#!/usr/bin/env python3
import hashlib
import json
import os
import pathlib
import sys
import tempfile

import bpy


def rounded(value):
    return round(float(value), 6)


def mesh_report():
    mesh = bpy.data.meshes.get("WebGapMesh")
    if mesh is None:
        raise RuntimeError("WebGapMesh is missing")
    mesh.calc_loop_triangles()
    positions = [rounded(value) for vertex in mesh.vertices for value in vertex.co]
    indices = [index for triangle in mesh.loop_triangles for index in triangle.vertices]
    uv_layer = mesh.uv_layers.get("WebGapUV")
    uvs = [rounded(value) for loop in uv_layer.data for value in loop.uv] if uv_layer else []
    return {
        "id": "mesh:WebGapMesh",
        "name": mesh.name,
        "vertexCount": len(mesh.vertices),
        "edgeCount": len(mesh.edges),
        "faceCount": len(mesh.polygons),
        "cornerCount": len(mesh.loops),
        "triangleCount": len(mesh.loop_triangles),
        "positions": positions,
        "indices": indices,
        "uvLayers": [layer.name for layer in mesh.uv_layers],
        "uvs": uvs,
    }


def main() -> None:
    arguments = sys.argv[sys.argv.index("--") + 1 :]
    if len(arguments) != 2:
        raise SystemExit("usage: blender -b --python check-mesh-desktop.py -- FIXTURE REPORT")
    fixture, output = (pathlib.Path(value).resolve() for value in arguments)
    bpy.ops.wm.open_mainfile(filepath=str(fixture), load_ui=False)
    before = mesh_report()
    descriptor, temporary = tempfile.mkstemp(prefix="m16-mesh-reopen-", suffix=".blend", dir=fixture.parent)
    os.close(descriptor)
    try:
        bpy.ops.wm.save_as_mainfile(filepath=temporary, check_existing=False, compress=True)
        bpy.ops.wm.open_mainfile(filepath=temporary, load_ui=False)
        after = mesh_report()
    finally:
        pathlib.Path(temporary).unlink(missing_ok=True)
    if before != after:
        raise RuntimeError(f"mesh save/reopen drift: {before} != {after}")
    report = {
        "schemaVersion": 1,
        "task": "M16-GAP-00014",
        "operation": "MESH_DATABLOCK_DESKTOP",
        "fixture": str(fixture),
        "fixtureSha256": hashlib.sha256(fixture.read_bytes()).hexdigest(),
        "mesh": after,
        "saveReopen": "EXACT",
        "blenderVersion": bpy.app.version_string,
    }
    output.parent.mkdir(parents=True, exist_ok=True)
    output.write_text(json.dumps(report, indent=2, sort_keys=True) + "\n", encoding="utf-8")
    print(f"mesh-desktop-ok id={after['id']} vertices={after['vertexCount']} triangles={after['triangleCount']} saveReopen=exact")


if __name__ == "__main__":
    main()