<?php
/**
 * Appearance → Header & Footer Code.
 *
 * @package Adminkeep
 */

namespace Adminkeep\Admin;

use Adminkeep\Feature\HeaderFooterCode;

defined( 'ABSPATH' ) || exit;

/**
 * The Header & Footer Code editing screen.
 *
 * Exists only while the feature is on: HeaderFooterCode::boot() is what builds it.
 */
class HeaderFooterCodeScreen {

	/**
	 * Page slug.
	 */
	const PAGE = 'adminkeep-header-footer-code';

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

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

	/**
	 * Textarea field name; each box posts as adminkeep_code[head] and so on.
	 */
	const CODE_FIELD = 'adminkeep_code';

	/**
	 * Form id, which the save script finds the form by.
	 */
	const FORM_ID = 'adminkeep-code-form';

	/**
	 * Capabilities, both required.
	 *
	 * The manage_options half keeps this to administrators: editors hold unfiltered_html on a single site.
	 * unfiltered_html is what makes raw script acceptable at all, and core already narrows it to
	 * super admins on multisite and to nobody when DISALLOW_UNFILTERED_HTML is set, so this screen
	 * follows the site's own policy on who may publish script.
	 *
	 * @var string[]
	 */
	const CAPABILITIES = array( 'manage_options', 'unfiltered_html' );

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

	/**
	 * A refused submission, kept so the screen can show every box's text back with the reason.
	 *
	 * @var array{codes: array<string, string>, message: string}|null
	 */
	private $refused = null;

	/**
	 * Whether the current user may edit the site's header and footer code.
	 *
	 * @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 );
	}

	/**
	 * Id of a box's textarea, which the code editor attaches to.
	 *
	 * @param string $location head, body or footer.
	 * @return string
	 */
	public static function editor_id( $location ) {
		return 'adminkeep-code-' . $location;
	}

	/**
	 * Id of the "Last changed by …" line under a box, which the save script rewrites.
	 *
	 * @param string $location head, body or footer.
	 * @return string
	 */
	public static function line_id( $location ) {
		return 'adminkeep-code-' . $location . '-changed';
	}

	/**
	 * 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',
			__( 'Header & Footer Code', 'adminkeep' ),
			__( 'Header & Footer Code', 'adminkeep' ),
			'manage_options',
			self::PAGE,
			array( $this, 'render' )
		);
	}

	/**
	 * Load WordPress's own code editor, once for all three boxes, and the save script, on this
	 * screen only.
	 *
	 * When the user has switched syntax highlighting off in their profile,
	 * wp_enqueue_code_editor() returns false and the plain textareas are the editors. The save
	 * script loads either way: it reads whichever of the two is there.
	 *
	 * @param string $hook_suffix Current admin page.
	 * @return void
	 */
	public function enqueue_editor( $hook_suffix ) {
		if ( '' === $this->hook || $hook_suffix !== $this->hook ) {
			return;
		}

		$this->enqueue_save_script();

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

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

		$ids = array();

		foreach ( HeaderFooterCode::LOCATIONS as $location ) {
			$ids[] = self::editor_id( $location );
		}

		wp_add_inline_script(
			'code-editor',
			sprintf(
				'jQuery( function() { var settings = %2$s; %1$s.forEach( function( id ) { wp.codeEditor.initialize( id, settings ); } ); } );',
				wp_json_encode( $ids ),
				wp_json_encode( $settings )
			)
		);

		wp_add_inline_style( 'code-editor', '.adminkeep-code-screen .CodeMirror{height:16em;border:1px solid #c3c4c7;}' );
	}

	/**
	 * Load the save script, with what it needs to rewrite each box's "Last changed" line.
	 *
	 * The route answers with each box's stamp as numbers: a user id and a timestamp. The line is
	 * turned back into words in the browser rather than by the route, so the route's shape stays
	 * the data it is for everyone else. A save from this screen stamps the boxes it changed with
	 * the current user, whose name is sent along; the date is formatted by core's wp-date with the
	 * site's own format and timezone, which is what wp_date() uses here. Another user's stamp can
	 * only appear if someone saved the same box between this page loading and the save; the script
	 * looks that name up through core's users route, and leaves the line alone if it cannot.
	 *
	 * @return void
	 */
	private function enqueue_save_script() {
		$fields = array();
		$boxes  = array();

		foreach ( HeaderFooterCode::codes() as $location => $box ) {
			$fields[ $location ] = self::editor_id( $location );
			$boxes[ $location ]  = array(
				'line' => self::line_id( $location ),
				'by'   => $box['changed_by'],
				'at'   => $box['changed_at'],
			);
		}

		$user_id = get_current_user_id();

		CodeScreenSave::enqueue(
			array(
				'route'  => esc_url_raw( rest_url( RestController::NAMESPACE_V1 . '/header-footer-code' ) ),
				'form'   => self::FORM_ID,
				'fields' => $fields,
				'i18n'   => array( 'saved' => __( 'Code saved.', 'adminkeep' ) ),
				'lines'  => array(
					'template' => self::line_template(),
					'format'   => get_option( 'date_format' ) . ' ' . get_option( 'time_format' ),
					'user'     => array(
						'id'   => $user_id,
						'name' => self::who( $user_id ),
					),
					'cli'      => self::who( 0 ),
					'users'    => esc_url_raw( rest_url( 'wp/v2/users/' ) ),
					'boxes'    => $boxes,
				),
			),
			array( 'wp-date' )
		);
	}

	/**
	 * 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 the header and footer code on this site.', 'adminkeep' ), '', 403 );
		}

		check_admin_referer( self::NONCE );

		// Not sanitized: this is raw HTML and script by design, from a user who holds
		// unfiltered_html. The feature checks size and encoding on save, and normalises line endings.
		// phpcs:ignore WordPress.Security.ValidatedSanitizedInput.InputNotSanitized -- Raw HTML by design; see above.
		$posted = isset( $_POST[ self::CODE_FIELD ] ) && is_array( $_POST[ self::CODE_FIELD ] ) ? wp_unslash( $_POST[ self::CODE_FIELD ] ) : array();
		$codes  = array();

		foreach ( HeaderFooterCode::LOCATIONS as $location ) {
			if ( isset( $posted[ $location ] ) && is_string( $posted[ $location ] ) ) {
				$codes[ $location ] = $posted[ $location ];
			}
		}

		$saved = HeaderFooterCode::save( $codes, get_current_user_id() );

		if ( is_wp_error( $saved ) ) {
			$shown = array();

			foreach ( HeaderFooterCode::codes() as $location => $box ) {
				$shown[ $location ] = isset( $codes[ $location ] ) ? $codes[ $location ] : $box['code'];
			}

			$this->refused = array(
				'codes'   => $shown,
				'message' => $saved->get_error_message(),
			);

			return;
		}

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

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

		$stored = HeaderFooterCode::codes();

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

		if ( null !== $this->refused ) {
			CodeScreenSave::print_notices( 'error', $this->refused['message'] );
		} elseif ( isset( $_GET['updated'] ) ) { // phpcs:ignore WordPress.Security.NonceVerification.Recommended -- Read-only flag choosing a static notice.
			CodeScreenSave::print_notices( 'success', __( 'Code saved.', 'adminkeep' ) );
		} else {
			CodeScreenSave::print_notices();
		}

		printf(
			'<p>%s</p>',
			esc_html__( 'Code saved here is printed on the front end of your site, on every page and exactly as you enter it. It is not added to the admin or the login page. Broken markup here can break your pages, so paste snippets as the service that issued them gave them to you.', 'adminkeep' )
		);

		echo '<form id="' . esc_attr( self::FORM_ID ) . '" 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 ) );

		foreach ( HeaderFooterCode::LOCATIONS as $location ) {
			$code = null === $this->refused ? $stored[ $location ]['code'] : $this->refused['codes'][ $location ];

			printf(
				'<h2><label for="%1$s">%2$s</label></h2><p class="description">%3$s</p>',
				esc_attr( self::editor_id( $location ) ),
				esc_html( HeaderFooterCode::location_label( $location ) ),
				esc_html( $this->location_help( $location ) )
			);
			// The newline after the opening tag is for the browser, which drops one there; without
			// it, code starting with a newline would lose it and save as changed when untouched.
			printf(
				'<textarea id="%1$s" name="%2$s[%3$s]" rows="10" class="large-text code" spellcheck="false">' . "\n" . '%4$s</textarea>',
				esc_attr( self::editor_id( $location ) ),
				esc_attr( self::CODE_FIELD ),
				esc_attr( $location ),
				esc_textarea( $code )
			);

			// Printed for a box never saved too, hidden, so the save script has a line to fill in.
			$changed = $this->last_changed( $stored[ $location ] );

			printf(
				'<p class="description" id="%1$s"%2$s>%3$s</p>',
				esc_attr( self::line_id( $location ) ),
				'' === $changed ? ' hidden' : '',
				esc_html( $changed )
			);
		}

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

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

	/**
	 * What a box is for.
	 *
	 * @param string $location head, body or footer.
	 * @return string
	 */
	private function location_help( $location ) {
		switch ( $location ) {
			case 'head':
				return __( 'Printed inside <head>, before your theme\'s own styles and scripts. The usual place for analytics tags and the meta tags that prove you own the site to search engines.', 'adminkeep' );
			case 'body':
				return __( 'Printed straight after <body> opens, on themes that support it (current ones do). Tag managers ask for their <noscript> fallback here.', 'adminkeep' );
			case 'footer':
				return __( 'Printed at the end of the page, after WordPress\'s own footer scripts. A good place for chat widgets and scripts that do not need to run first.', 'adminkeep' );
		}

		return '';
	}

	/**
	 * "Last changed by … on …" for a box, or nothing for a box that was never saved.
	 *
	 * @param array{code: string, changed_by: int, changed_at: int} $box A box from HeaderFooterCode::codes().
	 * @return string
	 */
	private function last_changed( array $box ) {
		if ( 0 === $box['changed_at'] ) {
			return '';
		}

		return sprintf(
			self::line_template(),
			self::who( $box['changed_by'] ),
			wp_date( get_option( 'date_format' ) . ' ' . get_option( 'time_format' ), $box['changed_at'] )
		);
	}

	/**
	 * The "Last changed" sentence, in one place for this screen and its save script.
	 *
	 * @return string
	 */
	private static function line_template() {
		/* translators: 1: a user's display name, or "WP-CLI", 2: date and time. */
		return __( 'Last changed by %1$s on %2$s.', 'adminkeep' );
	}

	/**
	 * Who a stamp names: a display name, WP-CLI, or an account since deleted.
	 *
	 * @param int $user_id The stamp's user id; 0 for WP-CLI.
	 * @return string
	 */
	private static function who( $user_id ) {
		if ( 0 === $user_id ) {
			// A change from `wp adminkeep code set` run without --user.
			return __( 'WP-CLI', 'adminkeep' );
		}

		$user = get_userdata( $user_id );

		/* translators: %d: the user ID of an account that no longer exists. */
		return $user ? $user->display_name : sprintf( __( 'a deleted user (#%d)', 'adminkeep' ), $user_id );
	}
}