"""Shared helpers for MIRPAMO's headless-Blender stages.

Every stage script is run as:
    blender -b --python bpy/<stage>.py -- <stage args>
"""
import os
import sys

import bpy


def stage_args():
    """Return the argv after the '--' separator (the stage's own args)."""
    argv = sys.argv
    if "--" in argv:
        return argv[argv.index("--") + 1:]
    return []


def clean_scene():
    bpy.ops.wm.read_factory_settings(use_empty=True)


def import_any(path):
    """Import a mesh/animation file; return the list of new objects."""
    path = os.path.abspath(path)
    if not os.path.exists(path):
        raise FileNotFoundError(path)
    ext = os.path.splitext(path)[1].lower()
    before = set(bpy.data.objects)
    if ext in (".glb", ".gltf"):
        bpy.ops.import_scene.gltf(filepath=path)
    elif ext == ".fbx":
        bpy.ops.import_scene.fbx(filepath=path)
    elif ext == ".obj":
        bpy.ops.wm.obj_import(filepath=path)
    elif ext == ".bvh":
        bpy.ops.import_anim.bvh(
            filepath=path,
            rotate_mode="NATIVE",
            update_scene_fps=True,
            update_scene_duration=True,
        )
    else:
        raise ValueError(f"unsupported file type: {ext}")
    return [o for o in bpy.data.objects if o not in before]


def find_armature(objects):
    for o in objects:
        if o.type == "ARMATURE":
            return o
    return None


def find_meshes(objects):
    """Mesh objects, excluding bone custom-shape helpers the glTF importer
    creates (e.g. 'Icosphere') — those are viewport display aids, not assets."""
    shapes = set()
    for o in bpy.data.objects:
        if o.type == "ARMATURE":
            for pb in o.pose.bones:
                if pb.custom_shape:
                    shapes.add(pb.custom_shape)
    return [o for o in objects if o.type == "MESH" and o not in shapes]


def count_fcurves(action):
    """Number of f-curves in an action, across legacy (<=4.x) and slotted
    (5.x layered actions) APIs."""
    try:
        return len(action.fcurves)
    except AttributeError:
        return sum(len(cb.fcurves)
                   for layer in action.layers
                   for strip in layer.strips
                   for cb in strip.channelbags)


def select_only(objects, active=None):
    bpy.ops.object.select_all(action="DESELECT")
    for o in objects:
        o.select_set(True)
    if active is not None:
        bpy.context.view_layer.objects.active = active


def export_glb(path, objects=None):
    """Export the given objects (or everything) as a GLB with animations."""
    path = os.path.abspath(path)
    os.makedirs(os.path.dirname(path) or ".", exist_ok=True)
    if objects:
        select_only(objects, active=objects[0])
        use_selection = True
    else:
        use_selection = False
    kwargs = dict(
        filepath=path,
        export_format="GLB",
        export_animations=True,
        export_yup=True,
        use_selection=use_selection,
    )
    # Export every action as its own named animation when the option exists
    # (property name is stable in 4.2+/5.x, but guard anyway).
    props = bpy.ops.export_scene.gltf.get_rna_type().properties.keys()
    if "export_animation_mode" in props:
        kwargs["export_animation_mode"] = "ACTIONS"
    bpy.ops.export_scene.gltf(**kwargs)
    print(f"[mirpamo] wrote {path}")


def die(msg):
    print(f"[mirpamo] ERROR: {msg}", file=sys.stderr)
    sys.exit(1)