package com.ankurm.distributedcache;

import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;

import static org.assertj.core.api.Assertions.assertThat;

/**
 * The same two behaviours, asserted identically, against whichever
 * CacheManager the active Spring profile wired up. That's deliberate:
 * the point of the Spring Cache abstraction is that ExchangeRateLookupService
 * and this test never change when the backend does - only the
 * subclass's @ActiveProfiles (and, for Redis, the container) changes.
 *
 * ExchangeRateLookupService's callCount() is a singleton counter shared
 * across every @Test method in a subclass's Spring context (JUnit does
 * not create a fresh context per test method), so each test reads the
 * counter before and after its own calls and asserts the *delta* rather
 * than an absolute value - that way test execution order inside one
 * class can never affect the result.
 */
abstract class CacheHitAndEvictionContractTest {

    @Autowired
    ExchangeRateLookupService service;

    abstract String backendName();

    @Test
    void secondCallForSameKeyIsServedFromCache() {
        int before = service.callCount();

        service.rateFor("USD/INR");
        int afterFirstCall = service.callCount();

        service.rateFor("USD/INR");
        int afterSecondCall = service.callCount();

        Transcript t = new Transcript("29-" + backendName() + "-cache-hit.txt");
        t.line("backend=%s", backendName());
        t.line("rateFor(\"USD/INR\") call 1 -> method body ran, callCount %d -> %d", before, afterFirstCall);
        t.line("rateFor(\"USD/INR\") call 2 -> served from cache, callCount stays %d", afterSecondCall);
        t.write();

        assertThat(afterFirstCall).isEqualTo(before + 1);
        assertThat(afterSecondCall).isEqualTo(afterFirstCall);
    }

    @Test
    void evictingAKeyForcesTheNextCallToRecompute() {
        int before = service.callCount();

        service.rateFor("USD/EUR");
        int afterFirstCall = service.callCount();

        service.evict("USD/EUR");
        service.rateFor("USD/EUR");
        int afterEvictAndRecall = service.callCount();

        Transcript t = new Transcript("29-" + backendName() + "-cache-evict.txt");
        t.line("backend=%s", backendName());
        t.line("rateFor(\"USD/EUR\") call 1 -> method body ran, callCount %d -> %d", before, afterFirstCall);
        t.line("evict(\"USD/EUR\") then rateFor(\"USD/EUR\") again -> method body ran again, callCount %d -> %d",
                afterFirstCall, afterEvictAndRecall);
        t.write();

        assertThat(afterFirstCall).isEqualTo(before + 1);
        assertThat(afterEvictAndRecall).isEqualTo(afterFirstCall + 1);
    }
}