<?php

/*
 * This file is part of the league/commonmark package.
 *
 * (c) Colin O'Dell <colinodell@gmail.com>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace League\CommonMark\Input;

use League\CommonMark\Exception\UnexpectedEncodingException;

final class MarkdownInput implements MarkdownInputInterface
{
    /** @var iterable<int, string>|null */
    private $lines;

    /** @var string */
    private $content;

    /** @var int|null */
    private $lineCount;

    public function __construct(string $content)
    {
        if (!\mb_check_encoding($content, 'UTF-8')) {
            throw new UnexpectedEncodingException('Unexpected encoding - UTF-8 or ASCII was expected');
        }

        $this->content = $content;
    }

    public function getContent(): string
    {
        return $this->content;
    }

    /**
     * @return \Traversable<int, string>
     */
    public function getLines(): \Traversable
    {
        $this->splitLinesIfNeeded();

        foreach ($this->lines as $lineNumber => $line) {
            yield $lineNumber => $line;
        }
    }

    public function getLineCount(): int
    {
        $this->splitLinesIfNeeded();

        return $this->lineCount;
    }

    private function splitLinesIfNeeded(): void
    {
        if ($this->lines !== null) {
            return;
        }

        $lines = \preg_split('/\r\n|\n|\r/', $this->content);
        if ($lines === false) {
            throw new UnexpectedEncodingException('Failed to split Markdown content by line');
        }

        $this->lines = $lines;

        // Remove any newline which appears at the very end of the string.
        // We've already split the document by newlines, so we can simply drop
        // any empty element which appears on the end.
        if (\end($this->lines) === '') {
            \array_pop($this->lines);
        }

        $this->lineCount = \count($this->lines);
    }
}
