# === core/context_processors.py ===
# Globals injected into every template render.
#
# `deployment_timestamp` is a cache-bust token on our CSS URL. Historically
# it was `int(time.time())` — a new value every second — which defeated
# Cloudflare's edge cache because every page load saw a different `?v=...`
# string. We now tie the token to `custom.css`'s mtime, so the URL
# changes ONLY when the CSS actually changes. Cloudflare can hold the
# file for its full 4h TTL, and users on repeat visits hit the browser
# cache (304 Not Modified).
import os
import time
from pathlib import Path

from django.conf import settings

# Path to the file whose mtime drives the cache-bust token. Module-level
# constant so tests can monkey-patch it to simulate "file missing".
_CSS_PATH_FOR_TOKEN = Path(settings.BASE_DIR) / 'static' / 'css' / 'custom.css'


def _compute_cache_bust_token():
    """Return an integer cache-bust token.

    Normal path: returns the CSS file's mtime (an integer).
    Fallback: if the file can't be stat'd (doesn't exist / permission
    error / disk issue), returns the current wall-clock time in seconds
    — that degrades to the PRE-FIX behaviour (new token per request)
    rather than crashing the whole request cycle.
    """
    try:
        return int(os.path.getmtime(_CSS_PATH_FOR_TOKEN))
    except (OSError, FileNotFoundError):
        return int(time.time())


def project_context(request):
    """Adds project-specific environment variables to the template context globally."""
    return {
        "project_description": os.getenv("PROJECT_DESCRIPTION", ""),
        "project_image_url": os.getenv("PROJECT_IMAGE_URL", ""),
        # Cache-busts static assets — see _compute_cache_bust_token().
        "deployment_timestamp": _compute_cache_bust_token(),
    }