From 14e6c6303f9419ee69d885812ed43f3f914fdb94 Mon Sep 17 00:00:00 2001
From: Peter Johnson <insomnia@rcpt.at>
Date: Mon, 29 Oct 2018 17:13:52 +0100
Subject: [PATCH] refactor middleware dedupe for readability

---
 helper/diffPlaces.js | 206 +++++++++++++++++--------------------------
 middleware/dedupe.js | 135 ++++++++++++++--------------
 2 files changed, 153 insertions(+), 188 deletions(-)

diff --git a/helper/diffPlaces.js b/helper/diffPlaces.js
index 712c7959..ea15bd79 100644
--- a/helper/diffPlaces.js
+++ b/helper/diffPlaces.js
@@ -1,176 +1,136 @@
-var _ = require('lodash');
-var placeTypes = require('./placeTypes');
+const _ = require('lodash');
+const placeTypes = require('./placeTypes');
+const field = require('../helper/fieldValue');
 
 /**
  * Compare the layer properties if they exist.
- * Returns false if the objects are the same, and throws
- * an exception with the message 'different' if not.
- *
- * @param {object} item1
- * @param {object} item2
- * @returns {boolean}
- * @throws {Error}
+ * Returns false if the objects are the same, else true.
  */
-function assertLayerMatch(item1, item2) {
-  if (item1.layer === item2.layer) {
-    return false;
-  }
-
-  throw new Error('different');
+function isLayerDifferent(item1, item2){
+  return isPropertyDifferent(item1, item2, 'layer');
 }
 
 /**
- * Compare the parent.*_id properties if they exist.
- * Returns false if the objects are the same, and throws
- * an exception with the message 'different' if not.
- *
- * @param {object} item1
- * @param {object} item2
- * @returns {boolean}
- * @throws {Error}
+ * Compare the parent properties if they exist.
+ * Returns false if the objects are the same, else true.
  */
-function assertParentHierarchyMatch(item1, item2) {
-  // if neither object has parent, assume same
-  if (!item1.hasOwnProperty('parent') && !item2.hasOwnProperty('parent')) {
-    return false;
-  }
+function isParentHierarchyDifferent(item1, item2){
+  let parent1 = _.get(item1, 'parent');
+  let parent2 = _.get(item2, 'parent');
 
-  // if both have parent, do the rest of the checking
-  if (item1.hasOwnProperty('parent') && item2.hasOwnProperty('parent')) {
-    placeTypes.forEach(function (placeType) {
-      // don't consider its own id
-      if (placeType === item1.layer) {
-        return;
-      }
-      propMatch(item1.parent, item2.parent, placeType + '_id');
+  // if neither object has parent info, we consider them the same
+  if( !parent1 && !parent2 ){ return false; }
+
+  // both have parent info
+  if( _.isPlainObject(parent1) && _.isPlainObject(parent2) ){
+
+    // iterate over all the placetypes, comparing between items
+    return placeTypes.some( placeType => {
+
+      // skip the parent field corresponding to the item placetype
+      if( placeType === item1.layer ){ return false; }
+
+      // ensure the parent ids are the same for all placetypes
+      return isPropertyDifferent( item1.parent, item2.parent, placeType + '_id' );
     });
-    return false;
   }
 
-  // if one has parent and the other doesn't consider different
-  throw new Error('different');
+  // if one has parent info and the other doesn't, we consider them different
+  return true;
 }
 
 /**
- * Compare the name.* properties if they exist.
- * Returns false if the objects are the same, and throws
- * an exception with the message 'different' if not.
- *
- * @param {object} item1
- * @param {object} item2
- * @returns {boolean}
- * @throws {Error}
+ * Compare the name properties if they exist.
+ * Returns false if the objects are the same, else true.
  */
-function assertNameMatch(item1, item2) {
-  if (item1.hasOwnProperty('name') && item2.hasOwnProperty('name')) {
-    for (var lang in item1.name) {
-      if(item2.name.hasOwnProperty(lang) || lang === 'default') {
+function isNameDifferent(item1, item2){
+  let names1 = _.get(item1, 'name');
+  let names2 = _.get(item2, 'name');
+
+  // if neither object has name info, we consider them the same
+  if( !names1 && !names2 ){ return false; }
+
+  // if both have name info
+  if( _.isPlainObject(names1) && _.isPlainObject(names2) ){
+
+    // iterate over all the languages in item1, comparing between items
+    return Object.keys(names1).some( lang => {
+
+      // do not consider absence of an additional name as a difference
+      // but strictly enfore that 'default' must be present and match
+      if( _.has(names2, lang) || lang === 'default' ){
+
         // do not consider absence of an additional name as a difference
-        propMatch(item1.name, item2.name, lang);
+        return isPropertyDifferent(names1, names2, lang);
       }
-    }
-  }
-  else {
-    propMatch(item1, item2, 'name');
+    });
   }
+
+  // if one has name info and the other doesn't, we consider them different
+  return true;
 }
 
 /**
  * Compare the address_parts properties if they exist.
- * Returns false if the objects are the same, and throws
- * an exception with the message 'different' if not.
- *
- * @param {object} item1
- * @param {object} item2
- * @returns {boolean}
- * @throws {Error}
+ * Returns false if the objects are the same, else true.
  */
-function assertAddressMatch(item1, item2) {
-  // if neither record has address, assume same
-  if (!item1.hasOwnProperty('address_parts') && !item2.hasOwnProperty('address_parts')) {
-    return false;
-  }
+function isAddressDifferent(item1, item2){
+  let address1 = _.get(item1, 'address_parts');
+  let address2 = _.get(item2, 'address_parts');
 
-  // if both have address, check parts
-  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');
+  // if neither object has address info, we consider them the same
+  if( !address1 && !address2 ){ return false; }
+
+  // if both have address info
+  if( _.isPlainObject(address1) && _.isPlainObject(address2) ){
+
+    if( isPropertyDifferent(address1, address2, 'number') ){ return true; }
+    if( isPropertyDifferent(address1, address2, 'street') ){ return true; }
 
     // only compare zip if both records have it, otherwise just ignore and assume it's the same
     // since by this time we've already compared parent hierarchies
-    if (item1.address_parts.hasOwnProperty('zip') && item2.address_parts.hasOwnProperty('zip')) {
-      propMatch(item1.address_parts, item2.address_parts, 'zip');
+    if( _.has(address1, 'zip') && _.has(address2, 'zip') ){
+      if( isPropertyDifferent(address1, address2, 'zip') ){ return true; }
     }
 
     return false;
   }
 
   // one has address and the other doesn't, different!
-  throw new Error('different');
+  return true;
 }
 
 /**
  * Compare the two records and return true if they differ and false if same.
- *
- * @param {object} item1
- * @param {object} item2
- * @returns {boolean}
- * @throws {Error}
  */
-function isDifferent(item1, item2) {
-  try {
-    assertLayerMatch(item1, item2);
-    assertParentHierarchyMatch(item1, item2);
-    assertNameMatch(item1, item2);
-    assertAddressMatch(item1, item2);
-  }
-  catch (err) {
-    if (err.message === 'different') {
-      return true;
-    }
-    throw err;
-  }
-
+function isDifferent(item1, item2){
+  if( isLayerDifferent( item1, item2 ) ){ return true; }
+  if( isParentHierarchyDifferent( item1, item2 ) ){ return true; }
+  if( isNameDifferent( item1, item2 ) ){ return true; }
+  if( isAddressDifferent( item1, item2 ) ){ return true; }
   return false;
 }
 
 /**
- * Throw exception if properties are different
- *
- * @param {object} item1
- * @param {object} item2
- * @param {string} prop
- * @throws {Error}
+ * return true if properties are different
  */
-function propMatch(item1, item2, prop) {
-  var prop1 = item1[prop];
-  var prop2 = item2[prop];
+function isPropertyDifferent(item1, 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 neither item has prop, we consider them the same
+  if( !_.has(item1, prop) && !_.has(item2, prop) ){ return false; }
 
-  if (normalizeString(prop1) !== normalizeString(prop2)) {
-    throw new Error('different');
-  }
+  // handle arrays and other non-string values
+  var prop1 = field.getStringValue( _.get( item1, prop ) );
+  var prop2 = field.getStringValue( _.get( item2, prop ) );
+
+  // compare strings
+  return normalizeString(prop1) !== normalizeString(prop2);
 }
 
 /**
- * Remove punctuation and lowercase
- *
- * @param {string} str
- * @returns {string}
+ * lowercase characters and remove some punctuation
  */
-function normalizeString(str) {
-  if (!_.isString(str)) {
-    return str;
-  }
-
-  if (_.isEmpty(str)) {
-    return '';
-  }
-
+function normalizeString(str){
   return str.toLowerCase().split(/[ ,-]+/).join(' ');
 }
 
diff --git a/middleware/dedupe.js b/middleware/dedupe.js
index 4b637ed5..ba9e70e7 100644
--- a/middleware/dedupe.js
+++ b/middleware/dedupe.js
@@ -3,87 +3,92 @@ const _ = require('lodash');
 const isDifferent = require('../helper/diffPlaces').isDifferent;
 const field = require('../helper/fieldValue');
 
-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 = [];
+  // do nothing if request data is invalid
+  if( _.isUndefined(res) || !_.isPlainObject(req.clean) ){ return next(); }
+
+  // do nothing if no result data is invalid
+  if( _.isUndefined(res) || !_.isArray(res.data) || _.isEmpty(res.data) ){ return next(); }
+
+  // loop through data items and only copy unique items to unique
+  // note: the first reqults must always be unique!
+  let unique = [ res.data[0] ];
+
+  // convenience function to search unique array for an existing element which matches a hit
+  let findMatch = (hit) => unique.findIndex(elem => !isDifferent(elem, hit));
+
+  // iterate over res.data using an old-school for loop starting at index 1
+  // we can call break at any time to end the iterator
+  for( let i=1; i<res.data.length; i++){
+    let hit = res.data[i];
+
+    // if there are multiple items in results, loop through them to find a dupe
+    // save off the index of the dupe if found
+    let dupeIndex = findMatch(hit);
+
+    // if a dupe is not found, just add to list of unique hits and continue
+    if( dupeIndex === -1 ){ unique.push(hit); }
+
+    // if dupe was found, we need to check which of the records is preferred
+    // since the order in which Elasticsearch returns identical text matches is arbitrary
+    // of course, if the new one is preferred we should replace previous with new
+    else if( isPreferred( unique[dupeIndex], hit ) ) {
 
-  _.some(res.data, function (hit) {
+      // replace previous dupe item with current hit
+      unique[dupeIndex] = hit;
 
-    if (_.isEmpty(uniqueResults)) {
-      uniqueResults.push(hit);
+      // logging
+      logger.debug('[dupe][replacing]', {
+        query: req.clean.text,
+        previous: unique[dupeIndex].source,
+        hit: field.getStringValue(hit.name.default) + ' ' + hit.source + ':' + hit._id
+      });
     }
+
+    // if not preferred over existing, just log and continue
     else {
-      // if there are multiple items in results, loop through them to find a dupe
-      // save off the index of the dupe if found
-      var dupeIndex = uniqueResults.findIndex(function (elem, index, array) {
-        return !isDifferent(elem, hit);
+      logger.debug('[dupe][skipping]', {
+        query: req.clean.text,
+        previous: unique[dupeIndex].source,
+        hit: field.getStringValue(hit.name.default) + ' ' + hit.source + ':' + hit._id
       });
-
-      // if a dupe is not found, just add to results and move on
-      if (dupeIndex === -1) {
-        uniqueResults.push(hit);
-      }
-      // if dupe was found, we need to check which of the records is preferred
-      // since the order in which Elasticsearch returns identical text matches is arbitrary
-      // of course, if the new one is preferred we should replace previous with new
-      else if (isPreferred(uniqueResults[dupeIndex], hit)) {
-        logger.debug('[dupe][replacing]', {
-          query: req.clean.text,
-          previous: uniqueResults[dupeIndex].source,
-          hit: field.getStringValue(hit.name.default) + ' ' + hit.source + ':' + hit._id
-        });
-        // replace previous dupe item with current hit
-        uniqueResults[dupeIndex] = hit;
-      }
-      // if not preferred over existing, just log and move on
-      else {
-        logger.debug('[dupe][skipping]', {
-          query: req.clean.text,
-          previous: uniqueResults[dupeIndex].source,
-          hit: field.getStringValue(hit.name.default) + ' ' + hit.source + ':' + hit._id
-        });
-      }
     }
 
-    // stop looping when requested size has been reached in uniqueResults
-    return req.clean.size <= uniqueResults.length;
-  });
+    // stop iterating when requested size has been reached in unique
+    if( unique.length >= req.clean.size ){ break; }
+  }
 
-  res.data = uniqueResults;
+  // replace the original data with only the unique hits
+  res.data = unique;
 
   next();
 }
 
-function isPreferred(existing, candidateReplacement) {
-  // NOTE: we are assuming here that the layer for both records is the same
-  const hasZip = _.bind(_.has, null, _.bind.placeholder, 'address_parts.zip');
+// return true if the second argument represents a hit which is preferred
+// to the hit in the first argument
+function isPreferred(existingHit, candidateHit) {
 
+  // prefer a record with a postcode
   // https://github.com/pelias/api/issues/872
-  const candidateHasZip = hasZip(candidateReplacement);
-  const existingHasZip = hasZip(existing);
-  if (candidateHasZip !== existingHasZip) {
-    return candidateHasZip;
-  }
+  if( !_.has(existingHit, 'address_parts.zip') &&
+       _.has(candidateHit, 'address_parts.zip') ){ return true; }
 
-  //bind the trumps function to the data items to keep the rest of the function clean
-  var trumpsFunc = trumps.bind(null, existing, candidateReplacement);
-
-  return trumpsFunc('geonames', 'whosonfirst') || // WOF has bbox and is generally preferred
-         trumpsFunc('openstreetmap', 'openaddresses') || // addresses are better in OA
-         trumpsFunc('whosonfirst', 'openstreetmap'); // venues are better in OSM, at this time
-}
-
-function trumps(existing, candidateReplacement, loserSource, winnerSource) {
-  return existing.source === loserSource && candidateReplacement.source === winnerSource;
+  // prefer certain sources over others
+  switch( existingHit.source ){
+    // sources are the same
+    case candidateHit.source: return false;
+    // WOF has bbox and is generally preferred
+    case 'geonames': return candidateHit.source === 'whosonfirst';
+    // addresses are generally better in OA
+    case 'openstreetmap': return candidateHit.source === 'openaddresses';
+    // venues are better in OSM
+    case 'whosonfirst': return candidateHit.source === 'openstreetmap';
+    // no preference, keep existing hit
+    default: return false;
+  }
 }
 
-module.exports = setup;
+module.exports = function() {
+  return dedupeResults;
+};