feat: Add Unwindow operation.

docs/pages/api.rst

@@ -1548,6 +1548,31 @@ Signature: ``Collection::until(callable ...$callbacks);``
             return 1 === $number;
         });
 
+unwindow
+~~~~~~~~
+
+Contrary of ``Collection::window()``, usually needed after a call to that operation.
+
+Interface: `Unwindowable`_
+
+Signature: ``Collection::unwindow();``
+
+.. code-block:: php
+
+    // Drop all the items before finding five 9 in a row.
+    $input = [1, 2, 3, 4, 5, 6, 7, 8, 9, 9, 9, 9, 9, 1, 2, 3, 4, 5, 6, 7, 8];
+
+    Collection::fromIterable($input)
+        ->window(4)
+        ->dropWhile(
+            static function (array $value): bool {
+                return $value !== [9, 9, 9, 9, 9];
+            }
+        )
+        ->unwindow()
+        ->drop(1)
+        ->normalize(); // [1, 2, 3, 4, 5, 6, 7, 8]
+
 unwrap
 ~~~~~~
 
@@ -1707,6 +1732,7 @@ Signature: ``Collection::zip(iterable ...$iterables);``
 .. _Unpackable: https://github.com/loophp/collection/blob/master/src/Contract/Operation/Unpackagle.php
 .. _Unpairable: https://github.com/loophp/collection/blob/master/src/Contract/Operation/Unpairable.php
 .. _Untilable: https://github.com/loophp/collection/blob/master/src/Contract/Operation/Untilable.php
+.. _Unwindowable: https://github.com/loophp/collection/blob/master/src/Contract/Operation/Unwindowable.php
 .. _Unwrapable: https://github.com/loophp/collection/blob/master/src/Contract/Operation/Unwrapable.php
 .. _Unzipable: https://github.com/loophp/collection/blob/master/src/Contract/Operation/Unzipable.php
 .. _Windowable: https://github.com/loophp/collection/blob/master/src/Contract/Operation/Windowable.php

spec/loophp/collection/CollectionSpec.php

@@ -2021,6 +2021,141 @@ public function it_can_until(): void
             ]);
     }
 
+    public function it_can_unwindow(): void
+    {
+        $this::fromIterable([
+            0 => [
+                0 => 'a',
+            ],
+            1 => [
+                0 => 'a',
+                1 => 'b',
+            ],
+            2 => [
+                0 => 'a',
+                1 => 'b',
+                2 => 'c',
+            ],
+            3 => [
+                0 => 'b',
+                1 => 'c',
+                2 => 'd',
+            ],
+            4 => [
+                0 => 'c',
+                1 => 'd',
+                2 => 'e',
+            ],
+            5 => [
+                0 => 'd',
+                1 => 'e',
+                2 => 'f',
+            ],
+            6 => [
+                0 => 'e',
+                1 => 'f',
+                2 => 'g',
+            ],
+            7 => [
+                0 => 'f',
+                1 => 'g',
+                2 => 'h',
+            ],
+            8 => [
+                0 => 'g',
+                1 => 'h',
+                2 => 'i',
+            ],
+            9 => [
+                0 => 'h',
+                1 => 'i',
+                2 => 'j',
+            ],
+            10 => [
+                0 => 'i',
+                1 => 'j',
+                2 => 'k',
+            ],
+            11 => [
+                0 => 'j',
+                1 => 'k',
+                2 => 'l',
+            ],
+            12 => [
+                0 => 'k',
+                1 => 'l',
+                2 => 'm',
+            ],
+            13 => [
+                0 => 'l',
+                1 => 'm',
+                2 => 'n',
+            ],
+            14 => [
+                0 => 'm',
+                1 => 'n',
+                2 => 'o',
+            ],
+            15 => [
+                0 => 'n',
+                1 => 'o',
+                2 => 'p',
+            ],
+            16 => [
+                0 => 'o',
+                1 => 'p',
+                2 => 'q',
+            ],
+            17 => [
+                0 => 'p',
+                1 => 'q',
+                2 => 'r',
+            ],
+            18 => [
+                0 => 'q',
+                1 => 'r',
+                2 => 's',
+            ],
+            19 => [
+                0 => 'r',
+                1 => 's',
+                2 => 't',
+            ],
+            20 => [
+                0 => 's',
+                1 => 't',
+                2 => 'u',
+            ],
+            21 => [
+                0 => 't',
+                1 => 'u',
+                2 => 'v',
+            ],
+            22 => [
+                0 => 'u',
+                1 => 'v',
+                2 => 'w',
+            ],
+            23 => [
+                0 => 'v',
+                1 => 'w',
+                2 => 'x',
+            ],
+            24 => [
+                0 => 'w',
+                1 => 'x',
+                2 => 'y',
+            ],
+            25 => [
+                0 => 'x',
+                1 => 'y',
+                2 => 'z',
+            ],
+        ])
+            ->unwindow()
+            ->shouldIterateAs(range('a', 'z'));
+    }
+
     public function it_can_unwrap()
     {
         $this::fromIterable([['a' => 'A'], ['b' => 'B'], ['c' => 'C']])

src/Collection.php

@@ -90,6 +90,7 @@
 use loophp\collection\Operation\Unpack;
 use loophp\collection\Operation\Unpair;
 use loophp\collection\Operation\Until;
+use loophp\collection\Operation\Unwindow;
 use loophp\collection\Operation\Unwrap;
 use loophp\collection\Operation\Unzip;
 use loophp\collection\Operation\Window;
@@ -733,6 +734,11 @@ public function until(callable ...$callbacks): CollectionInterface
         return $this->run(Until::of()(...$callbacks));
     }
 
+    public function unwindow(): CollectionInterface
+    {
+        return $this->run(Unwindow::of());
+    }
+
     public function unwrap(): CollectionInterface
     {
         return $this->run(Unwrap::of());

src/Contract/Collection.php

@@ -83,6 +83,7 @@
 use loophp\collection\Contract\Operation\Unpackable;
 use loophp\collection\Contract\Operation\Unpairable;
 use loophp\collection\Contract\Operation\Untilable;
+use loophp\collection\Contract\Operation\Unwindowable;
 use loophp\collection\Contract\Operation\Unwrapable;
 use loophp\collection\Contract\Operation\Unzipable;
 use loophp\collection\Contract\Operation\Windowable;
@@ -165,6 +166,7 @@
  * @template-extends Unpackable<TKey, T>
  * @template-extends Unpairable<TKey, T>
  * @template-extends Untilable<TKey, T>
+ * @template-extends Unwindowable<TKey, T>
  * @template-extends Unwrapable<TKey, T>
  * @template-extends Unzipable<TKey, T>
  * @template-extends Windowable<TKey, T>
@@ -252,6 +254,7 @@ interface Collection extends
     Unpackable,
     Unpairable,
     Untilable,
+    Unwindowable,
     Unwrapable,
     Unzipable,
     Windowable,

src/Contract/Operation/Unwindowable.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 Unwindowable
+{
+    /**
+     * @psalm-return \loophp\collection\Contract\Collection<TKey, T>
+     */
+    public function unwindow(): Collection;
+}

src/Operation/Unwindow.php

@@ -0,0 +1,39 @@
+<?php
+
+declare(strict_types=1);
+
+namespace loophp\collection\Operation;
+
+use Closure;
+use Generator;
+use Iterator;
+use loophp\collection\Iterator\IterableIterator;
+
+/**
+ * @psalm-template TKey
+ * @psalm-template TKey of array-key
+ * @psalm-template T
+ */
+final class Unwindow extends AbstractOperation
+{
+    /**
+     * @psalm-return Closure(Iterator<TKey, list<T>>): Generator<TKey, T>
+     */
+    public function __invoke(): Closure
+    {
+        return
+            /**
+             * @psalm-param Iterator<TKey, list<T>> $iterator
+             *
+             * @psalm-return Generator<TKey, T>
+             */
+            static function (Iterator $iterator): Generator {
+                foreach ($iterator as $key => $value) {
+                    /** @psalm-var Iterator<int, T> $lastIterator */
+                    $lastIterator = Last::of()(new IterableIterator($value));
+
+                    yield $key => $lastIterator->current();
+                }
+            };
+    }
+}