// Copyright 2015 The Bazel Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package com.google.devtools.build.lib.exec;

import static com.google.common.truth.Truth.assertThat;
import static com.google.devtools.build.lib.testutil.MoreAsserts.assertThrows;

import com.google.common.io.BaseEncoding;
import com.google.devtools.build.lib.actions.ActionInput;
import com.google.devtools.build.lib.actions.ActionInputHelper;
import com.google.devtools.build.lib.actions.DigestOfDirectoryException;
import com.google.devtools.build.lib.testutil.Suite;
import com.google.devtools.build.lib.testutil.TestSpec;
import com.google.devtools.build.lib.vfs.DigestHashFunction;
import com.google.devtools.build.lib.vfs.FileSystem;
import com.google.devtools.build.lib.vfs.FileSystemUtils;
import com.google.devtools.build.lib.vfs.Path;
import com.google.devtools.build.lib.vfs.inmemoryfs.InMemoryFileSystem;
import com.google.protobuf.ByteString;
import java.io.IOException;
import java.io.InputStream;
import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.util.HashMap;
import java.util.Map;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.JUnit4;

/** Tests SingleBuildFileCache. */
@RunWith(JUnit4.class)
@TestSpec(size = Suite.SMALL_TESTS)
public class SingleBuildFileCacheTest {
  private static final String EMPTY_MD5 = "d41d8cd98f00b204e9800998ecf8427e";

  private FileSystem fs;
  private Map<String, Integer> calls;
  private Map<String, byte[]> md5Overrides;

  private SingleBuildFileCache underTest;

  @Before
  public final void setUp() throws Exception {
    calls = new HashMap<>();
    md5Overrides = new HashMap<>();
    fs =
        new InMemoryFileSystem() {
          @Override
          protected InputStream getInputStream(Path path) throws IOException {
            int c = calls.containsKey(path.toString()) ? calls.get(path.toString()) : 0;
            c++;
            calls.put(path.toString(), c);
            return super.getInputStream(path);
          }

          @Override
          protected byte[] getDigest(Path path) throws IOException {
            assertThat(getDigestFunction()).isEqualTo(DigestHashFunction.MD5);
            byte[] override = md5Overrides.get(path.getPathString());
            return override != null ? override : super.getDigest(path);
          }

          @Override
          protected byte[] getFastDigest(Path path) throws IOException {
            return null;
          }
        };
    underTest = new SingleBuildFileCache("/", fs);
    FileSystemUtils.createEmptyFile(fs.getPath("/empty"));
  }

  @Test
  public void testNonExistentPath() throws Exception {
    ActionInput empty = ActionInputHelper.fromPath("/noexist");
    assertThrows(
        "non existent file should raise exception",
        IOException.class,
        () -> underTest.getMetadata(empty));
  }

  @Test
  public void testDirectory() throws Exception {
    Path file = fs.getPath("/directory");
    file.createDirectory();
    ActionInput input = ActionInputHelper.fromPath(file.getPathString());
    DigestOfDirectoryException expected =
        assertThrows(
            "directory should raise exception",
            DigestOfDirectoryException.class,
            () -> underTest.getMetadata(input));
    assertThat(expected).hasMessageThat().isEqualTo("Input is a directory: /directory");
  }

  @Test
  public void testCache() throws Exception {
    ActionInput empty = ActionInputHelper.fromPath("/empty");
    underTest.getMetadata(empty).getDigest();
    assertThat(calls).containsKey("/empty");
    assertThat((int) calls.get("/empty")).isEqualTo(1);
    underTest.getMetadata(empty).getDigest();
    assertThat((int) calls.get("/empty")).isEqualTo(1);
  }

  @Test
  public void testBasic() throws Exception {
    ActionInput empty = ActionInputHelper.fromPath("/empty");
    assertThat(underTest.getMetadata(empty).getSize()).isEqualTo(0);
    byte[] digestBytes = underTest.getMetadata(empty).getDigest();
    ByteString digest = ByteString.copyFromUtf8(
        BaseEncoding.base16().lowerCase().encode(digestBytes));
    assertThat(digest.toStringUtf8()).isEqualTo(EMPTY_MD5);
  }

  @Test
  public void testUnreadableFileWhenFileSystemSupportsDigest() throws Exception {
    byte[] expectedDigestRaw = MessageDigest.getInstance("md5").digest(
        "randomtext".getBytes(StandardCharsets.UTF_8));
    ByteString expectedDigest = ByteString.copyFrom(expectedDigestRaw);
    md5Overrides.put("/unreadable", expectedDigestRaw);

    ActionInput input = ActionInputHelper.fromPath("/unreadable");
    Path file = fs.getPath("/unreadable");
    FileSystemUtils.createEmptyFile(file);
    file.chmod(0);
    ByteString actualDigest = ByteString.copyFrom(underTest.getMetadata(input).getDigest());
    assertThat(actualDigest).isEqualTo(expectedDigest);
  }
}