package store

import (
	"context"
	"fmt"

	"github.com/jackc/pgx/v5/pgxpool"
)

const suggestLimit = 10

// SuggestStore provides autocomplete search over aggregated item names.
type SuggestStore struct {
	pool *pgxpool.Pool
}

// NewSuggestStore creates a SuggestStore backed by the given pool.
func NewSuggestStore(pool *pgxpool.Pool) *SuggestStore { return &SuggestStore{pool: pool} }

// Search returns up to suggestLimit item name suggestions matching q using
// pg_trgm similarity search.  Results are ordered by usage_count DESC so the
// most-used names appear first.
func (s *SuggestStore) Search(ctx context.Context, q string) ([]string, error) {
	rows, err := s.pool.Query(ctx, `
		SELECT name
		FROM item_names
		WHERE name % $1 OR name LIKE $2
		ORDER BY usage_count DESC, last_used_at DESC
		LIMIT $3`,
		q, q+"%", suggestLimit,
	)
	if err != nil {
		return nil, fmt.Errorf("suggeststore: search: %w", err)
	}
	defer rows.Close()

	var names []string
	for rows.Next() {
		var name string
		if err := rows.Scan(&name); err != nil {
			return nil, fmt.Errorf("suggeststore: scan name: %w", err)
		}
		names = append(names, name)
	}
	return names, rows.Err()
}