package com.evsuite.abrp;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;

import java.util.List;

import org.junit.Test;

/** The offline buffer for live samples — pure JVM. */
public class TelemetryQueueTest {

    @Test
    public void batchesOldestFirstAndKeepsThemUntilConfirmed() {
        TelemetryQueue queue = new TelemetryQueue();
        queue.add("a");
        queue.add("b");
        assertEquals(List.of("a", "b"), queue.peekBatch());
        // Not confirmed yet: a failed request must not lose them.
        assertEquals(2, queue.size());
        queue.remove(2);
        assertEquals(0, queue.size());
    }

    @Test
    public void aBatchNeverExceedsWhatTheServerAccepts() {
        TelemetryQueue queue = new TelemetryQueue();
        for (int i = 0; i < 1200; i++) queue.add(String.valueOf(i));
        List<String> batch = queue.peekBatch();
        assertEquals(TelemetryQueue.MAX_BATCH, batch.size());
        assertEquals("0", batch.get(0));
    }

    @Test
    public void whenFullTheOldestSamplesAreDropped() {
        TelemetryQueue queue = new TelemetryQueue(3);
        for (String s : new String[]{"a", "b", "c", "d", "e"}) queue.add(s);
        assertEquals(List.of("c", "d", "e"), queue.peekBatch());
        assertEquals(2, queue.dropped());
    }

    @Test
    public void aSavedQueueComesBackInOrder() {
        TelemetryQueue q = new TelemetryQueue(10);
        q.add("{\"utc\":1}");
        q.add("{\"utc\":2}");
        TelemetryQueue restarted = new TelemetryQueue(10);
        restarted.add("{\"utc\":3}");                 // taken after the restart
        assertEquals(2, restarted.restore(q.encode()));
        assertEquals(java.util.Arrays.asList("{\"utc\":1}", "{\"utc\":2}", "{\"utc\":3}"), restarted.peekBatch());
    }

    @Test
    public void restoringKeepsTheCapacityByDroppingTheOldest() {
        TelemetryQueue q = new TelemetryQueue(10);
        for (int i = 1; i <= 4; i++) q.add("{\"utc\":" + i + "}");
        TelemetryQueue small = new TelemetryQueue(3);
        small.restore(q.encode());
        assertEquals(java.util.Arrays.asList("{\"utc\":2}", "{\"utc\":3}", "{\"utc\":4}"), small.peekBatch());
        assertEquals(1, small.dropped());
    }

    @Test
    public void aDamagedFileRestoresNothing() {
        TelemetryQueue q = new TelemetryQueue(10);
        assertEquals(0, q.restore("[\"{\\\"utc\\\":1}\", trunc"));
        assertEquals(0, q.restore(""));
        assertEquals(0, q.restore(null));
        assertEquals(0, q.size());
    }

    @Test
    public void everyChangeMovesTheVersion() {
        TelemetryQueue q = new TelemetryQueue(10);
        long v0 = q.version();
        q.add("{\"utc\":1}");
        long v1 = q.version();
        q.remove(0);
        assertEquals(v1, q.version());                     // nothing removed, nothing to save
        q.remove(1);
        assertTrue(q.version() > v1 && v1 > v0);
    }
}