<?php
/**
 * Appearance → Custom CSS.
 *
 * @package Adminkeep
 */

namespace Adminkeep\Admin;

use Adminkeep\Feature\CustomCss;

defined( 'ABSPATH' ) || exit;

/**
 * The Custom CSS editing screen.
 *
 * Exists only while the feature is on: CustomCss::boot() is what builds it.
 */
class CustomCssScreen {

	/**
	 * Page slug.
	 */
	const PAGE = 'adminkeep-custom-css';

	/**
	 * Nonce action.
	 */
	const NONCE = 'adminkeep_custom_css';

	/**
	 * Hidden field marking this form's submission.
	 */
	const SAVE_FIELD = 'adminkeep_custom_css_save';

	/**
	 * Textarea field name.
	 */
	const CSS_FIELD = 'adminkeep_css';

	/**
	 * Textarea id, which the code editor attaches to.
	 */
	const EDITOR_ID = 'adminkeep-custom-css-editor';

	/**
	 * Capabilities, both required — the pair that guards core's own Additional CSS.
	 *
	 * edit_css alone is not enough: it resolves to unfiltered_html, which editors hold on a single
	 * site. Core's box is only administrator-only because the Customizer separately demands theme
	 * options; without the same second gate here, editors could restyle the whole site. On
	 * multisite edit_css narrows it further, to super admins.
	 *
	 * @var string[]
	 */
	const CAPABILITIES = array( 'edit_theme_options', 'edit_css' );

	/**
	 * Hook suffix of the registered page.
	 *
	 * @var string
	 */
	private $hook = '';

	/**
	 * A refused submission, kept so the screen can show the text back with the reason.
	 *
	 * @var array{css: string, message: string}|null
	 */
	private $refused = null;

	/**
	 * Whether the current user may edit the site's CSS.
	 *
	 * @return bool
	 */
	public static function can_edit() {
		foreach ( self::CAPABILITIES as $capability ) {
			if ( ! current_user_can( $capability ) ) {
				return false;
			}
		}

		return true;
	}

	/**
	 * URL of the screen.
	 *
	 * @return string
	 */
	public static function url() {
		return admin_url( 'themes.php?page=' . self::PAGE );
	}

	/**
	 * Register hooks.
	 *
	 * @return void
	 */
	public function boot() {
		add_action( 'admin_menu', array( $this, 'register_page' ) );
		add_action( 'admin_init', array( $this, 'handle_save' ), 10, 0 );
		add_action( 'admin_enqueue_scripts', array( $this, 'enqueue_editor' ) );
	}

	/**
	 * Add the page under Appearance.
	 *
	 * A menu item takes one capability and this screen needs two, so a user who would only be
	 * refused on arrival is not shown the entry at all.
	 *
	 * @return void
	 */
	public function register_page() {
		if ( ! self::can_edit() ) {
			return;
		}

		$this->hook = (string) add_submenu_page(
			'themes.php',
			__( 'Custom CSS', 'adminkeep' ),
			__( 'Custom CSS', 'adminkeep' ),
			'edit_theme_options',
			self::PAGE,
			array( $this, 'render' )
		);
	}

	/**
	 * Load WordPress's own code editor on this screen only.
	 *
	 * When the user has switched syntax highlighting off in their profile,
	 * wp_enqueue_code_editor() returns false and the plain textarea is the editor.
	 *
	 * @param string $hook_suffix Current admin page.
	 * @return void
	 */
	public function enqueue_editor( $hook_suffix ) {
		if ( '' === $this->hook || $hook_suffix !== $this->hook ) {
			return;
		}

		$settings = wp_enqueue_code_editor( array( 'type' => 'text/css' ) );

		if ( false === $settings ) {
			return;
		}

		wp_add_inline_script(
			'code-editor',
			sprintf(
				'jQuery( function() { wp.codeEditor.initialize( %s, %s ); } );',
				wp_json_encode( self::EDITOR_ID ),
				wp_json_encode( $settings )
			)
		);

		wp_add_inline_style( 'code-editor', '.adminkeep-css-screen .CodeMirror{height:60vh;border:1px solid #c3c4c7;}' );
	}

	/**
	 * Save a submission.
	 *
	 * @return void
	 */
	public function handle_save() {
		if ( empty( $_POST[ self::SAVE_FIELD ] ) ) { // phpcs:ignore WordPress.Security.NonceVerification.Missing -- Checked below, once this is known to be our form.
			return;
		}

		if ( ! self::can_edit() ) {
			wp_die( esc_html__( 'You are not allowed to edit CSS on this site.', 'adminkeep' ), '', 403 );
		}

		check_admin_referer( self::NONCE );

		// Not sanitized as text: CSS legitimately holds >, quotes and backslashes. It is validated
		// for markup instead, and tags are stripped again on output.
		// phpcs:ignore WordPress.Security.ValidatedSanitizedInput.InputNotSanitized
		$css = isset( $_POST[ self::CSS_FIELD ] ) && is_string( $_POST[ self::CSS_FIELD ] ) ? wp_unslash( $_POST[ self::CSS_FIELD ] ) : '';
		$css = str_replace( "\r\n", "\n", $css );

		$valid = CustomCss::validate( $css );

		if ( is_wp_error( $valid ) ) {
			$this->refused = array(
				'css'     => $css,
				'message' => $valid->get_error_message(),
			);

			return;
		}

		update_option( CustomCss::OPTION, $css, true );

		wp_safe_redirect( add_query_arg( 'updated', '1', self::url() ) );
		exit;
	}

	/**
	 * Render the screen.
	 *
	 * @return void
	 */
	public function render() {
		if ( ! self::can_edit() ) {
			return;
		}

		$css = null === $this->refused ? CustomCss::css() : $this->refused['css'];

		echo '<div class="wrap adminkeep-css-screen">';
		echo '<h1>' . Brand::heading_mark() . esc_html__( 'Custom CSS', 'adminkeep' ) . '</h1>'; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped -- The mark is escaped where it is built.

		if ( null !== $this->refused ) {
			printf( '<div class="notice notice-error inline"><p>%s</p></div>', esc_html( $this->refused['message'] ) );
		} elseif ( isset( $_GET['updated'] ) ) { // phpcs:ignore WordPress.Security.NonceVerification.Recommended -- Read-only flag choosing a static notice.
			printf( '<div class="notice notice-success inline"><p>%s</p></div>', esc_html__( 'CSS saved.', 'adminkeep' ) );
		}

		printf(
			'<p>%s</p>',
			esc_html__( 'This CSS applies to the front end of your site on every theme. Your theme\'s own Additional CSS is separate and is not changed here.', 'adminkeep' )
		);

		echo '<form method="post" action="' . esc_url( self::url() ) . '">';
		wp_nonce_field( self::NONCE );
		printf( '<input type="hidden" name="%s" value="1" />', esc_attr( self::SAVE_FIELD ) );
		printf(
			'<label class="screen-reader-text" for="%1$s">%2$s</label><textarea id="%1$s" name="%3$s" rows="24" class="large-text code" spellcheck="false">%4$s</textarea>',
			esc_attr( self::EDITOR_ID ),
			esc_html__( 'Custom CSS', 'adminkeep' ),
			esc_attr( self::CSS_FIELD ),
			esc_textarea( $css )
		);

		submit_button( __( 'Save CSS', 'adminkeep' ) );

		echo '</form></div>';
	}
}