from firebase_admin import credentials, db, initialize_app, auth
import os
import json
from typing import Optional, Any, Dict

class FirebaseClient:
    _instance = None

    def __new__(cls):
        if cls._instance is None:
            cls._instance = super(FirebaseClient, cls).__new__(cls)
            cls._instance._initialized = False
        return cls._instance

    def __init__(self):
        if self._initialized:
            return
        
        try:
            # Initialize Firebase credentials
            if os.path.exists('firebase-credentials.json'):
                cred = credentials.Certificate('firebase-credentials.json')
            else:
                cred_dict = json.loads(os.environ.get('FIRE_CRED'))
                cred = credentials.Certificate(cred_dict)
            
            self.app = initialize_app(cred, {
                'databaseURL': os.environ.get('FIRE_URL')
            })
            self._initialized = True
        except Exception as e:
            raise Exception(f"Firebase initialization failed: {e}")

    def get(self, path: str) -> Optional[Any]:
        """Read data from specified path"""
        try:
            ref = db.reference(path)
            return ref.get()
        except Exception as e:
            raise Exception(f"Firebase read error: {e}")

    def query_by_child(self, path: str, child_key: str, start_at: Optional[Any] = None, end_at: Optional[Any] = None) -> Optional[Dict]:
        """Query data ordered by child key with optional start/end filters"""
        try:
            ref = db.reference(path)
            query = ref.order_by_child(child_key)
            
            if start_at is not None:
                query = query.start_at(start_at)
            if end_at is not None:
                query = query.end_at(end_at)
                
            return query.get()
        except Exception as e:
            raise Exception(f"Firebase query error: {e}")

    def set(self, path: str, data: Dict) -> Dict:
        """Set data at specified path"""
        try:
            ref = db.reference(path)
            ref.set(data)
            return data
        except Exception as e:
            raise Exception(f"Firebase write error: {e}")

    def update(self, path: str, data: Dict) -> Dict:
        """Update data at specified path"""
        try:
            ref = db.reference(path)
            ref.update(data)
            return data
        except Exception as e:
            raise Exception(f"Firebase update error: {e}")

    def delete(self, path: str) -> bool:
        """Delete data at specified path"""
        try:
            ref = db.reference(path)
            ref.delete()
            return True
        except Exception as e:
            raise Exception(f"Firebase delete error: {e}")

    def push(self, path: str, data: Dict) -> str:
        """Push new data to specified path, returns generated key"""
        try:
            ref = db.reference(path)
            new_ref = ref.push(data)
            return new_ref.key
        except Exception as e:
            raise Exception(f"Firebase push error: {e}")
    
    def get_user_details(self, user_id: str) -> Dict:
        """Get authentication details for a user"""
        try:
            user_record = auth.get_user(user_id)
            return user_record
        except Exception as e:
            raise Exception(f"Firebase error fetching user data: {e}")

    def delete_user(self, user_id: str) -> Optional[Any]:
        """Delete a user"""
        try:
            auth.delete_user(user_id)
        except Exception as e:
            raise Exception(f"Firebase error fetching user data: {e}")