from typing import Dict, List, Optional
from datetime import datetime

# In-memory store for fruits since no model was provided
_fruits_store: List[Dict[str, any]] = []

def add_fruit(fruit_name: str, quantity: int) -> Dict[str, any]:
    """
    Adds a fruit to the in-memory store with the given quantity.

    Args:
        fruit_name (str): Name of the fruit to add
        quantity (int): Quantity of the fruit

    Returns:
        Dict[str, any]: The newly added fruit entry
    """
    if not validate_fruit_data(fruit_name, quantity):
        raise ValueError("Invalid fruit data provided")
    
    new_fruit = {
        "name": fruit_name.lower(),
        "quantity": quantity,
        "added_at": datetime.now()
    }
    
    # Check if fruit already exists
    existing_fruit = get_fruit_by_name(fruit_name)
    if existing_fruit:
        existing_fruit["quantity"] += quantity
        existing_fruit["updated_at"] = datetime.now()
        return existing_fruit
    
    _fruits_store.append(new_fruit)
    return new_fruit

def get_fruit_by_name(fruit_name: str) -> Optional[Dict[str, any]]:
    """
    Retrieves a fruit by its name from the in-memory store.

    Args:
        fruit_name (str): Name of the fruit to retrieve

    Returns:
        Optional[Dict[str, any]]: The fruit entry if found, None otherwise
    """
    fruit_name = fruit_name.lower()
    for fruit in _fruits_store:
        if fruit["name"] == fruit_name:
            return fruit
    return None

def get_all_fruits() -> List[Dict[str, any]]:
    """
    Retrieves all fruits from the in-memory store.

    Returns:
        List[Dict[str, any]]: List of all fruit entries
    """
    return _fruits_store

def update_fruit_quantity(fruit_name: str, new_quantity: int) -> Optional[Dict[str, any]]:
    """
    Updates the quantity of a specific fruit.

    Args:
        fruit_name (str): Name of the fruit to update
        new_quantity (int): New quantity value

    Returns:
        Optional[Dict[str, any]]: Updated fruit entry if found, None otherwise
    """
    if not validate_fruit_data(fruit_name, new_quantity):
        raise ValueError("Invalid fruit data provided")
    
    fruit = get_fruit_by_name(fruit_name)
    if fruit:
        fruit["quantity"] = new_quantity
        fruit["updated_at"] = datetime.now()
        return fruit
    return None

def delete_fruit(fruit_name: str) -> bool:
    """
    Deletes a fruit from the in-memory store.

    Args:
        fruit_name (str): Name of the fruit to delete

    Returns:
        bool: True if fruit was deleted, False if not found
    """
    fruit_name = fruit_name.lower()
    for i, fruit in enumerate(_fruits_store):
        if fruit["name"] == fruit_name:
            _fruits_store.pop(i)
            return True
    return False

def validate_fruit_data(fruit_name: str, quantity: int) -> bool:
    """
    Validates fruit data before processing.

    Args:
        fruit_name (str): Name of the fruit to validate
        quantity (int): Quantity to validate

    Returns:
        bool: True if data is valid, False otherwise
    """
    if not fruit_name or not isinstance(fruit_name, str) or len(fruit_name.strip()) == 0:
        return False
    if not isinstance(quantity, int) or quantity < 0:
        return False
    return True