"""B2 split_screen 分屏检测单元测试（旧文件的黑边剔除部分随裁黑边功能删去）。

钉死两件事的关键性质：
- ``detect_split_x``：合成左右两半（中间一列黑缝）→ 切分线落在中缝 ±2px；
  全黑 / 无缝 / 切分偏出中部合理范围 → ``SplitDetectionError``（不兜底）。
- ``view_rect``：horizontal_split 用检测到的 ``split_x`` 而非 ``W//2``；
  vertical_split / full / manual_crop 分支与参考一致；非法组合 ``RuntimeError``。

测试用真实数据的二次构造（合成左右分屏帧），边缘场景靠实现 raise 保证。
"""

import numpy as np
import pytest

from cadx.ceus import (
    SplitDetectionError,
    ViewRect,
    detect_split_x,
    view_rect,
)
from conftest import load_ceus_section

# 旧 detect_split_x 的参数默认值；新代码不设默认值，从 config/ceus.yaml 读。
_LO, _HI = load_ceus_section()["views"]["split_search_band"]
BAND = (float(_LO), float(_HI))


def _split_frame(
    height: int,
    width: int,
    split_x: int,
    *,
    left_gray: int = 180,
    right_gray: int = 120,
) -> np.ndarray:
    """合成一帧左右分屏 BGR 图：左右两半各为常量灰度，``split_x`` 处一列纯黑缝。"""
    frame = np.zeros((height, width, 3), dtype=np.uint8)
    frame[:, :split_x] = left_gray
    frame[:, split_x + 1 :] = right_gray
    frame[:, split_x] = 0
    return frame


# Phase 1: detect_split_x —— 中缝定位与防御
def test_detect_split_x_finds_centered_seam() -> None:
    frames = [_split_frame(120, 200, 100) for _ in range(5)]
    detected = detect_split_x(frames, search_band=BAND)
    assert abs(detected - 100) <= 2


def test_detect_split_x_finds_offcenter_seam_within_band() -> None:
    # 缝在 0.42*W 处，仍落在 band=(0.35,0.65) 内、左右宽度比合法。
    frames = [_split_frame(120, 200, 84) for _ in range(5)]
    detected = detect_split_x(frames, search_band=BAND)
    assert abs(detected - 84) <= 2


def test_detect_split_x_all_black_raises() -> None:
    frames = [np.zeros((120, 200, 3), dtype=np.uint8) for _ in range(3)]
    with pytest.raises(SplitDetectionError):
        detect_split_x(frames, search_band=BAND)


def test_detect_split_x_no_seam_raises() -> None:
    # 整幅均匀灰度、无暗缝：中部 band 内列均值平坦，找不到稳定低谷。
    frames = [np.full((120, 200, 3), 150, dtype=np.uint8) for _ in range(3)]
    with pytest.raises(SplitDetectionError):
        detect_split_x(frames, search_band=BAND)


def test_detect_split_x_empty_frames_raises() -> None:
    with pytest.raises(SplitDetectionError):
        detect_split_x([], search_band=BAND)


def test_detect_split_x_reversed_band_raises() -> None:
    # 逆序 band（lo>=hi）非法：要求 0<=lo<hi<=1，应直接报错而非兜底。
    frames = [_split_frame(120, 200, 100) for _ in range(3)]
    with pytest.raises(SplitDetectionError):
        detect_split_x(frames, search_band=(0.6, 0.4))


def test_detect_split_x_out_of_range_band_raises() -> None:
    # 越界 band（hi>1）非法。
    frames = [_split_frame(120, 200, 100) for _ in range(3)]
    with pytest.raises(SplitDetectionError):
        detect_split_x(frames, search_band=(0.35, 1.5))


def test_detect_split_x_width_ratio_violation_raises() -> None:
    # 把 band 放宽到几乎整宽，缝置于极偏位置（仍在 band 内），使左右宽度比越界。
    # split_x=20、W=200 → 左 20 / 右 180，比值 0.11 < 0.5 → SplitDetectionError。
    frames = [_split_frame(120, 200, 20) for _ in range(3)]
    with pytest.raises(SplitDetectionError):
        detect_split_x(frames, search_band=(0.05, 0.95))


# Phase 2: view_rect —— horizontal_split 用 split_x，而非 W//2
def test_view_rect_horizontal_split_uses_split_x() -> None:
    width, height, split_x = 200, 120, 84
    left = view_rect({"layout": "horizontal_split"}, "left", width, height, split_x=split_x)
    right = view_rect({"layout": "horizontal_split"}, "right", width, height, split_x=split_x)
    assert left == ViewRect(0, 0, split_x, height)
    assert right == ViewRect(split_x, 0, width, height)
    # 与朴素 W//2 不同，证明用了检测值。
    assert split_x != width // 2


def test_view_rect_vertical_split() -> None:
    width, height = 200, 120
    top = view_rect({"layout": "vertical_split"}, "top", width, height, split_x=None)
    bottom = view_rect({"layout": "vertical_split"}, "bottom", width, height, split_x=None)
    assert top == ViewRect(0, 0, width, height // 2)
    assert bottom == ViewRect(0, height // 2, width, height)


def test_view_rect_full() -> None:
    rect = view_rect({"layout": "full"}, "left", 200, 120, split_x=None)
    assert rect == ViewRect(0, 0, 200, 120)


def test_view_rect_manual_crop() -> None:
    cfg = {"layout": "manual_crop", "crops": {"left": [0.0, 0.0, 0.5, 1.0]}}
    rect = view_rect(cfg, "left", 200, 120, split_x=None)
    assert rect == ViewRect(0, 0, 100, 120)


def test_view_rect_unsupported_pair_raises() -> None:
    with pytest.raises(RuntimeError):
        view_rect({"layout": "horizontal_split"}, "top", 200, 120, split_x=100)