Pelican to Hugo reStructuredText post converter (Python static site generator to Go static site generator)

convert.php

<?php

/**
 * Requires pandoc to be installed and in your path
 * 
 * It will look for .rst files in __DIR__/content/* where it will expect to find
 * category folders. Inside these category folders your posts should be available.
 * 
 * So
 * 
 * - content
 *     - Computing
 *        - functional-php.rst
 *        - new-pc.rst
 *     - Misc
 *        - moving-house.rst
 *        - death-defying-stunts.rst
 */

// Path to the folder containing rst documents you want to convert
$content_path = __DIR__ . '/content';

// Output path where the posts will be saved to as markdown
$output_path = __DIR__ . '/hugo';

function map_directory($path, $func) {
    $results = [];
    $d = dir($path);
    while (false !== ($entry = $d->read())) {
        if ('.' !== $entry && '..' !== $entry) {
            $results[] = $func($entry, $d);
        }
    }
    $d->close();
    return $results;
}

map_directory($content_path, function($entry, $d) {
    $dir = $d->path . "/$entry";
    if (is_dir($dir)) {
        parse_posts($dir, $entry);
    }
});

function parse_posts($path, $category) {
    map_directory($path, function($entry, $d) {
        $item = $d->path . "/$entry";
        if (is_file($item) && false !== strstr($entry, '.rst')) {
            echo "$entry\n";
            $out_file = __DIR__ . '/hugo/' . str_replace('.rst', '.md', $entry);
            $f = file_get_contents($item);
            $f = mutate_file($f);
            file_put_contents($out_file, $f);
        }
    });
}

function mutate_file($f) {
    $matches = [];
    // add opening YAML front matter indicator
    $f = "---\n" . $f;
    // Change the rst title into a YAML key and value
    $f = preg_replace('/^(---\n+)(.+)\n[#^~\-=_+\'`]+/', '\1' . "\n:title: " . '\2', $f);
    // find the last rst key value pair and insert closing YAML front
    // matter indicator immediately after it
    if (preg_match_all('/^:([\w\d]+): +(.*) *$/m', $f, $matches)) {
        $last_key = end($matches[1]);
        $f = preg_replace('/^(:' . preg_quote($last_key) . ':.*)$/m', '\1' . "\n---\n", $f);
    }
    // convert all the rst key value pairs into YAML key value pairs
    $f = preg_replace_callback('/^:([\w\d]+): +(.*) *$/m', function($matches) {
        $out = '';
        if ($matches[2]) {
            switch ($matches[1]) {
                case 'date':
                    $date = strtotime($matches[2]);
                    $out = 'date: "' . date('Y-m-d\TH:i:s\Z', $date) . '"';
                    break;
                case 'tags':
                case 'categories':
                    $cats = explode(',', $matches[2]);
                    $cats = array_map(function($item) {
                        $tag = str_replace('.', '', trim($item));
                        return '  - "' . addslashes($tag) . '"';
                    }, $cats);
                    $out = "{$matches[1]}:\n" . implode("\n", $cats);
                    break;
                case 'category':
                    $out = "categories:\n  - " . '"' . addslashes($matches[2]) . '"';
                    break;
                default:
                    $out = "{$matches[1]}: " . '"' . addslashes($matches[2]) . '"';
                    break;
            }
        }
        return $out;
    }, $f);

    $split = preg_split('/^---$/m', $f);

    // remove empty lines
    $split[1] = preg_replace("/(^[\r\n]*|[\r\n]+)[\s\t]*[\r\n]+/", "\n", $split[1]);
    $content = $split[2];

    $pipes_map = array(
        0 => array('pipe', 'r'),
        1 => array('pipe', 'w'),
    );
    $arguments = array(
        '--smart',
        '-f rst',
        '-t markdown_github',
    );
    $exec_string = 'pandoc ' . implode(' ', $arguments);
    $proc_res = proc_open($exec_string, $pipes_map, $pipes);
    if (!is_resource($proc_res)) {
        return 'Could not process the file with pandoc.';
    }
    fwrite($pipes[0], $content);
    fclose($pipes[0]);
    $markdown = stream_get_contents($pipes[1]);

    $split[2] = "\n\n" . $markdown;
    $f = implode('---', $split);
    return $f;
}