<?php

declare(strict_types=1);

namespace Sarcio\WordPress\Assistant;

/**
 * The search title and description of a page or post, through the SEO
 * plugin the site uses: Yoast SEO or Rank Math. Both keep them as post meta;
 * Yoast also mirrors them into its own table when the post is saved, so a
 * change touches the post afterwards the way the editor would.
 */
final class SeoAbilities
{
    public const RANK_MATH = 'rankmath';
    public const YOAST = 'yoast';

    private const KEYS = [
        self::RANK_MATH => ['description' => 'rank_math_description', 'title' => 'rank_math_title'],
        self::YOAST => ['description' => '_yoast_wpseo_metadesc', 'title' => '_yoast_wpseo_title'],
    ];

    /** @return array<int,Ability> */
    public static function abilities(): array
    {
        $idSchema = ['minimum' => 1, 'type' => 'integer'];
        return [
            new Ability(
                'sarcio/seo-get',
                __('Look at a page’s search listing', 'sarcio'),
                Ability::READ,
                'The search engine title and description of a page, post or product, as set in the site’s SEO plugin (Yoast SEO or Rank Math), and which plugin that is. Empty values mean the plugin’s default is used.',
                ['properties' => ['id' => $idSchema], 'required' => ['id'], 'type' => 'object'],
                static fn (array $args): bool => isset($args['id']) ? current_user_can('edit_post', (int) $args['id']) : current_user_can('edit_posts'),
                static fn (array $args): array => self::get((int) $args['id']),
            ),
            new Ability(
                'sarcio/seo-update',
                __('Change a page’s search listing', 'sarcio'),
                Ability::WRITE,
                'Set the search engine title and/or description of a page, post or product in the site’s SEO plugin. Only the fields given change; an empty string goes back to the plugin’s default. Keep titles under 60 characters and descriptions under 160.',
                [
                    'properties' => [
                        'description' => ['maxLength' => 320, 'type' => 'string'],
                        'id' => $idSchema,
                        'title' => ['maxLength' => 200, 'type' => 'string'],
                    ],
                    'required' => ['id'],
                    'type' => 'object',
                ],
                static fn (array $args): bool => isset($args['id']) ? current_user_can('edit_post', (int) $args['id']) : current_user_can('edit_posts'),
                static fn (array $args): array => self::update($args),
                static fn (array $args): array => self::updatePreview($args),
                static fn (array $before, array $after): array => self::write((int) $before['id'], $before) + ['restored' => true],
            ),
        ];
    }

    /** Which SEO plugin holds the listing, or null. */
    public static function plugin(): ?string
    {
        if (defined('WPSEO_VERSION') || class_exists('WPSEO_Options')) {
            return self::YOAST;
        }
        if (class_exists('RankMath') || defined('RANK_MATH_VERSION')) {
            return self::RANK_MATH;
        }
        return null;
    }

    /** The post meta key holding the search description, for the plugin in use. */
    public static function descriptionKey(): ?string
    {
        $plugin = self::plugin();
        return $plugin === null ? null : self::KEYS[$plugin]['description'];
    }

    /** @return array{id:int,plugin:string,title:string,description:string} */
    public static function snapshot(int $id, string $plugin): array
    {
        return [
            'description' => (string) get_post_meta($id, self::KEYS[$plugin]['description'], true),
            'id' => $id,
            'plugin' => $plugin,
            'title' => (string) get_post_meta($id, self::KEYS[$plugin]['title'], true),
        ];
    }

    private static function get(int $id): array
    {
        $post = get_post($id);
        if ($post === null) {
            return ['error' => __('There is no page or post with that id.', 'sarcio')];
        }
        $plugin = self::plugin();
        if ($plugin === null) {
            return ['error' => __('This site has no SEO plugin the assistant can change (Yoast SEO or Rank Math).', 'sarcio')];
        }
        return self::snapshot($id, $plugin) + ['postTitle' => (string) $post->post_title, 'url' => (string) get_permalink($post)];
    }

    /**
     * @param array<string,mixed> $args
     * @return array{before:array<string,mixed>,after:array<string,mixed>,changed:array<int,string>,postTitle:string}|array{error:string}
     */
    private static function changes(array $args): array
    {
        $post = get_post((int) $args['id']);
        if ($post === null) {
            return ['error' => __('There is no page or post with that id.', 'sarcio')];
        }
        $plugin = self::plugin();
        if ($plugin === null) {
            return ['error' => __('This site has no SEO plugin the assistant can change (Yoast SEO or Rank Math).', 'sarcio')];
        }
        $before = self::snapshot((int) $post->ID, $plugin);
        $after = $before;
        foreach (['title', 'description'] as $field) {
            if (array_key_exists($field, $args)) {
                $after[$field] = sanitize_text_field((string) $args[$field]);
            }
        }
        $changed = array_values(array_filter(['title', 'description'], static fn (string $field): bool => $before[$field] !== $after[$field]));
        if ($changed === []) {
            return ['error' => __('Nothing would change.', 'sarcio')];
        }
        return ['after' => $after, 'before' => $before, 'changed' => $changed, 'postTitle' => (string) $post->post_title];
    }

    /** @param array<string,mixed> $args */
    private static function update(array $args): array
    {
        $changes = self::changes($args);
        if (isset($changes['error'])) {
            return $changes;
        }
        $written = self::write((int) $args['id'], $changes['after']);
        if (isset($written['error'])) {
            return $written;
        }
        return [
            'changed' => $changes['changed'],
            'id' => (int) $args['id'],
            'journal' => [
                'after' => $changes['after'],
                'before' => $changes['before'],
                'summary' => sprintf(
                    /* translators: 1: title and/or description, 2: the page title. */
                    __('Changed the search %1$s of “%2$s”', 'sarcio'),
                    implode(' and ', $changes['changed']),
                    $changes['postTitle'],
                ),
                'target' => 'post:' . $args['id'],
            ],
        ];
    }

    /** @param array<string,mixed> $args */
    private static function updatePreview(array $args): array
    {
        $changes = self::changes($args);
        if (isset($changes['error'])) {
            return $changes;
        }
        $line = static fn (array $fields, string $field): string => $field . ': ' . ($fields[$field] !== '' ? $fields[$field] : __('(the plugin’s default)', 'sarcio'));
        return [
            'after' => implode("\n", array_map(static fn (string $field): string => $line($changes['after'], $field), $changes['changed'])),
            'before' => implode("\n", array_map(static fn (string $field): string => $line($changes['before'], $field), $changes['changed'])),
            'summary' => sprintf(
                /* translators: %s: the page title. */
                __('Change the search listing of “%s”', 'sarcio'),
                $changes['postTitle'],
            ),
        ];
    }

    /** @param array<string,mixed> $fields the snapshot shape */
    private static function write(int $id, array $fields): array
    {
        $plugin = (string) ($fields['plugin'] ?? self::plugin());
        if (!isset(self::KEYS[$plugin]) || get_post($id) === null) {
            return ['error' => __('That page no longer exists.', 'sarcio')];
        }
        foreach (['title', 'description'] as $field) {
            $value = (string) ($fields[$field] ?? '');
            if ($value === '') {
                delete_post_meta($id, self::KEYS[$plugin][$field]);
            } else {
                update_post_meta($id, self::KEYS[$plugin][$field], $value);
            }
        }
        if ($plugin === self::YOAST) {
            // Yoast reads its own table at render time and rebuilds it when
            // the post is saved, so touch the post as the editor would.
            wp_update_post(['ID' => $id]);
        }
        return ['id' => $id];
    }
}