securityos/node_modules/regexp-tree/dist/optimizer/transforms/quantifiers-merge-transform.js

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

'use strict';

var _require = require('../../transform/utils'),
    increaseQuantifierByOne = _require.increaseQuantifierByOne;

/**
 * A regexp-tree plugin to merge quantifiers
 *
 * a+a+ -> a{2,}
 * a{2}a{3} -> a{5}
 * a{1,2}a{2,3} -> a{3,5}
 */


module.exports = {
  Repetition: function Repetition(path) {
    var node = path.node,
        parent = path.parent;


    if (parent.type !== 'Alternative' || !path.index) {
      return;
    }

    var previousSibling = path.getPreviousSibling();

    if (!previousSibling) {
      return;
    }

    if (previousSibling.node.type === 'Repetition') {
      if (!previousSibling.getChild().hasEqualSource(path.getChild())) {
        return;
      }

      var _extractFromTo = extractFromTo(previousSibling.node.quantifier),
          previousSiblingFrom = _extractFromTo.from,
          previousSiblingTo = _extractFromTo.to;

      var _extractFromTo2 = extractFromTo(node.quantifier),
          nodeFrom = _extractFromTo2.from,
          nodeTo = _extractFromTo2.to;

      // It's does not seem reliable to merge quantifiers with different greediness
      // when none of both is a greedy open range


      if (previousSibling.node.quantifier.greedy !== node.quantifier.greedy && !isGreedyOpenRange(previousSibling.node.quantifier) && !isGreedyOpenRange(node.quantifier)) {
        return;
      }

      // a*a* -> a*
      // a*a+ -> a+
      // a+a+ -> a{2,}
      // a{2}a{4} -> a{6}
      // a{1,2}a{2,3} -> a{3,5}
      // a{1,}a{2,} -> a{3,}
      // a+a{2,} -> a{3,}

      // a??a{2,} -> a{2,}
      // a*?a{2,} -> a{2,}
      // a+?a{2,} -> a{3,}

      node.quantifier.kind = 'Range';
      node.quantifier.from = previousSiblingFrom + nodeFrom;
      if (previousSiblingTo && nodeTo) {
        node.quantifier.to = previousSiblingTo + nodeTo;
      } else {
        delete node.quantifier.to;
      }
      if (isGreedyOpenRange(previousSibling.node.quantifier) || isGreedyOpenRange(node.quantifier)) {
        node.quantifier.greedy = true;
      }

      previousSibling.remove();
    } else {
      if (!previousSibling.hasEqualSource(path.getChild())) {
        return;
      }

      increaseQuantifierByOne(node.quantifier);
      previousSibling.remove();
    }
  }
};

function isGreedyOpenRange(quantifier) {
  return quantifier.greedy && (quantifier.kind === '+' || quantifier.kind === '*' || quantifier.kind === 'Range' && !quantifier.to);
}

function extractFromTo(quantifier) {
  var from = void 0,
      to = void 0;
  if (quantifier.kind === '*') {
    from = 0;
  } else if (quantifier.kind === '+') {
    from = 1;
  } else if (quantifier.kind === '?') {
    from = 0;
    to = 1;
  } else {
    from = quantifier.from;
    if (quantifier.to) {
      to = quantifier.to;
    }
  }
  return { from: from, to: to };
}