class Count

class Count extends Constraint {
    private readonly int $expectedCount;
    public function __construct(int $expected) {
        $this->expectedCount = $expected;
    }
    public function toString() : string {
        return sprintf('count matches %d', $this->expectedCount);
    }
    
    /**
     * Evaluates the constraint for parameter $other. Returns true if the
     * constraint is met, false otherwise.
     *
     * @throws Exception
     */
    protected function matches(mixed $other) : bool {
        return $this->expectedCount === $this->getCountOf($other);
    }
    
    /**
     * @throws Exception
     */
    protected function getCountOf(mixed $other) : ?int {
        if (is_countable($other)) {
            return count($other);
        }
        if ($other instanceof EmptyIterator) {
            return 0;
        }
        if ($other instanceof Traversable) {
            while ($other instanceof IteratorAggregate) {
                try {
                    $other = $other->getIterator();
                } catch (\Exception $e) {
                    throw new Exception($e->getMessage(), $e->getCode(), $e);
                }
            }
            $iterator = $other;
            if ($iterator instanceof Generator) {
                throw new GeneratorNotSupportedException();
            }
            if (!$iterator instanceof Iterator) {
                return iterator_count($iterator);
            }
            $key = $iterator->key();
            $count = iterator_count($iterator);
            // Manually rewind $iterator to previous key, since iterator_count
            // moves pointer.
            if ($key !== null) {
                $iterator->rewind();
                while ($iterator->valid() && $key !== $iterator->key()) {
                    $iterator->next();
                }
            }
            return $count;
        }
        return null;
    }
    
    /**
     * Returns the description of the failure.
     *
     * The beginning of failure messages is "Failed asserting that" in most
     * cases. This method should return the second part of that sentence.
     *
     * @throws Exception
     */
    protected function failureDescription(mixed $other) : string {
        return sprintf('actual size %d matches expected size %d', (int) $this->getCountOf($other), $this->expectedCount);
    }

}