BP_Attachment::upload( array $file, string $upload_dir_filter = '', string|null $time = null )

	public function upload( $file, $upload_dir_filter = '', $time = null ) {
		/**
		 * Upload action and the file input name are required parameters.
		 *
		 * @see BP_Attachment:__construct()
		 */
		if ( empty( $this->action ) || empty( $this->file_input ) ) {
			return false;
		}

		/**
		 * Add custom rules before enabling the file upload
		 */
		add_filter( "{$this->action}_prefilter", array( $this, 'validate_upload' ), 10, 1 );

		// Set Default overrides.
		$overrides = array(
			'action'               => $this->action,
			'upload_error_strings' => $this->upload_error_strings,
		);

		/**
		 * Add a mime override if needed
		 * Used to restrict uploads by extensions
		 */
		if ( ! empty( $this->allowed_mime_types ) ) {
			$mime_types = $this->validate_mime_types();

			if ( ! empty( $mime_types ) ) {
				$overrides['mimes'] = $mime_types;
			}
		}

		/**
		 * If you need to add some overrides we haven't thought of.
		 *
		 * @param array $overrides The wp_handle_upload overrides
		 */
		$overrides = apply_filters( 'bp_attachment_upload_overrides', $overrides );

		$this->includes();

		/**
		 * If the $base_dir was set when constructing the class,
		 * and no specific filter has been requested, use a default
		 * filter to create the specific $base dir
		 * @see  BP_Attachment->upload_dir_filter()
		 */
		if ( empty( $upload_dir_filter ) && ! empty( $this->base_dir ) ) {
			$upload_dir_filter = array( $this, 'upload_dir_filter' );
		}

		// Make sure the file will be uploaded in the attachment directory.
		if ( ! empty( $upload_dir_filter ) ) {
			add_filter( 'upload_dir', $upload_dir_filter, 10, $this->upload_dir_filter_args );
		}

		// Helper for utf-8 filenames.
		add_filter( 'sanitize_file_name', array( $this, 'sanitize_utf8_filename' ) );

		// Upload the attachment.
		$this->attachment = wp_handle_upload( $file[ $this->file_input ], $overrides, $time );

		remove_filter( 'sanitize_file_name', array( $this, 'sanitize_utf8_filename' ) );

		// Restore WordPress Uploads data.
		if ( ! empty( $upload_dir_filter ) ) {
			remove_filter( 'upload_dir', $upload_dir_filter, 10 );
		}

		// Finally return the uploaded file or the error.
		return $this->attachment;
	}