"""The grid fallback: an action space that needs nothing, and its guard rails."""

import pytest
from PIL import Image

from tiny_computer_agent import Action, Element, Observation, Policy, PolicyViolation
from tiny_computer_agent.perception import (
    AutoDetector, GridDetector, OcrDetector, detector_available, make_detector,
)

CELL = Element("cell 12", kind="grid", x=600, y=0, width=60, height=57)


class FixedOcr:
    name = "fixed"

    def __init__(self, elements=()):
        self.elements = tuple(elements)

    def detect(self, image):
        return self.elements


def test_grid_detector_needs_nothing_at_all():
    elements = GridDetector(rows=2, cols=2).detect(Image.new("RGB", (100, 80)))
    assert [e.label for e in elements] == ["cell 1", "cell 2", "cell 3", "cell 4"]
    assert all(e.kind == "grid" for e in elements)
    assert elements[0].center == (25, 20)
    assert elements[3].center == (75, 60)


def test_grid_detector_rejects_a_useless_shape():
    with pytest.raises(ValueError):
        GridDetector(rows=0)


def test_grid_detector_is_always_available_and_default_off():
    assert detector_available("grid")[0] is True
    assert isinstance(make_detector("grid"), GridDetector)


def test_auto_uses_ocr_when_it_finds_text():
    detector = AutoDetector(ocr=FixedOcr((Element("Save"),)), grid=GridDetector(rows=1, cols=1))
    assert [e.label for e in detector.detect(Image.new("RGB", (10, 10)))] == ["Save"]


def test_auto_falls_back_to_the_grid_when_ocr_finds_nothing():
    detector = AutoDetector(ocr=FixedOcr(()), grid=GridDetector(rows=1, cols=2))
    assert [e.label for e in detector.detect(Image.new("RGB", (10, 10)))] == ["cell 1", "cell 2"]


def test_a_grid_click_is_fine_while_planning():
    Policy(dry_run=True).check(Action("click", label="cell 12"), Observation(elements=(CELL,)))


def test_a_grid_click_is_refused_with_real_input():
    """A blind click on a real desktop must be a deliberate choice, not a default."""
    with pytest.raises(PolicyViolation, match="blind click"):
        Policy(dry_run=False).check(Action("click", label="cell 12"), Observation(elements=(CELL,)))


def test_a_grid_click_is_refused_even_when_the_index_is_stale():
    with pytest.raises(PolicyViolation, match="blind click"):
        Policy(dry_run=False).check(Action("click", label="cell 47"), Observation())


def test_a_grid_click_is_allowed_when_asked_for():
    Policy(dry_run=False, allow_grid_clicks=True).check(
        Action("click", label="cell 12"), Observation(elements=(CELL,))
    )


def test_an_ordinary_click_is_unaffected_by_the_grid_guard():
    Policy(dry_run=False).check(
        Action("click", label="Save"),
        Observation(elements=(Element("Save", x=1, y=2, width=3, height=4),)),
    )


@pytest.mark.skipif(not detector_available("ocr")[0], reason="no OCR engine installed")
def test_real_ocr_beats_the_grid_on_a_real_screenshot():
    from tiny_computer_agent.demo import fake_desktop

    elements = AutoDetector().detect(fake_desktop())
    assert elements and any(e.kind != "grid" for e in elements)
    assert isinstance(OcrDetector(), OcrDetector)