<?php

declare(strict_types=1);

class Search
{
    private Database $db;

    public function __construct()
    {
        $this->db = Database::getInstance();
    }

    /**
     * Full-text search across page OCR content.
     *
     * Uses PostgreSQL plainto_tsquery for safe, automatic query parsing.
     * Returns matching pages with document metadata, a highlighted snippet,
     * and a relevance rank.
     *
     * @param string      $query      Raw search terms
     * @param string|null $collection Optional source_section filter
     * @param int         $limit      Max results
     * @param int         $offset     Pagination offset
     * @return array<int, array<string, mixed>>
     */
    public function fullText(
        string $query,
        ?string $collection = null,
        int $limit = 50,
        int $offset = 0,
        ?string $topicFilter = null,
        ?string $stampFilter = null
    ): array {
        if (trim($query) === '') {
            return [];
        }

        $params = ['query' => $query];
        $joins = '';
        $extraWhere = '';

        if ($collection !== null && $collection !== '') {
            $extraWhere .= ' AND d.source_section = :collection';
            $params['collection'] = $collection;
        }

        if ($topicFilter !== null && $topicFilter !== '') {
            $joins .= " INNER JOIN document_features df_topic ON df_topic.document_id = d.id
                        AND df_topic.feature_name = 'topic_distribution'
                        AND (df_topic.feature_json->>:topicKey)::float > 0.5";
            $params['topicKey'] = $topicFilter;
        }

        if ($stampFilter !== null && $stampFilter !== '') {
            $joins .= " INNER JOIN document_features df_stamp ON df_stamp.document_id = d.id
                        AND df_stamp.feature_name = 'forensic_metadata'
                        AND EXISTS (SELECT 1 FROM jsonb_array_elements(df_stamp.feature_json->'stamps') s WHERE s->>'stamp' = :stampVal)";
            $params['stampVal'] = $stampFilter;
        }

        $params['limit']  = $limit;
        $params['offset'] = $offset;

        $sql = "
            SELECT
                p.id           AS page_id,
                p.document_id,
                p.page_number,
                p.ocr_confidence,
                p.word_count,
                d.file_path,
                d.source_section,
                d.total_pages,
                ts_headline(
                    'english',
                    p.ocr_text,
                    plainto_tsquery('english', :query),
                    'StartSel=<mark>, StopSel=</mark>, MaxWords=60, MinWords=20, MaxFragments=3, FragmentDelimiter= ... '
                ) AS snippet,
                ts_rank_cd(p.tsv, plainto_tsquery('english', :query)) AS rank
            FROM pages p
            INNER JOIN documents d ON d.id = p.document_id
            {$joins}
            WHERE p.tsv @@ plainto_tsquery('english', :query)
            {$extraWhere}
            ORDER BY rank DESC, p.document_id, p.page_number
            LIMIT :limit OFFSET :offset
        ";

        return $this->db->fetchAll($sql, $params);
    }

    /**
     * Semantic (vector) similarity search.
     *
     * Uses pgvector cosine distance to find pages with embeddings most
     * similar to the given page's embedding.
     *
     * @param int $pageId The source page whose embedding to compare against
     * @param int $limit  Max number of similar pages to return
     * @return array<int, array<string, mixed>>
     */
    public function semantic(int $pageId, int $limit = 20): array
    {
        $sql = "
            SELECT
                p2.id           AS page_id,
                p2.document_id,
                p2.page_number,
                p2.word_count,
                p2.ocr_confidence,
                d.file_path,
                d.source_section,
                d.total_pages,
                (p1.embedding <=> p2.embedding) AS distance
            FROM pages p1
            CROSS JOIN LATERAL (
                SELECT p.*
                FROM pages p
                WHERE p.id != p1.id
                  AND p.embedding IS NOT NULL
                ORDER BY p1.embedding <=> p.embedding
                LIMIT :limit
            ) p2
            INNER JOIN documents d ON d.id = p2.document_id
            WHERE p1.id = :pageId
              AND p1.embedding IS NOT NULL
            ORDER BY distance ASC
        ";

        return $this->db->fetchAll($sql, [
            'pageId' => $pageId,
            'limit'  => $limit,
        ]);
    }

    /**
     * Count the total number of full-text search results (for pagination).
     *
     * @param string      $query
     * @param string|null $collection
     * @return int
     */
    public function countResults(string $query, ?string $collection = null, ?string $topicFilter = null, ?string $stampFilter = null): int
    {
        if (trim($query) === '') {
            return 0;
        }

        $params = ['query' => $query];
        $joins = '';
        $extraWhere = '';

        if ($collection !== null && $collection !== '') {
            $extraWhere .= ' AND d.source_section = :collection';
            $params['collection'] = $collection;
        }

        if ($topicFilter !== null && $topicFilter !== '') {
            $joins .= " INNER JOIN document_features df_topic ON df_topic.document_id = d.id
                        AND df_topic.feature_name = 'topic_distribution'
                        AND (df_topic.feature_json->>:topicKey)::float > 0.5";
            $params['topicKey'] = $topicFilter;
        }

        if ($stampFilter !== null && $stampFilter !== '') {
            $joins .= " INNER JOIN document_features df_stamp ON df_stamp.document_id = d.id
                        AND df_stamp.feature_name = 'forensic_metadata'
                        AND EXISTS (SELECT 1 FROM jsonb_array_elements(df_stamp.feature_json->'stamps') s WHERE s->>'stamp' = :stampVal)";
            $params['stampVal'] = $stampFilter;
        }

        $sql = "
            SELECT COUNT(*)::int AS cnt
            FROM pages p
            INNER JOIN documents d ON d.id = p.document_id
            {$joins}
            WHERE p.tsv @@ plainto_tsquery('english', :query)
            {$extraWhere}
        ";

        $row = $this->db->fetchOne($sql, $params);

        return $row ? (int) $row['cnt'] : 0;
    }
}