From e1cfe138561b137e188c85a2691b98874bbe5d4c Mon Sep 17 00:00:00 2001
From: Chris Newell <chris.newell@rd.bbc.co.uk>
Date: Wed, 12 Mar 2014 11:15:03 +0000
Subject: [PATCH] Removed dependency on JQuery

---
 engine/receng-wknn-1.0.js | 112 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 112 insertions(+)
 create mode 100644 engine/receng-wknn-1.0.js

diff --git a/engine/receng-wknn-1.0.js b/engine/receng-wknn-1.0.js
new file mode 100644
index 0000000..5c5b24b
--- /dev/null
+++ b/engine/receng-wknn-1.0.js
@@ -0,0 +1,112 @@
+function Receng() {
+  var method = "WeightedItemKNN";
+}
+
+Receng.prototype.getChoices = function(genre, type, likes, dislikes) {
+  if(!genre) genre = "all";
+  if(!type) type = "all";
+  if(!likes) likes = [];
+  if(!dislikes) dislikes = [];
+  
+  // Filter available items 
+  var selection = new Array();
+  var date = new Date();
+  for(var i in Receng.items) {
+    var item = Receng.items[i];
+
+    // Omit expired items
+    var expires = item['x'];
+    if(expires != null) {
+      var expiryDate = new Date(expires);
+      if(expiryDate < date) continue;
+    }
+    
+    if(genre == "all" || genre == item['g']) {
+      if(type == "all" || type == item['v']) { 
+        var pid = item['p'];
+        if(likes.indexOf(pid) == -1 && dislikes.indexOf(pid) == -1) selection.push(item);
+      }
+    }
+  }
+  return selection;
+};
+
+Receng.prototype.getRecs = function(genre, type, likes, dislikes) {
+  var diversify = false;
+  if(!genre) genre = "all";
+  if(!type) type = "all";
+  if(!likes) likes = [];
+  if(!dislikes) dislikes = [];
+  
+  // Filter candidate items and predict weights
+  var weights = new Array();
+  var date = new Date();
+  for(i in Receng.items) {
+    var item = Receng.items[i];
+    var pid = item['p'];
+    
+    // Omit items in likes and dislikes
+    if(likes.indexOf(pid) !== -1 || dislikes.indexOf(pid) !== -1) continue;
+      
+    // Omit expired items
+    var expires = item['x'];
+    if(expires != null) {
+      var expiryDate = new Date(expires);
+      if(expiryDate < date) continue;
+    }
+    
+    // Filter by genre and type
+    if(genre == "all" || genre == item['g']) {
+      if(type == "all" || type == item['v']) { 
+        var weight = this.predict(i, likes, dislikes);
+        weights.push({n:i, w:weight});
+      }
+    }
+  }
+  
+  // Rank items
+  weights.sort(this.inverseSortWeight);
+  var results = new Array();
+  
+  if(genre != "all" || diversify == false) {
+    for(var i=0; i < weights.length; i++) results.push(Receng.items[weights[i]['n']]);
+  } else {
+    // Diversify genre
+    var lastGenre1 = "-";
+    var lastGenre2 = "-";
+    for(var i = 0; i < weights.length; i++) {
+      var index = 0;
+      while(index < weights.length) {
+        var item = Receng.items[weights[index]['n']];
+        var itemGenre = item['g'];
+        if(itemGenre != lastGenre1 && itemGenre != lastGenre2) {
+          results.push(item);
+          weights.splice(index, 1);
+          lastGenre2 = lastGenre1;
+          lastGenre1 = itemGenre;
+          break;
+        }
+        index++;
+      }
+    }
+  }
+  return results;
+};
+
+Receng.prototype.inverseSortWeight = function(a, b) {
+  var diff = b['w'] - a['w'];
+  if(diff == 0) diff = a['n'] - b['n'];  // Fix for Chrome and Opera - preserve original order when weights are identical.
+  return diff;
+};
+
+Receng.prototype.predict = function(itemId, likes, dislikes) {
+  var weight = 0.0;
+  var neighbors = Receng.nn[itemId];
+  var weights = Receng.weights[itemId]; 
+  for(var i in neighbors) {
+    var pid = Receng.items[neighbors[i]]['p'];
+    if(likes.indexOf(pid)    !== -1) weight += weights[i];   
+    if(dislikes.indexOf(pid) !== -1) weight -= weights[i];
+  }
+  return weight;
+};