<?php
/**
 * SEO fields (title tag, meta description, focus keyword) live in the SEO plugin's post meta. Yoast SEO and Rank Math are
 * read and written; without them, the title tag is the post title and the description is the excerpt.
 */
if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

function suiko_seo_plugin() {
	if ( defined( 'WPSEO_VERSION' ) ) {
		return 'yoast';
	}
	if ( defined( 'RANK_MATH_VERSION' ) ) {
		return 'rankmath';
	}
	return 'none';
}

function suiko_seo_keys() {
	switch ( suiko_seo_plugin() ) {
		case 'yoast':
			return array( 'title' => '_yoast_wpseo_title', 'description' => '_yoast_wpseo_metadesc', 'keyword' => '_yoast_wpseo_focuskw' );
		case 'rankmath':
			return array( 'title' => 'rank_math_title', 'description' => 'rank_math_description', 'keyword' => 'rank_math_focus_keyword' );
	}
	return null;
}

/** @return array{metaTitle: ?string, metaDescription: ?string, keyword: ?string} */
function suiko_seo_read( $post_id ) {
	$keys = suiko_seo_keys();
	if ( ! $keys ) {
		$post = get_post( $post_id );
		return array( 'metaTitle' => null, 'metaDescription' => $post && $post->post_excerpt ? $post->post_excerpt : null, 'keyword' => null );
	}
	$v = function ( $k ) use ( $post_id ) {
		$x = get_post_meta( $post_id, $k, true );
		return is_string( $x ) && '' !== $x ? $x : null;
	};
	return array( 'metaTitle' => $v( $keys['title'] ), 'metaDescription' => $v( $keys['description'] ), 'keyword' => $v( $keys['keyword'] ) );
}

/** Writes the fields given (null leaves a field untouched). Without an SEO plugin, the description goes to the excerpt. */
function suiko_seo_write( $post_id, $seo ) {
	if ( ! is_array( $seo ) ) {
		return;
	}
	$keys = suiko_seo_keys();
	if ( ! $keys ) {
		if ( isset( $seo['metaDescription'] ) && is_string( $seo['metaDescription'] ) ) {
			wp_update_post( array( 'ID' => $post_id, 'post_excerpt' => wp_strip_all_tags( $seo['metaDescription'] ) ) );
		}
		return;
	}
	foreach ( array( 'metaTitle' => 'title', 'metaDescription' => 'description', 'keyword' => 'keyword' ) as $field => $k ) {
		if ( isset( $seo[ $field ] ) && is_string( $seo[ $field ] ) ) {
			update_post_meta( $post_id, $keys[ $k ], wp_strip_all_tags( $seo[ $field ] ) );
		}
	}
}