"""Service for converting IFC files to glTF/glb for 3D visualization."""

import multiprocessing
import tempfile
from pathlib import Path

import ifcopenshell
import ifcopenshell.geom


def convert_ifc_to_glb(ifc_path: str, glb_path: str) -> None:
    """
    Convert an IFC file to glTF Binary (.glb) format.

    Uses IfcOpenShell's geometry serializer with element GUIDs preserved
    as mesh names, enabling click-to-inspect in the 3D viewer.
    """
    ifc_file = ifcopenshell.open(ifc_path)

    settings = ifcopenshell.geom.settings()
    settings.set(
        "dimensionality",
        ifcopenshell.ifcopenshell_wrapper.CURVES_SURFACES_AND_SOLIDS,
    )
    settings.set("apply-default-materials", True)

    serialiser_settings = ifcopenshell.geom.serializer_settings()
    serialiser_settings.set("use-element-guids", True)

    serialiser = ifcopenshell.geom.serializers.gltf(
        glb_path, settings, serialiser_settings
    )
    serialiser.setFile(ifc_file)
    serialiser.setUnitNameAndMagnitude("METER", 1.0)
    serialiser.writeHeader()

    num_threads = max(1, multiprocessing.cpu_count() - 1)
    iterator = ifcopenshell.geom.iterator(
        settings,
        ifc_file,
        num_threads,
        exclude=(
            "IfcSpace",
            "IfcOpeningElement",
        ),
    )

    if iterator.initialize():
        while True:
            serialiser.write(iterator.get())
            if not iterator.next():
                break

    serialiser.finalize()
    del serialiser  # Ensures temp files are cleaned up


async def convert_ifc_bytes_to_glb(content: bytes, glb_output_path: str) -> None:
    """
    Convert IFC file content (bytes) to a glb file.

    Writes IFC to a temporary file first, since IfcOpenShell
    requires a file path.
    """
    import asyncio

    with tempfile.NamedTemporaryFile(suffix=".ifc", delete=False) as tmp:
        tmp.write(content)
        tmp_ifc = tmp.name

    try:
        # Run CPU-intensive conversion in a thread pool
        loop = asyncio.get_event_loop()
        await loop.run_in_executor(
            None, convert_ifc_to_glb, tmp_ifc, glb_output_path
        )
    finally:
        Path(tmp_ifc).unlink(missing_ok=True)