hterm_parser.js

// Copyright (c) 2015 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

'use strict';

/**
 * Parses the key definition syntax used for user keyboard customizations.
 *
 * @constructor
 */
hterm.Parser = function() {
  /**
   * @type {string} The source string.
   */
  this.source = '';

  /**
   * @type {number} The current position.
   */
  this.pos = 0;

  /**
   * @type {?string} The character at the current position.
   */
  this.ch = null;
};

/**
 * @param {string} message
 * @return {!Error}
 */
hterm.Parser.prototype.error = function(message) {
  return new Error('Parse error at ' + this.pos + ': ' + message);
};

/** @return {boolean} */
hterm.Parser.prototype.isComplete = function() {
  return this.pos == this.source.length;
};

/**
 * @param {string} source
 * @param {number=} pos
 */
hterm.Parser.prototype.reset = function(source, pos = 0) {
  this.source = source;
  this.pos = pos;
  this.ch = source.substr(0, 1);
};

/**
 * Parse a key sequence.
 *
 * A key sequence is zero or more of the key modifiers defined in
 * hterm.Parser.identifiers.modifierKeys followed by a key code.  Key
 * codes can be an integer or an identifier from
 * hterm.Parser.identifiers.keyCodes.  Modifiers and keyCodes should be joined
 * by the dash character.
 *
 * An asterisk "*" can be used to indicate that the unspecified modifiers
 * are optional.
 *
 * For example:
 *   A: Matches only an unmodified "A" character.
 *   65: Same as above.
 *   0x41: Same as above.
 *   Ctrl+A: Matches only Ctrl+A.
 *   Ctrl+65: Same as above.
 *   Ctrl+0x41: Same as above.
 *   Ctrl+Shift+A: Matches only Ctrl+Shift+A.
 *   Ctrl+*+A: Matches Ctrl+A, as well as any other key sequence that includes
 *     at least the Ctrl and A keys.
 *
 * @return {!hterm.Keyboard.KeyDown} An object with shift, ctrl, alt, meta,
 *     keyCode properties.
 */
hterm.Parser.prototype.parseKeySequence = function() {
  const rv = {
    keyCode: null,
  };

  for (const k in hterm.Parser.identifiers.modifierKeys) {
    rv[hterm.Parser.identifiers.modifierKeys[k]] = false;
  }

  while (this.pos < this.source.length) {
    this.skipSpace();

    const token = this.parseToken();
    if (token.type == 'integer') {
      rv.keyCode = token.value;

    } else if (token.type == 'identifier') {
      const ucValue = token.value.toUpperCase();
      if (ucValue in hterm.Parser.identifiers.modifierKeys &&
          hterm.Parser.identifiers.modifierKeys.hasOwnProperty(ucValue)) {
        const mod = hterm.Parser.identifiers.modifierKeys[ucValue];
        if (rv[mod] && rv[mod] != '*') {
          throw this.error('Duplicate modifier: ' + token.value);
        }
        rv[mod] = true;

      } else if (ucValue in hterm.Parser.identifiers.keyCodes &&
                 hterm.Parser.identifiers.keyCodes.hasOwnProperty(ucValue)) {
        rv.keyCode = hterm.Parser.identifiers.keyCodes[ucValue];

      } else {
        throw this.error('Unknown key: ' + token.value);
      }

    } else if (token.type == 'symbol') {
      if (token.value == '*') {
        for (const id in hterm.Parser.identifiers.modifierKeys) {
          const p = hterm.Parser.identifiers.modifierKeys[id];
          if (!rv[p]) {
            rv[p] = '*';
          }
        }
      } else {
        throw this.error('Unexpected symbol: ' + token.value);
      }
    } else {
      throw this.error('Expected integer or identifier');
    }

    this.skipSpace();

    if (this.ch !== '-' && this.ch !== '+') {
      break;
    }

    if (rv.keyCode != null) {
      throw this.error('Extra definition after target key');
    }

    this.advance(1);
  }

  if (rv.keyCode == null) {
    throw this.error('Missing target key');
  }

  return rv;
};

/** @return {string} */
hterm.Parser.prototype.parseKeyAction = function() {
  this.skipSpace();

  const token = this.parseToken();

  if (token.type == 'string') {
    return token.value;
  }

  if (token.type == 'identifier') {
    if (token.value in hterm.Parser.identifiers.actions &&
        hterm.Parser.identifiers.actions.hasOwnProperty(token.value)) {
      return hterm.Parser.identifiers.actions[token.value];
    }

    throw this.error('Unknown key action: ' + token.value);
  }

  throw this.error('Expected string or identifier');

};

/** @return {boolean} */
hterm.Parser.prototype.peekString = function() {
  return this.ch == '\'' || this.ch == '"';
};

/** @return {boolean} */
hterm.Parser.prototype.peekIdentifier = function() {
  return !!this.ch.match(/[a-z_]/i);
};

/** @return {boolean} */
hterm.Parser.prototype.peekInteger = function() {
  return !!this.ch.match(/[0-9]/);
};

/** @return {!Object} */
hterm.Parser.prototype.parseToken = function() {
  if (this.ch == '*') {
    const rv = {type: 'symbol', value: this.ch};
    this.advance(1);
    return rv;
  }

  if (this.peekIdentifier()) {
    return {type: 'identifier', value: this.parseIdentifier()};
  }

  if (this.peekString()) {
    return {type: 'string', value: this.parseString()};
  }

  if (this.peekInteger()) {
    return {type: 'integer', value: this.parseInteger()};
  }

  throw this.error('Unexpected token');
};

/** @return {string} */
hterm.Parser.prototype.parseIdentifier = function() {
  if (!this.peekIdentifier()) {
    throw this.error('Expected identifier');
  }

  return this.parsePattern(/[a-z0-9_]+/ig);
};

/** @return {number} */
hterm.Parser.prototype.parseInteger = function() {
  if (this.ch == '0' && this.pos < this.source.length - 1 &&
      this.source.substr(this.pos + 1, 1) == 'x') {
    /* eslint-disable radix */
    return parseInt(this.parsePattern(/0x[0-9a-f]+/gi), undefined);
  }

  return parseInt(this.parsePattern(/\d+/g), 10);
};

/**
 * Parse a single or double quoted string.
 *
 * The current position should point at the initial quote character.  Single
 * quoted strings will be treated literally, double quoted will process escapes.
 *
 * TODO(rginda): Variable interpolation.
 *
 * @return {string}
 */
hterm.Parser.prototype.parseString = function() {
  let result = '';

  const quote = this.ch;
  if (quote != '"' && quote != '\'') {
    throw this.error('String expected');
  }

  this.advance(1);

  const re = new RegExp('[\\\\' + quote + ']', 'g');

  while (this.pos < this.source.length) {
    re.lastIndex = this.pos;
    if (!re.exec(this.source)) {
      throw this.error('Unterminated string literal');
    }

    result += this.source.substring(this.pos, re.lastIndex - 1);

    this.advance(re.lastIndex - this.pos - 1);

    if (quote == '"' && this.ch == '\\') {
      this.advance(1);
      result += this.parseEscape();
      continue;
    }

    if (quote == '\'' && this.ch == '\\') {
      result += this.ch;
      this.advance(1);
      continue;
    }

    if (this.ch == quote) {
      this.advance(1);
      return result;
    }
  }

  throw this.error('Unterminated string literal');
};


/**
 * Parse an escape code from the current position (which should point to
 * the first character AFTER the leading backslash.)
 *
 * @return {string}
 */
hterm.Parser.prototype.parseEscape = function() {
  const map = {
    '"': '"',
    '\'': '\'',
    '\\': '\\',
    'a': '\x07',
    'b': '\x08',
    'e': '\x1b',
    'f': '\x0c',
    'n': '\x0a',
    'r': '\x0d',
    't': '\x09',
    'v': '\x0b',
    'x': function() {
      const value = this.parsePattern(/[a-z0-9]{2}/ig);
      return String.fromCharCode(parseInt(value, 16));
    },
    'u': function() {
      const value = this.parsePattern(/[a-z0-9]{4}/ig);
      return String.fromCharCode(parseInt(value, 16));
    },
  };

  if (!(this.ch in map && map.hasOwnProperty(this.ch))) {
    throw this.error('Unknown escape: ' + this.ch);
  }

  let value = map[this.ch];
  this.advance(1);

  if (typeof value == 'function') {
    value = value.call(this);
  }

  return value;
};

/**
 * Parse the given pattern starting from the current position.
 *
 * @param {!RegExp} pattern A pattern representing the characters to span.  MUST
 *   include the "global" RegExp flag.
 * @return {string}
 */
hterm.Parser.prototype.parsePattern = function(pattern) {
  if (!pattern.global) {
    throw this.error('Internal error: Span patterns must be global');
  }

  pattern.lastIndex = this.pos;
  const ary = pattern.exec(this.source);

  if (!ary || pattern.lastIndex - ary[0].length != this.pos) {
    throw this.error('Expected match for: ' + pattern);
  }

  this.pos = pattern.lastIndex - 1;
  this.advance(1);

  return ary[0];
};


/**
 * Advance the current position.
 *
 * @param {number} count
 */
hterm.Parser.prototype.advance = function(count) {
  this.pos += count;
  this.ch = this.source.substr(this.pos, 1);
};

/**
 * @param {string=} expect A list of valid non-whitespace characters to
 *   terminate on.
 * @return {void}
 */
hterm.Parser.prototype.skipSpace = function(expect = undefined) {
  if (!/\s/.test(this.ch)) {
    return;
  }

  const re = /\s+/gm;
  re.lastIndex = this.pos;

  const source = this.source;
  if (re.exec(source)) {
    this.pos = re.lastIndex;
  }

  this.ch = this.source.substr(this.pos, 1);

  if (expect) {
    if (this.ch.indexOf(expect) == -1) {
      throw this.error(`Expected one of ${expect}, found: ${this.ch}`);
    }
  }
};