initial commit for bookish-server and local environment

bookish-server/mysql/inventory.go

@@ -0,0 +1,111 @@
+package mysql
+
+import (
+	"database/sql"
+	"errors"
+	"time"
+)
+
+// IsBookAvailable queries the database for available books.
+func (s *store) IsBookAvailable(title string) (available bool, err error) {
+	q := `
+		SELECT
+			*
+		FROM
+			rentals
+		WHERE
+			book_title = ?
+			AND return_date IS NULL;
+	`
+
+	var rr []struct {
+		ID         int          `db:"id"`
+		RenterID   int          `db:"renter_id"`
+		RentalDate time.Time    `db:"rental_date"`
+		ReturnDate sql.NullTime `db:"return_date"`
+		BookTitle  string       `db:"book_title"`
+	}
+
+	err = s.Select(&rr, q, title)
+	if err != nil {
+		// If no records are returned then the book is available for rent.
+		if errors.Is(sql.ErrNoRows, err) {
+			return true, nil
+		}
+
+		return false, err
+	}
+
+	// If 5 books are rented out this book is not available.
+	if len(rr) > 4 {
+		return false, nil
+	}
+
+	return true, nil
+}
+
+// RenterAlreadyCheckedOut queries the database for the given renterId and title. If a record is returned checkedOut will be true.
+func (s *store) RenterAlreadyCheckedOut(renterId int, title string) (checkedOut bool, err error) {
+	q := `
+		SELECT
+			*
+		FROM
+			rentals
+		WHERE
+			renter_id = ?
+			AND book_title = ?
+			AND return_date IS NULL;
+	`
+
+	var rr []struct {
+		ID         int          `db:"id"`
+		RenterID   int          `db:"renter_id"`
+		RentalDate time.Time    `db:"rental_date"`
+		ReturnDate sql.NullTime `db:"return_date"`
+		BookTitle  string       `db:"book_title"`
+	}
+
+	err = s.Select(&rr, q, renterId, title)
+	if err != nil {
+		if errors.Is(sql.ErrNoRows, err) {
+			return false, nil
+		}
+
+		return false, err
+	}
+
+	if len(rr) == 0 {
+		return false, nil
+	}
+
+	return true, nil
+}
+
+// CheckoutBook inserts a record indicating the book is checked out to the renter.
+func (s *store) CheckoutBook(renterId int, title string) error {
+	q := `
+		INSERT INTO
+			rentals (renter_id, rental_date, book_title)
+		VALUES
+			(?, ?, ?);
+	`
+
+	_, err := s.Exec(q, renterId, time.Now(), title)
+	return err
+}
+
+// ReturnBook sets the return_date field to now indicating the book has been returned.
+func (s *store) ReturnBook(renterId int, title string) error {
+	q := `
+		UPDATE
+			rentals
+		SET
+			return_date = ?
+		WHERE
+			renter_id = ?
+			AND book_title = ?;
+	`
+
+	_, err := s.Exec(q, time.Now(), renterId, title)
+	return err
+}