<?php
/**
 * @package Polylang
 */

namespace WP_Syntex\Polylang\Switcher\Settings;

defined( 'ABSPATH' ) || exit;

/**
 * Compatibility layer between new and legacy switcher settings.
 *
 * @since 3.9
 */
abstract class Abstract_Settings_Legacy {
	/**
	 * Legacy settings that don't exist anymore.
	 */
	protected const REMOVED_ENTRIES = array(
		'dropdown'           => 1,
		'show_names'         => 1,
		'display_names_as'   => 1,
		'item_spacing'       => 1,
		'admin_render'       => 1,
		'admin_current_lang' => 1,
		'classes'            => 1,
	);

	/**
	 * Legacy default settings.
	 */
	protected const DEFAULTS = array(
		'dropdown'               => 0, // Display as list and not as dropdown.
		'hide_if_empty'          => 1, // Hides languages with no posts (or pages).
		'show_flags'             => 0, // Don't show flags.
		'show_names'             => 1, // Show language names.
		'display_names_as'       => 'name', // Display the language name.
		'force_home'             => 0, // Tries to find a translation.
		'hide_if_no_translation' => 0, // Don't hide the link if there is no translation.
		'hide_current'           => 0, // Don't hide the current language.
		'post_id'                => null, // Link to the translations of the current page.
		'item_spacing'           => 'preserve', // Preserve whitespace between list items.
		'admin_render'           => 0, // Make the switcher in a frontend context.
		'admin_current_lang'     => null, // Use the global current language.
	);

	/**
	 * Tells if the given settings list contain legacy settings.
	 *
	 * @since 3.9
	 *
	 * @param array $settings Settings.
	 * @return bool
	 */
	public static function is_legacy( array $settings ): bool {
		return ! empty( array_intersect_key( $settings, self::REMOVED_ENTRIES ) );
	}

	/**
	 * Returns the values as an array after converting them to the legacy format.
	 *
	 * @since 3.9
	 *
	 * @return array
	 */
	public function get_legacy(): array {
		return $this->convert_to_legacy( get_object_vars( $this ) );
	}

	/**
	 * Converts new settings structure to the legacy one, then applies the deprecated filter `pll_the_languages_args`,
	 * then converts it back to new settings structure.
	 * This removes legacy settings.
	 *
	 * @since 3.9
	 *
	 * @param array $settings Settings in new structure.
	 * @return array
	 */
	protected function maybe_filter_legacy( array $settings ): array {
		if ( ! has_filter( 'pll_the_languages_args' ) ) {
			if ( ! self::is_legacy( $settings ) ) {
				return $settings;
			}

			return array_diff_key( $this->convert_from_legacy( $settings ), self::REMOVED_ENTRIES );
		}

		if ( ! self::is_legacy( $settings ) ) {
			$settings = $this->convert_to_legacy( $settings );
		}

		/**
		 * Filter the arguments of the 'pll_the_languages' template tag.
		 *
		 * @since 1.5
		 * @since 3.9 Deprecated.
		 * @deprecated
		 *
		 * @param array $args
		 */
		$settings = apply_filters_deprecated(
			'pll_the_languages_args',
			array( $settings ),
			'3.9.0',
			'pll_language_switcher_settings'
		);

		return array_diff_key( $this->convert_from_legacy( $settings ), self::REMOVED_ENTRIES );
	}

	/**
	 * Converts the legacy structure to the new one.
	 * This preserves the legacy structure's keys.
	 *
	 * @since 3.9
	 *
	 * @param array $settings The settings.
	 * @return array
	 */
	protected function convert_from_legacy( array $settings ): array {
		if ( ! isset( $settings['show_wrapper'] ) ) {
			// Legacy list and dropdown had no outer wrapper (div/nav). The `<select>`
			// tag itself is always output for the select layout.
			$settings['show_wrapper'] = false;
		}

		if ( isset( $settings['layout'], $settings['dropdown'] ) ) {
			// Set a new value to `layout` only if the value of `layout` and `dropdown` don't match, so we don't lose `layout`'s real value.
			if ( ! empty( $settings['dropdown'] ) && 'select' !== $settings['layout'] ) {
				$settings['layout'] = 'select';
			} elseif ( empty( $settings['dropdown'] ) && 'select' === $settings['layout'] ) {
				$settings['layout'] = 'vertical';
			}
		} elseif ( ! isset( $settings['layout'] ) ) {
			$settings['layout'] = ! empty( $settings['dropdown'] ) ? 'select' : 'vertical';
		}

		if ( isset( $settings['show_names'] ) && empty( $settings['show_names'] ) ) {
			$settings['show_labels'] = '';
		} elseif ( isset( $settings['display_names_as'] ) && 'slug' === $settings['display_names_as'] ) {
			$settings['show_labels'] = 'codes';
		}

		if ( isset( $settings['item_spacing'] ) && 'discard' === $settings['item_spacing'] ) {
			$settings['preserve_spacing'] = false;
		}

		if ( ! empty( $settings['classes'] ) && is_array( $settings['classes'] ) ) {
			$settings['item_classes'] = $settings['classes'];
		}

		return $settings;
	}

	/**
	 * Converts the new structure to the legacy one.
	 * This preserves the new structure's keys.
	 *
	 * @since 3.9
	 *
	 * @param array $settings Settings in new structure.
	 * @return array
	 */
	protected function convert_to_legacy( array $settings ): array {
		$args = self::DEFAULTS;

		if ( isset( $settings['layout'] ) && 'select' === $settings['layout'] ) {
			$args['dropdown'] = 1;
		}

		if ( isset( $settings['show_labels'] ) ) {
			if ( empty( $settings['show_labels'] ) ) {
				$args['show_names'] = 0;
			} elseif ( 'codes' === $settings['show_labels'] ) {
				$args['display_names_as'] = 'slug';
			}
		}

		foreach ( array( 'hide_if_empty', 'show_flags', 'force_home', 'hide_if_no_translation', 'hide_current' ) as $name ) {
			if ( isset( $settings[ $name ] ) ) {
				$args[ $name ] = (int) ! empty( $settings[ $name ] );
			}
		}

		if ( isset( $settings['preserve_spacing'] ) && ! $settings['preserve_spacing'] ) {
			$args['item_spacing'] = 'discard';
		}

		if ( ! empty( $settings['item_classes'] ) && is_array( $settings['item_classes'] ) ) {
			$args['classes'] = array_filter( $settings['item_classes'] );
		}

		return array_merge( $settings, $args );
	}
}