import logging
import os
import firebase_admin
from firebase_admin import credentials, storage, firestore, auth

# Initialize logging
logger = logging.getLogger("BIT-LOG")

class FirebaseManager:
    """
    V261.17: Manages Firebase Storage uploads for resilient audio playback.
    Replaces local static file serving which causes timeouts and 404s.
    """
    
    _instance = None
    _bucket = None
    _db = None

    def __new__(cls):
        if cls._instance is None:
            cls._instance = super(FirebaseManager, cls).__new__(cls)
            # We delay _initialize until first actual use of db or bucket
        return cls._instance

    def _initialize(self):
        """Initialize Firebase Admin SDK with service account."""
        if firebase_admin._apps:
            self._bucket = storage.bucket()
            self._db = firestore.client()
            return

        try:
            from config import STORAGE_BUCKET, IS_PRODUCTION
            import json

            logger.info("🛠️ [FIREBASE] Starting initialization...")
            
            cred_dict = None
            
            # Mission 1: Try loading from environment variables (checking multiple names for safety)
            creds_str = os.environ.get("FIREBASE_CREDENTIALS") or os.environ.get("FIREBASE_CREDENTIALS_JSON")
            
            if creds_str and len(creds_str.strip()) > 10:
                try:
                    cred_dict = json.loads(creds_str)
                    logger.info("✅ [FIREBASE] Successfully parsed credentials from Environment Secrets!")
                except Exception as e:
                    logger.error(f"❌ [FIREBASE] Failed to parse Environment Credentials: {e}")

            # Fallback to local file only for local development (if no secret is set)
            if not cred_dict and FIREBASE_CREDENTIALS_PATH:
                if os.path.exists(FIREBASE_CREDENTIALS_PATH):
                    with open(FIREBASE_CREDENTIALS_PATH, "r", encoding="utf-8") as f:
                        cred_dict = json.load(f)
                    logger.info(f"📂 [FIREBASE] Loading credentials from file: {FIREBASE_CREDENTIALS_PATH}.")
                else:
                    logger.warning(f"⚠️ [FIREBASE] Credentials file not found at {FIREBASE_CREDENTIALS_PATH}.")
            
            if cred_dict:
                cred = credentials.Certificate(cred_dict)
                firebase_admin.initialize_app(cred, {
                    'storageBucket': STORAGE_BUCKET
                })
                logger.info(f"🚀 [FIREBASE] SDK Initialized successfully for {'PROD' if IS_PRODUCTION else 'DEV'}.")
            else:
                logger.error("❌ [FIREBASE] CRITICAL ERROR: Firebase credentials not found! Firebase is OFFLINE.")
            
            self._bucket = storage.bucket()
            self._db = firestore.client()
            logger.info("✨ [FIREBASE] Storage and Firestore clients ready.")
        except Exception as e:
            logger.error(f"🔥 [FIREBASE] Initialization failed: {e}")

    def get_db(self):
        """V2: Returns the initialized Firestore client, initializing if needed."""
        if not self._db:
            self._initialize()
        return self._db

    def verify_token(self, id_token: str):
        """
        V2: Verifies a Firebase Auth ID token.
        Returns the decoded token dictionary (including 'uid') if valid, else None.
        """
        if not firebase_admin._apps:
            self._initialize()

        try:
            decoded_token = auth.verify_id_token(id_token)
            return decoded_token
        except Exception as e:
            if "expired" in str(e).lower():
                logger.warning("⚠️ [FIREBASE] Token expired.")
            else:
                logger.error(f"❌ [FIREBASE] Error verifying token: {e}")
            return None

    def upload_file(self, local_path: str, destination_blob_name: str) -> str:
        """
        V273.1: Uploads local file and returns a Signed URL (CORS proof).
        Signed URLs bypass public access restrictions and work reliably in production.
        """
        if not self._bucket:
            self._initialize()
        
        if not self._bucket:
            logger.error("❌ [FIREBASE] Not initialized. Cannot upload.")
            return None

        try:
            blob = self._bucket.blob(destination_blob_name)
            blob.upload_from_filename(local_path)
            
            # V273.1: Generate Signed URL instead of public_url to fix CORS
            import datetime
            signed_url = blob.generate_signed_url(
                version="v4",
                expiration=datetime.timedelta(hours=24),
                method="GET",
            )
            
            logger.info(f"UPLOAD: [FIREBASE] Signed URL generated for {destination_blob_name}")
            return signed_url
            
        except Exception as e:
            logger.error(f"ERROR: [FIREBASE] Upload failed for {local_path}: {e}")
            return None

# Singleton accessor
firebase_manager = FirebaseManager()