<?php
/**
 * The PageCore theme: is it here, and getting it here.
 *
 * Several modules only make sense with the PageCore FSE theme running - the
 * Style Library applies that theme's styles, the patterns are drawn with its
 * spacing and colours. This is the one place that says whether it is active,
 * and the one place that installs or activates it when somebody asks, so the
 * Settings screen can offer a button rather than only a warning.
 *
 * @package PageCore
 */

namespace PageCore;

defined( 'ABSPATH' ) || exit;

/**
 * State of the PageCore theme, and the action that fixes it.
 */
class Theme_Setup {

	/**
	 * Whether the PageCore theme, or a child theme of it, is running.
	 *
	 * @return bool
	 */
	public static function is_active() {
		return get_stylesheet() === PAGECORE_THEME_SLUG || get_template() === PAGECORE_THEME_SLUG;
	}

	/**
	 * Whether the theme is on this site at all.
	 *
	 * @return bool
	 */
	public static function is_installed() {
		return wp_get_theme( PAGECORE_THEME_SLUG )->exists();
	}

	/**
	 * Whether this site may switch to a theme.
	 *
	 * Always on a single site. On a network, only a theme enabled for the
	 * network or for this site, as Appearance > Themes offers, unless the
	 * current user can enable themes for the network themselves.
	 *
	 * @param \WP_Theme $theme Theme.
	 * @return bool
	 */
	public static function allowed_here( \WP_Theme $theme ) {
		if ( ! is_multisite() ) {
			return true;
		}

		return $theme->is_allowed() || current_user_can( 'manage_network_themes' );
	}

	/**
	 * What to say when the theme is installed but this site may not use it.
	 *
	 * @param string $name Theme name.
	 * @return string
	 */
	public static function not_allowed_message( $name ) {
		return sprintf(
			/* translators: %s: theme name. */
			__( 'The %s theme is installed but not enabled for this site. A network administrator can enable it under Network Admin, Themes.', 'pagecore' ),
			$name
		);
	}

	/**
	 * Everything the Settings screen needs to show the right button.
	 *
	 * @return array Keys: state (active|installed|missing), canFix, name, and
	 *               detail, which says why when canFix is false for a reason
	 *               of its own.
	 */
	public static function state() {
		if ( self::is_active() ) {
			$state = 'active';
		} elseif ( self::is_installed() ) {
			$state = 'installed';
		} else {
			$state = 'missing';
		}

		$name    = __( 'PageCore FSE', 'pagecore' );
		$allowed = 'installed' !== $state || self::allowed_here( wp_get_theme( PAGECORE_THEME_SLUG ) );

		if ( 'installed' === $state ) {
			$can_fix = $allowed && Capabilities::can( 'switch_themes' );
		} else {
			$can_fix = Capabilities::can( 'install_themes' ) && Capabilities::can( 'switch_themes' );
		}

		return array(
			'state'  => $state,
			'canFix' => 'active' !== $state && $can_fix,
			'name'   => $name,
			'detail' => $allowed ? '' : self::not_allowed_message( $name ),
		);
	}

	/**
	 * Install the theme if it is missing, then activate it.
	 *
	 * @return true|\WP_Error
	 */
	public static function install_and_activate() {
		if ( self::is_active() ) {
			return true;
		}

		if ( ! Capabilities::can( 'switch_themes' ) ) {
			return new \WP_Error( 'pagecore_cannot_switch_themes', __( 'Your account cannot change the theme.', 'pagecore' ), array( 'status' => 403 ) );
		}

		if ( ! self::is_installed() ) {
			$installed = self::install();

			if ( is_wp_error( $installed ) ) {
				return $installed;
			}
		}

		// On a network, a site may only use themes the network allows it,
		// unless the person asking is the one who decides that.
		if ( ! self::allowed_here( wp_get_theme( PAGECORE_THEME_SLUG ) ) ) {
			return new \WP_Error( 'pagecore_theme_not_allowed', self::not_allowed_message( __( 'PageCore FSE', 'pagecore' ) ), array( 'status' => 403 ) );
		}

		switch_theme( PAGECORE_THEME_SLUG );

		if ( ! self::is_active() ) {
			return new \WP_Error( 'pagecore_theme_switch_failed', __( 'The PageCore FSE theme could not be activated.', 'pagecore' ), array( 'status' => 500 ) );
		}

		return true;
	}

	/**
	 * Install the PageCore theme from WordPress.org.
	 *
	 * @return true|\WP_Error
	 */
	private static function install() {
		// The skin is built here, before install_from_directory() loads the
		// upgrader classes, and a REST or admin-post request has not loaded
		// them either.
		if ( ! class_exists( 'WP_Ajax_Upgrader_Skin' ) ) {
			require_once ABSPATH . 'wp-admin/includes/class-wp-upgrader.php';
		}

		return self::install_from_directory( PAGECORE_THEME_SLUG, new \WP_Ajax_Upgrader_Skin() );
	}

	/**
	 * Install a theme from the WordPress.org theme directory.
	 *
	 * The download address comes from WordPress.org's own Themes API, the same
	 * way Appearance > Themes > Add New installs one, so no theme code ever
	 * comes from anywhere else.
	 *
	 * @param string            $slug Theme slug on WordPress.org.
	 * @param \WP_Upgrader_Skin $skin Upgrader skin.
	 * @return true|\WP_Error
	 */
	public static function install_from_directory( $slug, $skin ) {
		$slug = sanitize_key( $slug );

		if ( ! Capabilities::can( 'install_themes' ) ) {
			return new \WP_Error( 'pagecore_cannot_install_themes', __( 'Your account cannot install themes.', 'pagecore' ), array( 'status' => 403 ) );
		}

		if ( ! class_exists( 'WP_Upgrader' ) ) {
			require_once ABSPATH . 'wp-admin/includes/class-wp-upgrader.php';
		}

		require_once ABSPATH . 'wp-admin/includes/file.php';
		require_once ABSPATH . 'wp-admin/includes/misc.php';
		require_once ABSPATH . 'wp-admin/includes/theme.php';

		$information = themes_api(
			'theme_information',
			array(
				'slug'   => $slug,
				'fields' => array( 'sections' => false ),
			)
		);

		if ( is_wp_error( $information ) || empty( $information->download_link ) ) {
			return new \WP_Error(
				'pagecore_theme_not_found',
				sprintf(
					/* translators: %s: theme slug. */
					__( 'The %s theme could not be found on WordPress.org. Install it from Appearance, Themes.', 'pagecore' ),
					$slug
				),
				array( 'status' => 404 )
			);
		}

		// WordPress refuses a theme this server cannot run, but only says the
		// install failed. WordPress.org already said what it needs.
		$needs_php = isset( $information->requires_php ) ? (string) $information->requires_php : '';
		$needs_wp  = isset( $information->requires ) ? (string) $information->requires : '';

		if ( '' !== $needs_php && ! is_php_version_compatible( $needs_php ) ) {
			return new \WP_Error(
				'pagecore_theme_requirements',
				sprintf(
					/* translators: 1: theme slug, 2: required PHP version, 3: PHP version of this site. */
					__( 'The %1$s theme needs PHP %2$s or newer, and this site runs PHP %3$s.', 'pagecore' ),
					$slug,
					$needs_php,
					PHP_VERSION
				),
				array( 'status' => 409 )
			);
		}

		if ( '' !== $needs_wp && ! is_wp_version_compatible( $needs_wp ) ) {
			return new \WP_Error(
				'pagecore_theme_requirements',
				sprintf(
					/* translators: 1: theme slug, 2: required WordPress version, 3: WordPress version of this site. */
					__( 'The %1$s theme needs WordPress %2$s or newer, and this site runs WordPress %3$s.', 'pagecore' ),
					$slug,
					$needs_wp,
					get_bloginfo( 'version' )
				),
				array( 'status' => 409 )
			);
		}

		$upgrader = new \Theme_Upgrader( $skin );
		$result   = $upgrader->install( $information->download_link );

		if ( is_wp_error( $result ) ) {
			return $result;
		}

		if ( ! $result || ! wp_get_theme( $slug )->exists() ) {
			return new \WP_Error(
				'pagecore_theme_install_failed',
				sprintf(
					/* translators: %s: theme slug. */
					__( 'The %s theme could not be installed.', 'pagecore' ),
					$slug
				),
				array( 'status' => 500 )
			);
		}

		return true;
	}
}