import hashlib
import json
import pathlib
import sys

import bpy


ROOT_OBJECT = "M12 Override Object"
MESH_NAME = "M12 Override Mesh"
MATERIAL_NAME = "M12 Override Material"
SOURCE_MARKER = "M12-03J"
PROJECT_ID = "m12-03j-project"
OVERRIDE_X = 2.5
OVERRIDE_PROPERTY_PATH = '["m12_override_value"]'


def sha256_file(path: pathlib.Path) -> str:
    return hashlib.sha256(path.read_bytes()).hexdigest()


def reset() -> None:
    bpy.ops.wm.read_factory_settings(use_empty=True)


def create_source(path: pathlib.Path) -> None:
    reset()
    material = bpy.data.materials.new(MATERIAL_NAME)
    material.diffuse_color = (0.15, 0.65, 0.35, 1.0)
    mesh = bpy.data.meshes.new(MESH_NAME)
    mesh.from_pydata([(-1.0, -1.0, 0.0), (1.0, -1.0, 0.0), (1.0, 1.0, 0.0), (-1.0, 1.0, 0.0)], [], [(0, 1, 2, 3)])
    mesh.materials.append(material)
    obj = bpy.data.objects.new(ROOT_OBJECT, mesh)
    obj["m12_source_marker"] = SOURCE_MARKER
    obj["m12_override_value"] = 1.0
    bpy.context.scene.collection.objects.link(obj)
    bpy.ops.wm.save_as_mainfile(filepath=str(path), check_existing=False)


def data_block(id_type: str, value: object) -> dict:
    library = value.library
    return {
        "idType": id_type,
        "name": value.name,
        "nameFull": value.name_full,
        "library": None if library is None else pathlib.Path(library.filepath).name,
        "isLibraryOverride": value.override_library is not None,
    }


def override_property(value: object) -> dict:
    override = value.override_library
    if override is None:
        raise RuntimeError("override library metadata is missing")
    properties = list(override.properties)
    matches = [item for item in properties if item.rna_path == OVERRIDE_PROPERTY_PATH]
    if not matches:
        print("DEBUG_OVERRIDE_PROPERTIES", [(item.rna_path, len(item.operations)) for item in properties], dir(override.properties))
        raise RuntimeError("custom property override path is missing")
    return {
        "rnaPath": OVERRIDE_PROPERTY_PATH,
        "index": 0,
        "value": float(value["m12_override_value"]),
        "operationCount": sum(len(item.operations) for item in matches),
        "propertyCount": len(properties),
    }


def inspect_override() -> dict:
    obj = bpy.data.objects[ROOT_OBJECT]
    override = obj.override_library
    if override is None or override.reference is None:
        raise RuntimeError("desktop override reference is missing")
    reference = override.reference
    if reference.library is None:
        raise RuntimeError("override reference did not retain source library")
    if obj.library is not None:
        raise RuntimeError("override object must be locally owned")
    return {
        "reference": {
            "dataBlockId": f"Object/{reference.name}",
            "idType": "OBJECT",
            "library": pathlib.Path(reference.library.filepath).name,
            "owner": "SOURCE_LIBRARY",
            "readOnly": True,
            "isLibraryOverride": False,
        },
        "local": {
            "dataBlockId": f"Object/{obj.name}",
            "idType": "OBJECT",
            "library": None,
            "owner": "LOCAL_OVERRIDE",
            "projectId": PROJECT_ID,
            "readOnly": False,
            "referenceSourceDataBlockId": f"Object/{reference.name}",
            "hierarchyRootDataBlockId": f"Object/{obj.name}",
            "isLibraryOverride": True,
        },
        "propertyOverride": override_property(obj),
        "sourceMarker": reference.get("m12_source_marker"),
    }


def create_override(source: pathlib.Path, target: pathlib.Path) -> dict:
    reset()
    with bpy.data.libraries.load(str(source), link=True) as (data_from, data_to):
        if ROOT_OBJECT not in data_from.objects:
            raise RuntimeError("source root object is missing")
        data_to.objects = [ROOT_OBJECT]
    if len(data_to.objects) != 1 or data_to.objects[0] is None:
        raise RuntimeError("desktop link did not return one object")
    linked = data_to.objects[0]
    bpy.context.scene.collection.objects.link(linked)
    bpy.context.view_layer.objects.active = linked
    linked.select_set(True)
    if bpy.ops.object.make_override_library() != {"FINISHED"}:
        raise RuntimeError("desktop override operator did not finish")
    obj = bpy.data.objects[ROOT_OBJECT]
    obj["m12_override_value"] = OVERRIDE_X
    prop = obj.override_library.properties.add(OVERRIDE_PROPERTY_PATH)
    prop.operations.add("REPLACE")
    before_save = inspect_override()
    if before_save["propertyOverride"]["value"] != OVERRIDE_X:
        raise RuntimeError("override property did not apply")
    bpy.ops.wm.save_as_mainfile(filepath=str(target), check_existing=False)
    bpy.ops.wm.open_mainfile(filepath=str(target), load_ui=False)
    reopened = inspect_override()
    if reopened != before_save:
        raise RuntimeError("desktop override metadata drifted after save/reopen")
    return reopened


def main() -> None:
    if "--" not in sys.argv or len(sys.argv[sys.argv.index("--") + 1 :]) != 2:
        raise SystemExit("usage: blender --background --factory-startup --python generate-library-override-fixture.py -- OUTPUT_DIR REPORT")
    output_arg, report_arg = sys.argv[sys.argv.index("--") + 1 :]
    output_dir = pathlib.Path(output_arg).resolve()
    report_path = pathlib.Path(report_arg).resolve()
    output_dir.mkdir(parents=True, exist_ok=True)
    report_path.parent.mkdir(parents=True, exist_ok=True)
    source = output_dir / "m12_override_source.blend"
    target = output_dir / "m12_override_target.blend"
    create_source(source)
    override_graph = create_override(source, target)
    report = {
        "schemaVersion": 1,
        "task": "M12-03J",
        "operation": "LIBRARY_OVERRIDE",
        "blenderVersion": "5.2.0",
        "source": {"file": source.name, "sha256": sha256_file(source)},
        "target": {"file": target.name, "sha256": sha256_file(target)},
        "selectedRoots": [f"Object/{ROOT_OBJECT}"],
        "overrideGraph": override_graph,
        "nextTask": "M12-03K",
    }
    report_path.write_text(json.dumps(report, indent=2, sort_keys=True) + "\n", encoding="utf-8")
    print(
        f"library-override-fixture-ok roots={len(report['selectedRoots'])} "
        f"reference={override_graph['reference']['library']} owner={override_graph['local']['owner']} "
        f"path={override_graph['propertyOverride']['rnaPath']} next={report['nextTask']}"
    )


main()