Boost results with exact text matches when _score ties.

query/sort.js
	-Use the elasticsearch script introduced in
	https://github.com/pelias/scripts/pull/7 to boost results with
	exact text matches when documents' `_score`s are tied.
	-Make `query/sort` export a function that creates the `sort`
	query component, rather than the query component as a singleton,
	to allow it to optionally add the exact-match script (that is,
	when an `input` is present in `params`).

query/reverse.js

@@ -11,9 +11,9 @@ function generate( params ){
   };
 
   var query  =  queries.distance( centroid, { size: params.size || 1 } );
-  query.sort = query.sort.concat(sort);
+  query.sort = query.sort.concat( sort() );
 
   return query;
 }
 
-module.exports = generate;
+module.exports = generate;

query/search.js

@@ -45,9 +45,9 @@ function generate( params ){
     });
   }
 
-  query.sort = query.sort.concat(sort);
+  query.sort = query.sort.concat( sort( params ) );
 
   return query;
 }
 
-module.exports = generate;
+module.exports = generate;

query/sort.js

@@ -3,36 +3,53 @@ var population = 'population';
 var popularity = 'popularity';
 var weights = require('pelias-suggester-pipeline').weights;
 
-module.exports = [
-  {
-    '_script': {
-      'file': admin_boost,
-      'type': 'number',
-      'order': 'desc'
-    }
-  },
-  {
-    '_script': {
-      'file': population,
-      'type': 'number',
-      'order': 'desc'
-    }
-  },
-  {
-    '_script': {
-      'file': popularity,
-      'type': 'number',
-      'order': 'desc'
-    }
-  },
-  {
-    '_script': {
-      'params': {
-        'weights': weights
-      },
-      'file': 'weights',
-      'type': 'number',
-      'order': 'desc'
+module.exports = function( params ){
+  var scriptsConfig = [
+    {
+      '_script': {
+        'file': admin_boost,
+        'type': 'number',
+        'order': 'desc'
+      }
+    },
+    {
+      '_script': {
+        'file': population,
+        'type': 'number',
+        'order': 'desc'
+      }
+    },
+    {
+      '_script': {
+        'file': popularity,
+        'type': 'number',
+        'order': 'desc'
+      }
+    },
+    {
+      '_script': {
+        'params': {
+          'weights': weights
+        },
+        'file': 'weights',
+        'type': 'number',
+        'order': 'desc'
+      }
     }
+  ];
+
+  if( typeof params === 'object' && params.hasOwnProperty( 'input' ) ){
+    scriptsConfig.push({
+      _script: {
+        params: {
+          input: params.input
+        },
+        file: 'exact_match',
+        type: 'number',
+        order: 'desc'
+      }
+    });
   }
-];
+
+  return scriptsConfig;
+};