ml ', 'html class="' . $add_classes . '" ', $match[0] );
				}

				$content = str_replace( $match[0], $new_tag, $content );
			}
		}

		return $content;
	}

	/**
	 * Adds a filter with detected images tags and the content.
	 *
	 * @param string $content The HTML content.
	 *
	 * @return mixed
	 */
	public function process_images_from_content( $content ) {
		if ( self::should_ignore_image_tags() ) {
			return $content;
		}
		$images = self::parse_images_from_html( $content );
		if ( empty( $images ) ) {
			return $content;
		}

		return apply_filters( 'optml_content_images_tags', $content, $images );
	}

	/**
	 * Check if we are on a amp endpoint.
	 *
	 * IMPORTANT: This needs to be  used after parse_query hook, otherwise will return false positives.
	 *
	 * @return bool
	 */
	public static function should_ignore_image_tags() {

		// Ignore image tag replacement in feed context as we don't need it.
		if ( is_feed() ) {
			return true;
		}

		// Ignore image tags replacement in amp context as they are not available.
		if ( function_exists( 'is_amp_endpoint' ) ) {
			return is_amp_endpoint();
		}

		if ( function_exists( 'ampforwp_is_amp_endpoint' ) ) {
			return ampforwp_is_amp_endpoint();
		}

		return apply_filters( 'optml_should_ignore_image_tags', false ) === true;
	}

	/**
	 * Match all images and any relevant <a> tags in a block of HTML.
	 *
	 * @param string $content Some HTML.
	 *
	 * @return array An array of $images matches, where $images[0] is
	 *         an array of full matches, and the link_url, img_tag,
	 *         and img_url keys are arrays of those matches.
	 */
	public static function parse_images_from_html( $content ) {
		$images = [];

		$header_start = null;
		$header_end   = null;

		if ( preg_match( '/<header.*<\/header>/ismU', $content, $matches, PREG_OFFSET_CAPTURE ) === 1 ) {
			$header_start = $matches[0][1];
			$header_end   = $header_start + strlen( $matches[0][0] );
		}
		$regex = '/(?:<a[^>]+?href=["|\'](?P<link_url>[^\s]+?)["|\'][^>]*?>\s*)?(?P<img_tag>(?:<noscript\s*>\s*)?<img[^>]*?\s?(?:' . implode( '|', array_merge( [ 'src' ], Optml_Tag_Replacer::possible_src_attributes() ) ) . ')=["\'\\\\]*?(?P<img_url>[' . Optml_Config::$chars . ']{10,}).*?>(?:\s*<\/noscript\s*>)?){1}(?:\s*<\/a>)?/ismu';

		if ( preg_match_all( $regex, $content, $images, PREG_OFFSET_CAPTURE ) ) {
			if ( OPTML_DEBUG ) {
				do_action( 'optml_log', $images );
			}
			foreach ( $images as $key => $unused ) {
				// Simplify the output as much as possible, mostly for confirming test results.
				if ( is_numeric( $key ) && $key > 0 ) {
					unset( $images[ $key ] );
					continue;
				}

				$is_no_script = false;
				foreach ( $unused as $url_key => $url_value ) {
					if ( $key === 'img_url' ) {
						$images[ $key ][ $url_key ] = rtrim( $url_value[0], '\\' );
						continue;
					}
					$images[ $key ][ $url_key ] = $url_value[0];

					if ( $key === 0 ) {
						$images['in_header'][ $url_key ] = $header_start !== null ? ( $url_value[1] > $header_start && $url_value[1] < $header_end ) : false;

						// Check if we are in the noscript context.
						if ( $is_no_script === false ) {
							$is_no_script = strpos( $images[0][ $url_key ], '<noscript' ) !== false ? true : false;
						}
						if ( $is_no_script ) {
							$images['in_header'][ $url_key ] = true;
							$is_no_script                    = strpos( $images[0][ $url_key ], '</noscript' ) !== false ? false : true;
						}
					}
				}
			}

			return $images;
		}

		return [];
	}

	/**
	 * Process url replacement from raw html strings.
	 *
	 * @param string $html Raw html.
	 *
	 * @return string Processed string.
	 */
	public function process_urls_from_content( $html ) {
		$extracted_urls = $this->extract_urls_from_content( $html );
		if ( OPTML_DEBUG ) {
			do_action( 'optml_log', 'matched urls' );
			do_action( 'optml_log', $extracted_urls );
		}
		return $this->do_url_replacement( $html, $extracted_urls );
	}

	/**
	 * Method to extract assets from content.
	 *
	 * @param string $content The HTML content.
	 *
	 * @return array
	 */
	public function extract_urls_from_content( $content ) {
		$extensions = array_keys( Optml_Config::$image_extensions );
		if ( $this->settings->use_cdn() && ! self::should_ignore_image_tags() ) {
			$extensions = array_merge( $extensions, array_keys( Optml_Config::$assets_extensions ) );
		}
		$regex = '/(?:[(|\s\';",=\]])((?:http|\/|\\\\){1}(?:[' . Optml_Config::$chars . ']{10,}\.(?:' . implode( '|', $extensions ) . ')))(?=(?:http|>|%3F|\?|"|&|,|\s|\'|\)|\||\\\\|}|\[))/Uu';
		preg_match_all(
			$regex,
			$content,
			$urls
		);

		return $this->normalize_urls( $urls[1] );
	}

	/**
	 * Normalize extracted urls.
	 *
	 * @param array $urls Raw urls extracted.
	 *
	 * @return array Normalized array.
	 */
	private function normalize_urls( $urls ) {

		$urls = array_map(
			function ( $value ) {
				$value = str_replace( '&quot;', '', $value );

				return rtrim( $value, '\\";\'' );
			},
			$urls
		);
		$urls = array_unique( $urls );

		return array_values( $urls );
	}

	/**
	 * Process string content and replace possible urls.
	 *
	 * @param string $html String content.
	 * @param array  $extracted_urls Urls to check.
	 *
	 * @return string Processed html.
	 */
	public function do_url_replacement( $html, $extracted_urls ) {
		$extracted_urls = apply_filters( 'optml_extracted_urls', $extracted_urls );

		if ( empty( $extracted_urls ) ) {
			return $html;
		}
		$slashed_config = addcslashes( Optml_Config::$service_url, '/' );

		$extracted_urls  = array_filter(
			$extracted_urls,
			function ( $value ) use ( $slashed_config ) {
				return strpos( $value, Optml_Config::$service_url ) === false && strpos( $value, $slashed_config ) === false || Optml_Media_Offload::is_not_processed_image( $value ) || $this->tag_replacer->url_has_dam_flag( $value );
			}
		);
		$upload_resource = $this->tag_replacer->get_upload_resource();
		$urls            = array_combine( $extracted_urls, $extracted_urls );

		$urls = array_map(
			function ( $url ) use ( $upload_resource ) {
				$is_slashed  = strpos( $url, '\/' ) !== false;
				$is_relative = strpos(
					$url,
					$is_slashed ?
										addcslashes( $upload_resource['content_path'], '/' ) :
										$upload_resource['content_path']
				) === 0;
				if ( $is_relative ) {
					$url = $upload_resource['content_host'] . $url;
				}

				return apply_filters( 'optml_content_url', $url );
			},
			$urls
		);

		foreach ( $urls as $origin => $replace ) {
			$html = preg_replace( '/(?<![\/|:|\\w])' . preg_quote( $origin, '/' ) . '/m', $replace, $html );
		}

		return $html;
	}

	/**
	 * Init html replacer handler.
	 */
	public function process_template_redirect_content() {
		// Early exit if function was already called, we don't want duplicate ob_start
		if ( self::$ob_started === true ) {
			return;
		}
		self::$ob_started = true;
		// We no longer need this if the handler was started.
		remove_filter( 'the_content', [ $this, 'process_images_from_content' ], PHP_INT_MAX );

		ob_start(
			[ &$this, 'replace_content' ]
		);
	}

	/**
	 * Close the buffer and flush the content.
	 */
	public function close_buffer() {
		if ( self::$ob_started && ob_get_length() ) {
			ob_end_flush();
		}
	}
	/**
	 * Throw error on object clone
	 *
	 * The whole idea of the singleton design pattern is that there is a single
	 * object therefore, we don't want the object to be cloned.
	 *
	 * @codeCoverageIgnore
	 * @access public
	 * @return void
	 * @since  1.0.0
	 */
	public function __clone() {
		// Cloning instances of the class is forbidden.
		_doing_it_wrong( __FUNCTION__, esc_html__( 'Cheatin&#8217; huh?', 'optimole-wp' ), '1.0.0' );
	}

	/**
	 * Disable unserializing of the class
	 *
	 * @codeCoverageIgnore
	 * @access public
	 * @return void
	 * @since  1.0.0
	 */
	public function __wakeup() {
		// Unserializing instances of the class is forbidden.
		_doing_it_wrong( __FUNCTION__, esc_html__( 'Cheatin&#8217; huh?', 'optimole-wp' ), '1.0.0' );
	}
}