mapRectFromView(self, obj):
        vt = self.viewTransform()
        if vt is None:
            return None
        vt = vt.inverted()[0]
        return vt.mapRect(obj)

    def pos(self):
        return Point(QtGui.QGraphicsObject.pos(self))
    
    def viewPos(self):
        return self.mapToView(self.mapFromParent(self.pos()))
    
    def parentItem(self):
        ## PyQt bug -- some items are returned incorrectly.
        return GraphicsScene.translateGraphicsItem(QtGui.QGraphicsObject.parentItem(self))
        
    
    def childItems(self):
        ## PyQt bug -- some child items are returned incorrectly.
        return list(map(GraphicsScene.translateGraphicsItem, QtGui.QGraphicsObject.childItems(self)))


    def sceneTransform(self):
        ## Qt bug: do no allow access to sceneTransform() until 
        ## the item has a scene.
        
        if self.scene() is None:
            return self.transform()
        else:
            return QtGui.QGraphicsObject.sceneTransform(self)


    def transformAngle(self, relativeItem=None):
        """Return the rotation produced by this item's transform (this assumes there is no shear in the transform)
        If relativeItem is given, then the angle is determined relative to that item.
        """
        if relativeItem is None:
            relativeItem = self.parentItem()
            

        tr = self.itemTransform(relativeItem)
        if isinstance(tr, tuple):  ## difference between pyside and pyqt
            tr = tr[0]  
        vec = tr.map(Point(1,0)) - tr.map(Point(0,0))
        return Point(vec).angle(Point(1,0))
        
        
    #def itemChange(self, change, value):
        #ret = QtGui.QGraphicsObject.itemChange(self, change, value)
        #if change == self.ItemParentHasChanged or change == self.ItemSceneHasChanged:
            #print "Item scene changed:", self
            #self.setChildScene(self)  ## This is bizarre.
        #return ret

    #def setChildScene(self, ch):
        #scene = self.scene()
        #for ch2 in ch.childItems():
            #if ch2.scene() is not scene:
                #print "item", ch2, "has different scene:", ch2.scene(), scene
                #scene.addItem(ch2)
                #QtGui.QApplication.processEvents()
                #print "   --> ", ch2.scene()
            #self.setChildScene(ch2)

    def _updateView(self):
        ## called to see whether this item has a new view to connect to
        ## NOTE: This is called from GraphicsObject.itemChange or GraphicsWidget.itemChange.

        ## It is possible this item has moved to a different ViewBox or widget;
        ## clear out previously determined references to these.
        self.forgetViewBox()
        self.forgetViewWidget()
        
        ## check for this item's current viewbox or view widget
        view = self.getViewBox()
        if view is None:
            #print "  no view"
            return

        if self._connectedView is not None and view is self._connectedView():
            #print "  already have view", view
            return

        ## disconnect from previous view
        if self._connectedView is not None:
            cv = self._connectedView()
            if cv is not None:
                #print "disconnect:", self
                cv.sigRangeChanged.disconnect(self.viewRangeChanged)

        ## connect to new view
        #print "connect:", self
        view.sigRangeChanged.connect(self.viewRangeChanged)
        self._connectedView = weakref.ref(view)
        self.viewRangeChanged()

    def viewRangeChanged(self):
        """
        Called whenever the view coordinates of the ViewBox containing this item have changed.
        """
        pass