Add DropWhile operation.

loophp · Sep 7, 2020 · cf816a3 · cf816a3
1 parent deb825d
commit cf816a3
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diff --git a/docs/pages/api.rst b/docs/pages/api.rst
@@ -463,6 +463,25 @@ Signature: ``Collection::distinct();``
     $collection = Collection::with(['a', 'b', 'c', 'd', 'a'])
         ->distinct()
 
+dropWhile
+~~~~~~~~~
+
+It inspects the original collection and takes from it its elements from the moment when the condition fails for the
+first time till the end of the list.
+
+Interface: `DropWhileable`_
+
+Signature: ``Collection::dropWhile(callable $callback);``
+
+.. code-block:: php
+
+    $isSmallerThanThree = static function (int $value): bool {
+        return 3 > $value;
+    };
+
+    Collection::fromIterable([1,2,3,4,5,6,7,8,9,1,2,3])
+        ->dropWhile($isSmallerThanThree); // [3,4,5,6,7,8,9,1,2,3]
+
 explode
 ~~~~~~~
 
@@ -1558,6 +1577,7 @@ Signature: ``Collection::zip(iterable ...$iterables);``
 .. _Diffable: https://github.com/loophp/collection/blob/master/src/Contract/Operation/Diffable.php
 .. _Diffkeysable: https://github.com/loophp/collection/blob/master/src/Contract/Operation/Diffkeysable.php
 .. _Distinctable: https://github.com/loophp/collection/blob/master/src/Contract/Operation/Distinctable.php
+.. _DropWhileable: https://github.com/loophp/collection/blob/master/src/Contract/Operation/DropWhileable.php
 .. _Explodeable: https://github.com/loophp/collection/blob/master/src/Contract/Operation/Explodeable.php
 .. _Falsyable: https://github.com/loophp/collection/blob/master/src/Contract/Operation/Falsyable.php
 .. _Filterable: https://github.com/loophp/collection/blob/master/src/Contract/Operation/Filterable.php

diff --git a/spec/loophp/collection/CollectionSpec.php b/spec/loophp/collection/CollectionSpec.php
@@ -543,6 +543,28 @@ public function it_can_do_the_cartesian_product(): void
             ->shouldIterateAs([0 => ['A', 1], 1 => ['A', 2], 2 => ['B', 1], 3 => ['B', 2], 4 => ['C', 1], 5 => ['C', 2]]);
     }
 
+    public function it_can_dropWhile(): void
+    {
+        $isSmallerThanThree = static function ($value) {
+            return 3 > $value;
+        };
+
+        $this::fromIterable([1, 2, 3, 4, 5, 6, 7, 8, 9, 1, 2, 3])
+            ->dropWhile($isSmallerThanThree)
+            ->shouldIterateAs([
+                2 => 3,
+                3 => 4,
+                4 => 5,
+                5 => 6,
+                6 => 7,
+                7 => 8,
+                8 => 9,
+                9 => 1,
+                10 => 2,
+                11 => 3,
+            ]);
+    }
+
     public function it_can_explode(): void
     {
         $string = 'I am just a random piece of text.';

diff --git a/src/Collection.php b/src/Collection.php
@@ -29,6 +29,7 @@
 use loophp\collection\Operation\Diff;
 use loophp\collection\Operation\DiffKeys;
 use loophp\collection\Operation\Distinct;
+use loophp\collection\Operation\DropWhile;
 use loophp\collection\Operation\Explode;
 use loophp\collection\Operation\Falsy;
 use loophp\collection\Operation\Filter;
@@ -324,6 +325,11 @@ public function distinct(): CollectionInterface
         return $this->run(Distinct::of());
     }
 
+    public function dropWhile(callable $callback): CollectionInterface
+    {
+        return $this->run(DropWhile::of()($callback));
+    }
+
     public static function empty(): Collection
     {
         return new self();

diff --git a/src/Contract/Collection.php b/src/Contract/Collection.php
@@ -23,6 +23,7 @@
 use loophp\collection\Contract\Operation\Diffable;
 use loophp\collection\Contract\Operation\Diffkeysable;
 use loophp\collection\Contract\Operation\Distinctable;
+use loophp\collection\Contract\Operation\DropWhileable;
 use loophp\collection\Contract\Operation\Explodeable;
 use loophp\collection\Contract\Operation\Falsyable;
 use loophp\collection\Contract\Operation\Filterable;
@@ -109,6 +110,7 @@
  * @template-extends Diffable<TKey, T>
  * @template-extends Diffkeysable<TKey, T>
  * @template-extends Distinctable<TKey, T>
+ * @template-extends DropWhileable<TKey, T>
  * @template-extends Explodeable<TKey, T>
  * @template-extends Filterable<TKey, T>
  * @template-extends Firstable<TKey, T>
@@ -185,6 +187,7 @@ interface Collection extends
     Diffable,
     Diffkeysable,
     Distinctable,
+    DropWhileable,
     Explodeable,
     Falsyable,
     Filterable,

diff --git a/src/Contract/Operation/DropWhileable.php b/src/Contract/Operation/DropWhileable.php
@@ -0,0 +1,20 @@
+<?php
+
+declare(strict_types=1);
+
+namespace loophp\collection\Contract\Operation;
+
+use loophp\collection\Contract\Collection;
+
+/**
+ * @psalm-template TKey
+ * @psalm-template TKey of array-key
+ * @psalm-template T
+ */
+interface DropWhileable
+{
+    /**
+     * @psalm-return \loophp\collection\Contract\Collection<TKey, T>
+     */
+    public function dropWhile(callable $callback): Collection;
+}
diff --git a/src/Operation/DropWhile.php b/src/Operation/DropWhile.php
@@ -0,0 +1,53 @@
+<?php
+
+declare(strict_types=1);
+
+namespace loophp\collection\Operation;
+
+use Closure;
+use Generator;
+use Iterator;
+
+/**
+ * @psalm-template TKey
+ * @psalm-template TKey of array-key
+ * @psalm-template T
+ *
+ * phpcs:disable Generic.Files.LineLength.TooLong
+ */
+final class DropWhile extends AbstractOperation
+{
+    /**
+     * @psalm-return Closure((callable(T, TKey, Iterator<TKey, T>): bool)): Closure(Iterator<TKey, T>): Generator<TKey, T>
+     */
+    public function __invoke(): Closure
+    {
+        return
+            /**
+             * @psalm-param callable(T, TKey, Iterator<TKey, T>):bool $callback
+             *
+             * @psalm-return Closure(Iterator<TKey, T>): Generator<TKey, T>
+             */
+            static function (callable $callback): Closure {
+                return
+                    /**
+                     * @psalm-param Iterator<TKey, T> $iterator
+                     *
+                     * @psalm-return Generator<TKey, T>
+                     */
+                    static function (Iterator $iterator) use ($callback): Generator {
+                        for (; $iterator->valid(); $iterator->next()) {
+                            if (true === $callback($iterator->current(), $iterator->key(), $iterator)) {
+                                continue;
+                            }
+
+                            break;
+                        }
+
+                        for (; $iterator->valid(); $iterator->next()) {
+                            yield $iterator->key() => $iterator->current();
+                        }
+                    };
+            };
+    }
+}