"""Contract for the shared motion system.

The product previously had no `QPropertyAnimation` at all, so these tests exist
to keep the two things that make added motion a liability from creeping back:
an animation that outlives or destroys the object it is animating, and a
graphics effect left attached after a fade, which would quietly move a whole
subtree onto Qt's offscreen composite path for the rest of the session.
"""

from __future__ import annotations

import os

os.environ.setdefault("QT_QPA_PLATFORM", "offscreen")
# The module disables itself under the offscreen platform so widget grabs in the
# other suites capture settled frames; these tests are about the animation, so
# they opt back in.
os.environ["DOCTOR_MOTION"] = "on"

import pytest
from PySide6.QtCore import QEvent, QPoint, QPointF, Qt
from PySide6.QtGui import QWheelEvent
from PySide6.QtWidgets import (
    QApplication,
    QLabel,
    QScrollArea,
    QStackedWidget,
    QVBoxLayout,
    QWidget,
)

from doctor_workstation.ui import motion


@pytest.fixture(scope="module")
def application() -> QApplication:
    return QApplication.instance() or QApplication([])


def _stack(application: QApplication) -> tuple[QWidget, QStackedWidget, QLabel]:
    host = QWidget()
    host.resize(320, 120)
    layout = QVBoxLayout(host)
    stack = QStackedWidget()
    first, second = QLabel("A"), QLabel("B")
    stack.addWidget(first)
    stack.addWidget(second)
    layout.addWidget(stack)
    host.show()
    application.processEvents()
    return host, stack, second


def test_page_transition_fades_and_settles_upward(application: QApplication) -> None:
    host, stack, incoming = _stack(application)
    origin = incoming.pos()

    motion.switch_stack(stack, 1)

    animations = incoming._doctor_motion
    rise, fade = animations["enter"], animations["fade"]
    assert rise.duration() == fade.duration() == motion.BASE

    samples = []
    for at in (0, motion.BASE // 2, motion.BASE - 1):
        rise.setCurrentTime(at)
        fade.setCurrentTime(at)
        samples.append((incoming.pos().y() - origin.y(), incoming.graphicsEffect().opacity()))

    offsets = [offset for offset, _ in samples]
    opacities = [opacity for _, opacity in samples]
    assert offsets == sorted(offsets, reverse=True), "the page must settle downward-to-up"
    assert opacities == sorted(opacities), "opacity must rise monotonically"
    assert offsets[0] == motion.RISE and opacities[0] == pytest.approx(0.0)
    host.close()


def test_fade_detaches_its_graphics_effect_when_it_finishes(
    application: QApplication,
) -> None:
    """A left-behind opacity effect is a permanent frame-rate tax, not a leak."""

    host, stack, incoming = _stack(application)
    motion.switch_stack(stack, 1)
    assert incoming.graphicsEffect() is not None

    fade = incoming._doctor_motion["fade"]
    fade.setCurrentTime(fade.duration())
    # The detach is deferred by one event-loop turn on purpose, so that the
    # effect is not destroyed from inside the signal it is emitting.
    application.processEvents()
    application.processEvents()

    assert incoming.graphicsEffect() is None
    host.close()


def test_motion_can_be_turned_off_without_leaving_widgets_mid_state(
    application: QApplication,
    monkeypatch: pytest.MonkeyPatch,
) -> None:
    monkeypatch.setenv("DOCTOR_MOTION", "off")
    assert motion.reduced_motion()

    host, stack, incoming = _stack(application)
    origin = incoming.pos()
    motion.switch_stack(stack, 1)

    assert stack.currentIndex() == 1
    assert incoming.pos() == origin
    assert incoming.graphicsEffect() is None
    host.close()


def _scroll_area(application: QApplication) -> QScrollArea:
    area = QScrollArea()
    area.setWidgetResizable(True)
    area.setWidget(QLabel("\n".join(f"line {index}" for index in range(300))))
    area.resize(300, 200)
    area.show()
    application.processEvents()
    return area


def _wheel(delta: int) -> QWheelEvent:
    return QWheelEvent(
        QPointF(50, 50),
        QPointF(50, 50),
        QPoint(0, 0),
        QPoint(0, delta),
        Qt.MouseButton.NoButton,
        Qt.KeyboardModifier.NoModifier,
        Qt.ScrollPhase.NoScrollPhase,
        False,
    )


def test_wheel_scrolling_is_eased_rather_than_jumped(application: QApplication) -> None:
    area = _scroll_area(application)
    motion.install_smooth_scroll(area)
    scroller = area._doctor_smooth_scroll
    bar = area.verticalScrollBar()

    assert scroller.eventFilter(area.viewport(), _wheel(-120))
    animation = scroller._animation
    assert animation.endValue() == motion.SCROLL_STEP

    values = []
    for at in (0, 60, 120, animation.duration() - 1):
        animation.setCurrentTime(at)
        values.append(bar.value())

    assert values[0] == 0
    assert values == sorted(values)
    assert values[-1] < motion.SCROLL_STEP, "an eased curve never reaches its end early"
    animation.stop()
    area.close()


def test_wheel_at_either_end_is_handed_back_to_the_enclosing_area(
    application: QApplication,
) -> None:
    """Swallowing the wheel at the extremes is what makes nested panes feel stuck."""

    area = _scroll_area(application)
    motion.install_smooth_scroll(area)
    scroller = area._doctor_smooth_scroll
    bar = area.verticalScrollBar()

    bar.setValue(bar.minimum())
    application.processEvents()
    assert not scroller.eventFilter(area.viewport(), _wheel(120))
    assert scroller.eventFilter(area.viewport(), _wheel(-120))

    scroller._animation.stop()
    bar.setValue(bar.maximum())
    application.processEvents()
    assert not scroller.eventFilter(area.viewport(), _wheel(-120))
    area.close()


def test_zoom_gestures_are_left_alone(application: QApplication) -> None:
    area = _scroll_area(application)
    motion.install_smooth_scroll(area)
    scroller = area._doctor_smooth_scroll

    ctrl_wheel = QWheelEvent(
        QPointF(50, 50),
        QPointF(50, 50),
        QPoint(0, 0),
        QPoint(0, -120),
        Qt.MouseButton.NoButton,
        Qt.KeyboardModifier.ControlModifier,
        Qt.ScrollPhase.NoScrollPhase,
        False,
    )

    assert not scroller.eventFilter(area.viewport(), ctrl_wheel)
    area.close()


def test_install_is_idempotent(application: QApplication) -> None:
    area = _scroll_area(application)
    motion.install_smooth_scroll(area)
    first = area._doctor_smooth_scroll
    motion.install_smooth_scroll(area)

    assert area._doctor_smooth_scroll is first
    area.close()


def test_reading_surfaces_get_smooth_scrolling_from_the_theme(
    application: QApplication,
) -> None:
    """A QScrollArea should not have to opt in page by page."""

    from doctor_workstation.ui.theme import apply_theme

    apply_theme(application)
    area = QScrollArea()
    area.setWidget(QLabel("content"))
    area.show()
    area.ensurePolished()
    application.sendEvent(area, QEvent(QEvent.Type.Polish))
    application.processEvents()

    assert getattr(area, "_doctor_smooth_scroll", None) is not None
    area.close()