changelog-from-github-api.php

<?php

/**
 * This script downloads the list of releases of a project via the GitHub API,
 * and generates a changelog out of it.
 *
 * Example, to generate a changelog for brick/math:
 *
 * php changelog-from-github-api.php brick/math > CHANGELOG.md
 */

(function(int $argc, array $argv) {
    if ($argc !== 2) {
        echo "Usage: {$argv[0]} <owner/repo>\n";
        exit(1);
    }

    $repo = $argv[1];

    $download = function(string $url): string {
        $options = [
            'http' => [
                'header' => 'User-Agent: changelog-from-github-api'
            ]
        ];

        $context = stream_context_create($options);

        $attempts = 5;

        for ($attempt = 1; $attempt <= $attempts; $attempt++) {
            $data = file_get_contents($url, false, $context);

            if ($data !== false) {
                return $data;
            }

            sleep(1);
        }

        echo "Could not download $url after $attempts attempts\n";
        exit(1);
    };

    $releases = [];

    for ($page = 1; ; $page++) {
        $url = 'https://api.github.com/repos/' . $repo . '/releases?page=' . $page;
        $json = $download($url);
        $data = json_decode($json, true);

        if ($data === null) {
            echo "Could not decode JSON data at $url\n";
            exit(1);
        }

        assert(is_array($data));

        if (! $data) {
            break;
        }

        foreach ($data as $release) {
            $releases[] = $release;
        }
    }

    usort($releases, function (array $a, array $b): int {
        return strnatcmp($b['name'], $a['name']);
    });

    echo "# Changelog\n\n";

    foreach ($releases as $release) {
        printf("## [%s](%s) - %s\n\n", $release['name'], $release['html_url'], substr($release['published_at'], 0, 10));
        echo trim($release['body']), "\n\n";
    }
})($argc, $argv);