package com.bookshop.structural.proxy;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertTrue;

import com.bookshop.domain.Book;
import java.util.Optional;
import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Test;

@DisplayName("Proxy -- a caching stand-in for the slow remote catalog")
class CachingCatalogProxyTest {

    private final RemoteBookCatalog remote = new RemoteBookCatalog();
    private final BookCatalog catalog = new CachingCatalogProxy(remote);

    @Test
    @DisplayName("repeat lookups are served from cache -- one remote round-trip, not three")
    void cachesRepeatLookups() {
        catalog.findByIsbn("978-0134685991");
        catalog.findByIsbn("978-0134685991");
        Optional<Book> book = catalog.findByIsbn("978-0134685991");

        assertEquals("Effective Java", book.orElseThrow().title());
        assertEquals(1, remote.lookupCount());
    }

    @Test
    @DisplayName("misses are cached too -- an unknown ISBN is only asked about once")
    void cachesMisses() {
        assertTrue(catalog.findByIsbn("no-such-isbn").isEmpty());
        assertTrue(catalog.findByIsbn("no-such-isbn").isEmpty());

        assertEquals(1, remote.lookupCount());
    }

    @Test
    @DisplayName("proxy and real catalog are interchangeable -- clients hold the same interface")
    void proxyIsTransparent() {
        BookCatalog direct = remote;
        BookCatalog proxied = catalog;

        assertEquals(direct.findByIsbn("978-0201633610"), proxied.findByIsbn("978-0201633610"));
    }
}

Raw file