"""Version only thumbnails that use a bundled font; preserve scene revisions."""
from __future__ import annotations

import hashlib
import json
from pathlib import Path

from app.persistence import atomic_write_bytes

STAMP_SUFFIX = ".font-version"


def scene_font_version(scene: dict, resolver) -> str | None:
    owner = getattr(resolver, "__self__", None)
    version_for = getattr(owner, "render_version", None)
    if version_for is None:
        return None
    elements = scene.get("elements", []) if scene.get("version") == 1 else [
        element for layer in scene.get("layers", []) if layer.get("type") == "text"
        for element in layer.get("elements", [])
    ]
    versions = sorted({version for element in elements
                       if (version := version_for(element.get("font", "default")))})
    if not versions:
        return None
    return hashlib.sha256(json.dumps(versions, separators=(",", ":")).encode("ascii")).hexdigest()[:16]


def stamp_path(path: Path) -> Path:
    return path.with_name(path.name + STAMP_SUFFIX)


def cache_stale(path: Path, scene: dict, resolver) -> bool:
    version = scene_font_version(scene, resolver)
    if version is None:
        return False
    try:
        return stamp_path(path).read_text(encoding="ascii").strip() != version
    except (OSError, UnicodeError):
        return True


def stamp_cache(path: Path, scene: dict, resolver) -> None:
    version = scene_font_version(scene, resolver)
    stamp = stamp_path(path)
    if version is not None:
        atomic_write_bytes(stamp, (version + "\n").encode("ascii"))
    else:
        stamp.unlink(missing_ok=True)


def versioned_url(url: str, scene: dict, resolver) -> str:
    version = scene_font_version(scene, resolver)
    return url + f"&font_v={version}" if version else url


def cached_versioned_url(url: str, path: Path) -> str:
    try:
        version = stamp_path(path).read_text(encoding="ascii").strip()
    except (OSError, UnicodeError):
        return url
    if len(version) == 16 and all(ch in "0123456789abcdef" for ch in version):
        return url + f"&font_v={version}"
    return url