"""
Firebase initialization and helper functions.
"""

import firebase_admin
from firebase_admin import credentials, firestore, auth
from pathlib import Path
from src.utils.config import settings
from src.utils.logger import setup_logger

logger = setup_logger(__name__)

_db = None

def get_firebase_db():
    """
    Initialize Firebase Admin SDK and return Firestore client.
    """
    global _db
    if _db is not None:
        return _db

    try:
        # Priority 1: Check if credentials string is provided (e.g., from HF Secrets)
        if settings.firebase_service_account_json:
            import json
            service_account_info = json.loads(settings.firebase_service_account_json)
            cred = credentials.Certificate(service_account_info)
            
            # Explicitly extract project_id from JSON if possible
            project_id = service_account_info.get('project_id') or settings.firebase_project_id
            
            firebase_admin.initialize_app(cred, {
                'storageBucket': settings.firebase_storage_bucket,
                'projectId': project_id
            })
            _db = firestore.client()
            logger.info(f"Firebase initialized successfully for project: {project_id} (using JSON)")
            return _db

        # Priority 2: Check for service account file
        service_account_path = Path(settings.firebase_service_account_path)
        
        if not service_account_path.exists():
            logger.warning(f"Firebase service account file not found at {service_account_path}. Using fallback/mock behavior if applicable.")
            return None

        cred = credentials.Certificate(str(service_account_path))
        firebase_admin.initialize_app(cred, {
            'storageBucket': settings.firebase_storage_bucket,
            'projectId': settings.firebase_project_id
        })
        
        _db = firestore.client()
        logger.info(f"Firebase initialized successfully for project: {settings.firebase_project_id} (using file)")
        return _db
    except Exception as e:
        logger.error(f"Failed to initialize Firebase: {e}")
        return None

def verify_token(id_token: str):
    """
    Verify a Firebase ID token and return the payload or error.
    Returns: {"payload": decoded_token, "error": error_message}
    """
    try:
        # Check if any app is initialized, if not try to initialize
        if not firebase_admin._apps:
            logger.warning("Firebase app not initialized. Attempting default initialization...")
            get_firebase_db()
            
        if not firebase_admin._apps:
            return {"payload": None, "error": "Firebase app could not be initialized."}

        decoded_token = auth.verify_id_token(id_token)
        
        if decoded_token is None:
             return {"payload": None, "error": "Firebase SDK returned None for token verification."}
             
        logger.info(f"Firebase token successfully verified for UID: {decoded_token.get('uid')}")
        return {"payload": decoded_token, "error": None}
    except Exception as e:
        error_msg = str(e) or repr(e)
        logger.error(f"Firebase token verification failed: {error_msg}")
        return {"payload": None, "error": error_msg}