<?php
/**
 * The receipt code of a request.
 *
 * @package Careback
 */

namespace Careback;

defined( 'ABSPATH' ) || exit;

/**
 * A short code worked out from what a customer declared and the moment it
 * arrived, keyed by the plugin's key (N-70). The confirmation email carries
 * it and the request card shows it again, worked out afresh from the request
 * as stored: when the two match, the stored request is the one the customer
 * was sent. How to work it out by hand: api/data.md §2b.
 *
 * What it covers is fixed when the request is filed and never changes with
 * its handling: the request and order numbers, the moment it arrived (UTC),
 * whether it carries a statutory withdrawal, the customer's name, the items
 * (order line, quantity, name), the reason and the comment. The status, the
 * history and a later change of type are not part of it.
 */
class Receipt {

	/** First field of the text the code is worked out from; a later format gets a new one. */
	const VERSION = 'careback-receipt-1';

	/** Hex digits kept: 64 bits, in four groups of four. */
	const LENGTH = 16;

	/**
	 * Shows the code on the card of a request sent through the form.
	 *
	 * @return void
	 */
	public static function init() {
		add_filter( Admin_Requests::DETAIL_BLOCKS, array( __CLASS__, 'card_block' ), 10, 2 );
	}

	/**
	 * The code of a request, e.g. "4F2A-9C1E-0B7D-33A1".
	 *
	 * @param array $row The request as stored (items as stored JSON or as an array).
	 * @return string
	 */
	public static function code( array $row ) {
		$hex = strtoupper( substr( Hash::hmac( self::text( $row ) ), 0, self::LENGTH ) );

		return implode( '-', str_split( $hex, 4 ) );
	}

	/**
	 * The text the code is worked out from: a JSON list of strings, written
	 * with unescaped slashes and unescaped Unicode.
	 *
	 *   [ "careback-receipt-1", id, order number, moment received (UTC,
	 *     "Y-m-d H:i:s"), "withdrawal" or "", customer name,
	 *     [ [ order line id, quantity, item name ], … ], reason, comment ]
	 *
	 * @param array $row The request as stored.
	 * @return string
	 */
	public static function text( array $row ) {
		$items = isset( $row['items'] ) ? $row['items'] : array();

		if ( is_string( $items ) ) {
			$items = json_decode( $items, true );
		}

		$lines = array();

		foreach ( is_array( $items ) ? $items : array() as $item ) {
			$item    = (array) $item;
			$lines[] = array(
				(string) ( isset( $item['line_item_id'] ) ? (int) $item['line_item_id'] : 0 ),
				(string) ( isset( $item['quantity'] ) ? (int) $item['quantity'] : 0 ),
				isset( $item['name'] ) ? (string) $item['name'] : '',
			);
		}

		$fields = array(
			self::VERSION,
			(string) ( isset( $row['id'] ) ? (int) $row['id'] : 0 ),
			self::field( $row, 'order_number' ),
			self::field( $row, 'declaration_received_at' ),
			Requests_Repository::is_statutory( $row ) ? 'withdrawal' : '',
			self::field( $row, 'customer_name' ),
			$lines,
			self::field( $row, 'reason' ),
			self::field( $row, 'comment' ),
		);

		return (string) wp_json_encode( $fields, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE );
	}

	/**
	 * A column as text; a missing or NULL one is "".
	 *
	 * @param array  $row Row.
	 * @param string $key Column.
	 * @return string
	 */
	private static function field( array $row, $key ) {
		return isset( $row[ $key ] ) ? (string) $row[ $key ] : '';
	}

	/**
	 * Adds the code to the card of a request sent through the form: only those
	 * were confirmed by email. A request recorded by hand has none to compare.
	 *
	 * @param array $blocks The card's blocks.
	 * @param array $row    Request row.
	 * @return array
	 */
	public static function card_block( $blocks, $row ) {
		$blocks = is_array( $blocks ) ? $blocks : array();
		$row    = is_array( $row ) ? $row : array();

		if ( empty( $row['id'] ) || ( isset( $row['channel'] ) && 'portal' !== (string) $row['channel'] ) ) {
			return $blocks;
		}

		$blocks['receipt'] = array(
			'region'   => 'grid',
			'position' => 15,
			'render'   => array( __CLASS__, 'render_block' ),
		);

		return $blocks;
	}

	/**
	 * Prints the code on the card.
	 *
	 * @param array $row Request row.
	 * @return void
	 */
	public static function render_block( $row ) {
		?>
		<div class="careback-detail-block careback-detail-receipt">
			<h4><?php esc_html_e( 'Receipt code', 'careback' ); ?></h4>
			<p>
				<code><?php echo esc_html( self::code( (array) $row ) ); ?></code>
				<?php Admin_Tip::render( __( 'The code in the confirmation email the customer received, worked out again from this request as it is stored now. When it matches the code in their email, the request has not changed since they sent it.', 'careback' ) ); ?>
			</p>
		</div>
		<?php
	}
}