<?php
/**
 * Validation of XML namespace declarations.
 *
 * @package FeedWeaver
 */

namespace FeedWeaver\Mapping;

defined( 'ABSPATH' ) || exit;

/**
 * A feed may declare up to MAX namespaces (prefix + URI), written once on the root element.
 * Namespaces are optional: ordinary feeds never need one.
 */
class Namespace_Validator {

	const MAX = 10;

	/** URIs the XML specifications reserve; they can never be bound to a user prefix. */
	const RESERVED_URIS = array(
		'http://www.w3.org/XML/1998/namespace',
		'http://www.w3.org/2000/xmlns/',
	);

	/**
	 * Whether a namespace URI is acceptable: an http(s) or urn: URI of sensible length with no
	 * whitespace, control characters, quotes or angle brackets.
	 *
	 * @param mixed $uri Candidate.
	 * @return bool
	 */
	public static function is_valid_uri( $uri ): bool {
		if ( ! is_string( $uri ) || '' === $uri || strlen( $uri ) > 200 ) {
			return false;
		}
		if ( 1 !== preg_match( '#^(https?://[^\s"\'<>&\\\\\x00-\x1F\x7F]+|urn:[A-Za-z0-9][A-Za-z0-9-]*:[^\s"\'<>&\\\\\x00-\x1F\x7F]+)$#D', $uri ) ) {
			return false;
		}
		return ! in_array(
			rtrim( $uri, '/' ),
			array_map(
				static function ( $reserved ) {
					return rtrim( $reserved, '/' );
				},
				self::RESERVED_URIS
			),
			true
		);
	}

	/**
	 * Validates a list of declarations.
	 *
	 * @param array $namespaces List of array{prefix:string,uri:string}.
	 * @return string[] Messages that name the affected row; empty when valid.
	 */
	public static function validate( array $namespaces ): array {
		$errors = array();
		if ( count( $namespaces ) > self::MAX ) {
			/* translators: %d: maximum number of namespaces. */
			return array( sprintf( __( 'Declare at most %d XML namespaces.', 'feedweaver' ), self::MAX ) );
		}
		$seen_prefix = array();
		$seen_uri    = array();
		foreach ( array_values( $namespaces ) as $i => $row ) {
			$n      = $i + 1;
			$prefix = isset( $row['prefix'] ) ? $row['prefix'] : '';
			$uri    = isset( $row['uri'] ) ? $row['uri'] : '';
			if ( ! Path_Validator::is_valid_prefix( $prefix ) ) {
				/* translators: %d: namespace row number. */
				$errors[] = sprintf( __( 'Namespace %d: the prefix must be letters, numbers, hyphens or underscores, start with a letter or underscore, and not start with "xml".', 'feedweaver' ), $n );
			} elseif ( isset( $seen_prefix[ $prefix ] ) ) {
				/* translators: 1: namespace row number, 2: prefix. */
				$errors[] = sprintf( __( 'Namespace %1$d: the prefix "%2$s" is already used.', 'feedweaver' ), $n, $prefix );
			} else {
				$seen_prefix[ $prefix ] = true;
			}
			if ( ! self::is_valid_uri( $uri ) ) {
				/* translators: %d: namespace row number. */
				$errors[] = sprintf( __( 'Namespace %d: the address must start with http://, https:// or urn: and contain no spaces or quotes (and cannot be an address reserved by XML).', 'feedweaver' ), $n );
			} elseif ( isset( $seen_uri[ $uri ] ) ) {
				/* translators: %d: namespace row number. */
				$errors[] = sprintf( __( 'Namespace %d: this address is already declared with another prefix.', 'feedweaver' ), $n );
			} else {
				$seen_uri[ $uri ] = true;
			}
		}//end foreach
		return $errors;
	}

	/**
	 * The declared prefixes.
	 *
	 * @param array $namespaces Declarations.
	 * @return string[]
	 */
	public static function prefixes( array $namespaces ): array {
		$out = array();
		foreach ( $namespaces as $row ) {
			if ( isset( $row['prefix'] ) && is_string( $row['prefix'] ) ) {
				$out[] = $row['prefix'];
			}
		}
		return $out;
	}

	/**
	 * Prefix => URI map.
	 *
	 * @param array $namespaces Declarations.
	 * @return array<string,string>
	 */
	public static function map( array $namespaces ): array {
		$out = array();
		foreach ( $namespaces as $row ) {
			if ( isset( $row['prefix'], $row['uri'] ) && is_string( $row['prefix'] ) && is_string( $row['uri'] ) ) {
				$out[ $row['prefix'] ] = $row['uri'];
			}
		}
		return $out;
	}
}