<?php
if ( ! defined( 'ABSPATH' ) ) {
    exit;
}

class DarkShield_Performance {

    public function extract_resources( $page_url = '' ) {
        if ( empty( $page_url ) ) {
            $page_url = home_url( '/' );
        }

        $response = wp_remote_get( $page_url, array(
            'timeout'   => 30,
            'sslverify' => false,
            'user-agent' => 'DarkShield Performance/1.0',
        ) );

        if ( is_wp_error( $response ) ) {
            return array( 'error' => $response->get_error_message(), 'resources' => array() );
        }

        $html = wp_remote_retrieve_body( $response );
        if ( empty( $html ) ) {
            return array( 'error' => 'Empty response.', 'resources' => array() );
        }

        $resources = array();

        // <link> stylesheets and preloads
        if ( preg_match_all( '#<link[^>]+href=["\']([^"\']+)["\'][^>]*>#i', $html, $m ) ) {
            foreach ( $m[0] as $i => $tag ) {
                $rel = '';
                if ( preg_match( '#rel=["\']([^"\']+)["\']#i', $tag, $rm ) ) {
                    $rel = strtolower( $rm[1] );
                }
                if ( in_array( $rel, array( 'stylesheet', 'preload', 'preconnect', 'dns-prefetch' ), true ) ) {
                    $resources[] = array(
                        'url'  => $this->abs_url( $m[1][ $i ], $page_url ),
                        'type' => 'stylesheet' === $rel ? 'css' : $rel,
                        'tag'  => 'link',
                    );
                }
            }
        }

        // <script src>
        if ( preg_match_all( '#<script[^>]+src=["\']([^"\']+)["\']#i', $html, $m ) ) {
            foreach ( $m[1] as $src ) {
                $resources[] = array(
                    'url'  => $this->abs_url( $src, $page_url ),
                    'type' => 'js',
                    'tag'  => 'script',
                );
            }
        }

        // <img src>
        if ( preg_match_all( '#<img[^>]+src=["\']([^"\']+)["\']#i', $html, $m ) ) {
            foreach ( $m[1] as $src ) {
                if ( strpos( $src, 'data:' ) !== 0 ) {
                    $resources[] = array(
                        'url'  => $this->abs_url( $src, $page_url ),
                        'type' => 'image',
                        'tag'  => 'img',
                    );
                }
            }
        }

        // <iframe src>
        if ( preg_match_all( '#<iframe[^>]+src=["\']([^"\']+)["\']#i', $html, $m ) ) {
            foreach ( $m[1] as $src ) {
                $resources[] = array(
                    'url'  => $this->abs_url( $src, $page_url ),
                    'type' => 'iframe',
                    'tag'  => 'iframe',
                );
            }
        }

        // @import and url() inside <style> blocks
        if ( preg_match_all( '#<style[^>]*>(.*?)</style>#is', $html, $sm ) ) {
            foreach ( $sm[1] as $css ) {
                if ( preg_match_all( '#(?:@import\s+(?:url\s*\()?\s*[\'"]?\s*|url\s*\(\s*[\'"]?\s*)((?:https?:)?//[^\s\'"<>\)]+)#i', $css, $um ) ) {
                    foreach ( $um[1] as $u ) {
                        $resources[] = array(
                            'url'  => $this->abs_url( $u, $page_url ),
                            'type' => 'css_inline',
                            'tag'  => 'style',
                        );
                    }
                }
            }
        }

        // Deduplicate
        $seen   = array();
        $unique = array();
        foreach ( $resources as $r ) {
            $key = md5( $r['url'] );
            if ( ! isset( $seen[ $key ] ) ) {
                $seen[ $key ] = true;
                $unique[]     = $r;
            }
        }

        return array(
            'error'     => '',
            'resources' => $unique,
            'page_url'  => $page_url,
            'html_size' => strlen( $html ),
            'total'     => count( $unique ),
        );
    }

    /**
     * Ping a single URL and measure response time.
     */
    public function check_url( $url ) {
        $start = microtime( true );

        $response = wp_remote_head( $url, array(
            'timeout'     => 10,
            'sslverify'   => false,
            'redirection' => 3,
            'user-agent'  => 'DarkShield Performance/1.0',
        ) );

        $elapsed = round( ( microtime( true ) - $start ) * 1000 );

        if ( is_wp_error( $response ) ) {
            $domain     = DarkShield_Utils::extract_domain( $url );
            $is_blocked = DarkShield_Utils::should_block( $url );

            return array(
                'url'            => $url,
                'domain'         => $domain,
                'status'         => 'error',
                'status_code'    => 0,
                'response_time'  => $elapsed,
                'rating'         => 'slow',
                'error'          => $response->get_error_message(),
                'content_type'   => '',
                'content_length' => 0,
                'cache_control'  => '',
                'server'         => '',
                'is_external'    => ( $domain !== DarkShield_Utils::get_site_domain() ),
                'is_blocked'     => $is_blocked,
            );
        }

        $code    = wp_remote_retrieve_response_code( $response );
        $headers = wp_remote_retrieve_headers( $response );
        $domain  = DarkShield_Utils::extract_domain( $url );

        $ct  = isset( $headers['content-type'] ) ? $headers['content-type'] : '';
        $cl  = isset( $headers['content-length'] ) ? (int) $headers['content-length'] : 0;
        $cc  = isset( $headers['cache-control'] ) ? $headers['cache-control'] : '';
        $srv = isset( $headers['server'] ) ? $headers['server'] : '';

        $rating = 'fast';
        if ( $elapsed > 1000 ) {
            $rating = 'slow';
        } elseif ( $elapsed > 500 ) {
            $rating = 'medium';
        }

        return array(
            'url'            => $url,
            'domain'         => $domain,
            'status'         => 'ok',
            'status_code'    => $code,
            'response_time'  => $elapsed,
            'rating'         => $rating,
            'error'          => '',
            'content_type'   => $ct,
            'content_length' => $cl,
            'cache_control'  => $cc,
            'server'         => $srv,
            'is_external'    => ( $domain !== DarkShield_Utils::get_site_domain() ),
            'is_blocked'     => DarkShield_Utils::should_block( $url ),
        );
    }

    /**
     * Convert relative/protocol-relative URL to absolute.
     */
    private function abs_url( $url, $base ) {
        $url = trim( $url );

        if ( strpos( $url, '//' ) === 0 ) {
            return 'https:' . $url;
        }
        if ( strpos( $url, 'http' ) === 0 ) {
            return $url;
        }
        if ( strpos( $url, '/' ) === 0 ) {
            $p = wp_parse_url( $base );
            $scheme = isset( $p['scheme'] ) ? $p['scheme'] : 'https';
            $host   = isset( $p['host'] ) ? $p['host'] : '';
            return $scheme . '://' . $host . $url;
        }

        return rtrim( $base, '/' ) . '/' . $url;
    }
}