"""Behavioural tests for the AZ-408 multi_segment injector.

Covers AC-5 (≥3 disjoint windows, ≥30 s gaps, ≤25 % total coverage) and
AC-6 (tmpfs scratch isolation).
"""

from __future__ import annotations

import json
from pathlib import Path

import pytest

from fixtures.injectors import multi_segment


def _build_synthetic_frames_dir(parent: Path, count: int) -> Path:
    from PIL import Image  # noqa: PLC0415

    frames_dir = parent / "frames"
    frames_dir.mkdir(parents=True, exist_ok=True)
    img = Image.new("RGB", (256, 256), color=(60, 60, 60))
    for i in range(count):
        img.save(
            frames_dir / f"AD{i + 1:06d}.jpg",
            format="JPEG", quality=85, optimize=False, progressive=False, subsampling=2,
        )
    return frames_dir


def test_produces_three_disjoint_segments(tmp_path: Path) -> None:
    """AC-5: 3 disjoint blackout windows."""
    # Arrange
    frames = _build_synthetic_frames_dir(tmp_path / "src", count=9000)  # 5 min @ 30 fps
    plan = multi_segment.MultiSegmentPlan(
        source_frames_dir=frames, n_segments=3, segment_seconds=15.0
    )

    # Act
    report = multi_segment.build(plan, tmp_path / "out")

    # Assert
    assert len(report.segments) == 3
    # Each segment is non-empty
    for s in report.segments:
        assert s.end_ms > s.start_ms
    # Disjoint
    for prev, nxt in zip(report.segments, report.segments[1:]):
        assert prev.end_ms < nxt.start_ms


def test_segments_are_at_least_30_seconds_apart(tmp_path: Path) -> None:
    """AC-5: consecutive segments separated by ≥30 s of normal frames."""
    # Arrange
    frames = _build_synthetic_frames_dir(tmp_path / "src", count=9000)
    plan = multi_segment.MultiSegmentPlan(
        source_frames_dir=frames, n_segments=3, segment_seconds=12.0
    )

    # Act
    report = multi_segment.build(plan, tmp_path / "out")

    # Assert
    for prev, nxt in zip(report.segments, report.segments[1:]):
        gap_ms = nxt.start_ms - prev.end_ms
        assert gap_ms >= 30_000, f"gap {gap_ms} ms < 30 s between segments"


def test_total_blackout_below_25_percent(tmp_path: Path) -> None:
    """AC-5: total blackout coverage ≤ 25 %."""
    # Arrange
    frames = _build_synthetic_frames_dir(tmp_path / "src", count=9000)
    plan = multi_segment.MultiSegmentPlan(
        source_frames_dir=frames, n_segments=3, segment_seconds=15.0
    )

    # Act
    report = multi_segment.build(plan, tmp_path / "out")

    # Assert
    assert report.total_blackout_fraction <= 0.25


def test_rejects_overlapping_gap(tmp_path: Path) -> None:
    """Infeasible plan: too many segments inside too short a source."""
    # Arrange — 30 s source can't fit 3×12 s segments with 30 s gaps
    frames = _build_synthetic_frames_dir(tmp_path / "src", count=900)
    plan = multi_segment.MultiSegmentPlan(
        source_frames_dir=frames, n_segments=3, segment_seconds=12.0
    )
    # Act / Assert
    with pytest.raises(ValueError, match="gap between segment|blackout fraction"):
        multi_segment.build(plan, tmp_path / "out")


def test_rejects_too_few_segments(tmp_path: Path) -> None:
    """AC-5: n_segments must be ≥3."""
    # Arrange
    frames = _build_synthetic_frames_dir(tmp_path / "src", count=900)
    plan = multi_segment.MultiSegmentPlan(
        source_frames_dir=frames, n_segments=2, segment_seconds=5.0
    )
    # Act / Assert
    with pytest.raises(ValueError, match="n_segments must be ≥3"):
        multi_segment.build(plan, tmp_path / "out")


def test_rejects_zero_segment_seconds(tmp_path: Path) -> None:
    # Arrange
    frames = _build_synthetic_frames_dir(tmp_path / "src", count=900)
    plan = multi_segment.MultiSegmentPlan(
        source_frames_dir=frames, n_segments=3, segment_seconds=0.0
    )
    # Act / Assert
    with pytest.raises(ValueError, match="segment_seconds"):
        multi_segment.build(plan, tmp_path / "out")


def test_blackout_frames_are_black(tmp_path: Path) -> None:
    """Frames inside any segment are all-zero (black) on disk."""
    # Arrange
    from PIL import Image  # noqa: PLC0415

    frames = _build_synthetic_frames_dir(tmp_path / "src", count=9000)
    plan = multi_segment.MultiSegmentPlan(
        source_frames_dir=frames, n_segments=3, segment_seconds=10.0
    )
    out_root = tmp_path / "out"
    report = multi_segment.build(plan, out_root)

    # Act
    for seg in report.segments[:1]:  # spot-check first segment
        for idx in range(seg.first_frame_idx, min(seg.first_frame_idx + 5, seg.last_frame_idx)):
            name = f"AD{idx + 1:06d}.jpg"
            img = Image.open(out_root / "frames" / name).convert("RGB")
            r, g, b = img.getpixel((128, 128))  # type: ignore[misc]
            # Assert
            assert r < 5 and g < 5 and b < 5


def test_summary_json_present_with_expected_fields(tmp_path: Path) -> None:
    # Arrange
    frames = _build_synthetic_frames_dir(tmp_path / "src", count=9000)
    plan = multi_segment.MultiSegmentPlan(
        source_frames_dir=frames, n_segments=3, segment_seconds=10.0
    )

    # Act
    multi_segment.build(plan, tmp_path / "out")
    payload = json.loads((tmp_path / "out" / "summary.json").read_text())

    # Assert
    assert payload["scenario"] == "multi-segment-derkachi"
    assert payload["n_segments"] == 3
    assert payload["total_blackout_fraction"] <= 0.25


def test_overwrites_existing_out_root(tmp_path: Path) -> None:
    # Arrange
    frames = _build_synthetic_frames_dir(tmp_path / "src", count=9000)
    plan = multi_segment.MultiSegmentPlan(
        source_frames_dir=frames, n_segments=3, segment_seconds=10.0
    )
    out_root = tmp_path / "out"
    multi_segment.build(plan, out_root)
    (out_root / "stale.txt").write_text("stale")

    # Act
    multi_segment.build(plan, out_root)

    # Assert
    assert not (out_root / "stale.txt").exists()