MIL-003: Step 2 - New flash cards

Review record RC-025 (Go, autonomous mode, not independent).

Task: MIL-003#1
Task: MIL-003#2
Task: MIL-003#3
Task: MIL-003#4
Task: MIL-003#5

src/flash_card/domain/entities/deck.py

@@ -0,0 +1,95 @@
+"""The cards still to learn.
+
+@file deck.py
+@brief The Deck entity: holds cards, draws one and removes one.
+"""
+
+from collections.abc import Callable, Iterable, Sequence
+
+from flash_card.domain.entities.card import Card
+from flash_card.domain.entities.vocabulary import Vocabulary
+from flash_card.domain.errors.vocabulary_errors import EmptyDeckError
+from flash_card.domain.value_objects.language_pair import LanguagePair
+
+
+class Deck:
+    """The cards still to learn, of one language pair."""
+
+    def __init__(self, language_pair: LanguagePair, cards: Iterable[Card]) -> None:
+        """Create a deck.
+
+        @param language_pair The languages of the cards.
+        @param cards The cards of the deck.
+        """
+        ## @brief The languages of the cards.
+        self._language_pair = language_pair
+        ## @brief The cards still in the deck.
+        self._cards = list(cards)
+
+    @classmethod
+    def from_vocabulary(cls, vocabulary: Vocabulary) -> "Deck":
+        """Create a deck holding every card of a vocabulary.
+
+        @param vocabulary The delivered word list.
+        @return A new deck.
+        """
+        return cls(vocabulary.language_pair, vocabulary.cards)
+
+    @property
+    def language_pair(self) -> LanguagePair:
+        """Return the languages of the cards.
+
+        @return The language pair.
+        """
+        return self._language_pair
+
+    @property
+    def cards(self) -> tuple[Card, ...]:
+        """Return a copy of the cards.
+
+        @return The cards in deck order.
+        """
+        return tuple(self._cards)
+
+    @property
+    def is_empty(self) -> bool:
+        """Tell whether the deck has no card.
+
+        @return True when no card is left.
+        """
+        return not self._cards
+
+    def __len__(self) -> int:
+        """Return the number of cards.
+
+        @return The card count.
+        """
+        return len(self._cards)
+
+    def draw(
+        self,
+        choose: Callable[[Sequence[Card]], Card],
+        exclude: Card | None = None,
+    ) -> Card:
+        """Pick a card without removing it.
+
+        The pick avoids the excluded card when another card exists.
+
+        @param choose Picks one card from a non-empty sequence.
+        @param exclude A card to avoid, usually the one shown now.
+        @return The picked card.
+        @throws EmptyDeckError When the deck has no card.
+        """
+        if not self._cards:
+            raise EmptyDeckError("cannot draw from an empty deck")
+        others = [card for card in self._cards if card != exclude]
+        return choose(others or self._cards)
+
+    def remove(self, card: Card) -> None:
+        """Remove the first card equal to the given one.
+
+        @param card The card to remove.
+        @return Nothing.
+        @throws ValueError When the deck holds no such card.
+        """
+        self._cards.remove(card)