refactor: Add a $seed parameter to RandomIterator.

loophp · Dec 6, 2020 · be7a0c1 · be7a0c1
1 parent bbf0045
commit be7a0c1
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Showing 5 changed files with 122 additions and 26 deletions.
diff --git a/spec/loophp/collection/Iterator/RandomIteratorSpec.php b/spec/loophp/collection/Iterator/RandomIteratorSpec.php
@@ -5,11 +5,75 @@
 namespace spec\loophp\collection\Iterator;
 
 use ArrayIterator;
+use Exception;
 use loophp\collection\Iterator\RandomIterator;
 use PhpSpec\ObjectBehavior;
 
 class RandomIteratorSpec extends ObjectBehavior
 {
+    public function it_can_build_an_iterator_with_a_random_seed()
+    {
+        $input = new ArrayIterator(range('a', 'z'));
+        $seed = 123;
+
+        $this->beConstructedWith(
+            $input,
+            $seed
+        );
+
+        $expected = [
+            2 => 'c',
+            4 => 'e',
+            22 => 'w',
+            21 => 'v',
+            20 => 'u',
+            14 => 'o',
+            5 => 'f',
+            17 => 'r',
+            25 => 'z',
+            24 => 'y',
+            10 => 'k',
+            13 => 'n',
+            23 => 'x',
+            15 => 'p',
+            8 => 'i',
+            11 => 'l',
+            0 => 'a',
+            7 => 'h',
+            19 => 't',
+            9 => 'j',
+            3 => 'd',
+            16 => 'q',
+            18 => 's',
+            1 => 'b',
+            12 => 'm',
+            6 => 'g',
+        ];
+
+        if (iterator_to_array($this->getWrappedObject()) !== $expected) {
+            throw new Exception('Iterator is not equal to the expected array.');
+        }
+
+        $iterator1 = new RandomIterator($input, $seed);
+        $iterator2 = new RandomIterator($input, $seed + $seed);
+
+        if (iterator_to_array($iterator1) === iterator_to_array($iterator2)) {
+            throw new Exception('Iterator1 is equal to Iterator2');
+        }
+    }
+
+    public function it_can_build_an_iterator_without_a_random_seed()
+    {
+        $input = new ArrayIterator(range('a', 'z'));
+        $this->beConstructedWith($input);
+
+        $iterator1 = new RandomIterator($input);
+
+        if (iterator_to_array($iterator1) === iterator_to_array($this->getWrappedObject())) {
+            throw new Exception('Iterator1 is equal to Iterator2');
+        }
+    }
+
     public function it_can_get_the_innerIterator()
     {
         $this->getInnerIterator()->shouldBeAnInstanceOf(ArrayIterator::class);
@@ -19,7 +83,7 @@ public function it_can_rewind()
     {
         $iterator = new ArrayIterator(['a']);
 
-        $this->beConstructedWith($iterator);
+        $this->beConstructedWith($iterator, 1);
 
         $this
             ->valid()
@@ -56,6 +120,6 @@ public function let()
     {
         $iterator = new ArrayIterator(range('a', 'c'));
 
-        $this->beConstructedWith($iterator);
+        $this->beConstructedWith($iterator, 1);
     }
 }
diff --git a/src/Collection.php b/src/Collection.php
@@ -115,6 +115,7 @@
 
 use const INF;
 use const PHP_INT_MAX;
+use const PHP_INT_MIN;
 
 /**
  * @psalm-template TKey
@@ -588,9 +589,13 @@ public function product(iterable ...$iterables): CollectionInterface
         return new self(Product::of()(...$iterables), $this->getIterator());
     }
 
-    public function random(int $size = 1): CollectionInterface
+    public function random(int $size = 1, ?int $seed = null): CollectionInterface
     {
-        return new self(Random::of()($size), $this->getIterator());
+        if (null === $seed) {
+            $seed = random_int(PHP_INT_MIN, PHP_INT_MAX);
+        }
+
+        return new self(Random::of()($seed)($size), $this->getIterator());
     }
 
     public static function range(float $start = 0.0, float $end = INF, float $step = 1.0): CollectionInterface
@@ -643,9 +648,13 @@ public function scanRight1(callable $callback): CollectionInterface
         return new self(ScanRight1::of()($callback), $this->getIterator());
     }
 
-    public function shuffle(): CollectionInterface
+    public function shuffle(?int $seed = null): CollectionInterface
     {
-        return new self(Shuffle::of(), $this->getIterator());
+        if (null === $seed) {
+            $seed = random_int(PHP_INT_MIN, PHP_INT_MAX);
+        }
+
+        return new self(Shuffle::of()($seed), $this->getIterator());
     }
 
     public function since(callable ...$callbacks): CollectionInterface

diff --git a/src/Iterator/RandomIterator.php b/src/Iterator/RandomIterator.php
@@ -7,6 +7,11 @@
 use ArrayIterator;
 use Iterator;
 
+use function array_slice;
+
+use const PHP_INT_MAX;
+use const PHP_INT_MIN;
+
 /**
  * @psalm-template TKey
  * @psalm-template TKey of array-key
@@ -36,12 +41,13 @@ final class RandomIterator extends ProxyIterator
     /**
      * @psalm-param Iterator<TKey, T> $iterator
      */
-    public function __construct(Iterator $iterator)
+    public function __construct(Iterator $iterator, ?int $seed = null)
     {
         $this->iterator = $iterator;
+        $this->seed = $seed ?? random_int(PHP_INT_MIN, PHP_INT_MAX);
         $this->wrappedIterator = $this->buildArrayIterator($iterator);
         $this->indexes = array_keys($this->wrappedIterator->getArrayCopy());
-        $this->key = array_rand($this->indexes);
+        $this->key = current($this->customArrayRand($this->indexes, 1, $this->seed));
     }
 
     public function current()
@@ -63,7 +69,7 @@ public function next(): void
         unset($this->indexes[$this->key]);
 
         if ($this->valid()) {
-            $this->key = array_rand($this->indexes);
+            $this->key = current($this->customArrayRand($this->indexes, 1, $this->seed));
         }
     }
 
@@ -94,4 +100,13 @@ private function buildArrayIterator(Iterator $iterator): ArrayIterator
 
         return $arrayIterator;
     }
+
+    private function customArrayRand(array $array, int $num, int $seed): array
+    {
+        mt_srand($seed);
+        shuffle($array);
+        mt_srand();
+
+        return array_slice($array, 0, $num);
+    }
 }
diff --git a/src/Operation/Random.php b/src/Operation/Random.php
@@ -16,23 +16,25 @@
 final class Random extends AbstractOperation
 {
     /**
-     * @psalm-return Closure(int): Closure(Iterator<TKey, T>): Generator<TKey, T>
+     * @psalm-return Closure(int): Closure(int): Closure(Iterator<TKey, T>): Generator<TKey, T>
      */
     public function __invoke(): Closure
     {
         return
-            /**
-             * @psalm-return Closure(Iterator<TKey, T>): Generator<TKey, T>
-             */
-            static function (int $size): Closure {
-                /** @psalm-var Closure(Iterator<TKey, T>): Generator<TKey, T> $pipe */
-                $pipe = Pipe::of()(
-                    Shuffle::of(),
-                    Limit::of()($size)(0)
-                );
+            static function (int $seed): Closure {
+                /**
+                 * @psalm-return Closure(Iterator<TKey, T>): Generator<TKey, T>
+                 */
+                return static function (int $size) use ($seed): Closure {
+                    /** @psalm-var Closure(Iterator<TKey, T>): Generator<TKey, T> $pipe */
+                    $pipe = Pipe::of()(
+                        Shuffle::of()($seed),
+                        Limit::of()($size)(0)
+                    );
 
-                // Point free style.
-                return $pipe;
+                    // Point free style.
+                    return $pipe;
+                };
             };
     }
 }
diff --git a/src/Operation/Shuffle.php b/src/Operation/Shuffle.php
@@ -17,16 +17,22 @@
 final class Shuffle extends AbstractOperation
 {
     /**
-     * @psalm-return Closure(Iterator<TKey, T>): Generator<TKey, T, mixed, void>
+     * @psalm-return Closure(int): Closure(Iterator<TKey, T>): Generator<TKey, T, mixed, void>
      */
     public function __invoke(): Closure
     {
         return
             /**
-             * @psalm-param Iterator<TKey, T> $iterator
-             *
-             * @psalm-return Generator<TKey, T, mixed, void>
+             * @return Closure(Iterator<TKey, T>): Generator<TKey, T, mixed, void>
              */
-            static fn (Iterator $iterator): Generator => yield from new RandomIterator($iterator);
+            static function (int $seed): Closure {
+                return
+                /**
+                 * @psalm-param Iterator<TKey, T> $iterator
+                 *
+                 * @psalm-return Generator<TKey, T, mixed, void>
+                 */
+                static fn (Iterator $iterator): Generator => yield from new RandomIterator($iterator, $seed);
+            };
     }
 }