Allows to deduplicate values using a function

Author: pitchart

src/Reducer/Dedupe.php

@@ -18,6 +18,11 @@ class Dedupe implements Reducer
      */
     private $next;
 
+    /**
+     * @var callable|null
+     */
+    private $callback;
+
     /**
      * @var null|mixed
      */
@@ -28,9 +33,10 @@ class Dedupe implements Reducer
      */
     private $started = false;
 
-    public function __construct(Reducer $next)
+    public function __construct(Reducer $next, ?callable $callback = null)
     {
         $this->next = $next;
+        $this->callback = $callback;
     }
 
     public function init()
@@ -40,21 +46,22 @@ public function init()
 
     public function step($result, $current)
     {
-        if (!$this->started || $current !== $this->last) {
+        $compare = $this->callback === null ? $current : ($this->callback)($current);
+        if (!$this->started || $compare !== $this->last) {
             $return = $this->next->step($result, $current);
         } else {
             $return = $result;
         }
         $this->started = true;
-        $this->last = $current;
+        $this->last = $compare;
 
         return $return;
     }
 
     public function complete($result)
     {
         $this->last = null;
-        $this->started  = false;
+        $this->started = false;
 
         return $this->next->complete($result);
     }

src/Transducer/transducers.php

@@ -343,15 +343,15 @@ function distinct($sequence = null, ?callable $callback = null)
  * @param null|mixed $sequence
  * @return \Closure
  */
-function dedupe($sequence = null)
+function dedupe($sequence = null, ?callable $callback = null)
 {
     if ($sequence === null) {
-        return function (Reducer $reducer) {
-            return new Reducer\Dedupe($reducer);
+        return function (Reducer $reducer) use ($callback) {
+            return new Reducer\Dedupe($reducer, $callback);
         };
     }
 
-    return transduce(dedupe(), to_array(), $sequence);
+    return transduce(dedupe(null, $callback), to_array(), $sequence);
 }
 
 /**

src/Transformer.php

@@ -242,9 +242,9 @@ public function distinct(?callable $callback = null)
     /**
      * @return static
      */
-    public function dedupe()
+    public function dedupe(?callable $callback = null)
     {
-        return $this->appendComposition(t\dedupe());
+        return $this->appendComposition(t\dedupe(null, $callback));
     }
 
     /**

tests/Reducer/DedupeTest.php

@@ -33,6 +33,14 @@ public function test_removes_consecutive_equals_items()
         self::assertEquals([1, 2, 3, 2, 4, 6, 5, 1, 0, 1], $deduped);
     }
 
+    public function test_removes_consecutive_equals_items_using_a_callable()
+    {
+        $deduped = (new Transformer([1, 2, 3, 2, 2, 4, 6, 5, 1, 0, 0, 1]))
+            ->dedupe(function (int $item) { return $item % 2; })->toArray();
+
+        self::assertEquals([1, 2, 3, 2, 5, 0, 1], $deduped);
+    }
+
     public function test_is_immutable()
     {
         $transformer = (new Transformer([1, 2, 3, 2, 2, 4, 6, 5, 1, 0, 0, 1]));