import numpy as np
from PySide6.QtCore import QPointF, Qt


class CanvasInteractionMixin:
    @staticmethod
    def _distance_sq(pos_xy, point_xy):
        dx = float(pos_xy[0] - point_xy[0])
        dy = float(pos_xy[1] - point_xy[1])
        return dx * dx + dy * dy

    def _iter_slice_indices_for_hit_test(self):
        active = self.active_slice_index
        if active is not None and 0 <= int(active) < len(self.slices):
            active_idx = int(active)
            yield active_idx
            for si in reversed(range(len(self.slices))):
                if si != active_idx:
                    yield si
            return
        for si in reversed(range(len(self.slices))):
            yield si

    def _find_corner(self, pos):
        p = np.array([pos.x(), pos.y()], dtype=np.float64)
        hit_radius = float(getattr(self, "CORNER_HANDLE_HIT_RADIUS", 12.0))
        radius_sq = hit_radius * hit_radius
        for si in self._iter_slice_indices_for_hit_test():
            s = self.slices[si]
            for ci, c in enumerate(s.bbox):
                view_c = self._image_to_view(c)
                if self._distance_sq(p, (view_c.x(), view_c.y())) <= radius_sq:
                    return si, ci
        return None

    def _point_in_polygon(self, point, polygon):
        x, y = point
        inside = False
        vertices = np.array(polygon, dtype=np.float64).reshape(-1, 2)
        count = len(vertices)
        for i in range(count):
            x1, y1 = vertices[i]
            x2, y2 = vertices[(i + 1) % count]

            if (y1 > y) != (y2 > y):
                xinters = (x2 - x1) * (y - y1) / ((y2 - y1) + 1e-12) + x1
                if x <= xinters:
                    inside = not inside
        return inside

    def _find_slice_containing_point(self, pos):
        point_img = self._view_to_image(pos)
        for si in reversed(range(len(self.slices))):
            if self._point_in_polygon(point_img, self.slices[si].bbox):
                return si
        return None

    def _find_side_handle(self, pos):
        p = np.array([pos.x(), pos.y()], dtype=np.float64)
        hit_radius = float(getattr(self, "SIDE_HANDLE_HIT_RADIUS", 14.0))
        radius_sq = hit_radius * hit_radius
        for si in self._iter_slice_indices_for_hit_test():
            s = self.slices[si]
            if not s.side_handles_enabled or not s.is_perfect_rectangle():
                continue
            for ei in range(4):
                mid = (s.bbox[ei] + s.bbox[(ei + 1) % 4]) / 2.0
                mid_view = self._image_to_view(mid)
                if self._distance_sq(p, (mid_view.x(), mid_view.y())) <= radius_sq:
                    return si, ei
        return None

    def _try_begin_handle_drag(self, pos):
        # Side handles are checked before corners to make squarized edge-drag
        # interactions easier to grab.
        side = self._find_side_handle(pos)
        if side is not None:
            si, ei = side
            self.set_active_slice(si)
            self.side_dragging = (si, ei)
            return True

        corner = self._find_corner(pos)
        if corner is not None:
            si, _ = corner
            if self.rotate_handles_mode:
                self.set_active_slice(si)
                self.rotation_dragging = self._start_rotation_drag(si, pos)
            else:
                self.corner_dragging = corner
            return True

        return False

    def _drag_side(self, si, ei, pos):
        s = self.slices[si]
        pts = np.array(s.bbox, dtype=np.float64).reshape(4, 2)

        i0 = ei
        i1 = (ei + 1) % 4
        o0 = (ei + 2) % 4
        o1 = (ei + 3) % 4

        mid_edge = (pts[i0] + pts[i1]) / 2.0
        mid_opp = (pts[o0] + pts[o1]) / 2.0
        normal = mid_opp - mid_edge
        normal_len = np.linalg.norm(normal)
        if normal_len < 1e-6:
            return
        normal /= normal_len

        pointer_img = self._view_to_image(self._clamp_view_pos_to_canvas(pos))
        delta = np.dot(pointer_img - pts[i0], normal)
        max_delta = normal_len - 1.0
        if max_delta <= 0.0:
            return
        delta = min(delta, max_delta)

        shift = normal * delta
        pts[i0] += shift
        pts[i1] += shift
        s.bbox = self._clamp_bbox_to_image(pts)

    def _start_rotation_drag(self, si, pos):
        s = self.slices[si]
        center = np.mean(s.bbox, axis=0)
        pointer = self._view_to_image(self._clamp_view_pos_to_canvas(pos))
        vector = pointer - center
        if np.linalg.norm(vector) < 1e-6:
            return None

        return {
            "slice_index": si,
            "center": center,
            "start_angle": np.arctan2(vector[1], vector[0]),
            "start_bbox": np.array(s.bbox, dtype=np.float64),
        }

    def _drag_rotation(self, pos):
        if self.rotation_dragging is None:
            return

        si = self.rotation_dragging["slice_index"]
        if not (0 <= si < len(self.slices)):
            return

        center = self.rotation_dragging["center"]
        pointer = self._view_to_image(self._clamp_view_pos_to_canvas(pos))
        vector = pointer - center
        if np.linalg.norm(vector) < 1e-6:
            return

        angle = np.arctan2(vector[1], vector[0])
        delta = angle - self.rotation_dragging["start_angle"]
        cos_a = np.cos(delta)
        sin_a = np.sin(delta)
        rotation = np.array(
            [
                [cos_a, -sin_a],
                [sin_a, cos_a],
            ],
            dtype=np.float64,
        )

        start_bbox = self.rotation_dragging["start_bbox"]
        rotated = (start_bbox - center) @ rotation.T + center
        self.slices[si].bbox = self._clamp_bbox_to_image(rotated)

    def _start_box_drag(self, si, pos):
        return {
            "slice_index": si,
            "start_pointer": self._view_to_image(self._clamp_view_pos_to_canvas(pos)),
            "start_bbox": np.array(self.slices[si].bbox, dtype=np.float64),
        }

    def _drag_box(self, pos):
        if self.box_dragging is None:
            return

        si = self.box_dragging["slice_index"]
        if not (0 <= si < len(self.slices)):
            return

        pointer = self._view_to_image(self._clamp_view_pos_to_canvas(pos))
        delta = pointer - self.box_dragging["start_pointer"]
        moved = self.box_dragging["start_bbox"] + delta
        self.slices[si].bbox = self._clamp_bbox_to_image(moved)

    def mousePressEvent(self, event):
        pos = event.position()

        if event.button() == Qt.RightButton:
            self.panning = True
            self.last_mouse_pos = pos
            return

        if event.button() != Qt.LeftButton:
            return

        if self.image is None:
            self.set_active_slice(None)
            return

        if not self._image_rect_view().contains(pos):
            # Allow selecting edge handles in a small margin outside the
            # displayed image, then fall back to the black-area deactivate rule.
            edge_margin = max(
                float(getattr(self, "CORNER_HANDLE_HIT_RADIUS", 12.0)),
                float(getattr(self, "SIDE_HANDLE_HIT_RADIUS", 14.0)),
            )
            if self._image_rect_view().adjusted(-edge_margin, -edge_margin, edge_margin, edge_margin).contains(pos):
                if self._try_begin_handle_drag(pos):
                    return
            self.set_active_slice(None)
            return

        if self._try_begin_handle_drag(pos):
            return

        inside = self._find_slice_containing_point(pos)
        if inside is not None:
            self.set_active_slice(inside)

    def mouseDoubleClickEvent(self, event):
        if event.button() != Qt.LeftButton or self.image is None:
            return

        pos = event.position()
        inside = self._find_slice_containing_point(pos)
        if inside is None:
            return

        self.corner_dragging = None
        self.side_dragging = None
        self.rotation_dragging = None
        self.set_active_slice(inside)
        self.box_dragging = self._start_box_drag(inside, pos)

    def mouseMoveEvent(self, event):
        pos = event.position()

        if self.panning:
            self.user_transformed_view = True
            delta = pos - self.last_mouse_pos
            self.pan_offset = QPointF(self.pan_offset.x() + delta.x(), self.pan_offset.y() + delta.y())
            self.last_mouse_pos = pos
            self.update()
            return

        if self.corner_dragging is not None:
            si, ci = self.corner_dragging
            p = self._view_to_image(self._clamp_view_pos_to_canvas(pos))
            p = self._clamp_image_point(p)
            self.slices[si].update_corner(ci, p[0], p[1])
            self.update()
            return

        if self.rotation_dragging is not None:
            self._drag_rotation(pos)
            self.update()
            return

        if self.side_dragging is not None:
            si, ei = self.side_dragging
            self._drag_side(si, ei, pos)
            self.update()
            return

        if self.box_dragging is not None:
            self._drag_box(pos)
            self.update()

    def mouseReleaseEvent(self, event):
        if event.button() == Qt.RightButton:
            self.panning = False
        if event.button() == Qt.LeftButton:
            self.corner_dragging = None
            self.side_dragging = None
            self.rotation_dragging = None
            self.box_dragging = None

    def wheelEvent(self, event):
        if self.image is None:
            return

        pos = event.position()
        if not self.rect().contains(pos.toPoint()):
            return

        delta = event.angleDelta().y()
        if delta == 0:
            return

        scale = 1.05 if delta > 0 else (1.0 / 1.05)
        new_zoom = self.zoom * scale

        if new_zoom < 0.01 or new_zoom > 20.0:
            return

        self.user_transformed_view = True
        image_pos = self._view_to_image(pos)
        self.zoom = new_zoom
        self.pan_offset = QPointF(
            pos.x() - image_pos[0] * self.zoom,
            pos.y() - image_pos[1] * self.zoom,
        )
        self.update()

    def resizeEvent(self, event):
        super().resizeEvent(event)
        if self.image is not None and not self.user_transformed_view:
            self.fit_image_to_view()
            self.update()