/*
 * Copyright 2012-present Facebook, Inc.
 *
 * 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.facebook.buck.util;

import com.google.common.base.StandardSystemProperty;
import com.google.common.collect.ImmutableList;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.io.Reader;
import java.util.concurrent.Callable;

public final class InputStreamConsumer implements Callable<Void> {

  /** Interface to handle a line of input from the stream. */
  public interface Handler {
    void handleLine(String line);
  }

  private final LineFetcher inputReader;
  private final ImmutableList<Handler> handlers;

  public InputStreamConsumer(InputStream inputStream, Handler... handlers) {
    this(new InputStreamReader(inputStream), handlers);
  }

  public InputStreamConsumer(Reader reader, Handler... handlers) {
    this.inputReader = new LineFetcher(reader);
    this.handlers = ImmutableList.copyOf(handlers);
  }

  @Override
  public Void call() throws IOException {
    String line;
    while ((line = inputReader.readLine()) != null) {
      for (Handler handler : handlers) {
        handler.handleLine(line);
      }
    }
    return null;
  }

  public static Handler createAnsiHighlightingHandler(
      boolean flagOutputWrittenToStream, PrintStream printStream, Ansi ansi) {
    return new HighlightingOutput(flagOutputWrittenToStream, printStream, ansi);
  }

  private static class HighlightingOutput implements Handler {

    private static final String LINE_SEPARATOR = StandardSystemProperty.LINE_SEPARATOR.value();
    private final boolean flagOutputWrittenToStream;
    private final PrintStream printStream;
    private final Ansi ansi;

    public HighlightingOutput(
        boolean flagOutputWrittenToStream, PrintStream printStream, Ansi ansi) {
      this.flagOutputWrittenToStream = flagOutputWrittenToStream;
      this.printStream = printStream;
      this.ansi = ansi;
    }

    @Override
    public void handleLine(String line) {
      String highlightOn = flagOutputWrittenToStream ? ansi.getHighlightedWarningSequence() : "";
      String highlightOff = flagOutputWrittenToStream ? ansi.getHighlightedResetSequence() : "";

      // We pass `line + LINE_SEPARATOR` to print() rather than invoke println() because
      // we want the line and the separator to be guaranteed to be printed together.
      // println() is implemented by calling print() then newLine(). Because those calls could be
      // interleaved when stdout and stderr are being consumed simultaneously (and I have seen
      // this happen), then you could end up with confusing output when stdout and stderr are
      // connected to the same terminal (which is often the case).
      printStream.print(highlightOn + line + LINE_SEPARATOR + highlightOff);
    }
  }
}