<?php

namespace Yoast\WP\SEO\Integrations\Front_End;

use Yoast\WP\SEO\Conditionals\Front_End_Conditional;
use Yoast\WP\SEO\Conditionals\WP_Robots_Conditional;
use Yoast\WP\SEO\Integrations\Integration_Interface;
use Yoast\WP\SEO\Memoizers\Meta_Tags_Context_Memoizer;
use Yoast\WP\SEO\Presenters\Robots_Presenter;

/**
 * Class WP_Robots_Integration
 *
 * @package Yoast\WP\SEO\Integrations\Front_End
 */
class WP_Robots_Integration implements Integration_Interface {

	/**
	 * The meta tags context memoizer.
	 *
	 * @var Meta_Tags_Context_Memoizer
	 */
	protected $context_memoizer;

	/**
	 * Sets the dependencies for this integration.
	 *
	 * @param Meta_Tags_Context_Memoizer $context_memoizer The meta tags context memoizer.
	 */
	public function __construct( Meta_Tags_Context_Memoizer $context_memoizer ) {
		$this->context_memoizer = $context_memoizer;
	}

	/**
	 * Initializes the integration.
	 *
	 * This is the place to register hooks and filters.
	 *
	 * @return void
	 */
	public function register_hooks() {
		/**
		 * Allow control of the `wp_robots` filter by prioritizing our hook 10 less than max.
		 * Use the `wpseo_robots` filter to filter the Yoast robots output, instead of WordPress core.
		 */
		\add_filter( 'wp_robots', [ $this, 'add_robots' ], ( \PHP_INT_MAX - 10 ) );
	}

	/**
	 * Returns the conditionals based on which this loadable should be active.
	 *
	 * @return array The conditionals.
	 */
	public static function get_conditionals() {
		return [
			Front_End_Conditional::class,
			WP_Robots_Conditional::class,
		];
	}

	/**
	 * Adds our robots tag value to the WordPress robots tag output.
	 *
	 * @param array $robots The current robots data.
	 *
	 * @return array The robots data.
	 */
	public function add_robots( $robots ) {
		if ( ! \is_array( $robots ) ) {
			return $this->get_robots_value();
		}

		$merged_robots   = \array_merge( $robots, $this->get_robots_value() );
		$filtered_robots = $this->enforce_robots_congruence( $merged_robots );
		$sorted_robots   = $this->sort_robots( $filtered_robots );

		// Filter all falsy-null robot values.
		return \array_filter( $sorted_robots );
	}

	/**
	 * Retrieves the robots key-value pairs.
	 *
	 * @return array The robots key-value pairs.
	 */
	protected function get_robots_value() {
		$context = $this->context_memoizer->for_current_page();

		$robots_presenter               = new Robots_Presenter();
		$robots_presenter->presentation = $context->presentation;
		return $this->format_robots( $robots_presenter->get() );
	}

	/**
	 * Formats our robots fields, to match the pattern WordPress is using.
	 *
	 * Our format: `[ 'index' => 'noindex', 'max-image-preview' => 'max-image-preview:large', ... ]`
	 * WordPress format: `[ 'noindex' => true, 'max-image-preview' => 'large', ... ]`
	 *
	 * @param array $robots Our robots value.
	 *
	 * @return array The formatted robots.
	 */
	protected function format_robots( $robots ) {
		foreach ( $robots as $key => $value ) {
			// When the entry represents for example: max-image-preview:large.
			$colon_position = \strpos( $value, ':' );
			if ( $colon_position !== false ) {
				$robots[ $key ] = \substr( $value, ( $colon_position + 1 ) );

				continue;
			}

			// When index => noindex, we want a separate noindex as entry in array.
			if ( \strpos( $value, 'no' ) === 0 ) {
				$robots[ $key ]   = false;
				$robots[ $value ] = true;

				continue;
			}

			// When the key is equal to the value, just make its value a boolean.
			if ( $key === $value ) {
				$robots[ $key ] = true;
			}
		}

		return $robots;
	}

	/**
	 * Ensures all other possible robots values are congruent with nofollow and or noindex.
	 *
	 * WordPress might add some robot values again.
	 * When the page is set to noindex we want to filter out these values.
	 *
	 * @param array $robots The robots.
	 *
	 * @return array The filtered robots.
	 */
	protected function enforce_robots_congruence( $robots ) {
		if ( ! empty( $robots['nofollow'] ) ) {
			$robots['follow'] = null;
		}
		if ( ! empty( $robots['noarchive'] ) ) {
			$robots['archive'] = null;
		}
		if ( ! empty( $robots['noimageindex'] ) ) {
			$robots['imageindex'] = null;

			// `max-image-preview` should set be to `none` when `noimageindex` is present.
			// Using `isset` rather than `! empty` here so that in the rare case of `max-image-preview`
			// being equal to an empty string due to filtering, its value would still be set to `none`.
			if ( isset( $robots['max-image-preview'] ) ) {
				$robots['max-image-preview'] = 'none';
			}
		}
		if ( ! empty( $robots['nosnippet'] ) ) {
			$robots['snippet'] = null;
		}
		if ( ! empty( $robots['noindex'] ) ) {
			$robots['index']             = null;
			$robots['imageindex']        = null;
			$robots['noimageindex']      = null;
			$robots['archive']           = null;
			$robots['noarchive']         = null;
			$robots['snippet']           = null;
			$robots['nosnippet']         = null;
			$robots['max-snippet']       = null;
			$robots['max-image-preview'] = null;
			$robots['max-video-preview'] = null;
		}

		return $robots;
	}

	/**
	 * Sorts the robots array.
	 *
	 * @param array $robots The robots array.
	 *
	 * @return array The sorted robots array.
	 */
	protected function sort_robots( $robots ) {
		\uksort(
			$robots,
			static function ( $a, $b ) {
				$order = [
					'index'             => 0,
					'noindex'           => 1,
					'follow'            => 2,
					'nofollow'          => 3,
				];
				$ai    = ( $order[ $a ] ?? 4 );
				$bi    = ( $order[ $b ] ?? 4 );

				return ( $ai - $bi );
			}
		);

		return $robots;
	}
}