"""CanvasView: zoomable/pannable QGraphicsView that accepts node drops."""
from __future__ import annotations

from PyQt6.QtCore import Qt
from PyQt6.QtGui import QPainter
from PyQt6.QtWidgets import QGraphicsView

from ..panels.node_panel import NODE_MIME

MIN_SCALE = 0.15
MAX_SCALE = 6.0


class CanvasView(QGraphicsView):
    def __init__(self, scene, parent=None):
        super().__init__(scene, parent)
        self.setRenderHints(
            QPainter.RenderHint.Antialiasing | QPainter.RenderHint.SmoothPixmapTransform)
        self.setDragMode(QGraphicsView.DragMode.RubberBandDrag)
        self.setTransformationAnchor(QGraphicsView.ViewportAnchor.AnchorUnderMouse)
        self.setResizeAnchor(QGraphicsView.ViewportAnchor.AnchorViewCenter)
        self.setAcceptDrops(True)
        self._scale = 1.0
        self._panning = False

    # -- zoom -------------------------------------------------------------
    def wheelEvent(self, event):
        factor = 1.2 if event.angleDelta().y() > 0 else 1 / 1.2
        new_scale = self._scale * factor
        if new_scale < MIN_SCALE or new_scale > MAX_SCALE:
            return
        self._scale = new_scale
        self.scale(factor, factor)

    def reset_zoom(self):
        self.resetTransform()
        self._scale = 1.0

    def fit_to_contents(self):
        rect = self.scene().itemsBoundingRect()
        if rect.isNull():
            return
        self.fitInView(rect.adjusted(-40, -40, 40, 40), Qt.AspectRatioMode.KeepAspectRatio)
        self._scale = self.transform().m11()

    # -- panning (space or middle mouse) ----------------------------------
    def keyPressEvent(self, event):
        if event.key() == Qt.Key.Key_Space and not self._panning:
            self._panning = True
            self.setDragMode(QGraphicsView.DragMode.ScrollHandDrag)
        super().keyPressEvent(event)

    def keyReleaseEvent(self, event):
        if event.key() == Qt.Key.Key_Space:
            self._panning = False
            self.setDragMode(QGraphicsView.DragMode.RubberBandDrag)
        super().keyReleaseEvent(event)

    def mousePressEvent(self, event):
        if event.button() == Qt.MouseButton.MiddleButton:
            self._panning = True
            self.setDragMode(QGraphicsView.DragMode.ScrollHandDrag)
            # forward as a left press so ScrollHandDrag engages
            from PyQt6.QtGui import QMouseEvent
            fake = QMouseEvent(event.type(), event.position(), event.globalPosition(),
                               Qt.MouseButton.LeftButton, Qt.MouseButton.LeftButton,
                               event.modifiers())
            super().mousePressEvent(fake)
            return
        super().mousePressEvent(event)

    def mouseReleaseEvent(self, event):
        if event.button() == Qt.MouseButton.MiddleButton and self._panning:
            self._panning = False
            self.setDragMode(QGraphicsView.DragMode.RubberBandDrag)
            return
        super().mouseReleaseEvent(event)

    # -- drops from the node panel ---------------------------------------
    def dragEnterEvent(self, event):
        if event.mimeData().hasFormat(NODE_MIME):
            event.acceptProposedAction()
        else:
            super().dragEnterEvent(event)

    def dragMoveEvent(self, event):
        if event.mimeData().hasFormat(NODE_MIME):
            event.acceptProposedAction()
        else:
            super().dragMoveEvent(event)

    def dropEvent(self, event):
        if event.mimeData().hasFormat(NODE_MIME):
            key = bytes(event.mimeData().data(NODE_MIME)).decode("utf-8")
            scene_pos = self.mapToScene(event.position().toPoint())
            self.scene().create_node(key, scene_pos.x(), scene_pos.y())
            event.acceptProposedAction()
        else:
            super().dropEvent(event)