<?php

declare(strict_types=1);

namespace Sarcio\WordPress\Assistant;

/**
 * A block theme's header, footer and other template parts. The theme ships
 * them as files (often as patterns); a change is saved the way the Site
 * Editor saves one, as a `wp_template_part` post that overrides the file for
 * the active theme, and undone by removing that override (or restoring the
 * earlier one). Patterns inside a part are expanded first, so the text in
 * them can be changed; the theme's own files are never written.
 */
final class ThemeAbilities
{
    public const MAX_CONTENT_CHARS = 60000;
    public const TYPE = 'wp_template_part';

    /** @return array<int,Ability> */
    public static function abilities(): array
    {
        $allowed = static fn (array $args): bool => current_user_can('edit_theme_options');
        $slugSchema = ['maxLength' => 200, 'minLength' => 1, 'pattern' => '^[a-z0-9-]+$', 'type' => 'string'];
        return [
            new Ability(
                'sarcio/theme-parts-list',
                __('Look at the header and footer', 'sarcio'),
                Ability::READ,
                'The active block theme’s template parts (header, footer, sidebar…): slug, title, area, whether the site has customised it, and the text each shows. Text that is not on a page or post (a phone number in the footer, a header link) usually lives here. Only on a block theme.',
                ['properties' => [], 'type' => 'object'],
                $allowed,
                static fn (array $args): array => self::list(),
            ),
            new Ability(
                'sarcio/theme-part-get',
                __('Read a header or footer part', 'sarcio'),
                Ability::READ,
                'Read one template part by slug: its full block markup (patterns expanded) and the text it shows. Read before you change text, so the search string is exact.',
                ['properties' => ['slug' => $slugSchema], 'required' => ['slug'], 'type' => 'object'],
                $allowed,
                static fn (array $args): array => self::get((string) $args['slug']),
            ),
            new Ability(
                'sarcio/theme-part-replace',
                __('Change text in the header or footer', 'sarcio'),
                Ability::WRITE,
                'Replace an exact piece of text inside a template part’s markup (patterns expanded). Refused when the text is not found, or found more than once unless all is true. The theme’s files are not touched: the change is saved as the site’s own copy of the part, which can be removed again.',
                [
                    'properties' => [
                        'all' => ['type' => 'boolean'],
                        'replace' => ['maxLength' => 20000, 'type' => 'string'],
                        'search' => ['maxLength' => 20000, 'minLength' => 1, 'type' => 'string'],
                        'slug' => $slugSchema,
                    ],
                    'required' => ['slug', 'search', 'replace'],
                    'type' => 'object',
                ],
                $allowed,
                static fn (array $args): array => self::replace($args),
                null,
                static fn (array $before, array $after): array => self::restore($before),
                false,
                static fn (array $args, Overlay $overlay): array => self::stageReplace($args, $overlay),
            ),
        ];
    }

    public static function supported(): bool
    {
        return function_exists('wp_is_block_theme') && wp_is_block_theme() && function_exists('get_block_templates');
    }

    /**
     * One part as the site shows it: the override post when there is one,
     * else the theme file, with patterns expanded either way.
     *
     * @return array{slug:string,title:string,area:string,content:string,postId:int,custom:bool}|null
     */
    public static function part(string $slug, ?Overlay $overlay = null): ?array
    {
        if (!self::supported()) {
            return null;
        }
        $template = get_block_template((string) get_stylesheet() . '//' . $slug, self::TYPE);
        if (!is_object($template) || !isset($template->content)) {
            return null;
        }
        $postId = (string) ($template->source ?? 'theme') === 'custom' ? (int) ($template->wp_id ?? 0) : 0;
        if ($postId > 0) {
            $post = $overlay !== null ? $overlay->post($postId) : get_post($postId);
            return [
                'area' => (string) ($template->area ?? 'uncategorized'),
                'content' => self::expand((string) ($post !== null ? $post->post_content : $template->content)),
                'custom' => true,
                'postId' => $postId,
                'slug' => $slug,
                'title' => (string) ($template->title ?? $slug),
            ];
        }
        $content = $overlay !== null && isset($overlay->templateParts[$slug]) ? $overlay->templateParts[$slug] : self::expand((string) $template->content);
        return [
            'area' => (string) ($template->area ?? 'uncategorized'),
            'content' => $content,
            'custom' => false,
            'postId' => 0,
            'slug' => $slug,
            'title' => (string) ($template->title ?? $slug),
        ];
    }

    private static function list(): array
    {
        if (!self::supported()) {
            return ['error' => __('This theme has no header and footer parts the assistant can change. Its text is set in Appearance → Customize or in the theme itself.', 'sarcio')];
        }
        $overlay = Stage::active() ? Stage::overlay() : null;
        $parts = [];
        foreach ((array) get_block_templates([], self::TYPE) as $template) {
            if (!is_object($template) || !isset($template->slug)) {
                continue;
            }
            $part = self::part((string) $template->slug, $overlay);
            if ($part === null) {
                continue;
            }
            $parts[] = [
                'area' => $part['area'],
                'custom' => $part['custom'],
                'slug' => $part['slug'],
                'text' => mb_substr(ContentAbilities::readable($part['content']), 0, 4000),
                'title' => $part['title'],
            ];
        }
        return ['parts' => $parts];
    }

    private static function get(string $slug): array
    {
        $part = self::part($slug, Stage::active() ? Stage::overlay() : null);
        if ($part === null) {
            return ['error' => self::supported() ? __('There is no template part with that slug.', 'sarcio') : __('This theme has no header and footer parts the assistant can change.', 'sarcio')];
        }
        $truncated = mb_strlen($part['content']) > self::MAX_CONTENT_CHARS;
        return [
            'area' => $part['area'],
            'content' => $truncated ? mb_substr($part['content'], 0, self::MAX_CONTENT_CHARS) : $part['content'],
            'custom' => $part['custom'],
            'slug' => $part['slug'],
            'text' => ContentAbilities::readable($part['content']),
            'title' => $part['title'],
            'truncated' => $truncated,
        ];
    }

    /** @param array<string,mixed> $args */
    private static function replace(array $args): array
    {
        $part = self::part((string) $args['slug']);
        if ($part === null) {
            return ['error' => __('There is no template part with that slug.', 'sarcio')];
        }
        $result = ContentAbilities::replaceText($part['content'], (string) $args['search'], (string) $args['replace'], (bool) ($args['all'] ?? false));
        if (isset($result['error'])) {
            return ['error' => $result['error']];
        }
        $saved = self::save($part, (string) $result['content']);
        if (isset($saved['error'])) {
            return $saved;
        }
        return [
            'journal' => [
                'after' => ['content' => (string) $result['content'], 'postId' => $saved['postId'], 'slug' => $part['slug']],
                'before' => ['content' => $part['content'], 'custom' => $part['custom'], 'postId' => $part['postId'], 'slug' => $part['slug']],
                'summary' => sprintf(
                    /* translators: 1: the old text, 2: the new text, 3: the part title. */
                    __('Changed “%1$s” to “%2$s” in the %3$s', 'sarcio'),
                    mb_substr((string) $args['search'], 0, 60),
                    mb_substr((string) $args['replace'], 0, 60),
                    $part['title'],
                ),
                'target' => 'template_part:' . $part['slug'],
            ],
            'postId' => $saved['postId'],
            'replaced' => $result['count'],
            'slug' => $part['slug'],
        ];
    }

    /** @param array<string,mixed> $args */
    private static function stageReplace(array $args, Overlay $overlay): array
    {
        $part = self::part((string) $args['slug'], $overlay);
        if ($part === null) {
            return ['error' => __('There is no template part with that slug.', 'sarcio')];
        }
        $result = ContentAbilities::replaceText($part['content'], (string) $args['search'], (string) $args['replace'], (bool) ($args['all'] ?? false));
        if (isset($result['error'])) {
            return ['error' => $result['error']];
        }
        if ($part['postId'] > 0) {
            $overlay->setPost($part['postId'], ['post_content' => (string) $result['content']]);
        } else {
            $overlay->templateParts[$part['slug']] = (string) $result['content'];
        }
        return [
            'after' => ContentAbilities::readable((string) $result['content']),
            'before' => ContentAbilities::readable($part['content']),
            'summary' => sprintf(
                /* translators: %s: the part title. */
                __('Change this text in the %s', 'sarcio'),
                $part['title'],
            ),
        ];
    }

    /**
     * Writes the site's own copy of the part, as the Site Editor does.
     *
     * @param array{slug:string,title:string,area:string,content:string,postId:int,custom:bool} $part
     * @return array{postId:int}|array{error:string}
     */
    private static function save(array $part, string $content): array
    {
        if ($part['postId'] > 0) {
            $result = wp_update_post(['ID' => $part['postId'], 'post_content' => $content], true);
            if (is_wp_error($result) || (int) $result <= 0) {
                return ['error' => __('WordPress could not save the change.', 'sarcio')];
            }
            return ['postId' => $part['postId']];
        }
        $id = wp_insert_post([
            'post_content' => $content,
            'post_name' => $part['slug'],
            'post_status' => 'publish',
            'post_title' => $part['title'],
            'post_type' => self::TYPE,
        ], true);
        if (is_wp_error($id) || !is_int($id) || $id <= 0) {
            return ['error' => __('WordPress could not save the change.', 'sarcio')];
        }
        wp_set_post_terms($id, [(string) get_stylesheet()], 'wp_theme');
        wp_set_post_terms($id, [$part['area']], 'wp_template_part_area');
        update_post_meta($id, 'origin', 'theme');
        return ['postId' => $id];
    }

    /** @param array<string,mixed> $before */
    private static function restore(array $before): array
    {
        $slug = (string) ($before['slug'] ?? '');
        $current = self::part($slug);
        $post = $current !== null && $current['postId'] > 0 ? get_post($current['postId']) : null;
        if (!empty($before['custom'])) {
            $id = $post !== null ? (int) $post->ID : (int) ($before['postId'] ?? 0);
            if ($id <= 0 || get_post($id) === null) {
                return ['error' => __('That part no longer exists.', 'sarcio')];
            }
            $result = wp_update_post(['ID' => $id, 'post_content' => (string) ($before['content'] ?? '')], true);
            if (is_wp_error($result) || (int) $result <= 0) {
                return ['error' => __('WordPress could not restore the part.', 'sarcio')];
            }
            return ['postId' => $id, 'restored' => true, 'slug' => $slug];
        }
        if ($post === null) {
            return ['restored' => true, 'slug' => $slug];
        }
        if (!wp_delete_post((int) $post->ID, true)) {
            return ['error' => __('WordPress could not remove the site’s copy of the part.', 'sarcio')];
        }
        return ['restored' => true, 'slug' => $slug, 'themeVersion' => true];
    }

    /** Patterns a part pulls in are expanded, so their text is there to be changed. */
    private static function expand(string $content): string
    {
        if (!function_exists('resolve_pattern_blocks') || !function_exists('parse_blocks') || !function_exists('serialize_blocks')) {
            return $content;
        }
        return (string) serialize_blocks(resolve_pattern_blocks(parse_blocks($content)));
    }
}