<?php
/**
 * Building blocks of the generated PHP code.
 *
 * @package Antwork\FieldCode
 */

namespace Antwork\FieldCode;

defined( 'ABSPATH' ) || exit;

/**
 * Turns names typed by administrators into safe pieces of PHP code: string literals, variable names, comments.
 * Nothing typed in a field group reaches the generated code in any other way.
 */
final class Code {

	/**
	 * Variables that WordPress uses as globals: a template that assigns them would break the page. With them,
	 * `args`: the widget() method of a widget, where the code of a field group shown on widgets goes, reads `$args`.
	 */
	const RESERVED = array(
		'this',
		'args',
		'globals',
		'post',
		'posts',
		'wp_query',
		'wp_the_query',
		'query',
		'wp',
		'wpdb',
		'wp_rewrite',
		'authordata',
		'page',
		'pages',
		'more',
		'numpages',
		'multipage',
		'id',
		'comment',
		'comments',
		'user',
		'current_user',
		'pagenow',
		'menu',
		'submenu',
		'year',
		'monthnum',
		'day',
		'withcomments',
		'tag',
		'cat',
		'category',
		'taxonomy',
		'term',
		'name',
		'author',
		'paged',
		'search',
		'order',
		'orderby',
		's',
		'wp_version',
		'wp_did_header',
		'wp_db_version',
		'wp_locale',
		'wp_scripts',
		'wp_styles',
		'wp_filter',
		'wp_embed',
		'content_width',
		'shortcode_tags',
		'blog_id',
	);

	/**
	 * Longest variable name generated (before suffixes).
	 */
	const MAX_NAME = 48;

	/**
	 * PHP single-quoted string literal of any text: only \ and ' need escaping inside single quotes.
	 *
	 * @param string $text Text.
	 * @return string
	 */
	public static function string( string $text ): string {
		return "'" . str_replace( array( '\\', "'" ), array( '\\\\', "\\'" ), $text ) . "'";
	}

	/**
	 * Valid PHP variable name (without $) made from a field name: lowercase ASCII letters, digits and underscores.
	 *
	 * @param string $name     Field name.
	 * @param bool   $variable Whether the name is a whole variable (false for the end of a sub-field's variable,
	 *                         which cannot be a WordPress global since it follows its group's name).
	 * @return string
	 */
	public static function name( string $name, bool $variable = true ): string {
		if ( function_exists( 'remove_accents' ) ) {
			$name = remove_accents( $name );
		}
		$name = strtolower( (string) preg_replace( '/[^A-Za-z0-9]+/', '_', $name ) );
		$name = trim( substr( trim( $name, '_' ), 0, self::MAX_NAME ), '_' );
		if ( '' === $name ) {
			return 'field';
		}
		if ( $variable && ctype_digit( $name[0] ) ) {
			$name = 'field_' . $name;
		}
		if ( $variable && in_array( $name, self::RESERVED, true ) ) {
			$name .= '_field';
		}
		return $name;
	}

	/**
	 * A variable made of another one and a suffix (`$hero` and `title` give `$hero_title`), never a WordPress global.
	 *
	 * @param string $variable Variable, with its $.
	 * @param string $suffix   Suffix, already a valid part of a name.
	 * @return string
	 */
	public static function suffix( string $variable, string $suffix ): string {
		$name = ltrim( $variable, '$' ) . '_' . $suffix;
		return '$' . ( in_array( $name, self::RESERVED, true ) ? $name . '_field' : $name );
	}

	/**
	 * Text that can sit in a // comment of the generated code: a few safe characters, on one line.
	 * Keeps "?>" (which would end the PHP block) and line breaks out.
	 *
	 * @param string $text Text.
	 * @return string
	 */
	public static function comment( string $text ): string {
		$text = (string) preg_replace( '/[^A-Za-z0-9 _.,:\/\\\\-]+/', ' ', $text );
		return trim( (string) preg_replace( '/\s+/', ' ', $text ) );
	}

	/**
	 * The get_field() call that reads a field.
	 *
	 * @param string $field_name Field name.
	 * @param string $post_id    PHP expression of the post ID, or '' for the current post.
	 * @return string
	 */
	public static function get_field( string $field_name, string $post_id = '' ): string {
		$args = self::string( $field_name );
		if ( '' !== $post_id ) {
			$args .= ', ' . $post_id;
		}
		return 'get_field( ' . $args . ' )';
	}
}