<?php
namespace Syntopia_Pay;

defined( 'ABSPATH' ) || exit;

class Codec {
	private const NOTIFICATION_KEYS = [ 'invoice', 'status', 'pay_time', 'stan', 'bcode' ];

	/**
	 * @param array<string,string> $fields
	 */
	public static function encode( array $fields ): string {
		$lines = [];
		foreach ( $fields as $key => $value ) {
			$lines[] = $key . '=' . $value;
		}
		return base64_encode( implode( "\n", $lines ) ); // phpcs:ignore WordPress.PHP.DiscouragedPHPFunctions.obfuscation_base64_encode -- ePay.bg wire format, not obfuscation.
	}

	public static function checksum( string $encoded, string $secret ): string {
		return '' === $secret ? '' : hash_hmac( 'sha1', $encoded, $secret );
	}

	public static function verify( string $encoded, string $checksum, string $secret ): bool {
		$checksum = strtolower( trim( $checksum ) );
		if ( '' === $secret || 1 !== preg_match( '/^[0-9a-f]{40}$/', $checksum ) ) {
			return false;
		}
		return hash_equals( self::checksum( $encoded, $secret ), $checksum );
	}

	/**
	 * @return list<array<string,string>>
	 */
	public static function parse_notification( string $encoded ): array {
		$decoded = base64_decode( $encoded, true ); // phpcs:ignore WordPress.PHP.DiscouragedPHPFunctions.obfuscation_base64_decode -- ePay.bg wire format, not obfuscation.
		if ( false === $decoded ) {
			return [];
		}

		$entries = [];
		foreach ( preg_split( '/\r\n|\n|\r/', $decoded ) as $line ) {
			$entry = [];
			foreach ( explode( ':', $line ) as $part ) {
				$pair = explode( '=', $part, 2 );
				if ( 2 !== count( $pair ) ) {
					continue;
				}
				$key = strtolower( trim( $pair[0] ) );
				if ( in_array( $key, self::NOTIFICATION_KEYS, true ) ) {
					$entry[ $key ] = trim( $pair[1] );
				}
			}
			if ( 1 === preg_match( '/^\d{1,20}$/', $entry['invoice'] ?? '' ) ) {
				$entry['status'] ??= '';
				$entries[]        = $entry;
			}
		}
		return $entries;
	}

	public static function request_field( string $encoded, string $key ): string {
		$decoded = base64_decode( $encoded, true ); // phpcs:ignore WordPress.PHP.DiscouragedPHPFunctions.obfuscation_base64_decode -- ePay.bg wire format, not obfuscation.
		if ( false === $decoded ) {
			return '';
		}
		foreach ( preg_split( '/\r\n|\n|\r/', $decoded ) as $line ) {
			$pair = explode( '=', $line, 2 );
			if ( 2 === count( $pair ) && $pair[0] === $key ) {
				return $pair[1];
			}
		}
		return '';
	}

	/**
	 * @param array<string,string> $statuses Invoice => OK|ERR|NO.
	 */
	public static function reply( array $statuses ): string {
		$out = '';
		foreach ( $statuses as $invoice => $status ) {
			$out .= 'INVOICE=' . self::clean( (string) $invoice ) . ':STATUS=' . self::clean( $status ) . "\n";
		}
		return $out;
	}

	public static function error_reply( string $code ): string {
		return 'ERR=' . self::clean( $code ) . "\n";
	}

	private static function clean( string $value ): string {
		return (string) preg_replace( '/[\x00-\x1f:]/', '', $value );
	}
}