char-class-to-meta-transform.js

/**
 * The MIT License (MIT)
 * Copyright (c) 2017-present Dmitry Soshnikov <dmitry.soshnikov@gmail.com>
 */

'use strict';

/**
 * A regexp-tree plugin to replace standard character classes with
 * their meta symbols equivalents.
 */

module.exports = {
  _hasIFlag: false,
  _hasUFlag: false,
  init: function init(ast) {
    this._hasIFlag = ast.flags.includes('i');
    this._hasUFlag = ast.flags.includes('u');
  },
  CharacterClass: function CharacterClass(path) {

    // [0-9] -> \d
    rewriteNumberRanges(path);

    // [a-zA-Z_0-9] -> \w
    rewriteWordRanges(path, this._hasIFlag, this._hasUFlag);

    // [ \t\r\n\f] -> \s
    rewriteWhitespaceRanges(path);
  }
};

/**
 * Rewrites number ranges: [0-9] -> \d
 */
function rewriteNumberRanges(path) {
  var node = path.node;


  node.expressions.forEach(function (expression, i) {
    if (isFullNumberRange(expression)) {
      path.getChild(i).replace({
        type: 'Char',
        value: '\\d',
        kind: 'meta'
      });
    }
  });
}

/**
 * Rewrites word ranges: [a-zA-Z_0-9] -> \w
 * Thus, the ranges may go in any order, and other symbols/ranges
 * are kept untouched, e.g. [a-z_\dA-Z$] -> [\w$]
 */
function rewriteWordRanges(path, hasIFlag, hasUFlag) {
  var node = path.node;


  var numberPath = null;
  var lowerCasePath = null;
  var upperCasePath = null;
  var underscorePath = null;
  var u017fPath = null;
  var u212aPath = null;

  node.expressions.forEach(function (expression, i) {

    // \d
    if (isMetaChar(expression, '\\d')) {
      numberPath = path.getChild(i);
    }

    // a-z
    else if (isLowerCaseRange(expression)) {
        lowerCasePath = path.getChild(i);
      }

      // A-Z
      else if (isUpperCaseRange(expression)) {
          upperCasePath = path.getChild(i);
        }

        // _
        else if (isUnderscore(expression)) {
            underscorePath = path.getChild(i);
          } else if (hasIFlag && hasUFlag && isU017fPath(expression)) {
            u017fPath = path.getChild(i);
          } else if (hasIFlag && hasUFlag && isU212aPath(expression)) {
            u212aPath = path.getChild(i);
          }
  });

  // If we found the whole pattern, replace it.
  if (numberPath && (lowerCasePath && upperCasePath || hasIFlag && (lowerCasePath || upperCasePath)) && underscorePath && (!hasUFlag || !hasIFlag || u017fPath && u212aPath)) {

    // Put \w in place of \d.
    numberPath.replace({
      type: 'Char',
      value: '\\w',
      kind: 'meta'
    });

    // Other paths are removed.
    if (lowerCasePath) {
      lowerCasePath.remove();
    }
    if (upperCasePath) {
      upperCasePath.remove();
    }
    underscorePath.remove();
    if (u017fPath) {
      u017fPath.remove();
    }
    if (u212aPath) {
      u212aPath.remove();
    }
  }
}

/**
 * Rewrites whitespace ranges: [ \t\r\n\f] -> \s.
 */
function rewriteWhitespaceRanges(path) {
  var node = path.node;


  var spacePath = null;
  var tPath = null;
  var nPath = null;
  var rPath = null;
  var fPath = null;

  node.expressions.forEach(function (expression, i) {

    // Space
    if (isChar(expression, ' ')) {
      spacePath = path.getChild(i);
    }

    // \t
    else if (isMetaChar(expression, '\\t')) {
        tPath = path.getChild(i);
      }

      // \n
      else if (isMetaChar(expression, '\\n')) {
          nPath = path.getChild(i);
        }

        // \r
        else if (isMetaChar(expression, '\\r')) {
            rPath = path.getChild(i);
          }

          // \f
          else if (isMetaChar(expression, '\\f')) {
              fPath = path.getChild(i);
            }
  });

  // If we found the whole pattern, replace it.
  // Make \f optional.
  if (spacePath && tPath && nPath && rPath) {

    // Put \s in place of \n.
    nPath.node.value = '\\s';

    // Other paths are removed.
    spacePath.remove();
    tPath.remove();
    rPath.remove();

    if (fPath) {
      fPath.remove();
    }
  }
}

function isFullNumberRange(node) {
  return node.type === 'ClassRange' && node.from.value === '0' && node.to.value === '9';
}

function isChar(node, value) {
  var kind = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : 'simple';

  return node.type === 'Char' && node.value === value && node.kind === kind;
}

function isMetaChar(node, value) {
  return isChar(node, value, 'meta');
}

function isLowerCaseRange(node) {
  return node.type === 'ClassRange' && node.from.value === 'a' && node.to.value === 'z';
}

function isUpperCaseRange(node) {
  return node.type === 'ClassRange' && node.from.value === 'A' && node.to.value === 'Z';
}

function isUnderscore(node) {
  return node.type === 'Char' && node.value === '_' && node.kind === 'simple';
}

function isU017fPath(node) {
  return node.type === 'Char' && node.kind === 'unicode' && node.codePoint === 0x017f;
}
function isU212aPath(node) {
  return node.type === 'Char' && node.kind === 'unicode' && node.codePoint === 0x212a;
}