<?php
/**
 * youtube thumbnail to posthumbnail
 */
function generate_youtube_thumbnail() {
    global $post;

    // Ensure we're in the post editor and the post has an ID
    if ( ! is_admin() || ! isset( $post->ID ) ) {
        return;
    }

    // Get the post content and search for a YouTube URL
    $content = $post->post_content;
    preg_match_all('~(https?://www\.youtube\.com/watch\?v=)([a-zA-Z0-9_-]+)~', $content, $matches);

    if ( empty($matches[2]) ) {
        return;
    }

    $videoId = $matches[2][0];
    $youtubeImageSrc = "https://img.youtube.com/vi/$videoId/";

    // Determine the best available thumbnail size
    $possibleThumbnails = ['maxresdefault.jpg', 'hqdefault.jpg', 'mqdefault.jpg'];
    $youtubeImage = '';

    foreach ($possibleThumbnails as $thumbnail) {
        $headers = get_headers($youtubeImageSrc . $thumbnail, 1);
        if ($headers && strpos($headers[0], '200 OK') !== false) {
            $youtubeImage = $thumbnail;
            break;
        }
    }

    if (!$youtubeImage) {
        error_log('No valid YouTube thumbnail found.');
        return;
    }

    $thumbnailUrl = $youtubeImageSrc . $youtubeImage;

    // Fetch the image
    $response = wp_safe_remote_get($thumbnailUrl);
    if (is_wp_error($response) || wp_remote_retrieve_response_code($response) !== 200) {
        error_log('Error fetching the thumbnail: ' . $response->get_error_message());
        return;
    }

    $imageData = wp_remote_retrieve_body($response);

    if (empty($imageData)) {
        error_log('Failed to retrieve image data.');
        return;
    }

    // Get image dimensions
    list($width, $height) = getimagesizefromstring($imageData);

    // Prepare the file for upload
    $uploadDir = wp_upload_dir();
    $filename = wp_unique_filename($uploadDir['path'], 'youtube-thumbnail-' . $post->ID . '.webp');
    $filePath = $uploadDir['path'] . '/' . $filename;

    // Create an image resource and save it as WebP
    $image = imagecreatefromstring($imageData);
    if (!$image) {
        error_log('Failed to create image resource.');
        return;
    }

    if (!imagewebp($image, $filePath)) {
        error_log('Failed to save the image as WebP.');
        imagedestroy($image);
        return;
    }
    imagedestroy($image);

    // Create an attachment for the image
    $attachment = array(
        'post_mime_type' => 'image/webp',
        'guid' => $uploadDir['url'] . '/' . $filename,
        'post_parent' => $post->ID,
        'post_title' => 'YouTube Thumbnail',
        'post_content' => '',
        'post_status' => 'inherit'
    );

    $attachmentId = wp_insert_attachment($attachment, $filePath);

    // Set the thumbnail as the featured image and update meta information
    if (!is_wp_error($attachmentId)) {
        set_post_thumbnail($post->ID, $attachmentId);
        update_post_meta($attachmentId, '_wp_attachment_image_alt', get_the_title());
    } else {
        error_log('Error creating attachment: ' . $attachmentId->get_error_message());
    }
}

add_action('save_post', 'generate_youtube_thumbnail');