<?php
// StringIterator.php
// Created: 2022-02-02
// Updated: 2022-02-02

namespace Index;

use Iterator;

/**
 * Provides an iterator for IString types.
 */
class StringIterator implements Iterator {
    private IString $value;
    private int $length;
    private int $index = 0;
    private bool $wasValid = false;

    /**
     * Creates the iterator.
     *
     * @param IString $string String to iterate.
     */
    public function __construct(IString $string) {
        $this->value = $string;
        $this->length = $string->getLength();
    }

    /**
     * Returns the current character.
     *
     * @see https://www.php.net/manual/en/iterator.current.php
     * @return mixed Current character.
     */
    public function current(): mixed {
        return $this->value[$this->index];
    }

    /**
     * Returns the index of the current character.
     *
     * @see https://www.php.net/manual/en/iterator.key.php
     * @return int Index of the current character.
     */
    public function key(): mixed {
        return $this->index;
    }

    /**
     * Move forward to the next character.
     *
     * @see https://www.php.net/manual/en/iterator.next.php
     */
    public function next(): void {
        $next = $this->index + 1;
        $this->wasValid = $next < $this->length;

        if($this->wasValid)
            $this->index = $next;
    }

    /**
     * Rewind to the first character.
     *
     * @see https://www.php.net/manual/en/iterator.rewind.php
     */
    public function rewind(): void {
        $this->index = 0;
        $this->wasValid = true;
    }

    /**
     * Checks if the current index is valid.
     *
     * @see https://www.php.net/manual/en/iterator.rewind.php
     * @return bool Whether the current index is valid.
     */
    public function valid(): bool {
        return $this->wasValid;
    }
}