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/*
 * Copyright (C) 2015 The Android Open Source Project
 *
 * 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.android.voicemail.impl.mail.store.imap;

import com.android.voicemail.impl.mail.FixedLengthInputStream;
import com.android.voicemail.impl.mail.TempDirectory;
import com.android.voicemail.impl.mail.utils.LogUtils;
import com.android.voicemail.impl.mail.utils.Utility;
import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import org.apache.commons.io.IOUtils;

/** Subclass of {@link ImapString} used for literals backed by a temp file. */
public class ImapTempFileLiteral extends ImapString {
  private final String TAG = "ImapTempFileLiteral";

  /* package for test */ final File file;

  /** Size is purely for toString() */
  private final int size;

  /* package */ ImapTempFileLiteral(FixedLengthInputStream stream) throws IOException {
    size = stream.getLength();
    file = File.createTempFile("imap", ".tmp", TempDirectory.getTempDirectory());

    // Unfortunately, we can't really use deleteOnExit(), because temp filenames are random
    // so it'd simply cause a memory leak.
    // deleteOnExit() simply adds filenames to a static list and the list will never shrink.
    // mFile.deleteOnExit();
    OutputStream out = new FileOutputStream(file);
    IOUtils.copy(stream, out);
    out.close();
  }

  /**
   * Make sure we delete the temp file.
   *
   * <p>We should always be calling {@link ImapResponse#destroy()}, but it's here as a last resort.
   */
  @Override
  protected void finalize() throws Throwable {
    try {
      destroy();
    } finally {
      super.finalize();
    }
  }

  @Override
  public InputStream getAsStream() {
    checkNotDestroyed();
    try {
      return new FileInputStream(file);
    } catch (FileNotFoundException e) {
      // It's probably possible if we're low on storage and the system clears the cache dir.
      LogUtils.w(TAG, "ImapTempFileLiteral: Temp file not found");

      // Return 0 byte stream as a dummy...
      return new ByteArrayInputStream(new byte[0]);
    }
  }

  @Override
  public String getString() {
    checkNotDestroyed();
    try {
      byte[] bytes = IOUtils.toByteArray(getAsStream());
      // Prevent crash from OOM; we've seen this, but only rarely and not reproducibly
      if (bytes.length > ImapResponseParser.LITERAL_KEEP_IN_MEMORY_THRESHOLD) {
        throw new IOException();
      }
      return Utility.fromAscii(bytes);
    } catch (IOException e) {
      LogUtils.w(TAG, "ImapTempFileLiteral: Error while reading temp file", e);
      return "";
    }
  }

  @Override
  public void destroy() {
    try {
      if (!isDestroyed() && file.exists()) {
        file.delete();
      }
    } catch (RuntimeException re) {
      // Just log and ignore.
      LogUtils.w(TAG, "Failed to remove temp file: " + re.getMessage());
    }
    super.destroy();
  }

  @Override
  public String toString() {
    return String.format("{%d byte literal(file)}", size);
  }

  public boolean tempFileExistsForTest() {
    return file.exists();
  }
}