gemini-php/src/Pango.php

<?php

declare(strict_types=1);

namespace Yggverse\Gemini;

class Pango
{
    public static function fromGemtext(
        string $gemtext
    ): string
    {
        return self::fromGemtextBody(
            new \Yggverse\Gemini\Gemtext\Body(
                $gemtext
            )
        );
    }

    public static function fromGemtextBody(
        \Yggverse\Gemini\Gemtext\Body $body
    ): string
    {
        $lines = $body->getLines();

        $raw = [];

        $escaped = [];

        // Code
        $code = $body->getCode();

        if (count($code) % 2 == 0) // make sure tags has pairs
        {
            $i = 1;

            foreach ($code as $index => $capture)
            {
                // Replace code tags
                if ($i % 2 == 0)
                {
                    $lines[$index] = '</tt>';

                    // Skip code format inside the tags by raw registry
                    foreach (array_slice($lines, $offset, $index - $offset) as $start => $line)
                    {
                        $raw[$start + $offset] = $line;
                    }
                }

                else
                {
                    if ($capture)
                    {
                        $lines[$index] = sprintf(
                            '<b>%s</b><tt>',
                            self::escape(
                                $capture
                            )
                        );
                    }

                    else
                    {
                        $lines[$index] = '<tt>';
                    }

                    $offset = $index + 1;
                }

                $escaped[] = $index;

                $i++;
            }
        }

        // H1
        foreach ($body->getH1() as $index => $value)
        {
            if (!isset($raw[$index]))
            {
                $lines[$index] = sprintf(
                    '<span size="xx-large">%s</span>',
                    self::escape(
                        $value
                    )
                );

                $escaped[] = $index;
            }
        }

        // H2
        foreach ($body->getH2() as $index => $value)
        {
            if (!isset($raw[$index]))
            {
                $lines[$index] = sprintf(
                    '<span size="x-large">%s</span>',
                    self::escape(
                        $value
                    )
                );

                $escaped[] = $index;
            }
        }

        // H3
        foreach ($body->getH3() as $index => $value)
        {
            if (!isset($raw[$index]))
            {
                $lines[$index] = sprintf(
                    '<span size="large">%s</span>',
                    self::escape(
                        $value
                    )
                );

                $escaped[] = $index;
            }
        }

        // Quote
        foreach ($body->getQuote() as $index => $value)
        {
            if (!isset($raw[$index]))
            {
                $lines[$index] = sprintf(
                    '<i>%s</i>',
                    self::escape(
                        $value
                    )
                );

                $escaped[] = $index;
            }
        }

        // Links
        foreach ($body->getLinks() as $index => $line)
        {
            if (!isset($raw[$index]))
            {
                $link = new \Yggverse\Gemini\Gemtext\Link(
                    $line
                );

                if (!$address = $link->getAddress())
                {
                    continue;
                }

                if (!$alt = $link->getAlt())
                {
                    if (!$alt = $link->getDate())
                    {
                        $alt = $address;
                    }
                }

                if ($alt == $address)
                {
                    $lines[$index] = sprintf(
                        '<a href="%s">%s</a>',
                        $address,
                        self::escape(
                            $alt
                        )
                    );
                }

                else
                {
                    $lines[$index] = sprintf(
                        '<a href="%s" title="%s">%s</a>',
                        $address,
                        self::escape(
                            urldecode(
                                $address
                            )
                        ),
                        self::escape(
                            $alt
                        )
                    );
                }

                $escaped[] = $index;
            }
        }

        // Escape special chars for non escaped lines
        foreach ($body->getLines() as $index => $value)
        {
            if (!in_array($index, $escaped))
            {
                $lines[$index] = self::escape(
                    $value
                );
            }
        }

        return implode(
            PHP_EOL,
            $lines
        );
    }

    public static function escape(
        string $value
    ): string
    {
        return htmlspecialchars(
            $value
        );
    }
}