/*
 * Copyright (C) 2015, Google Inc. and others
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Distribution License v. 1.0 which is available at
 * https://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

package org.eclipse.jgit.internal.storage.dfs;

import static org.eclipse.jgit.lib.Constants.OBJ_BLOB;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotNull;
import static org.junit.Assert.assertNull;
import static org.junit.Assert.assertSame;

import org.eclipse.jgit.internal.storage.dfs.DeltaBaseCache.Entry;
import org.eclipse.jgit.junit.TestRng;
import org.junit.Before;
import org.junit.Test;

public class DeltaBaseCacheTest {
	private static final int SZ = 512;

	private DfsStreamKey key;
	private DeltaBaseCache cache;
	private TestRng rng;

	@Before
	public void setUp() {
		DfsRepositoryDescription repo = new DfsRepositoryDescription("test");
		key = DfsStreamKey.of(repo, "test.key", null);
		cache = new DeltaBaseCache(SZ);
		rng = new TestRng(getClass().getSimpleName());
	}

	@Test
	public void testObjectLargerThanCacheDoesNotEvict() {
		byte[] obj12 = put(12, 32);
		put(24, SZ + 5);
		assertNull("does not store large object", cache.get(key, 24));
		get(obj12, 12);
	}

	@Test
	public void testCacheLruExpires1() {
		byte[] obj1 = put(1, SZ / 4);
		put(2, SZ / 4);
		byte[] obj3 = put(3, SZ / 4);
		put(4, SZ / 4);
		assertEquals(SZ, cache.getMemoryUsed());

		get(obj3, 3);
		get(obj1, 1);
		put(5, SZ / 2);
		assertEquals(SZ, cache.getMemoryUsed());
		assertEquals(SZ, cache.getMemoryUsedByTableForTest());
		assertEquals(SZ, cache.getMemoryUsedByLruChainForTest());
		assertNull(cache.get(key, 4));
		assertNull(cache.get(key, 2));

		get(obj1, 1);
		get(obj3, 3);
	}

	@Test
	public void testCacheLruExpires2() {
		int pos0 = (0 << 10) | 2;
		int pos1 = (1 << 10) | 2;
		int pos2 = (2 << 10) | 2;
		int pos5 = (5 << 10) | 2;
		int pos6 = (6 << 10) | 2;

		put(pos0, SZ / 4);
		put(pos5, SZ / 4);
		byte[] obj1 = put(pos1, SZ / 4);
		byte[] obj2 = put(pos2, SZ / 4);
		assertEquals(SZ, cache.getMemoryUsed());

		byte[] obj6 = put(pos6, SZ / 2);
		assertEquals(SZ, cache.getMemoryUsed());
		assertEquals(SZ, cache.getMemoryUsedByTableForTest());
		assertEquals(SZ, cache.getMemoryUsedByLruChainForTest());
		assertNull(cache.get(key, pos0));
		assertNull(cache.get(key, pos5));

		get(obj1, pos1);
		get(obj2, pos2);
		get(obj6, pos6);
	}

	@Test
	public void testCacheMemoryUsedConsistentWithExpectations() {
		put(1, 32);
		put(2, 32);
		put(3, 32);

		assertNotNull(cache.get(key, 1));
		assertNotNull(cache.get(key, 1));

		assertEquals(32 * 3, cache.getMemoryUsed());
		assertEquals(32 * 3, cache.getMemoryUsedByTableForTest());
		assertEquals(32 * 3, cache.getMemoryUsedByLruChainForTest());
	}

	private void get(byte[] data, int position) {
		Entry e = cache.get(key, position);
		assertNotNull("expected entry at " + position, e);
		assertEquals("expected blob for " + position, OBJ_BLOB, e.type);
		assertSame("expected data for " + position, data, e.data);
	}

	private byte[] put(int position, int sz) {
		byte[] data = rng.nextBytes(sz);
		cache.put(key, position, OBJ_BLOB, data);
		return data;
	}
}