pattern_matching.js

function parse(pattern, query) {
  const patternWords = pattern.split(' ');
  const queryWords = query.split(' ');
  const sol = {};

  if (!match(patternWords, 0, queryWords, 0, sol)) {
    return null;
  }

  return sol;
}

function isParameterPattern(word) {
  return Boolean(word.charAt(0) == '$');
}

function isParameterName(word) {
  return word.substr(1);
}

const NUMBER_TEST = /^[0-9]+$/;

function isValidValue(paramName, value) {
  if (paramName == 'Number') {
    return NUMBER_TEST.test(value);
  }
  return value != '';
}

function match(patternWords, i, queryWords, j, sol) {
  if (i >= patternWords.length && j >= queryWords.length) {
    return true;
  }
  if (i >= patternWords.length || j >= queryWords.length) {
    return false;
  }
  if (isParameterPattern(patternWords[i])) {
    const paramName = isParameterName(patternWords[i]);

    const currParamValue = sol[paramName] || '';
    const newValue = currParamValue + queryWords[j];

    if (isValidValue(paramName, newValue)) {
      sol[paramName] = newValue;
      if (
        match(patternWords, i, queryWords, j + 1, sol) ||
        match(patternWords, i + 1, queryWords, j + 1, sol)
      ) {
        return true;
      }
      sol[paramName] = currParamValue;
    } else {
      sol[paramName] = newValue;
      if (match(patternWords, i, queryWords, j + 1, sol)) {
        return true;
      }
      sol[paramName] = currParamValue;
    }
  } else {
    if (patternWords[i] === queryWords[j]) {
      if (match(patternWords, i + 1, queryWords, j + 1, sol)) {
        return true;
      }
    }
  }
  return false;
}