api/middleware/dedupe.js

var logger = require('pelias-logger').get('api');
var _ = require('lodash');

function setup() {
  return dedupeResults;
}

function dedupeResults(req, res, next) {
  // do nothing if no result data set
  if (_.isUndefined(req.clean) || _.isUndefined(res) || _.isUndefined(res.data)) {
    return next();
  }

  // loop through data items and only copy unique items to uniqueResults
  var uniqueResults = [];

  _.some(res.data, function (hit) {
    if (uniqueResults.length === 0 || _.every(uniqueResults, isDifferent.bind(null, hit)) ) {
      uniqueResults.push(hit);
    }
    else {
      logger.info('[dupe]', { query: req.clean.text, hit: hit.name.default });
    }

    // stop looping when requested size has been reached in uniqueResults
    return req.clean.size <= uniqueResults.length;
  });

  res.data = uniqueResults;

  next();
}

/**
 * @param {object} item1
 * @param {object} item2
 * @returns {boolean}
 * @throws {Error}
 */
function isDifferent(item1, item2) {
  try {
    if (item1.hasOwnProperty('parent') && item2.hasOwnProperty('parent')) {
      propMatch(item1.parent, item2.parent, 'region_a');
      propMatch(item1.parent, item2.parent, 'country');
      propMatch(item1.parent, item2.parent, 'locality');
      propMatch(item1.parent, item2.parent, 'neighbourhood');
    }
    else if (item1.parent !== item2.parent) {
      throw new Error('different');
    }

    if (item1.hasOwnProperty('name') && item2.hasOwnProperty('name')) {
      for (var lang in item1.name) {
        if(item2.name[lang] || lang === 'default') {
          // do not consider absence of an additional name as a difference
          propMatch(item1.name, item2.name, lang);
        }
      }
    }
    else {
      propMatch(item1, item2, 'name');
    }

    if (item1.hasOwnProperty('address_parts') && item2.hasOwnProperty('address_parts')) {
      propMatch(item1.address_parts, item2.address_parts, 'number');
      propMatch(item1.address_parts, item2.address_parts, 'street');
      propMatch(item1.address_parts, item2.address_parts, 'zip');
    }
    else if (item1.address_parts !== item2.address_parts) {
      throw new Error('different');
    }
  }
  catch (err) {
    if (err.message === 'different') {
      return true;
    }
    throw err;
  }

  return false;
}

/**
 * Throw exception if properties are different
 *
 * @param {object} item1
 * @param {object} item2
 * @param {string} prop
 * @throws {Error}
 */
function propMatch(item1, item2, prop) {
  var prop1 = item1[prop];
  var prop2 = item2[prop];

  // in the case the property is an array (currently only in parent schema)
  // simply take the 1st item. this will change in the near future to support multiple hierarchies
  if (_.isArray(prop1)) { prop1 = prop1[0]; }
  if (_.isArray(prop2)) { prop2 = prop2[0]; }

  if (normalizeString(prop1) !== normalizeString(prop2)) {
    throw new Error('different');
  }
}

/**
 * Remove punctuation and lowercase
 *
 * @param {string} str
 * @returns {string}
 */
function normalizeString(str) {
  if (!str) {
    return '';
  }
  return str.toLowerCase().split(/[ ,-]+/).join(' ');
}


module.exports = setup;