<?php
/**
 * Metasync_Dimension_Injector
 * Scans HTML for <img> tags missing width/height and injects them
 * based on file metadata to prevent Cumulative Layout Shift (CLS).
 *
 * @package     Search Atlas SEO
 * @copyright   Copyright (C) 2021-2025, Search Atlas Group - support@searchatlas.com
 * @since       2.6.0
 */

if (!defined('ABSPATH')) {
    exit;
}

class Metasync_Dimension_Injector {

    /** In-memory cache to avoid repeated file lookups within a request. */
    private array $cache = [];

    public function __construct() {
        add_filter('the_content', [$this, 'inject_dimensions'], 30);
        add_filter('post_thumbnail_html', [$this, 'inject_dimensions'], 30);
        add_filter('widget_text', [$this, 'inject_dimensions'], 30);
    }

    /**
     * Find <img> tags missing width or height and inject dimensions.
     */
    public function inject_dimensions(string $content): string {
        if (empty($content) || is_admin()) {
            return $content;
        }

        return preg_replace_callback('/<img\s[^>]+>/i', function ($matches) {
            $tag = $matches[0];

            $has_width  = preg_match('/\swidth\s*=/i', $tag);
            $has_height = preg_match('/\sheight\s*=/i', $tag);

            // Both already present - nothing to do
            if ($has_width && $has_height) {
                return $tag;
            }

            $dims = $this->get_dimensions($tag);
            if (!$dims) {
                return $tag;
            }

            if (!$has_width) {
                $tag = $this->add_attribute($tag, 'width', (string) $dims['width']);
            }
            if (!$has_height) {
                $tag = $this->add_attribute($tag, 'height', (string) $dims['height']);
            }

            return $tag;
        }, $content);
    }

    /**
     * Try to determine image dimensions from multiple sources.
     */
    private function get_dimensions(string $img_tag): ?array {
        if (!preg_match('/src=["\']([^"\']+)["\']/i', $img_tag, $m)) {
            return null;
        }
        $src = $m[1];

        if (isset($this->cache[$src])) {
            return $this->cache[$src];
        }

        $dims = null;

        // Strategy 1: Try to find WordPress attachment by URL
        $dims = $this->get_dims_from_attachment($src);

        // Strategy 2: Try to read the local file directly
        if (!$dims) {
            $dims = $this->get_dims_from_local_file($src);
        }

        // Strategy 3: For external images, try getimagesize with URL (slower)
        if (!$dims) {
            $dims = $this->get_dims_from_remote($src);
        }

        if ($dims) {
            $this->cache[$src] = $dims;
        }

        return $dims;
    }

    /**
     * Look up dimensions from WP attachment metadata.
     */
    private function get_dims_from_attachment(string $url): ?array {
        $attachment_id = attachment_url_to_postid($url);

        if (!$attachment_id) {
            // Try without size suffix (e.g., image-300x200.jpg -> image.jpg)
            $clean_url = preg_replace('/-\d+x\d+(\.\w+)$/', '$1', $url);
            $attachment_id = attachment_url_to_postid($clean_url);
        }

        if (!$attachment_id) {
            return null;
        }

        $meta = wp_get_attachment_metadata($attachment_id);
        if (!$meta) {
            return null;
        }

        // Check sub-sizes first
        if (!empty($meta['sizes'])) {
            $filename = wp_basename($url);
            foreach ($meta['sizes'] as $size_data) {
                if ($size_data['file'] === $filename) {
                    return [
                        'width'  => (int) $size_data['width'],
                        'height' => (int) $size_data['height'],
                    ];
                }
            }
        }

        // Fall back to full size
        if (!empty($meta['width']) && !empty($meta['height'])) {
            return [
                'width'  => (int) $meta['width'],
                'height' => (int) $meta['height'],
            ];
        }

        return null;
    }

    /**
     * Convert URL to local path and use getimagesize().
     */
    private function get_dims_from_local_file(string $url): ?array {
        $upload_dir = wp_get_upload_dir();

        if (strpos($url, $upload_dir['baseurl']) === false) {
            return null;
        }

        $relative = str_replace($upload_dir['baseurl'], '', $url);
        $file     = $upload_dir['basedir'] . $relative;

        if (!file_exists($file)) {
            return null;
        }

        $info = @getimagesize($file);
        if ($info && $info[0] > 0 && $info[1] > 0) {
            return ['width' => $info[0], 'height' => $info[1]];
        }

        return null;
    }

    /**
     * Fetch dimensions from a remote URL.
     * Downloads just enough bytes to read image headers.
     */
    private function get_dims_from_remote(string $url): ?array {
        if (strpos($url, 'http') !== 0) {
            return null;
        }

        $response = wp_remote_get($url, [
            'timeout' => 3,
            'headers' => ['Range' => 'bytes=0-32767'],
        ]);

        if (is_wp_error($response)) {
            return null;
        }

        $tmp = wp_tempnam($url);
        $body = wp_remote_retrieve_body($response);
        if (empty($body)) {
            return null;
        }

        file_put_contents($tmp, $body);
        $info = @getimagesize($tmp);
        @unlink($tmp);

        if ($info && $info[0] > 0 && $info[1] > 0) {
            return ['width' => $info[0], 'height' => $info[1]];
        }

        return null;
    }

    /**
     * Insert an attribute into an <img> tag.
     */
    private function add_attribute(string $tag, string $name, string $value): string {
        return preg_replace(
            '/(<img\s)/i',
            sprintf('$1%s="%s" ', esc_attr($name), esc_attr($value)),
            $tag,
            1
        );
    }
}