<?php

namespace NoccyLabs\PhpCalc;
/**
 * Helper class to iterate over a list of tokens
 * 
 * @license GPL V3 or later
 * @copyright (c) 2022, NoccyLabs
 */
class TokenList
{

    private array $toks;

    private int $ptr = 0;

    public function __construct(array $toks)
    {
        $this->toks = $toks;
    }

    public function current(): ?string
    {
        return ($this->ptr >= count($this->toks) ? null : $this->toks[$this->ptr]);
    }

    public function read(): ?string
    {
        $v  = $this->current();
        $this->next();
        return $v;
    }

    public function next(): ?string
    {
        if ($this->ptr < count($this->toks)) {
            $this->ptr++;
            return ($this->ptr < count($this->toks) ? $this->toks[$this->ptr] : null);
        }
        return null;
    }
}