<?php
/**
 * Class ReaderThemeLoader.
 *
 * @package AmpProject\AmpWP
 */

namespace AmpProject\AmpWP;

use AmpProject\AmpWP\Infrastructure\Registerable;
use AmpProject\AmpWP\Infrastructure\Service;
use AMP_Options_Manager;
use AMP_Theme_Support;
use AmpProject\AmpWP\Admin\ReaderThemes;
use WP_Theme;
use WP_Customize_Manager;

/**
 * Switches to the designated Reader theme when template mode enabled and when requesting an AMP page.
 *
 * This class does not implement Conditional because other services need to always be able to access this
 * service in order to determine whether or a Reader theme is loaded, and if so, what the previously-active theme was.
 *
 * @package AmpProject\AmpWP
 * @since 2.0
 * @internal
 */
final class ReaderThemeLoader implements Service, Registerable {

	/**
	 * Paired routing service.
	 *
	 * @var PairedRouting
	 */
	private $paired_routing;

	/**
	 * Reader theme.
	 *
	 * @var WP_Theme|null
	 */
	private $reader_theme;

	/**
	 * Active theme.
	 *
	 * Theme which was active before switching to the Reader theme.
	 *
	 * @var WP_Theme
	 */
	private $active_theme;

	/**
	 * Whether the active theme was overridden with the Reader theme.
	 *
	 * @var bool
	 */
	private $theme_overridden = false;

	/**
	 * ReaderThemeLoader constructor.
	 *
	 * @param PairedRouting $paired_routing Paired routing service.
	 */
	public function __construct( PairedRouting $paired_routing ) {
		$this->paired_routing = $paired_routing;
	}

	/**
	 * Is Reader mode with a Reader theme selected.
	 *
	 * @param array $options Options to check. If omitted, the currently-saved options are used.
	 * @return bool Whether new Reader mode.
	 */
	public function is_enabled( $options = null ) {
		// If the theme was overridden then we know it is enabled. We can't check get_template() at this point because
		// it will be identical to $reader_theme.
		if ( $this->is_theme_overridden() ) {
			return true;
		}

		if ( null === $options ) {
			$options = AMP_Options_Manager::get_options();
		}

		// If Reader mode is not enabled, then a Reader theme is definitely not going to be served.
		if (
			! isset( $options[ Option::THEME_SUPPORT ] )
			||
			AMP_Theme_Support::READER_MODE_SLUG !== $options[ Option::THEME_SUPPORT ]
		) {
			return false;
		}

		// If the Legacy Reader mode is active, then a Reader theme is not going to be served.
		if ( ! isset( $options[ Option::READER_THEME ] ) ) {
			return false;
		}
		$reader_theme = $options[ Option::READER_THEME ];
		if ( ReaderThemes::DEFAULT_READER_THEME === $reader_theme ) {
			return false;
		}

		// If the Reader theme does not exist, then we cannot switch to the reader theme. The Legacy Reader theme will
		// be used as a fallback instead.
		if ( ! wp_get_theme( $reader_theme )->exists() ) {
			return false;
		}

		// Lastly, if the active theme is not the same as the reader theme, then we can switch to the reader theme.
		// Otherwise, the site should instead be in Transitional mode. Note that get_stylesheet() is used as opposed
		// to get_template() because the active theme should be allowed to be a child theme of a Reader theme.
		return get_stylesheet() !== $reader_theme;
	}

	/**
	 * Whether the active theme was overridden with the reader theme.
	 *
	 * @return bool Whether theme overridden.
	 */
	public function is_theme_overridden() {
		return $this->theme_overridden;
	}

	/**
	 * Register the service with the system.
	 *
	 * @return void
	 */
	public function register() {
		// The following needs to run at plugins_loaded because that is when _wp_customize_include runs. Otherwise, the
		// most logical action would be setup_theme.
		add_action( 'plugins_loaded', [ $this, 'override_theme' ], 9 );

		add_filter( 'wp_prepare_themes_for_js', [ $this, 'filter_wp_prepare_themes_to_indicate_reader_theme' ] );
		add_action( 'admin_print_footer_scripts-themes.php', [ $this, 'inject_theme_single_template_modifications' ] );
	}

	/**
	 * Filter themes for JS to remove action to delete the selected Reader theme and show a notice.
	 *
	 * @param array $prepared_themes Array of theme data.
	 * @return array Themes.
	 */
	public function filter_wp_prepare_themes_to_indicate_reader_theme( $prepared_themes ) {
		if ( ! $this->is_enabled() ) {
			return $prepared_themes;
		}

		$reader_theme_obj = $this->get_reader_theme();
		if ( ! $reader_theme_obj instanceof WP_Theme ) {
			return $prepared_themes;
		}
		$reader_theme = $reader_theme_obj->get_stylesheet();

		if ( isset( $prepared_themes[ $reader_theme ] ) ) {

			// Make sure the AMP Reader theme appears right after the active theme in the list.
			$stylesheet = get_stylesheet();
			if ( isset( $prepared_themes[ $stylesheet ] ) ) {
				$prepared_themes = array_merge(
					[
						$stylesheet   => $prepared_themes[ $stylesheet ],
						$reader_theme => $prepared_themes[ $reader_theme ],
					],
					$prepared_themes
				);
			}

			// Prevent Reader theme from being deleted.
			unset( $prepared_themes[ $reader_theme ]['actions']['delete'] );

			// Make sure the Customize link goes to AMP.
			$prepared_themes[ $reader_theme ]['actions']['customize'] = amp_get_customizer_url();

			// Force the theme to be styled as Active.
			$prepared_themes[ $reader_theme ]['active'] = true;

			// Make sure the hacked Backbone template will use the AMP action links.
			$prepared_themes[ $reader_theme ]['ampActiveReaderTheme'] = true;

			// Add AMP Reader theme notice.
			$prepared_themes[ $reader_theme ]['ampReaderThemeNotice'] = sprintf(
				wp_kses(
					/* translators: placeholder is link to AMP settings screen */
					__( 'This has been <a href="%s">selected</a> as the AMP Reader theme.', 'amp' ),
					[
						'a' => [ 'href' => true ],
					]
				),
				esc_url( add_query_arg( 'page', AMP_Options_Manager::OPTION_NAME, admin_url( 'admin.php' ) ) . '#reader-themes' )
			);
		}

		return $prepared_themes;
	}

	/**
	 * Inject new logic into the Backbone templates for rendering a theme lightbox.
	 *
	 * This is admittedly hacky, but WordPress doesn't provide a much better option.
	 */
	public function inject_theme_single_template_modifications() {
		if ( ! $this->is_enabled() ) {
			return;
		}

		$reader_theme = $this->get_reader_theme();
		if ( ! $reader_theme instanceof WP_Theme ) {
			return;
		}

		?>
		<script>
			(function( themeSingleTmpl ) {
				if ( ! themeSingleTmpl ) {
					return;
				}
				let text = themeSingleTmpl.text;

				text = text.replace(
					/(?=<p class="theme-description">)/,
					`
					<# if ( data.ampReaderThemeNotice ) { #>
						<div class="notice notice-info notice-alt inline">
							<p>{{{ data.ampReaderThemeNotice }}}</p><?php // phpcs:ignore WordPressVIPMinimum.Security.Mustache.OutputNotation -- Contains link and already sanitized with Kses. ?>
						</div>
					<# } #>
					`
				);

				// Inject our action links.
				text = text.replace(
					/(<div class="active-theme">)((?:.|\s)+?)(<\/div>)/,
					( match, startDiv, actionLinks, endDiv ) => {
						return `
							${startDiv}
							<# if ( data.ampActiveReaderTheme ) { #>
								<a href="{{ data.actions.customize }}" class="button button-primary customize load-customize hide-if-no-customize">
									<?php esc_html_e( 'Customize', 'default' ); ?>
								</a>
								<a href="<?php echo esc_url( add_query_arg( 'page', AMP_Options_Manager::OPTION_NAME, admin_url( 'admin.php' ) ) ); ?>" class="button button-secondary">
									<?php esc_html_e( 'AMP Settings', 'amp' ); ?>
								</a>
							<# } else { #>
								${actionLinks}
							<# } #>
							${endDiv}
						`;
					}
				);

				themeSingleTmpl.text = text;
			})( document.getElementById( 'tmpl-theme-single' ) );

			(function ( themeTmpl, ssrThemeNamePrefixElement ) {
				// First update the card that was rendered server-side in wp-admin/themes.php.
				if ( ssrThemeNamePrefixElement ) {
					ssrThemeNamePrefixElement.textContent = <?php echo wp_json_encode( _x( 'Reader:', 'prefix for theme card in list', 'amp' ) ); ?>;
				}

				// Then update the Mustache template so that future renders will also have the proper prefix.
				if ( themeTmpl ) {
					themeTmpl.text = themeTmpl.text.replace(
						/(<div class="theme-id-container">)(\s*<# if)/,
						function ( match, startDiv ) {
							return `
							${startDiv}
							<# if ( data.ampActiveReaderTheme ) { #>
								<h2 class="theme-name" id="{{ data.id }}-name">
									<span><?php echo esc_html( _x( 'Reader:', 'prefix for theme card in list', 'amp' ) ); ?></span> {{ data.name }}
								</h2>
							<# } else if
						`;
						}
					);
				}
			}) (
				document.getElementById( 'tmpl-theme' ),
				document.querySelector( <?php echo wp_json_encode( sprintf( '#%s-name > span', $reader_theme->get_stylesheet() ) ); ?> )
			);
		</script>
		<?php
	}

	/**
	 * Get reader theme.
	 *
	 * If the Reader template mode is enabled
	 *
	 * @return WP_Theme|null Theme if selected and no errors.
	 */
	public function get_reader_theme() {
		if ( $this->reader_theme instanceof WP_Theme ) {
			return $this->reader_theme;
		}

		$reader_theme_slug = AMP_Options_Manager::get_option( Option::READER_THEME );
		if ( ! $reader_theme_slug ) {
			return null;
		}

		$reader_theme = wp_get_theme( $reader_theme_slug );
		if ( $reader_theme->errors() ) {
			return null;
		}

		return $reader_theme;
	}

	/**
	 * Get active theme.
	 *
	 * The theme that was active before switching to the Reader theme.
	 *
	 * @return WP_Theme WP_Theme instance.
	 */
	public function get_active_theme() {
		return $this->active_theme;
	}

	/**
	 * Switch theme if in Reader mode, a Reader theme was selected, and the AMP query var is present.
	 *
	 * Note that AMP_Theme_Support will redirect to the non-AMP version if AMP is not available for the query.
	 *
	 * @see WP_Customize_Manager::start_previewing_theme() which provides for much of the inspiration here.
	 * @see switch_theme() which ensures the new theme includes the old theme's theme mods.
	 */
	public function override_theme() {
		$this->theme_overridden = false;

		if ( ! $this->is_enabled() || ! $this->paired_routing->has_endpoint() ) {
			return;
		}

		$theme = $this->get_reader_theme();
		if ( ! $theme instanceof WP_Theme ) {
			return;
		}

		$this->active_theme     = wp_get_theme();
		$this->reader_theme     = $theme;
		$this->theme_overridden = true;

		$get_template   = function () {
			return $this->reader_theme->get_template();
		};
		$get_stylesheet = function () {
			return $this->reader_theme->get_stylesheet();
		};

		add_filter( 'stylesheet', $get_stylesheet );
		add_filter( 'template', $get_template );
		add_filter(
			'pre_option_current_theme',
			function () {
				return $this->reader_theme->display( 'Name' );
			}
		);

		// @link: https://core.trac.wordpress.org/ticket/20027
		add_filter( 'pre_option_stylesheet', $get_stylesheet );
		add_filter( 'pre_option_template', $get_template );

		// Handle custom theme roots.
		add_filter(
			'pre_option_stylesheet_root',
			function () {
				return get_raw_theme_root( $this->reader_theme->get_stylesheet(), true );
			}
		);
		add_filter(
			'pre_option_template_root',
			function () {
				return get_raw_theme_root( $this->reader_theme->get_template(), true );
			}
		);

		$this->disable_widgets();
		add_filter( 'customize_previewable_devices', [ $this, 'customize_previewable_devices' ] );
		add_action( 'customize_register', [ $this, 'remove_customizer_themes_panel' ], 11 );
	}

	/**
	 * Disable widgets.
	 */
	public function disable_widgets() {
		add_filter( 'sidebars_widgets', '__return_empty_array', PHP_INT_MAX );
		add_filter(
			'customize_loaded_components',
			static function ( $components ) {
				return array_diff( $components, [ 'widgets' ] );
			}
		);
		remove_theme_support( 'widgets-block-editor' );
	}

	/**
	 * Make tablet (smartphone) the default device when opening AMP Customizer.
	 *
	 * @param array $devices Devices.
	 * @return array Devices.
	 */
	public function customize_previewable_devices( $devices ) {
		if ( isset( $devices['tablet'] ) ) {
			unset( $devices['desktop']['default'] );
			$devices['tablet']['default'] = true;
		}
		return $devices;
	}

	/**
	 * Remove themes panel from AMP Customizer.
	 *
	 * @param WP_Customize_Manager $wp_customize Customize manager.
	 */
	public function remove_customizer_themes_panel( WP_Customize_Manager $wp_customize ) {
		$wp_customize->remove_panel( 'themes' );
	}
}
