<?php
/**
 * Dropbox Files Downloader.
 */

/**
 * Class BackWPup_Destination_Dropbox_Downloader.
 *
 * @since   3.5.0
 */
final class BackWPup_Destination_Dropbox_Downloader implements BackWPup_Destination_Downloader_Interface {

	public const OPTION_ROOT  = 'dropboxroot';
	public const OPTION_TOKEN = 'dropboxtoken';

	/**
	 * Downloader data object.
	 *
	 * @var \BackWpUp_Destination_Downloader_Data
	 */
	private $data;

	/**
	 * Local file handler.
	 *
	 * @var resource
	 */
	private $local_file_handler;

	/**
	 * Dropbox API client.
	 *
	 * @var BackWPup_Destination_Dropbox_API
	 */
	private $dropbox_api;

	/**
	 * BackWPup_Destination_Dropbox_Downloader constructor.
	 *
	 * @param \BackWpUp_Destination_Downloader_Data $data Download data.
	 *
	 * @throws \BackWPup_Destination_Dropbox_API_Exception When the API cannot be initialized.
	 */
	public function __construct( BackWpUp_Destination_Downloader_Data $data ) {
		$this->data = $data;

		$this->dropbox_api();
	}

	/**
	 * Clean up things.
	 */
	public function __destruct() {
		fclose( $this->local_file_handler ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_fclose
	}

	/**
	 * Download a chunk from Dropbox.
	 *
	 * @param int $start_byte Start byte offset.
	 * @param int $end_byte   End byte offset.
	 *
	 * @return void
	 * @throws \RuntimeException When the local file cannot be opened.
	 */
	public function download_chunk( $start_byte, $end_byte ) {
		$this->local_file_handler( $start_byte );

		try {
			$data = $this->dropbox_api->download(
				[ 'path' => $this->data->source_file_path() ],
				$start_byte,
				$end_byte
			);

			$bytes = (int) fwrite( $this->local_file_handler, (string) $data ); //phpcs:ignore
			if ( 0 === $bytes ) {
				throw new \RuntimeException( esc_html__( 'Could not write data to file.', 'backwpup' ) );
			}
		} catch ( \Exception $e ) {
			BackWPup_Admin::message( 'Dropbox: ' . $e->getMessage() );
		}
	}

	/**
	 * Calculate the total file size.
	 *
	 * @return int
	 */
	public function calculate_size() {
		$metadata = $this->dropbox_api->files_get_metadata( [ 'path' => $this->data->source_file_path() ] );

		return $metadata['size'];
	}

	/**
	 * Set local file hanlder.
	 *
	 * @param int $start_byte Start byte offset.
	 *
	 * @return void
	 * @throws \RuntimeException When the local file cannot be opened.
	 */
	private function local_file_handler( $start_byte ) {
		if ( is_resource( $this->local_file_handler ) ) {
			return;
		}

		// Open file; write mode if $start_byte is 0, else append.
		$this->local_file_handler = fopen( $this->data->local_file_path(), 0 === $start_byte ? 'wb' : 'ab' ); // phpcs:ignore WordPress.WP.AlternativeFunctions.file_system_operations_fopen

		if ( ! is_resource( $this->local_file_handler ) ) {
			throw new \RuntimeException( esc_html__( 'File could not be opened for writing.', 'backwpup' ) );
		}
	}

	/**
	 * Set the dropbox api instance.
	 *
	 * @throws \BackWPup_Destination_Dropbox_API_Exception When the Dropbox API cannot be initialized.
	 */
	private function dropbox_api(): void {
		$this->dropbox_api = new \BackWPup_Destination_Dropbox_API(
			\BackWPup_Option::get( $this->data->job_id(), self::OPTION_ROOT )
		);

		$this->dropbox_api->set_o_auth_tokens( \BackWPup_Option::get( $this->data->job_id(), self::OPTION_TOKEN ) );
	}
}