added objective function addition to function score query

Query/FunctionScoreQuery.php

@@ -24,6 +24,10 @@ class FunctionScoreQuery implements BuilderInterface
     use DslTypeAwareTrait;
 
     /**
+     * Query of filter.
+     *
+     * In Function score could be used query or filter. Use setDslType() to change type.
+     *
      * @var BuilderInterface
      */
     private $query;
@@ -35,13 +39,11 @@ class FunctionScoreQuery implements BuilderInterface
 
     /**
      * @param BuilderInterface $query
-     * @param array            $functions
      * @param array            $parameters
      */
-    public function __construct(BuilderInterface $query, array $functions, array $parameters = [])
+    public function __construct(BuilderInterface $query, array $parameters = [])
     {
         $this->query = $query;
-        $this->functions = $functions;
         $this->setParameters($parameters);
         $this->setDslType('query');
     }
@@ -54,6 +56,167 @@ class FunctionScoreQuery implements BuilderInterface
         return 'function_score';
     }
 
+    /**
+     * Modifier to apply filter to the function score function.
+     *
+     * @param array            $function
+     * @param BuilderInterface $filter
+     */
+    private function applyFilter(array &$function, BuilderInterface $filter = null)
+    {
+        if ($filter) {
+            $function['filter'] = [
+                $filter->getType() => $filter->toArray(),
+            ];
+        }
+    }
+
+    /**
+     * Creates field_value_factor function.
+     *
+     * @param string           $field
+     * @param float            $factor
+     * @param string           $modifier
+     * @param BuilderInterface $filter
+     *
+     * @return $this
+     */
+    public function addFieldValueFactorFunction($field, $factor, $modifier, BuilderInterface $filter = null)
+    {
+        $function = [
+            'field_value_factor' => [
+                'field' => $field,
+                'factor' => $factor,
+                'modifier' => $modifier,
+            ],
+        ];
+
+        $this->applyFilter($function, $filter);
+
+        $this->functions[] = $function;
+
+        return $this;
+    }
+
+    /**
+     * Add decay function to function score. Weight and filter are optional.
+     *
+     * @param string           $type
+     * @param string           $field
+     * @param array            $function
+     * @param array            $options
+     * @param BuilderInterface $filter
+     *
+     * @return $this
+     */
+    public function addDecayFunction(
+        $type,
+        $field,
+        array $function,
+        array $options = [],
+        BuilderInterface $filter = null
+    ) {
+        $function = [
+            $type => [
+                $field => $function,
+            ],
+            $options
+        ];
+
+        $this->applyFilter($function, $filter);
+
+        $this->functions[] = $function;
+
+        return $this;
+    }
+
+    /**
+     * Adds function to function score without decay function. Influence search score only for specific filter.
+     *
+     * @param float            $weight
+     * @param BuilderInterface $filter
+     *
+     * @return $this
+     */
+    public function addWeightFunction($weight, BuilderInterface $filter = null)
+    {
+        $function = [
+            'weight' => $weight,
+        ];
+
+        $this->applyFilter($function, $filter);
+
+        $this->functions[] = $function;
+
+        return $this;
+    }
+
+    /**
+     * Adds random score function. Seed is optional.
+     *
+     * @param mixed            $seed
+     * @param BuilderInterface $filter
+     *
+     * @return $this
+     */
+    public function addRandomFunction($seed = null, BuilderInterface $filter = null)
+    {
+        $function = [
+            'random_score' => $seed ? [ 'seed' => $seed ] : [],
+        ];
+
+        $this->applyFilter($function, $filter);
+
+        $this->functions[] = $function;
+
+        return $this;
+    }
+
+    /**
+     * Adds script score function.
+     *
+     * @param string           $script
+     * @param array            $params
+     * @param array            $options
+     * @param BuilderInterface $filter
+     *
+     * @return $this
+     */
+    public function addScriptScoreFunction(
+        $script,
+        array $params = [],
+        array $options = [],
+        BuilderInterface $filter = null
+    ) {
+        $function = [
+            'script_score' => [
+                'script' => $script,
+                'params' => $params,
+                $options
+            ],
+        ];
+
+        $this->applyFilter($function, $filter);
+
+        $this->functions[] = $function;
+
+        return $this;
+    }
+
+    /**
+     * Adds custom simple function. You can add to the array whatever you want.
+     *
+     * @param array $function
+     *
+     * @return $this
+     */
+    public function addSimpleFunction(array $function)
+    {
+        $this->functions[] = $function;
+
+        return $this;
+    }
+
     /**
      * {@inheritdoc}
      */
@@ -63,7 +226,7 @@ class FunctionScoreQuery implements BuilderInterface
             strtolower($this->getDslType()) => [
                 $this->query->getType() => $this->query->toArray(),
             ],
-            'functions' => [$this->functions],
+            'functions' => $this->functions,
         ];
 
         $output = $this->processArray($query);