package search

import (
	"strings"

	"verstak/internal/core/storage"
)

// Result is a single search hit.
type Result struct {
	NodeID  string `json:"id"`
	Title   string `json:"title"`
	Type    string `json:"type"`
	Snippet string `json:"snippet,omitempty"`
}

// Service manages FTS5 search index.
type Service struct {
	db *storage.DB
}

// NewService creates a search service.
func NewService(db *storage.DB) *Service {
	return &Service{db: db}
}

// Index adds or updates a document in the FTS5 index.
func (s *Service) Index(nodeID, title, content, path, tags, docType string) error {
	// Delete old entry first (FTS5 doesn't support UPDATE).
	s.db.Exec("DELETE FROM search_index WHERE node_id=?", nodeID)
	_, err := s.db.Exec(
		`INSERT INTO search_index (node_id,title,content,path,tags,type)
		 VALUES (?,?,?,?,?,?)`,
		nodeID, title, content, path, tags, docType,
	)
	return err
}

// Remove deletes a document from the index.
func (s *Service) Remove(nodeID string) error {
	_, err := s.db.Exec("DELETE FROM search_index WHERE node_id=?", nodeID)
	return err
}

// Rebuild clears and rebuilds the entire index.
// Creates the FTS5 table if it doesn't exist (requires FTS5 support).
func (s *Service) Rebuild() error {
	_, _ = s.db.Exec(`CREATE VIRTUAL TABLE IF NOT EXISTS search_index USING fts5(
		node_id UNINDEXED, title, content, path, tags, type)`)
	_, err := s.db.Exec("DELETE FROM search_index")
	return err
}

// Search queries the FTS5 index. Returns up to 20 results.
func (s *Service) Search(query string) ([]Result, error) {
	if strings.TrimSpace(query) == "" {
		return nil, nil
	}

	// Escape FTS5 special characters.
	fts := sanitizeFTS(query)

	rows, err := s.db.Query(
		`SELECT node_id, title, type, snippet(search_index, 0, '', '', '...', 32) as snip
		 FROM search_index WHERE search_index MATCH ?
		 ORDER BY rank LIMIT 20`, fts)
	if err != nil {
		// FTS5 table may not exist (no FTS5 support or not rebuilt yet).
		return nil, nil
	}
	defer rows.Close()

	var out []Result
	for rows.Next() {
		var r Result
		var snip sqlNullString
		if err := rows.Scan(&r.NodeID, &r.Title, &r.Type, &snip); err != nil {
			return nil, err
		}
		if snip.Valid {
			r.Snippet = snip.String
		}
		out = append(out, r)
	}
	return out, rows.Err()
}

func sanitizeFTS(q string) string {
	// Wrap in double quotes for phrase search, escape inner quotes.
	q = strings.TrimSpace(q)
	q = strings.ReplaceAll(q, `"`, `""`)
	return `"` + q + `"`
}

type sqlNullString = struct {
	String string
	Valid  bool
}