from __future__ import annotations

from pathlib import Path

from OCP.StlAPI import StlAPI_Writer

from common.render import REPO_ROOT, part_stl_path
from common.step_scene import (
    LoadedStepScene,
    scene_export_shape,
)


def _display_path(path: Path) -> str:
    resolved = path.resolve()
    try:
        return resolved.relative_to(REPO_ROOT).as_posix()
    except ValueError:
        return resolved.as_posix()


def export_part_stl_from_scene(step_path: Path, scene: LoadedStepScene, *, target_path: Path | None = None) -> Path:
    target_path = target_path or part_stl_path(step_path)
    export_shape_stl(scene_export_shape(scene), target_path)
    return target_path


def export_shape_stl(shape: object, target_path: Path) -> Path:
    target_path.parent.mkdir(parents=True, exist_ok=True)
    writer = StlAPI_Writer()
    writer.ASCIIMode = False
    if not writer.Write(shape, str(target_path)):
        raise RuntimeError(f"Failed to write STL output: {_display_path(target_path)}")
    return target_path


def write_empty_stl(target_path: Path) -> Path:
    target_path.parent.mkdir(parents=True, exist_ok=True)
    header = b"cad-harness empty STL".ljust(80, b"\0")
    target_path.write_bytes(header + (0).to_bytes(4, byteorder="little", signed=False))
    return target_path