array  $args   Arguments.
			 * @param string $src    Image src.
			 * @param string $image  Image tag.
			 */
			$args = apply_filters( 'smush_image_cdn_args', array(), $image );
		}

		/**
		 * Filter hook to alter image src before going through cdn.
		 *
		 * @param string $src    Image src.
		 * @param string $image  Image tag.
		 */
		$src = apply_filters( 'smush_image_src_before_cdn', $src, $image );

		// Generate cdn url from local url.
		$src = $this->generate_cdn_url( $src, $args );

		/**
		 * Filter hook to alter image src after replacing with CDN base.
		 *
		 * @param string $src    Image src.
		 * @param string $image  Image tag.
		 */
		return apply_filters( 'smush_image_src_after_cdn', $src, $image );
	}

	/**
	 * Filters an array of image srcset values, replacing each URL with resized CDN urls.
	 *
	 * Keep the existing srcset sizes if already added by WP, then calculate extra sizes
	 * if required.
	 *
	 * @since 3.0
	 *
	 * @param array  $sources        One or more arrays of source data to include in the 'srcset'.
	 * @param array  $size_array     Array of width and height values in pixels.
	 * @param string $image_src      The 'src' of the image.
	 * @param array  $image_meta     The image metadata as returned by 'wp_get_attachment_metadata()'.
	 * @param int    $attachment_id  Image attachment ID or 0.
	 *
	 * @return array $sources
	 */
	public function update_image_srcset( $sources, $size_array, $image_src, $image_meta, $attachment_id = 0 ) {
		if ( ! is_array( $sources ) || ! $this->is_supported_path( $image_src ) ) {
			return $sources;
		}

		$main_image_url = false;

		// Try to get image URL from attachment ID.
		if ( empty( $attachment_id ) ) {
			$url            = wp_get_attachment_url( $attachment_id );
			$main_image_url = $url;
		}

		foreach ( $sources as $i => $source ) {
			if ( ! $this->is_valid_url( $source['url'] ) ) {
				continue;
			}

			if ( apply_filters( 'smush_cdn_skip_image', false, $source['url'], $source ) ) {
				continue;
			}

			list( $width, $height ) = $this->get_size_from_file_name( $source['url'] );

			// The file already has a resized version as a thumbnail.
			if ( 'w' === $source['descriptor'] && $width === (int) $source['value'] ) {
				$sources[ $i ]['url'] = $this->generate_cdn_url( $source['url'] );
				continue;
			}

			// If don't have attachment id, get original image by removing dimensions from url.
			if ( empty( $url ) ) {
				$url = $this->get_url_without_dimensions( $source['url'] );
			}

			$args = array();
			// If we got size from url, add them.
			if ( ! empty( $width ) && ! empty( $height ) ) {
				// Set size arg.
				$args = array(
					'size' => "{$width}x{$height}",
				);
			}

			// Replace with CDN url.
			$sources[ $i ]['url'] = $this->generate_cdn_url( $url, $args );
		}

		// Set additional sizes if required.
		if ( $this->settings->get( 'auto_resize' ) ) {
			$sources = $this->set_additional_srcset( $sources, $size_array, $main_image_url, $image_meta, $image_src );

			// Make it look good.
			ksort( $sources );
		}

		return $sources;
	}

	/**
	 * Update image sizes for responsive size.
	 *
	 * @since 3.0
	 *
	 * @param string $sizes A source size value for use in a 'sizes' attribute.
	 * @param array  $size  Requested size.
	 *
	 * @return string
	 */
	public function update_image_sizes( $sizes, $size ) {
		if ( ! doing_filter( 'the_content' ) ) {
			return $sizes;
		}

		// Get maximum content width.
		$content_width = $this->max_content_width();

		if ( is_array( $size ) && $size[0] < $content_width ) {
			return $sizes;
		}

		return sprintf( '(max-width: %1$dpx) 100vw, %1$dpx', $content_width );
	}

	/**
	 * Add resize arguments to content image src.
	 *
	 * @since 3.0
	 *
	 * @param array  $args  Current arguments.
	 * @param object $image Image tag object from DOM.
	 *
	 * @return array $args
	 */
	public function update_cdn_image_src_args( $args, $image ) {
		// Get registered image sizes.
		$image_sizes = WP_Smush::get_instance()->core()->image_dimensions();

		// Find the width and height attributes.
		$width  = false;
		$height = false;

		// Try to get the width and height from img tag.
		if ( preg_match( '/width=["|\']?(\b[[:digit:]]+(?!%)\b)["|\']?/i', $image, $width_string ) ) {
			$width = $width_string[1];
		}

		if ( preg_match( '/height=["|\']?(\b[[:digit:]]+(?!%)\b)["|\']?/i', $image, $height_string ) ) {
			$height = $height_string[1];
		}

		$size = array();

		// Detect WP registered image size from HTML class.
		if ( preg_match( '/size-([^"\'\s]+)[^"\']*["|\']?/i', $image, $size ) ) {
			$size = array_pop( $size );

			if ( ! array_key_exists( $size, $image_sizes ) ) {
				return $args;
			}

			// This is probably a correctly sized thumbnail - no need to resize.
			if ( (int) $width === $image_sizes[ $size ]['width'] || (int) $height === $image_sizes[ $size ]['height'] ) {
				return $args;
			}

			// If this size exists in registered sizes, add argument.
			if ( 'full' !== $size ) {
				$args['size'] = (int) $image_sizes[ $size ]['width'] . 'x' . (int) $image_sizes[ $size ]['height'];
			}
		} else {
			// It's not a registered thumbnail size.
			if ( $width && $height ) {
				$args['size'] = (int) $width . 'x' . (int) $height;
			}
		}

		return $args;
	}

	/**
	 * Process CDN status.
	 *
	 * @since 3.0
	 * @since 3.1  Moved from Ajax class.
	 *
	 * @param array|WP_Error $status  Status in JSON format.
	 *
	 * @return stdClass|WP_Error
	 */
	public function process_cdn_status( $status ) {
		if ( is_wp_error( $status ) ) {
			return $status;
		}

		$status = json_decode( $status['body'] );

		// Too many requests.
		if ( is_null( $status ) ) {
			return new WP_Error( 'too_many_requests', __( 'Too many requests, please try again in a moment.', 'wp-smushit' ) );
		}

		// Some other error from API.
		if ( ! $status->success ) {
			return new WP_Error( $status->data->error_code, $status->data->message );
		}

		return $status->data;
	}

	/**
	 * Update CDN stats (daily) cron task or via the get_cdn_stats ajax request.
	 *
	 * @since 3.1.0
	 */
	public function update_stats() {
		$status = $this->settings->get_setting( 'wp-smush-cdn_status' );

		$smush = WP_Smush::get_instance();

		if ( isset( $status->cdn_enabling ) && $status->cdn_enabling ) {
			$new_status = $this->process_cdn_status( $smush->api()->enable() );
		} elseif ( wp_doing_cron() ) {
			// Verify CDN status via Cron.
			$new_status = $this->process_cdn_status( WP_Smush::get_instance()->api()->check() );
		}

		// For ajax.
		if ( ! isset( $new_status ) ) {
			// At this point we already know that $status->data is valid.
			return wp_send_json_success( $status );
		}

		// Return in case of error.
		if ( is_wp_error( $new_status ) ) {
			$code = is_numeric( $new_status->get_error_code() ) ? $new_status->get_error_code() : null;
			wp_send_json_error(
				array(
					'message' => $new_status->get_error_message(),
				),
				$code
			);
		}

		$this->settings->set_setting( 'wp-smush-cdn_status', $new_status );

		// For ajax.
		if ( ! wp_doing_cron() ) {
			// At this point we already know that $status->data is valid.
			wp_send_json_success( $new_status );
		}
	}

	/**
	 * Disable CDN stats update cron task.
	 *
	 * @since 3.1.0
	 */
	public static function unschedule_cron() {
		$timestamp = wp_next_scheduled( 'smush_update_cdn_stats' );
		wp_unschedule_event( $timestamp, 'smush_update_cdn_stats' );
	}

	/**
	 * Set cron task to update CDN stats daily.
	 *
	 * @since 3.1.0
	 */
	public function schedule_cron() {
		if ( ! wp_next_scheduled( 'smush_update_cdn_stats' ) ) {
			// Schedule first run for next day, as we've already checked just now.
			wp_schedule_event( time() + DAY_IN_SECONDS, 'daily', 'smush_update_cdn_stats' );
		}
	}

	/**
	 * Filters the API response.
	 *
	 * Allows modification of the response data after inserting
	 * embedded data (if any) and before echoing the response data.
	 *
	 * @since 3.6.0
	 *
	 * @param array $response  Response data to send to the client.
	 *
	 * @return array
	 */
	public function filter_rest_api_response( $response ) {
		if ( ! $this->settings->get( 'rest_api_support' ) ) {
			return $response;
		}

		if ( ! is_array( $response ) || ! isset( $response['content']['rendered'] ) ) {
			return $response;
		}

		$images = Helpers\Parser::get_links_from_content( $response['content']['rendered'] );

		if ( ! isset( $images[0] ) || empty( $images[0] ) ) {
			return $response;
		}

		foreach ( $images[0] as $key => $image ) {
			$image = $this->is_supported_path( $image );
			if ( ! $image ) {
				continue;
			}

			// Replace the data-envira-srcset of the image with CDN link.
			$image = $this->generate_cdn_url( $image );
			if ( $image ) {
				// Replace the src of the image with CDN link.
				$response['content']['rendered'] = str_replace( $images[0][ $key ], $image, $response['content']['rendered'] );
			}
		}

		return $response;
	}

	/**************************************
	 *
	 * PRIVATE METHODS
	 *
	 * Functions that are used by the public methods of this CDN class.
	 *
	 * @since 3.0.0:
	 *
	 * @see is_valid_url()
	 * @see get_size_from_file_name()
	 * @see get_url_without_dimensions()
	 * @see max_content_width()
	 * @see set_additional_srcset()
	 * @see generate_srcset()
	 * @see maybe_generate_srcset()
	 * @see is_supported_path()
	 */

	/**
	 * Check if we can use the image URL in CDN.
	 *
	 * @since 3.0
	 *
	 * @param string $url  Image URL.
	 *
	 * @return bool
	 */
	private function is_valid_url( $url ) {
		$parsed_url = wp_parse_url( $url );

		if ( ! $parsed_url ) {
			return false;
		}

		// No host or path found.
		if ( ! isset( $parsed_url['host'] ) || ! isset( $parsed_url['path'] ) ) {
			return false;
		}

		// If not supported extension - return false.
		if ( ! in_array( strtolower( pathinfo( $parsed_url['path'], PATHINFO_EXTENSION ) ), $this->supported_extensions, true ) ) {
			return false;
		}

		return true;
	}

	/**
	 * Try to determine height and width from strings WP appends to resized image filenames.
	 *
	 * @since 3.0
	 *
	 * @param string $src The image URL.
	 *
	 * @return array An array consisting of width and height.
	 */
	private function get_size_from_file_name( $src ) {
		$size = array();

		if ( preg_match( '/-(\d+)x(\d+)\.(?:' . implode( '|', $this->supported_extensions ) . ')$/i', $src, $size ) ) {
			// Get size and width.
			$width  = (int) $size[1];
			$height = (int) $size[2];

			// Handle retina images.
			if ( strpos( $src, '@2x' ) ) {
				$width  = 2 * $width;
				$height = 2 * $height;
			}

			// Return width and height as array.
			if ( $width && $height ) {
				return array( $width, $height );
			}
		}

		return array( false, false );
	}

	/**
	 * Get full size image url from resized one.
	 *
	 * @since 3.0
	 *
	 * @param string $src Image URL.
	 *
	 * @return string
	 */
	private function get_url_without_dimensions( $src ) {
		if ( ! preg_match( '/(-\d+x\d+)\.(' . implode( '|', $this->supported_extensions ) . ')(?:\?.+)?$/i', $src, $src_parts ) ) {
			return $src;
		}

		// Remove WP's resize string to get the original image.
		$original_src = str_replace( $src_parts[1], '', $src );

		// Upload directory.
		$upload_dir = wp_get_upload_dir();

		// Extracts the file path to the image minus the base url.
		$file_path = substr( $original_src, strlen( $upload_dir['baseurl'] ) );

		// Continue only if the file exists.
		if ( file_exists( $upload_dir['basedir'] . $file_path ) ) {
			return $original_src;
		}

		// Revert to source if file does not exist.
		return $src;
	}

	/**
	 * Get $content_width global var value.
	 *
	 * @since 3.0
	 *
	 * @return bool|string
	 */
	private function max_content_width() {
		// Get global content width (if content width is empty, set 1900).
		$content_width = isset( $GLOBALS['content_width'] ) ? (int) $GLOBALS['content_width'] : 1920;

		// Avoid situations, when themes misuse the global.
		if ( 0 === $content_width ) {
			$content_width = 1920;
		}

		// Check to see if we are resizing the images (can not go over that value).
		$resize_sizes = $this->settings->get_setting( 'wp-smush-resize_sizes' );

		if ( isset( $resize_sizes['width'] ) && $resize_sizes['width'] < $content_width ) {
			return $resize_sizes['width'];
		}

		return $content_width;
	}

	/**
	 * Filters an array of image srcset values, and add additional values.
	 *
	 * @since 3.0
	 *
	 * @param array  $sources    An array of image urls and widths.
	 * @param array  $size_array Array of width and height values in pixels.
	 * @param string $url        Image URL.
	 * @param array  $image_meta The image metadata.
	 * @param string $image_src  The src of the image.
	 *
	 * @return array $sources
	 */
	private function set_additional_srcset( $sources, $size_array, $url, $image_meta, $image_src = '' ) {
		$content_width = $this->max_content_width();

		// If url is empty, try to get from src.
		if ( empty( $url ) ) {
			$url = $this->get_url_without_dimensions( $image_src );
		}

		// We need to add additional dimensions.
		$full_width     = $image_meta['width'];
		$full_height    = $image_meta['height'];
		$current_width  = $size_array[0];
		$current_height = $size_array[1];
		// Get width and height calculated by WP.
		list( $constrained_width, $constrained_height ) = wp_constrain_dimensions( $full_width, $full_height, $current_width, $current_height );

		// Calculate base width.
		// If $constrained_width sizes are smaller than current size, set maximum content width.
		if ( abs( $constrained_width - $current_width ) <= 1 && abs( $constrained_height - $current_height ) <= 1 ) {
			$base_width = $content_width;
		} else {
			$base_width = $current_width;
		}

		$current_widths = array_keys( $sources );
		$new_sources    = array();

		/**
		 * Filter to add/update/bypass additional srcsets.
		 *
		 * If empty value or false is retured, additional srcset
		 * will not be generated.
		 *
		 * @param array|bool $additional_multipliers Additional multipliers.
		 */
		$additional_multipliers = apply_filters(
			'smush_srcset_additional_multipliers',
			array(
				0.2,
				0.4,
				0.6,
				0.8,
				1,
				2,
				3,
			)
		);

		// Continue only if additional multipliers found or not skipped.
		// Filter already documented in class-cdn.php.
		if ( apply_filters( 'smush_skip_image_from_cdn', false, $url, false ) || empty( $additional_multipliers ) ) {
			return $sources;
		}

		// Loop through each multipliers and generate image.
		foreach ( $additional_multipliers as $multiplier ) {
			// New width by multiplying with original size.
			$new_width = (int) ( $base_width * $multiplier );

			// In most cases - going over the current width is not recommended and probably not what the user is expecting.
			if ( $new_width > $current_width ) {
				continue;
			}

			// If a nearly sized image already exist, skip.
			foreach ( $current_widths as $_width ) {
				// If +- 50 pixel difference - skip.
				if ( abs( $_width - $new_width ) < 50 || ( $new_width > $full_width ) ) {
					continue 2;
				}
			}

			// We need the width as well...
			$dimensions = wp_constrain_dimensions( $current_width, $current_height, $new_width );

			// Arguments for cdn url.
			$args = array(
				'size' => "{$new_width}x{$dimensions[1]}",
			);

			// Add new srcset item.
			$new_sources[ $new_width ] = array(
				'url'        => $this->generate_cdn_url( $url, $args ),
				'descriptor' => 'w',
				'value'      => $new_width,
			);
		}

		// Assign new srcset items to existing ones.
		if ( ! empty( $new_sources ) ) {
			// Loop through each items and replace/add.
			foreach ( $new_sources as $_width_key => $_width_values ) {
				$sources[ $_width_key ] = $_width_values;
			}
		}

		return $sources;
	}

	/**
	 * Try to generate the srcset for the image.
	 *
	 * @since 3.0
	 *
	 * @param string $src  Image source.
	 *
	 * @return array|bool
	 */
	private function generate_srcset( $src ) {
		/**
		 * Try to get the attachment URL.
		 *
		 * TODO: attachment_url_to_postid() can be resource intensive and cause 100% CPU spikes.
		 *
		 * @see https://core.trac.wordpress.org/ticket/41281
		 */
		$attachment_id = attachment_url_to_postid( $src );
		$image_meta    = array();
		$width         = 0;
		$height        = 0;

		// Try to get width and height from image.
		if ( $attachment_id ) {
			list( $src, $width, $height ) = wp_get_attachment_image_src( $attachment_id, 'full' );
			$image_meta                   = wp_get_attachment_metadata( $attachment_id );
		}

		// Revolution slider fix: images will always return 0 height and 0 width.
		if ( $src && ( empty( $width ) || empty( $height ) ) ) {
			// Try to get the dimensions directly from the file.
			list( $width, $height ) = $this->get_image_size( $src );
		}

		if ( empty( $width ) || empty( $height ) ) {
			return false;
		}

		// This is an image placeholder - do not generate srcset.
		if ( $width === $height && 1 === $width ) {
			return false;
		}

		if ( empty( $image_meta ) ) {
			$image_meta = array(
				'width'  => $width,
				'height' => $height,
			);
		}

		$size_array = array( absint( $width ), absint( $height ) );
		$srcset     = wp_calculate_image_srcset( $size_array, $src, $image_meta, $attachment_id );

		/**
		 * In some rare cases, the wp_calculate_image_srcset() will not generate any srcset, because there are
		 * not image sizes defined. If that is the case, try to revert to our custom maybe_generate_srcset() to
		 * generate the srcset string.
		 *
		 * Also srcset will not be generated for images that are not part of the media library (no $attachment_id).
		 */
		if ( ! $srcset ) {
			$srcset = $this->maybe_generate_srcset( $width, $height, $src, $image_meta );
		}

		$sizes = $srcset ? wp_calculate_image_sizes( $size_array, $src, $image_meta, $attachment_id ) : false;

		return array( $srcset, $sizes );
	}

	/**
	 * Try to generate srcset.
	 *
	 * @since 3.0
	 *
	 * @param int    $width   Attachment width.
	 * @param int    $height  Attachment height.
	 * @param string $src     Image source.
	 * @param array  $meta    Image meta.
	 *
	 * @return bool|string
	 */
	private function maybe_generate_srcset( $width, $height, $src, $meta ) {
		$sources[ $width ] = array(
			'url'        => $this->generate_cdn_url( $src ),
			'descriptor' => 'w',
			'value'      => $width,
		);

		$sources = $this->set_additional_srcset(
			$sources,
			array( absint( $width ), absint( $height ) ),
			$src,
			$meta
		);

		$srcsets = array();

		if ( 1 < count( $sources ) ) {
			foreach ( $sources as $source ) {
				$srcsets[] = str_replace( ' ', '%20', $source['url'] ) . ' ' . $source['value'] . $source['descriptor'];
			}
			return implode( ',', $srcsets );
		}

		return false;
	}

	/**
	 * Check if the image path is supported by the CDN.
	 *
	 * @since 3.0
	 * @since 3.3.0 Changed access to public.
	 *
	 * @param string $src  Image path.
	 *
	 * @return bool|string
	 */
	public function is_supported_path( $src ) {
		// Remove whitespaces.
		$src = trim( $src );

		// No image? Return.
		if ( empty( $src ) ) {
			return false;
		}

		// Allow only these extensions in CDN.
		$path = wp_parse_url( $src, PHP_URL_PATH );
		// Make sure $path is not null, because passing null to parameter is deprecated in PHP 8.1.
		if ( empty( $path ) ) {
			return false;
		}
		$ext = strtolower( pathinfo( $path, PATHINFO_EXTENSION ) );
		if ( ! in_array( $ext, $this->supported_extensions, true ) ) {
			return false;
		}

		$url_parts = wp_parse_url( $src );

		// Unsupported scheme.
		if ( isset( $url_parts['scheme'] ) && 'http' !== $url_parts['scheme'] && 'https' !== $url_parts['scheme'] ) {
			return false;
		}

		if ( ! isset( $url_parts['scheme'] ) && 0 === strpos( $src, '//' ) ) {
			$src = is_ssl() ? 'https:' . $src : 'http:' . $src;
		}

		// This is a relative path, try to get the URL.
		if ( ! isset( $url_parts['host'] ) && ! isset( $url_parts['scheme'] ) ) {
			$src = site_url( $src );
		}

		$mapped_domain = $this->check_mapped_domain();

		/**
		 * There are chances for a custom uploads directory using UPLOADS constant.
		 *
		 * But some security plugins (for example, WP Hide & Security Enhance) will allow replacing paths via Nginx/Apache
		 * rules. So for this reason, we don't want the path to be replaced everywhere with the custom UPLOADS constant,
		 * we just want to let the user redefine it here, in the CDN.
		 *
		 * @since 3.4.0
		 *
		 * @param array $uploads {
		 *     Array of information about the upload directory.
		 *
		 *     @type string       $path    Base directory and subdirectory or full path to upload directory.
		 *     @type string       $url     Base URL and subdirectory or absolute URL to upload directory.
		 *     @type string       $subdir  Subdirectory if uploads use year/month folders option is on.
		 *     @type string       $basedir Path without subdir.
		 *     @type string       $baseurl URL path without subdir.
		 *     @type string|false $error   False or error message.
		 * }
		 *
		 * Usage (replace /wp-content/uploads/ with /media/ directory):
		 *
		 * add_filter(
		 *     'smush_cdn_custom_uploads_dir',
		 *     function( $uploads ) {
		 *         $uploads['baseurl'] = 'https://example.com/media';
		 *         return $uploads;
		 *     }
		 * );
		 */
		$uploads = apply_filters( 'smush_cdn_custom_uploads_dir', wp_get_upload_dir() );
		// Check if the src is within custom uploads directory.
		$uploads = ! isset( $uploads['baseurl'] ) || false !== strpos( $src, $uploads['baseurl'] );

		if ( ( false === strpos( $src, content_url() ) && ! $uploads ) || ( is_multisite() && $mapped_domain && false === strpos( $src, $mapped_domain ) ) ) {
			return false;
		}

		return $src;
	}

	/**
	 * Support for domain mapping plugin.
	 *
	 * @since 3.1.1
	 */
	private function check_mapped_domain() {
		if ( ! is_multisite() ) {
			return false;
		}

		if ( ! defined( 'DOMAINMAP_BASEFILE' ) ) {
			return false;
		}

		$domain = wp_cache_get( 'smush_mapped_site_domain', 'smush' );

		if ( ! $domain ) {
			global $wpdb;

			$domain = $wpdb->get_var(
				$wpdb->prepare(
					"SELECT domain FROM {$wpdb->base_prefix}domain_mapping WHERE blog_id = %d ORDER BY id LIMIT 1",
					get_current_blog_id()
				)
			); // Db call ok.

			if ( null !== $domain ) {
				wp_cache_add( 'smush_mapped_site_domain', $domain, 'smush' );
			}
		}

		return $domain;
	}

	/**
	 * Init the page parser.
	 */
	private function init_parser() {
		$background_images = $this->settings->get( 'background_images' );

		if ( $background_images ) {
			$this->parser->enable( 'background_images' );
		}

		$this->parser->enable( $this->slug );
	}

	/**
	 * Try to get the image dimensions from a local file.
	 *
	 * @since 3.4.0
	 * @param string $url  Image URL.
	 *
	 * @return array|false
	 */
	private function get_image_size( $url ) {
		if ( $this->site_url !== $this->home_url ) {
			$url = str_replace( $this->site_url, $this->home_url, $url );
		}

		$path = wp_make_link_relative( $url );
		$path = wp_normalize_path( ABSPATH . $path );

		if ( ! file_exists( $path ) ) {
			return false;
		}

		return wp_getimagesize( $path );
	}

}