<?php

declare(strict_types=1);

namespace LIT\MCP\Integrations\Divi\Library;

use LIT\MCP\Abilities\Ability;
use LIT\MCP\Abilities\Annotations;
use LIT\MCP\Abilities\Cursor;
use LIT\MCP\Abilities\Errors;
use LIT\MCP\Abilities\Rev;
use LIT\MCP\Integrations\Divi\BlockTree\Block;
use LIT\MCP\Integrations\Divi\BlockTree\Fingerprint;
use LIT\MCP\Integrations\Divi\BlockTree\LibraryContent;
use LIT\MCP\Integrations\Divi\BlockTree\MalformedMarkup;
use LIT\MCP\Integrations\Divi\BlockTree\NodeIndex;
use LIT\MCP\Integrations\Divi\BlockTree\NodeSummary;
use LIT\MCP\Integrations\Divi\BlockTree\Parser;
use LIT\MCP\Integrations\Divi\Pages\DiviErrors;
use LIT\MCP\Integrations\Divi\Pages\DiviPageLoader;
use LIT\MCP\Integrations\Divi\Release\DiviFeature;
use LIT\MCP\Integrations\Divi\Release\RequiresDiviFeatures;
use LIT\MCP\Integrations\Divi\ThemeBuilder\DiviThemeBuilder;
use LIT\MCP\Integrations\WordPress\PostGuard;
use LIT\MCP\Integrations\WordPress\Schema\ContentSchema;
use WP_Error;
use WP_Post;

defined('ABSPATH') || exit;

/**
 * lit/library-find-similar (spec §5.7, E11): nodes across the site built like a reference node (post_id + id) or a
 * library entry (library_id) – "identical" (Fingerprint::content) or "structure" (Fingerprint::structure, other
 * values). Scans at most MAX_POSTS entries per call in ID order (cursor), only of Divi-enabled managed types – never
 * library entries or Theme Builder layouts, which have their own gates –, only entries the user may edit (query
 * restricted to own posts without edit_others_posts, like content-query), no index or meta (F31). Contents come in
 * chunks of CONTENT_CHUNK through one primed post cache each (no query per post, bounded memory, as GlobalUsages).
 * A call stops after the post that reaches MAX_MATCHES matches or MAX_NODES fingerprinted nodes; `note` says so
 * and next_cursor resumes behind it. Needs the library right (canList); a hidden library answers its entries like
 * missing IDs (LibraryAccess::item, P9/P12). Only hashes and the matched nodes' labels are returned.
 */
final class LibraryFindSimilarAbility implements Ability, RequiresDiviFeatures
{
    public const MAX_POSTS = 200;
    public const DEFAULT_POSTS = 100;
    public const MAX_MATCHES = 200;

    /** At most this many nodes of the reference's type are fingerprinted per call. */
    public const MAX_NODES = 5000;

    /** Post contents read with one primed cache (bounded memory). */
    public const CONTENT_CHUNK = 50;


    private const LIVING = ['publish', 'draft', 'pending', 'private', 'future'];

    public function __construct(
        private LibraryAccess $access,
        private DiviPageLoader $loader,
        private ContentSchema $schema,
        private Parser $parser = new Parser()
    ) {
    }

    public function name(): string
    {
        return 'lit/library-find-similar';
    }

    public function label(): string
    {
        return 'Ähnliche Abschnitte finden';
    }

    public function description(): string
    {
        return 'Sucht seitenübergreifend Knoten, die wie ein gegebener Knoten (post_id und id aus '
            . 'lit-divi-outline) oder ein Bibliothekseintrag (library_id) aufgebaut sind: match "identical" = gleicher '
            . 'Inhalt (Admin-Labels ausgenommen), "structure" = gleicher Aufbau (Modultypen, Spalten, Presets) mit '
            . 'anderen Inhalten. Nur Einträge, die dieses Konto bearbeiten darf; höchstens 200 Einträge je Aufruf '
            . '(limit), weiter mit next_cursor. Inhaltsgleiche Vorkommen in Seiten und Beiträgen (replaceable: true) '
            . 'ersetzt lit/library-make-global (library_id, targets).';
    }

    public function inputSchema(): array
    {
        return [
            'type' => 'object',
            'properties' => [
                'post_id' => ['type' => 'integer', 'minimum' => 1],
                'id' => ['type' => 'string', 'description' => 'Pfad-ID des Vergleichsknotens, z. B. "s1".'],
                'library_id' => ['type' => 'integer', 'minimum' => 1, 'description' => 'Statt post_id und id.'],
                'post_type' => ['type' => 'string', 'description' => 'Nur diesen Inhaltstyp durchsuchen.'],
                'limit' => ['type' => 'integer', 'minimum' => 1, 'maximum' => self::MAX_POSTS],
                'cursor' => ['type' => 'string'],
            ],
            'additionalProperties' => false,
        ];
    }

    public function outputSchema(): ?array
    {
        return [
            'type' => 'object',
            'properties' => [
                'reference' => ['type' => 'object'],
                'matches' => ['type' => 'array', 'items' => ['type' => 'object']],
                'scanned' => ['type' => 'integer'],
                'next_cursor' => ['type' => ['string', 'null']],
                'note' => ['type' => 'string'],
            ],
            'required' => ['reference', 'matches', 'scanned', 'next_cursor'],
        ];
    }

    public function annotations(): array
    {
        return Annotations::read();
    }

    public function isDirect(): bool
    {
        return false;
    }

    /**
     * Scans Divi pages (PageRead) of the types that use the builder (Catalog), after the library right (Roles). A
     * library entry as reference is read through LibraryAccess (Roles), no Divi call beyond that.
     */
    public function diviFeatures(array $input): array
    {
        return [DiviFeature::PageRead, DiviFeature::Catalog, DiviFeature::Roles];
    }

    public function permission(array $input): bool|WP_Error
    {
        return $this->access->canList() ?? true;
    }

    public function execute(array $input): mixed
    {
        $refusal = $this->access->canList();
        if ($refusal !== null) {
            return $refusal;
        }

        $reference = $this->reference($input);
        if ($reference instanceof WP_Error) {
            return $reference;
        }

        $offset = Cursor::decode(is_string($input['cursor'] ?? null) ? $input['cursor'] : null);
        if ($offset === null) {
            return Cursor::invalid();
        }

        $types = $this->postTypes($input['post_type'] ?? null);
        if ($types instanceof WP_Error) {
            return $types;
        }

        $limit = is_int($input['limit'] ?? null)
            ? max(1, min(self::MAX_POSTS, $input['limit']))
            : self::DEFAULT_POSTS;
        $args = [
            'post_type' => $types,
            'post_status' => self::LIVING,
            'posts_per_page' => $limit + 1,
            'offset' => $offset,
            'orderby' => 'ID',
            'order' => 'ASC',
            'fields' => 'ids',
            'no_found_rows' => true,
            'suppress_filters' => false,
        ];
        foreach ($types as $type) {
            $own = PostGuard::ownPostsOnly($type);
            if ($own !== null) {
                $args['author'] = $own;
                break;
            }
        }
        $ids = array_values(array_map('intval', (array) get_posts($args)));
        $scan = array_slice($ids, 0, $limit);

        $matches = [];
        $nodes = 0;
        $scanned = 0;
        foreach (array_chunk($scan, self::CONTENT_CHUNK) as $chunk) {
            $fresh = _get_non_cached_ids($chunk, 'posts');
            _prime_post_caches($chunk, false, false);
            foreach ($chunk as $id) {
                if (self::full($matches, $nodes)) {
                    break;
                }
                ++$scanned;
                $post = current_user_can('edit_post', $id) ? get_post($id) : null;
                if ($post instanceof WP_Post && ! in_array((string) $post->post_type, self::notScanned(), true)) {
                    $this->collect($post, $reference, $matches, $nodes);
                }
            }
            foreach ($fresh as $id) {
                wp_cache_delete((int) $id, 'posts');
            }
            if (self::full($matches, $nodes)) {
                break;
            }
        }

        $stopped = $scanned < count($scan);
        $result = [
            'reference' => $reference['info'],
            'matches' => $matches,
            'scanned' => $scanned,
            'next_cursor' => $stopped || count($ids) > $limit ? Cursor::encode($offset + $scanned) : null,
        ];
        if (self::full($matches, $nodes)) {
            $result['note'] = sprintf(
                'Suche nach %d Einträgen angehalten (höchstens %d Treffer bzw. %d verglichene Knoten je Aufruf); '
                    . 'der letzte Eintrag kann weitere Treffer enthalten. Weiter mit next_cursor, oder mit post_type '
                    . 'eingrenzen.',
                $scanned,
                self::MAX_MATCHES,
                self::MAX_NODES
            );
        }

        return $result;
    }

    /** @param list<array<string, mixed>> $matches */
    private static function full(array $matches, int $nodes): bool
    {
        return count($matches) >= self::MAX_MATCHES || $nodes >= self::MAX_NODES;
    }

    /**
     * @param array<string, mixed> $input
     * @return array{block: Block, info: array<string, mixed>, post_id: ?int, id: ?string}|WP_Error
     */
    private function reference(array $input): array|WP_Error
    {
        if (isset($input['library_id'])) {
            $item = $this->access->item($input['library_id'], false);
            if ($item === null) {
                return PostGuard::notFound((int) PostGuard::id($input['library_id']));
            }
            if ($item instanceof WP_Error) {
                return $item;
            }

            try {
                $roots = LibraryContent::roots(LibraryContent::load($this->parser, (string) $item->post_content));
            } catch (MalformedMarkup) {
                $roots = [];
            }
            if (count($roots) !== 1 || $roots[0]->isOpaque()) {
                return Errors::invalidInput(
                    sprintf('Bibliothekseintrag %d hat nicht genau einen lesbaren Knoten.', (int) $item->ID),
                    ['library_id' => 'Eintrag mit genau einem Abschnitt, einer Zeile oder einem Modul']
                );
            }

            return self::describe($roots[0], null, null, (int) $item->ID);
        }

        if (! isset($input['post_id'])) {
            return Errors::invalidInput('Vergleich fehlt: library_id oder post_id und id angeben.', [
                'library_id' => 'oder post_id und id',
            ]);
        }

        $page = $this->loader->load($input['post_id'], false);
        if ($page instanceof WP_Error) {
            return $page;
        }

        $id = is_string($input['id'] ?? null) ? $input['id'] : '';
        $node = $page->index->find($id);
        if ($node === null) {
            return DiviErrors::unknownNode($id, $page->post);
        }
        if ($node->isOpaque()) {
            return Errors::invalidInput(
                'Der Knoten ist ein globales Modul oder nicht lesbar; nichts wurde gesucht.',
                ['id' => 'lesbarer Knoten']
            );
        }

        return self::describe($node, (int) $page->post->ID, $id, null);
    }

    /** @return array{block: Block, info: array<string, mixed>, post_id: ?int, id: ?string} */
    private static function describe(Block $block, ?int $postId, ?string $id, ?int $libraryId): array
    {
        $info = array_filter([
            'type' => $block->name(),
            'structure' => Fingerprint::structure($block),
            'content' => Fingerprint::content($block),
            'post_id' => $postId,
            'id' => $id,
            'library_id' => $libraryId,
        ], static fn (mixed $value): bool => $value !== null);

        return ['block' => $block, 'info' => $info, 'post_id' => $postId, 'id' => $id];
    }

    /**
     * Types with gates of their own (LibraryAccess, ThemeBuilderAccess): never scanned, even if a filter lists them
     * (review M-3: the Theme Builder types from DiviThemeBuilder::postTypes()).
     *
     * @return list<string>
     */
    private static function notScanned(): array
    {
        return array_merge([DiviLibraryStore::POST_TYPE], DiviThemeBuilder::postTypes());
    }

    /** @return list<string>|WP_Error */
    private function postTypes(mixed $postType): array|WP_Error
    {
        if ($postType !== null) {
            // Review M-7: an excluded type answers like any unavailable one, by its name.
            $type = in_array($postType, self::notScanned(), true)
                ? PostGuard::unavailableType((string) $postType)
                : PostGuard::postType($postType, $this->schema, 'edit_posts');

            return $type instanceof WP_Error ? $type : [(string) $postType];
        }

        $types = array_values(array_filter(
            array_diff($this->schema->postTypeNames(), self::notScanned()),
            fn (string $type): bool => $this->schema->diviEnabled($type)
        ));

        return $types !== [] ? $types : Errors::notFound(
            'Kein Inhaltstyp mit Divi-Builder verfügbar; nichts wurde gesucht.',
            'Inhaltstypen mit lit/content-types (direkt: lit-content-types) prüfen.'
        );
    }

    /**
     * @param array{block: Block, info: array<string, mixed>, post_id: ?int, id: ?string} $reference
     * @param list<array<string, mixed>> $matches
     */
    private function collect(WP_Post $post, array $reference, array &$matches, int &$nodes): void
    {
        $content = (string) $post->post_content;
        if (! str_contains($content, '<!-- wp:divi/')) {
            return;
        }

        try {
            $index = NodeIndex::build($this->parser->parse($content));
        } catch (MalformedMarkup) {
            return;
        }

        $name = $reference['block']->name();
        foreach ($index->entries() as $entry) {
            $block = $entry['block'];
            $self = (int) $post->ID === $reference['post_id'] && $entry['id'] === $reference['id'];
            if ($self || $block->isOpaque() || $block->name() !== $name) {
                continue;
            }
            if (++$nodes > self::MAX_NODES) {
                return;
            }
            if (Fingerprint::structure($block) !== $reference['info']['structure']) {
                continue;
            }

            $identical = Fingerprint::content($block) === $reference['info']['content'];
            $matches[] = [
                'post_id' => (int) $post->ID,
                'title' => (string) $post->post_title,
                'status' => (string) $post->post_status,
                'type' => (string) $post->post_type,
                'id' => $entry['id'],
                'label' => NodeSummary::label($block),
                'tree_rev' => Rev::of($content),
                'match' => $identical ? 'identical' : 'structure',
                // Review M-8: lit/library-make-global replaces identical occurrences in pages and posts only.
                'replaceable' => $identical
                    && in_array((string) $post->post_type, LibraryMakeGlobalAbility::POST_TYPES, true),
            ];
            if (count($matches) >= self::MAX_MATCHES) {
                return;
            }
        }
    }
}