"""
In-memory mock data store for CRUD example.

This module intentionally avoids persistence and concurrency guarantees.
It is suitable for demos, tests, and scaffolding only.

It intentionally avoids
- persistence
- concurrency guarantees
- validation
- error handling

The implementation is suitable for:
- demonstrations
- tests
- scaffolding and example services

It is explicitly NOT suitable for production use.

This module is not part of the ``openapi_first`` library API surface.
"""

from typing import Dict


# In-memory storage keyed by item ID.
_items: Dict[int, dict] = {
    1: {"id": 1, "name": "Apple", "price": 0.5},
    2: {"id": 2, "name": "Banana", "price": 0.3},
}

# Auto-incrementing ID counter.
_next_id = 3


def list_items():
    """
    Return all items in the data store.

    This function performs no filtering, pagination, or sorting.
    The returned collection reflects the current in-memory state.

    Returns
    -------
    list[dict]
        A list of item representations.
    """
    return list(_items.values())


def get_item(item_id: int):
    """
    Retrieve a single item by ID.

    This function assumes the item exists and will raise ``KeyError``
    if the ID is not present in the store.

    Parameters
    ----------
    item_id : int
        Identifier of the item to retrieve.

    Returns
    -------
    dict
        The stored item representation.
    """
    return _items[item_id]


def create_item(payload: dict):
    """
    Create a new item in the data store.

    A new integer ID is assigned automatically. No validation is
    performed on the provided payload.

    Parameters
    ----------
    payload : dict
        Item attributes excluding the ``id`` field.

    Returns
    -------
    dict
        The newly created item, including its assigned ID.
    """
    global _next_id
    item = {"id": _next_id, **payload}
    _items[_next_id] = item
    _next_id += 1
    return item


def update_item(item_id: int, payload: dict):
    """
    Replace an existing item in the data store.

    This function overwrites the existing item entirely and does not
    perform partial updates or validation. If the item does not exist,
    it will be created implicitly.

    Parameters
    ----------
    item_id : int
        Identifier of the item to update.
    payload : dict
        Item attributes excluding the ``id`` field.

    Returns
    -------
    dict
        The updated item representation.
    """
    item = {"id": item_id, **payload}
    _items[item_id] = item
    return item


def delete_item(item_id: int):
    """
    Remove an item from the data store.

    This function assumes the item exists and will raise ``KeyError``
    if the ID is not present.

    Parameters
    ----------
    item_id : int
        Identifier of the item to delete.
    """
    del _items[item_id]