fuj-management/scripts/cache_utils.py

import json
import os
import socket
import logging
from datetime import datetime
from pathlib import Path
from google.oauth2 import service_account
from googleapiclient.discovery import build

logger = logging.getLogger(__name__)

# Constants
CACHE_DIR = Path(__file__).parent.parent / "tmp"
CREDS_PATH = Path(__file__).parent.parent / ".secret" / "fuj-management-bot-credentials.json"
DRIVE_TIMEOUT = 10  # seconds
CACHE_TTL_SECONDS = int(os.environ.get("CACHE_TTL_SECONDS", 300))  # 30 min default for max cache age
CACHE_API_CHECK_TTL_SECONDS = int(os.environ.get("CACHE_API_CHECK_TTL_SECONDS", 300))  # 5 min default

# Known mappings mapping "cache name" to Google Sheet ID
CACHE_SHEET_MAP = {
    "attendance_regular": "1E2e_gT_K5AwSRCDLDTa2UetZTkHmBOcz0kFbBUNUNBA",
    "attendance_juniors": "1E2e_gT_K5AwSRCDLDTa2UetZTkHmBOcz0kFbBUNUNBA",
    "exceptions_dict": "1Om0YPoDVCH5cV8BrNz5LG5eR5MMU05ypQC7UMN1xn_Y",
    "payments_transactions": "1Om0YPoDVCH5cV8BrNz5LG5eR5MMU05ypQC7UMN1xn_Y"
}

# Global state to track last Drive API check time per sheet
_LAST_CHECKED = {}
_DRIVE_SERVICE = None

def _get_drive_service():
    global _DRIVE_SERVICE
    if _DRIVE_SERVICE is not None:
        return _DRIVE_SERVICE

    if not CREDS_PATH.exists():
        logger.warning(f"Credentials not found at {CREDS_PATH}. Cannot check Google Drive API.")
        return None
        
    try:
        creds = service_account.Credentials.from_service_account_file(
            str(CREDS_PATH), 
            scopes=["https://www.googleapis.com/auth/drive.readonly"]
        )
        
        # Apply timeout safely to the httplib2 connection without mutating global socket
        import httplib2
        import google_auth_httplib2
        http = httplib2.Http(timeout=DRIVE_TIMEOUT)
        http = google_auth_httplib2.AuthorizedHttp(creds, http=http)
        
        _DRIVE_SERVICE = build("drive", "v3", http=http, cache_discovery=False)
        return _DRIVE_SERVICE
    except Exception as e:
        logger.error(f"Failed to build Drive API service: {e}")
        return None

import time

def get_sheet_modified_time(cache_key: str) -> str | None:
    """Gets the modifiedTime from Google Drive API for a given cache_key.
    Returns the ISO timestamp string if successful.
    If the Drive API fails (e.g., lack of permissions for public sheets),
    it generates a virtual time bucket string to provide a 5-minute TTL cache.
    """
    sheet_id = CACHE_SHEET_MAP.get(cache_key, cache_key)
    
    cache_file = CACHE_DIR / f"{cache_key}_cache.json"
    
    # 1. Check if we should skip the Drive API check entirely (global memory TTL)
    now = time.time()
    last_check = _LAST_CHECKED.get(sheet_id, 0)
    
    if CACHE_API_CHECK_TTL_SECONDS > 0 and (now - last_check) < CACHE_API_CHECK_TTL_SECONDS:
        # We checked recently. Return cached modifiedTime if cache file exists.
        if cache_file.exists():
            try:
                with open(cache_file, "r", encoding="utf-8") as f:
                    cache_data = json.load(f)
                    cached_time = cache_data.get("modifiedTime")
                    if cached_time:
                        logger.info(f"Skipping Drive API check for {sheet_id} due to {CACHE_API_CHECK_TTL_SECONDS}s API check TTL")
                        return cached_time
            except Exception as e:
                logger.warning(f"Error reading existing cache during API skip for {sheet_id}: {e}")
                
    # 2. Check if the cache file is simply too new (legacy check)
    if CACHE_TTL_SECONDS > 0 and cache_file.exists():
        try:
            file_mtime = os.path.getmtime(cache_file)
            if time.time() - file_mtime < CACHE_TTL_SECONDS:
                with open(cache_file, "r", encoding="utf-8") as f:
                    cache_data = json.load(f)
                    cached_time = cache_data.get("modifiedTime")
                    if cached_time:
                        logger.info(f"Skipping Drive API check for {sheet_id} due to {CACHE_TTL_SECONDS}s max CACHE_TTL")
                        # We consider this a valid check, update the global state
                        _LAST_CHECKED[sheet_id] = now
                        return cached_time
        except Exception as e:
            logger.warning(f"Error checking cache TTL for {sheet_id}: {e}")

    def _fallback_ttl():
        bucket = int(time.time() // 300)
        return f"ttl-5m-{bucket}"

    logger.info(f"Checking Drive API for {sheet_id}")
    drive_service = _get_drive_service()
    if not drive_service:
        return _fallback_ttl()
        
    try:
        file_meta = drive_service.files().get(fileId=sheet_id, fields="modifiedTime", supportsAllDrives=True).execute()
        # Successfully checked API, update the global state
        _LAST_CHECKED[sheet_id] = time.time()
        return file_meta.get("modifiedTime")
    except Exception as e:
        logger.warning(f"Could not get modifiedTime for sheet {sheet_id}: {e}. Falling back to 5-minute TTL.")
        return _fallback_ttl()

def read_cache(sheet_id: str, current_modified_time: str) -> list | dict | None:
    """Reads the JSON cache for the given sheet_id.
    Returns the cached data if it exists AND the cached modifiedTime matches
    current_modified_time.
    Otherwise, returns None.
    """
    if not current_modified_time:
        return None
        
    cache_file = CACHE_DIR / f"{sheet_id}_cache.json"
    if not cache_file.exists():
        return None
        
    try:
        with open(cache_file, "r", encoding="utf-8") as f:
            cache_data = json.load(f)
            
        cached_time = cache_data.get("modifiedTime")
        if cached_time == current_modified_time:
            logger.info(f"Cache hit for {sheet_id} ({current_modified_time})")
            return cache_data.get("data")
        else:
            logger.info(f"Cache miss for {sheet_id}. Cached: {cached_time}, Current: {current_modified_time}")
            return None
    except Exception as e:
        logger.error(f"Failed to read cache {cache_file}: {e}")
        return None

def write_cache(sheet_id: str, modified_time: str, data: list | dict) -> None:
    """Writes the data to a JSON cache file with the given modified_time."""
    if not modified_time:
        return
        
    try:
        CACHE_DIR.mkdir(parents=True, exist_ok=True)
        cache_file = CACHE_DIR / f"{sheet_id}_cache.json"
        
        cache_data = {
            "modifiedTime": modified_time,
            "data": data,
            "cachedAt": datetime.now().isoformat()
        }
        
        with open(cache_file, "w", encoding="utf-8") as f:
            json.dump(cache_data, f, ensure_ascii=False)
            
        logger.info(f"Wrote cache for {sheet_id}")
    except Exception as e:
        logger.error(f"Failed to write cache {sheet_id}: {e}")