"""Native QGraphicsScene primitives for the fallback (non-WebEngine) graph
view (R08-T14, split out of ``graph_renderer.py`` to keep it under the
400-line cap; originally ``ui/structure_graph_view.py``, lines 65-186 of the
original 1035-line file: ``_Bridge``, ``_Edge``, ``_Node``, ``_GraphView``).
"""
from __future__ import annotations

import math

from PySide6.QtCore import QObject, QPointF, Qt, Slot
from PySide6.QtGui import QBrush, QColor, QFont, QPen
from PySide6.QtWidgets import QGraphicsEllipseItem, QGraphicsLineItem, QGraphicsSimpleTextItem, QGraphicsView

from cowork_local.core.structure_graph import EDGE_KIND_COLORS, NODE_KIND_COLORS
from cowork_local.theme import current_palette
from cowork_local.ui.osutil import open_folder, open_location


class _Bridge(QObject):
    """Exposed to the D3 page so a Shift+click on a node can open its
    storage folder/link (local path or URL — see osutil.open_location)."""

    @Slot(str)
    def openPath(self, path: str) -> None:  # noqa: N802 - JS-facing name
        if path:
            open_location(path)


class _Edge(QGraphicsLineItem):
    def __init__(self, a: "_Node", b: "_Node", type_: str = ""):
        super().__init__()
        self.a, self.b = a, b
        self.type = type_
        # Colour the edge by its RELATIONSHIP type (contains/defines/method/…),
        # so the graph shows what each connection MEANS — falling back to the
        # source node's tint for any untyped edge.
        color = QColor(EDGE_KIND_COLORS.get(type_, "")) if type_ else QColor()
        if not color.isValid():
            color = a.brush().color().lighter(130)
        self._color = color
        self.setPen(QPen(color, 1.4))
        self.setZValue(-1)
        # A small label naming the relationship, shown at the edge midpoint.
        self._label = None
        if type_:
            self._label = QGraphicsSimpleTextItem(type_, self)
            self._label.setBrush(QBrush(color.lighter(140)))
            f = QFont()
            f.setPointSize(7)
            self._label.setFont(f)
            self._label.setZValue(0)
        a.edges.append(self)
        b.edges.append(self)
        self.adjust()

    def adjust(self) -> None:
        pa, pb = self.a.scenePos(), self.b.scenePos()
        self.setLine(pa.x(), pa.y(), pb.x(), pb.y())
        if self._label is not None:
            br = self._label.boundingRect()
            self._label.setPos((pa.x() + pb.x()) / 2 - br.width() / 2,
                                (pa.y() + pb.y()) / 2 - br.height() / 2)


class _Node(QGraphicsEllipseItem):
    def __init__(self, data, radius: int):
        super().__init__(-radius, -radius, 2 * radius, 2 * radius)
        self.data = data
        self.edges = []
        tok = current_palette()
        # NODE_KIND_COLORS is a categorical data encoding (one hue per node
        # kind), not UI chrome — it stays fixed across themes on purpose so a
        # given kind is always the same colour. Only the chrome follows tokens.
        color = QColor(NODE_KIND_COLORS.get(data.kind, tok.text_muted))
        self.setBrush(QBrush(color))
        self.setPen(QPen(color.darker(160), 1.5))
        self.setFlags(
            QGraphicsEllipseItem.ItemIsMovable
            | QGraphicsEllipseItem.ItemIsSelectable
            | QGraphicsEllipseItem.ItemSendsGeometryChanges
        )
        self.setZValue(1)
        label = QGraphicsSimpleTextItem(data.label, self)
        label.setBrush(QBrush(QColor(tok.text)))
        label.setPos(radius + 3, -8)

    def itemChange(self, change, value):  # noqa: N802
        if change == QGraphicsEllipseItem.ItemPositionHasChanged:
            for edge in self.edges:
                edge.adjust()
        return super().itemChange(change, value)


class _GraphView(QGraphicsView):
    def __init__(self, scene):
        super().__init__(scene)
        self.setDragMode(QGraphicsView.NoDrag)
        self._panning = False
        self._pan_start = QPointF()

    def wheelEvent(self, e):  # noqa: N802
        self.scale(1.15 if e.angleDelta().y() > 0 else 1 / 1.15,
                   1.15 if e.angleDelta().y() > 0 else 1 / 1.15)

    def mousePressEvent(self, e):  # noqa: N802
        if e.button() == Qt.LeftButton and self.itemAt(e.pos()) is None:
            self._panning = True
            self._pan_start = e.position()
            self.setCursor(Qt.ClosedHandCursor)
            e.accept()
            return
        super().mousePressEvent(e)

    def mouseMoveEvent(self, e):  # noqa: N802
        if self._panning:
            delta = e.position() - self._pan_start
            self._pan_start = e.position()
            self.horizontalScrollBar().setValue(int(self.horizontalScrollBar().value() - delta.x()))
            self.verticalScrollBar().setValue(int(self.verticalScrollBar().value() - delta.y()))
            e.accept()
            return
        super().mouseMoveEvent(e)

    def mouseReleaseEvent(self, e):  # noqa: N802
        if self._panning:
            self._panning = False
            self.setCursor(Qt.ArrowCursor)
            e.accept()
            return
        super().mouseReleaseEvent(e)

    def mouseDoubleClickEvent(self, e):  # noqa: N802
        """Double-click or Ctrl+click on a node opens its storage folder."""
        item = self.itemAt(e.pos())
        if isinstance(item, _Node) and getattr(item.data, "path", ""):
            open_folder(item.data.path)
            e.accept()
            return
        super().mouseDoubleClickEvent(e)


__all__ = ["_Bridge", "_Edge", "_Node", "_GraphView"]