silverstripe-framework/Assets/Storage/GeneratedAssetHandler.php

<?php

namespace SilverStripe\Assets\Storage;

/**
 * Interface to define a handler for persistent generated files
 */
interface GeneratedAssetHandler {

	/**
     * Returns a URL to a generated asset, if one is available.
     *
	 * Given a filename, determine if a file is available. If the file is unavailable,
     * and a callback is supplied, invoke it to regenerate the content.
	 *
	 * @param string $filename
	 * @param callable $callback To generate content. If none provided, url will only be returned
	 * if there is valid content.
	 * @return string URL to generated file
	 */
	public function getContentURL($filename, $callback = null);

	/**
	 * Returns the content for a generated asset, if one is available.
     *
	 * Given a filename, determine if a file is available. If the file is unavailable,
     * and a callback is supplied, invoke it to regenerate the content.
	 *
	 * @param string $filename
	 * @param callable $callback To generate content. If none provided, content will only be returned
	 * if there is valid content.
	 * @return string Content for this generated file
	 */
	public function getContent($filename, $callback = null);

	/**
	 * Update content with new value
	 *
	 * @param string $filename
	 * @param string $content Content to write to the backend
	 */
	public function setContent($filename, $content);

    /**
     * Remove any content under the given file.
     *
     * If $filename is a folder, it should delete all files underneath it also.
     *
     * @param string $filename
     */
    public function removeContent($filename);
}