<?php
/**
 * Class description
 *
 * @package   package_name
 * @author    Cherry Team
 * @license   GPL-2.0+
 */

// If this file is called directly, abort.
if ( ! defined( 'WPINC' ) ) {
	die;
}

if ( ! class_exists( 'Jet_Elements_Download_Handler' ) ) {

	/**
	 * Define Jet_Elements_Download_Handler class
	 */
	class Jet_Elements_Download_Handler {

		/**
		 * A reference to an instance of this class.
		 *
		 * @since 1.0.0
		 * @var   object
		 */
		private static $instance = null;

		/**
		 * Download hook
		 *
		 * @var string
		 */
		private $hook = 'jet_download';

		/**
		 * Return nonce key for hashing URL
		 * 
		 * @return [type] [description]
		 */
		public function get_nonce_key() {

			if ( defined( 'NONCE_SALT' ) ) {
				return NONCE_SALT;
			}

			$encrypt_key = get_option( 'jet_elements_download_button_encrypt_key_start' );

			if ( ! $encrypt_key ) {
				$encrypt_key = $this->generate_security_key();
				add_option( 'jet_elements_download_button_encrypt_key_start', $encrypt_key );
			}

			return $encrypt_key;

		}

		/**
		 * Constructor for the class
		 */
		public function init() {
			add_action( 'init', array( $this, 'process_download' ), 99 );
			add_action( 'init', array( $this, 'reset_download_hashes' ), 99 );
		}

		public function get_reset_hashes_url() {
			return add_query_arg(
				array( $this->hook() . '_reset' => 1, 'nonce' => wp_create_nonce( $this->hook() ) ),
				esc_url( home_url( '/' ) )
			);
		}

		public function reset_download_hashes() {

			if ( empty( $_GET[ $this->hook() . '_reset' ] ) ) {
				return;
			}

			$nonce = ! empty( $_GET['nonce'] ) ? $_GET['nonce'] : false;

			if ( ! $nonce || ! wp_verify_nonce( $nonce, $this->hook() ) ) {
				wp_die( 
					esc_html__( 'Your link is expired, please return to the previous page, reload it and try again.', 'jet-elements' ),
					esc_html__( 'Error', 'jet-elements' )
				);
			}

			if ( ! current_user_can( 'manage_options' ) ) {
				wp_die( 
					esc_html__( 'Only site admins allowed to do this.', 'jet-elements' ),
					esc_html__( 'Error', 'jet-elements' )
				);
			}

			delete_option( 'jet_elements_download_button_hashes' );

			wp_die( 
				esc_html__( 'Download hashes successfully reseted. If you are using any caching plugins, you also need to reset cache to ensure all valid hashes regenerated.', 'jet-elements' ),
				esc_html__( 'Success!', 'jet-elements' )
			);

		}

		/**
		 * Generate security key
		 *
		 * @var string
		 */
		private function generate_security_key() {
			return absint( (int)( ( time() / random_int( 11, 100 ) ) * random_int( 2, 1000 ) ) );
		}

		/**
		 * Returns download hook name
		 *
		 * @return string
		 */
		public function hook() {
			return $this->hook;
		}

		/**
		 * Get plain encrypted ID
		 * 
		 * @param  [type] $id [description]
		 * @return [type]     [description]
		 */
		public function get_encrypted_id( $id ) {
			return sha1( $this->get_nonce_key() . $id );
		}

		/**
		 * Encrypt download ID
		 *
		 * @return string
		 */
		private function encrypt_id( $id ) {

			$hash = $this->get_encrypted_id( $id );
			$hash_map = get_option( 'jet_elements_download_button_hashes', [] );
			$sanitize_hashes = false;
			$hash_map[ $hash ] = $id;

			update_option( 'jet_elements_download_button_hashes', $hash_map, false );

			return $hash;
		}

		/**
		 * Decrypt download ID
		 *
		 * @return string
		 */
		private function decrypt_id( $id ) {
			$hash_map = get_option( 'jet_elements_download_button_hashes', [] );
			return isset( $hash_map[ $id ] ) ? $hash_map[ $id ] : false;
		}

		/**
		 * Get download link for passed ID.
		 *
		 * @param  integer $id Media post ID.
		 * @return string
		 */
		public function get_download_link( $id = 0, $is_encrypted = '' ) {
			
			// For security reasons now is encrypted in any case
			$id = $this->encrypt_id( $id );

			return add_query_arg(
				array( $this->hook() => $id ),
				esc_url( home_url( '/' ) )
			);
		}

		/**
		 * Get file size by attachment ID
		 * @param  integer $id [description]
		 * @return [type]      [description]
		 */
		public function get_file_size( $id = 0 ) {

			$file_path = get_attached_file( $id );

			if ( ! $file_path ) {
				return;
			}

			$file_size = filesize( $file_path );

			return size_format( $file_size );
		}

		/**
		 * Check if is download request and handle it.
		 */
		public function process_download() {

			if ( empty( $_GET[ $this->hook() ] ) ) {
				return;
			}

			$encrypted_id = $_GET[ $this->hook() ];
			$id           = absint( $this->decrypt_id( $encrypted_id ) );

			if ( ! $id ) {
				return;
			}

			$post = get_post( $id );

			if ( 'attachment' !== $post->post_type ) {
				return;
			}

			$file_path = get_attached_file( $id );

			if ( ! is_file( $file_path ) ) {
				return;
			}

			// Clear all output buffers to prevent file corruption
			while ( ob_get_level() ) {
				@ob_end_clean();
			}

			if ( ini_get( 'zlib.output_compression' ) ) {
				ini_set('zlib.output_compression', 'Off');
			}

			// get the file mime type using the file extension
			switch( strtolower( substr( strrchr( $file_path, '.' ), 1 ) ) ) {
				case 'pdf':
					$mime = 'application/pdf';
					break;
				case 'zip':
					$mime = 'application/zip';
					break;
				case 'jpeg':
				case 'jpg':
					$mime = 'image/jpg';
					break;
				default:
					$mime = 'application/force-download';
					break;
			}

			header( 'Pragma: public' );
			header( 'Expires: 0' );
			header( 'Cache-Control: must-revalidate, post-check=0, pre-check=0');
			header( 'Last-Modified: ' . gmdate( 'D, d M Y H:i:s', @filemtime( $file_path ) ) . ' GMT' );
			header( 'Cache-Control: private', false );
			header( 'Content-Type: ' . $mime );
			header( 'Content-Disposition: attachment; filename="' . basename( $file_path ) . '"' );
			header( 'Content-Transfer-Encoding: binary' );
			header( 'Content-Length: ' . @filesize( $file_path ) );
			header( 'Connection: close' );

			$this->readfile_chunked( $file_path );

			die();

		}

		/**
		 * Process chuncked download
		 *
		 * @param  string $file     Filepath
		 * @param  bool   $retbytes
		 * @return mixed
		 */
		public function readfile_chunked( $filename, $retbytes = true ) {

			$chunksize = 1 * ( 1024 * 1024 );
			$buffer    = '';
			$cnt       = 0;
			$handle    = fopen( $filename, 'rb' );

			if ( false === $handle ) {
				return false;
			}

			while ( ! feof( $handle ) ) {
				$buffer = fread( $handle, $chunksize );
				echo $buffer;

				if ( ob_get_level() > 0 ) {
					ob_flush();
				}
				flush();
				if ( $retbytes ) {
					$cnt += strlen( $buffer );
				}
			}

			$status = fclose($handle);

			if ( $retbytes && $status ) {
				return $cnt; // return num. bytes delivered like readfile() does.
			}

			return $status;
		}

		/**
		 * Returns the instance.
		 *
		 * @since  1.0.0
		 * @return object
		 */
		public static function get_instance() {

			// If the single instance hasn't been set, set it now.
			if ( null == self::$instance ) {
				self::$instance = new self;
			}
			return self::$instance;
		}
	}

}

/**
 * Returns instance of Jet_Elements_Download_Handler
 *
 * @return object
 */
function jet_elements_download_handler() {
	return Jet_Elements_Download_Handler::get_instance();
}
