feat(inventory): create inventory class

src/bookstore/inventory.py

@@ -0,0 +1,59 @@
+from pathlib import Path
+
+from .book import Book
+from .isbn import ISBN
+
+
+class Inventory:
+    def __init__(self, books: list[Book]) -> None:
+        self.books: dict[ISBN, Book] = {book.isbn: book for book in books}
+
+    def read_from_file(self, path: Path) -> None:
+        """Read `Inventory` from `path` csv file."""
+
+    def save_to_file(self, path: Path) -> None:
+        """Save `Inventory` to `path` csv file."""
+
+    def add(self, book: Book) -> None:
+        """Add `Book` to the `Inventory`. `Book`s ISBN must be unique."""
+        if book.isbn in self.books:
+            raise BaseException(f"Book with this ISBN: {book.isbn} already exists!")  # TODO: create custom exception
+
+        self.books[book.isbn] = book
+
+    def delete(self, isbn: ISBN) -> Book | None:
+        """Deletes `Book` from `Inventory` by `isbn` and returns deleted `Book`"""
+        return self.books.pop(isbn, None)
+
+    def find_by_isbn(self, isbn: ISBN) -> Book | None:
+        """Looks up `Book` within `Inventory` by book `ISBN` and returns it. Returns `None` if it doesn't exist."""
+        if isbn not in self.books.keys():
+            return None
+        return self.books.get(isbn)
+
+    def find_by_title(self, title: str) -> list[Book] | None:
+        """Looks up `Book`s within `Inventory` by book title and returns them as a `List`. Returns `None` if none were found"""
+        found_books = []
+        for book in self.books.values():
+            if book.title.lower() == title.strip().lower():
+                found_books.append(book)
+
+        if found_books:
+            return found_books
+        return None
+
+    def find_by_author(self, author: str) -> list[Book] | None:
+        """Looks up `Book`s within `Inventory` by book author and returns them as a `List`. Returns `None` if none were found"""
+
+        found_books = []
+        for book in self.books.values():
+            if book.author.lower() == author.strip().lower():
+                found_books.append(book)
+
+        if found_books:
+            return found_books
+        return None
+
+    def list_all(self) -> list[Book]:
+        """Returns `List` of all `Book`s."""
+        return list(self.books.values())