"""find_blender / run_blender_script：model_decimate 与 model_bake 共享的
headless Blender 运行器。"""
import json
import os
import shutil
import subprocess
import sys

DEFAULT_BLENDER = r"D:\tools\Blender\blender-5.0.0-windows-x64\blender.exe"
HERE = os.path.dirname(os.path.abspath(__file__))


def find_blender(cli_arg):
    """Resolve blender.exe from --blender / BLENDER_EXE / BLENDER_PATH / default / PATH."""
    candidates = (
        cli_arg,
        os.environ.get("BLENDER_EXE"),
        os.environ.get("BLENDER_PATH"),
        DEFAULT_BLENDER,
        shutil.which("blender"),
    )
    for cand in candidates:
        if not cand:
            continue
        path = cand
        # Allow BLENDER_PATH to point at a directory containing blender.exe
        if os.path.isdir(path):
            nested = os.path.join(path, "blender.exe")
            if os.path.isfile(nested):
                return nested
            continue
        if os.path.isfile(path):
            return path
    sys.exit(
        "找不到 blender.exe，请用 --blender 指定，或设置环境变量 BLENDER_EXE / BLENDER_PATH"
    )


def run_blender_script(blender, script, script_args, blender_args=()):
    """跑 HERE 下的 bl_*.py，返回 MT_SUMMARY JSON；失败或 summary 带 error 则退出。"""
    cmd = [
        blender,
        "-b",
        *blender_args,
        "--factory-startup",
        "--python",
        os.path.join(HERE, script),
        "--",
    ] + list(script_args)
    proc = subprocess.run(
        cmd,
        capture_output=True,
        text=True,
        encoding="utf-8",
        errors="replace",
    )
    summary = None
    for line in (proc.stdout or "").splitlines():
        if line.startswith("MT_SUMMARY "):
            summary = json.loads(line[len("MT_SUMMARY ") :])
    if proc.returncode != 0 or summary is None or "error" in summary:
        sys.stderr.write(
            (proc.stdout or "")[-2000:] + "\n" + (proc.stderr or "")[-2000:] + "\n"
        )
        err = summary["error"] if summary and "error" in summary else script
        sys.exit("Blender 执行失败：%s" % err)
    return summary