Script to condense Jekyll front matter for Jigsaw

condense-front-matter.php

<?php

require 'vendor/autoload.php';

$parser = new \Mni\FrontYAML\Parser();

$config = [
    'whitelist' => ['title', 'excerpt', 'comments', 'categories', 'seo_image'],
    'merge' => [
        'extends' => '_layouts.post',
        'section' => 'content',
        'date' => 'generate_date',
        'categories' => 'verify_categories'
    ]
];

foreach (new DirectoryIterator('source/_posts') as $file) {
    if (!$file->isFile()) {
        continue;
    }

    $contents = file_get_contents($file->getRealPath());

    $document = $parser->parse($contents, false);

    $front_matter = $document->getYAML();

    $refined = array_filter($front_matter, function ($key) use ($config) {
        return in_array($key, $config['whitelist']);
    }, ARRAY_FILTER_USE_KEY);


    foreach ($config['merge'] as $key => $value) {
        if (function_exists($value)) {
            $value = call_user_func($value, $front_matter, $file->getFilename());
        }

        $refined[$key] = $value;
    }

    $contents = str_replace($document->getContent(), \Symfony\Component\Yaml\Yaml::dump($refined), $contents);

    file_put_contents($file->getRealPath(), $contents);
}

function generate_date(array $front_matter, $filename)
{
    if (isset($front_matter['date'])) {
        return strtotime($front_matter['date']);
    }

    return strtotime(substr($filename, 0, 10));
}

function verify_categories(array $front_matter, $filename)
{
    if (isset($front_matter['categories'])) {
        return $front_matter['categories'];
    }

    return ['Main Thread'];
}