package com.baiyue.eventbridge.metrics;

import com.baiyue.common.event.EventTypes;
import com.baiyue.eventbridge.mapper.BridgeInboxMapper;
import io.micrometer.core.instrument.simple.SimpleMeterRegistry;
import org.junit.jupiter.api.Test;

import java.util.List;

import static org.assertj.core.api.Assertions.assertThat;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.verify;
import static org.mockito.Mockito.verifyNoMoreInteractions;
import static org.mockito.Mockito.when;

class EventBridgeInboxMetricsSamplerTest {

    @Test
    void samplesDatabaseOnceAndServesCachedLowCardinalityGauges() {
        BridgeInboxMapper mapper = mock(BridgeInboxMapper.class);
        SimpleMeterRegistry registry = new SimpleMeterRegistry();
        InboxMetricsSnapshot known = snapshot("OVERSEAS", EventTypes.FIRST_LEG_LOADING_PLAN_COMPLETED,
                7, 121.5, 2);
        InboxMetricsSnapshot unknown = snapshot("region-123", "dynamic-event-123", 3, 900.0, 1);
        when(mapper.observabilitySnapshots()).thenReturn(List.of(known, unknown));
        EventBridgeInboxMetricsSampler sampler = new EventBridgeInboxMetricsSampler(mapper, registry);

        sampler.sample();

        verify(mapper).observabilitySnapshots();
        assertThat(gauge(registry, EventBridgeInboxMetricsSampler.BACKLOG_METRIC,
                "OVERSEAS", EventTypes.FIRST_LEG_LOADING_PLAN_COMPLETED)).isEqualTo(7.0);
        assertThat(gauge(registry, EventBridgeInboxMetricsSampler.OLDEST_AGE_METRIC,
                "OVERSEAS", EventTypes.FIRST_LEG_LOADING_PLAN_COMPLETED)).isEqualTo(121.5);
        assertThat(gauge(registry, EventBridgeInboxMetricsSampler.DEAD_METRIC,
                "OTHER", "OTHER")).isEqualTo(1.0);
        verifyNoMoreInteractions(mapper);
    }

    private InboxMetricsSnapshot snapshot(String region, String eventType, long backlog,
                                            double oldestAge, long dead) {
        InboxMetricsSnapshot snapshot = new InboxMetricsSnapshot();
        snapshot.setTargetRegion(region);
        snapshot.setEventType(eventType);
        snapshot.setBacklogCount(backlog);
        snapshot.setOldestPendingAgeSeconds(oldestAge);
        snapshot.setDeadCount(dead);
        return snapshot;
    }

    private double gauge(SimpleMeterRegistry registry, String name, String region, String eventType) {
        return registry.get(name).tags("target_region", region, "event_type", eventType).gauge().value();
    }
}