src/main/java/com/google/devtools/build/lib/util/io/AnsiTerminal.java

// Copyright 2014 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.util.io;

import java.io.IOException;
import java.io.OutputStream;

/**
 * A class which encapsulates the fancy curses-type stuff that you can do using
 * standard ANSI terminal control sequences.
 */
public class AnsiTerminal {
  private static final byte[] ESC = {27, (byte) '['};
  private static final byte BEL = 7;
  private static final byte UP = (byte) 'A';
  private static final byte ERASE_LINE = (byte) 'K';
  private static final byte SET_GRAPHICS = (byte) 'm';
  private static final byte TEXT_BOLD = (byte) '1';
  private static final byte[] SET_TERM_TITLE = {27, (byte) ']', (byte) '0', (byte) ';'};

  public static final String FG_BLACK = "30";
  public static final String FG_RED = "31";
  public static final String FG_GREEN = "32";
  public static final String FG_YELLOW = "33";
  public static final String FG_BLUE = "34";
  public static final String FG_MAGENTA = "35";
  public static final String FG_CYAN = "36";
  public static final String FG_GRAY = "37";
  public static final String BG_BLACK = "40";
  public static final String BG_RED = "41";
  public static final String BG_GREEN = "42";
  public static final String BG_YELLOW = "43";
  public static final String BG_BLUE = "44";
  public static final String BG_MAGENTA = "45";
  public static final String BG_CYAN = "46";
  public static final String BG_GRAY = "47";

  public static byte[] CR = { 13 };

  private final OutputStream out;

  /**
   * Creates an AnsiTerminal object wrapping an output stream which is going to
   * be displayed in an ANSI compatible terminal or shell window.
   *
   * @param out the output stream
   */
  public AnsiTerminal(OutputStream out) {
    this.out = out;
  }

  /**
   * Moves the cursor upwards by a specified number of lines. This will not
   * cause any scrolling if it tries to move above the top of the terminal
   * window.
   */
  public void cursorUp(int numLines) throws IOException {
    writeBytes(ESC, ("" + numLines).getBytes(), new byte[] { UP });
  }

  /**
   * Clear the current terminal line from the cursor position to the end.
   */
  public void clearLine() throws IOException {
    writeEscapeSequence(ERASE_LINE);
  }

  /**
   * Makes any text output to the terminal appear in bold.
   */
  public void textBold() throws IOException {
    writeEscapeSequence(TEXT_BOLD,  SET_GRAPHICS);
  }

  /**
   * Set the color of the foreground or background of the terminal.
   *
   * @param color one of the foreground or background color
   * constants
   */
  public void setTextColor(String color) throws IOException {
    writeBytes(ESC, color.getBytes(), new byte[] { SET_GRAPHICS });
  }

  /**
   * Resets the terminal colors and fonts to defaults.
   */
  public void resetTerminal() throws IOException {
    writeEscapeSequence((byte)'0', (byte)'m');
  }

  /**
   * Makes text print on the terminal in red.
   */
  public void textRed() throws IOException {
    setTextColor(FG_RED);
  }

  /**
   * Makes text print on the terminal in blue.
   */
  public void textBlue() throws IOException {
    setTextColor(FG_BLUE);
  }

  /**
   * Makes text print on the terminal in red.
   */
  public void textGreen() throws IOException {
    setTextColor(FG_GREEN);
  }

  /**
   * Makes text print on the terminal in red.
   */
  public void textMagenta() throws IOException {
    setTextColor(FG_MAGENTA);
  }

  /**
   * Set the terminal title.
   */
  public void setTitle(String title) throws IOException {
    writeBytes(SET_TERM_TITLE, title.getBytes(), new byte[] { BEL });
  }

  /**
   * Writes a string to the terminal using the current font, color and cursor
   * position settings.
   *
   * @param text the text to write
   */
  public void writeString(String text) throws IOException {
    out.write(text.getBytes());
  }

  /**
   * Writes a byte sequence to the terminal using the current font, color and
   * cursor position settings.
   *
   * @param bytes the bytes to write
   */
  public void writeBytes(byte[] bytes) throws IOException {
    out.write(bytes);
  }

  /**
   * Utility method which makes it easier to generate the control sequences for
   * the terminal.
   *
   * @param bytes bytes which should be prefixed with the terminal escape
   *        sequence to produce a valid control sequence
   */
  private void writeEscapeSequence(byte... bytes) throws IOException {
    writeBytes(ESC, bytes);
  }

  /**
   * Utility method for generating control sequences. Takes a collection of byte
   * arrays, which contain the components of a control sequence, concatenates
   * them, and prints them to the terminal.
   *
   * @param stuff the byte arrays that make up the sequence to be sent to the
   *        terminal
   */
  private void writeBytes(byte[]... stuff) throws IOException {
    for (byte[] bytes : stuff) {
      out.write(bytes);
    }
  }

  /**
   * Sends a carriage return to the terminal.
   */
  public void cr() throws IOException {
    writeBytes(CR);
  }

  /**
   * Flushes the underlying stream.
   * This class does not do any buffering of its own, but the underlying
   * OutputStream may.
   */
  public void flush() throws IOException {
    out.flush();
  }
}