Add strikethrough support

[BentiGorlich]

Add a StrikethroughConverter which converts

• <strike>Some Text</strike> -> ~~Some Text~~
• <del>Some Text</del> -> ~~Some Text~~

[BentiGorlich]

Sorry about this change, but PHPStork wouldn't let me revert this 😅

[mare96]

@BentiGorlich Thank you, but <strike> is deprecated can you use <s> also ?

@melroy89 Do you have any thoughts on when this will be merged?

[BentiGorlich]

Well it might be deprecated, but that doesn't mean that it isn't used anymore. The issue we received about the parsing problem contained the <strike> tag. I can certainly add the <s> tag :)
Since there is not a review from a maintainer yet I have no clue when this will be merged :)

[melroy89]

Do you have any thoughts on when this will be merged?

although I approved it. I don't have merge rights on this repo. Better ask @colinodell

[mrdezzods]

please merge this @colinodell

[NineBitsLTD]

Incorrect implementation. EmphasisConverter exists for this purpose. Your code loses flexible configuration settings.

[BentiGorlich]

Incorrect implementation. EmphasisConverter exists for this purpose. Your code loses flexible configuration settings.

How would I solve this? And what settings are lost?

[margarizaldi]

Incorrect implementation. EmphasisConverter exists for this purpose. Your code loses flexible configuration settings.

How would I solve this? And what settings are lost?

@BentiGorlich I think you need to see the EmphasisConverter, not sure should merge into it or keep them separated

here's my own implementation for my project

class StrikethroughConverter implements ConverterInterface, ConfigurationAwareInterface
{
    public const STYLE_NAME = 'strikethrough_style';

    /** @var Configuration */
    protected $config;

    protected function getNormTag(?ElementInterface $element): string
    {
        if ($element !== null && ! $element->isText()) {
            $tag = $element->getTagName();
            if (in_array($tag, $this->getSupportedTags())) {
                return 'del';
            }
        }

        return '';
    }

    public function setConfig(Configuration $config): void
    {
        $this->config = $config;
    }

    public function convert(ElementInterface $element): string
    {
        $tag = $this->getNormTag($element);
        $value = $element->getValue();

        if (! \trim($value)) {
            return $value;
        }

        $style = $this->config->getOption(self::STYLE_NAME, '~~');
        $prefix = \ltrim($value) !== $value ? ' ' : '';
        $suffix = \rtrim($value) !== $value ? ' ' : '';

        /* If this node is immediately preceded or followed by one of the same type don't emit
         * the start or end $style, respectively. This prevents <del>foo</del><del>bar</del> from
         * being converted to ~~foo~~~~bar~~ which is incorrect. We want ~~foobar~~ instead.
         */

        $preStyle = $this->getNormTag($element->getPreviousSibling()) === $tag ? '' : $style;
        $postStyle = $this->getNormTag($element->getNextSibling()) === $tag ? '' : $style;

        return $prefix . $preStyle . \trim($value) . $postStyle . $suffix;
    }

    /**
     * @return string[]
     */
    public function getSupportedTags(): array
    {
        return ['del', 'strike', 's'];
    }
}