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