"""法线球面编码 round-trip 测试。运行：
blender -b --factory-startup --python tests/bl_test_encode.py
成功打印 ENCODE_TEST_OK，失败非零退出。"""
import os
import sys

import numpy as np

sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
from bl_convert import encode_normal_rg, decode_sphere_map


def main():
    rng = np.random.default_rng(7)
    # 随机切线空间法线（z>=0 半球），含边缘方向
    n = rng.normal(size=(4096, 3))
    n[:, 2] = np.abs(n[:, 2])
    n /= np.linalg.norm(n, axis=1, keepdims=True)
    n = np.vstack([n, [[0, 0, 1], [1, 0, 0], [-1, 0, 0], [0, -1, 0], [0.707, -0.707, 0]]])

    enc = encode_normal_rg(n)                     # (N,2) in [0,1]
    assert enc.min() >= 0.0 and enc.max() <= 1.0, "encode out of [0,1]"

    enc8 = np.round(enc * 255.0) / 255.0          # 模拟 8bit PNG 存储
    dec = decode_sphere_map(enc8)                 # shader 同款公式
    dec /= np.linalg.norm(dec, axis=1, keepdims=True)

    cos = np.clip(np.sum(n * dec, axis=1), -1.0, 1.0)
    max_err = np.degrees(np.arccos(cos)).max()
    assert max_err < 2.0, "max angle error %.3f deg >= 2" % max_err

    # 平面法线编码值应为 (0.5, 0.5)
    flat = encode_normal_rg(np.array([[0.0, 0.0, 1.0]]))
    assert np.allclose(flat, 0.5, atol=1e-6), "flat normal must encode to 0.5"

    print("ENCODE_TEST_OK max_err=%.4f deg" % max_err)


try:
    main()
except Exception as e:
    print("ENCODE_TEST_FAIL:", e)
    sys.exit(1)