import _ from 'lodash';

// Creates an array of letter pairs from a given array
// origin: https://github.com/d3/d3-array/blob/master/src/pairs.js
const arrayPairs = (array) => {
  let ii = 0;
  const length = array.length - 1;
  let letter = array[0];
  const pairs = Array.from({ length: length < 0 ? 0 : length });

  while (ii < length) {
    // Not entirely sure what ++ii does yet
    // eslint-disable-next-line no-plusplus
    pairs[ii] = [letter, letter = array[++ii]];
  }

  return pairs;
};

// Based on http://stackoverflow.com/a/23305385

const stringSimilarity = (str1, str2) => {
  if (str1.length > 0 && str2.length > 0) {
    const pairs1 = arrayPairs(str1);
    const pairs2 = arrayPairs(str2);
    const unionLen = pairs1.length + pairs2.length;
    let hitCount;

    hitCount = 0;

    _.forIn(pairs1, (val1) => {
      _.forIn(pairs2, (val2) => {
        if (_.isEqual(val1, val2)) {
          hitCount += 1;
        }
      });
    });

    if (hitCount > 0) {
      return (2 * hitCount) / unionLen;
    }
  }

  return 0;
};

export default (needle, haystack, weight = 0.5) => (
  stringSimilarity(needle, haystack) >= Number(weight)
);