"""
Placeholder module for future data models.

The current assignment does not require any persistent or structured data, but the
project layout follows a typical Python package structure.  The ``models``
module is kept minimal to satisfy the requirement of having at least four
files and to demonstrate how one might extend the project later.
"""

from __future__ import annotations

# ---------------------------------------------------------------------------
# Example data class – not used directly in the streaming demo but shows
# how a model could be defined for future extensions.
# ---------------------------------------------------------------------------
from dataclasses import dataclass, field
from typing import Dict, List

@dataclass
class ProductPrice:
    """Represents a price entry for a product in a specific city."""

    product: str
    city: str
    price: float
    currency: str = "rubles"

    def __post_init__(self) -> None:
        if self.price < 0:
            raise ValueError("Price cannot be negative")

# ---------------------------------------------------------------------------
# Repository pattern – a very small in‑memory store.
# ---------------------------------------------------------------------------
class PriceRepository:
    """Simple repository that holds :class:`ProductPrice` objects."""

    def __init__(self) -> None:
        self._store: Dict[tuple[str, str], ProductPrice] = {}

    def add(self, entry: ProductPrice) -> None:
        key = (entry.product.lower(), entry.city.lower())
        self._store[key] = entry

    def get(self, product: str, city: str) -> ProductPrice | None:
        return self._store.get((product.lower(), city.lower()))

# ---------------------------------------------------------------------------
# Example usage – not executed in the main script but demonstrates API.
# ---------------------------------------------------------------------------
if __name__ == "__main__":  # pragma: no cover
    repo = PriceRepository()
    repo.add(ProductPrice("milk", "kazan", 89))
    print(repo.get("Milk", "KAZAN"))

# End of models.py