"""
Zentrales Canvas-Widget: zeigt das Logo mit Zoom, Pan und Rasterlinien an.
"""
from __future__ import annotations

from PySide6.QtWidgets import QGraphicsView, QGraphicsScene, QGraphicsPixmapItem
from PySide6.QtCore import Qt, Signal, QPointF
from PySide6.QtGui import (
    QPainter, QPen, QColor, QPixmap, QWheelEvent, QMouseEvent,
)


class LogoCanvas(QGraphicsView):
    zoom_changed = Signal(float)

    def __init__(self, parent=None):
        super().__init__(parent)
        self._scene = QGraphicsScene(self)
        self.setScene(self._scene)

        self._pixmap_item: QGraphicsPixmapItem | None = None
        self._overlay_item: QGraphicsPixmapItem | None = None
        self._zoom = 1.0
        self._pan_active = False
        self._pan_start = QPointF()

        self.setRenderHints(
            QPainter.RenderHint.Antialiasing
            | QPainter.RenderHint.SmoothPixmapTransform
        )
        self.setDragMode(QGraphicsView.DragMode.NoDrag)
        self.setTransformationAnchor(QGraphicsView.ViewportAnchor.AnchorUnderMouse)
        self.setBackgroundBrush(QColor("#2b2b2b"))
        self.setMinimumSize(400, 300)

        self._draw_checkerboard()

    def _draw_checkerboard(self):
        """Schachbrettmuster als Transparenz-Indikator."""
        self.setStyleSheet("""
            QGraphicsView {
                background-color: #2b2b2b;
            }
        """)

    def set_original_image(self, pixmap: QPixmap):
        """Zeigt das Original-PNG an."""
        if self._pixmap_item:
            self._scene.removeItem(self._pixmap_item)
        self._pixmap_item = self._scene.addPixmap(pixmap)
        self._pixmap_item.setZValue(0)
        self.fitInView(self._pixmap_item, Qt.AspectRatioMode.KeepAspectRatio)
        self._zoom = self.transform().m11()
        self.zoom_changed.emit(self._zoom)

    def set_overlay(self, pixmap: QPixmap):
        """Zeigt die gerenderten Vektorpfade als Overlay an."""
        if self._overlay_item:
            self._scene.removeItem(self._overlay_item)
        self._overlay_item = self._scene.addPixmap(pixmap)
        self._overlay_item.setZValue(1)
        self._overlay_item.setOpacity(0.85)

    def clear_overlay(self):
        if self._overlay_item:
            self._scene.removeItem(self._overlay_item)
            self._overlay_item = None

    # --- Zoom via Mausrad ---
    def wheelEvent(self, event: QWheelEvent):
        factor = 1.15 if event.angleDelta().y() > 0 else 1 / 1.15
        self._zoom *= factor
        self.scale(factor, factor)
        self.zoom_changed.emit(self._zoom)

    # --- Pan via mittlere Maustaste oder Leertaste + Links ---
    def mousePressEvent(self, event: QMouseEvent):
        if event.button() == Qt.MouseButton.MiddleButton:
            self._pan_active = True
            self._pan_start = event.position()
            self.setCursor(Qt.CursorShape.ClosedHandCursor)
        else:
            super().mousePressEvent(event)

    def mouseMoveEvent(self, event: QMouseEvent):
        if self._pan_active:
            delta = event.position() - self._pan_start
            self._pan_start = event.position()
            self.horizontalScrollBar().setValue(
                self.horizontalScrollBar().value() - int(delta.x())
            )
            self.verticalScrollBar().setValue(
                self.verticalScrollBar().value() - int(delta.y())
            )
        else:
            super().mouseMoveEvent(event)

    def mouseReleaseEvent(self, event: QMouseEvent):
        if event.button() == Qt.MouseButton.MiddleButton:
            self._pan_active = False
            self.setCursor(Qt.CursorShape.ArrowCursor)
        else:
            super().mouseReleaseEvent(event)

    def set_zoom(self, zoom: float):
        factor = zoom / self._zoom
        self._zoom = zoom
        self.scale(factor, factor)
        self.zoom_changed.emit(self._zoom)

    def fit_to_view(self):
        if self._pixmap_item:
            self.fitInView(self._pixmap_item, Qt.AspectRatioMode.KeepAspectRatio)
            self._zoom = self.transform().m11()
            self.zoom_changed.emit(self._zoom)