package clickhouse_api

import (
	"context"
	"fmt"
	"reflect"

	"github.com/shopspring/decimal"
)

func DynamicScan() error {
	conn, err := GetNativeConnection(nil, nil, nil)
	if err != nil {
		return err
	}

	if err := conn.Exec(context.Background(), "CREATE TABLE IF NOT EXISTS dynamic_scan_table (Col1 Nullable(Decimal64(2))) ENGINE = Memory"); err != nil {
		return err
	}

	if err := conn.Exec(context.Background(), "INSERT INTO dynamic_scan_table VALUES (NULL), (NULL), (NULL), (123.1), (NULL), (124.1), (NULL), (NULL), (NULL), (NULL)"); err != nil {
		return err
	}

	rows, err := conn.Query(context.Background(), "SELECT Col1 FROM dynamic_scan_table")
	if err != nil {
		return err
	}

	var (
		columnTypes = rows.ColumnTypes()
		vars        = make([]interface{}, len(columnTypes))
	)
	for i := range columnTypes {
		vars[i] = reflect.New(columnTypes[i].ScanType()).Interface()
	}
	for rows.Next() {
		if err := rows.Scan(vars...); err != nil {
			return err
		}
		for _, v := range vars {
			switch v := v.(type) {
			case **decimal.Decimal:
				if *v == nil {
					fmt.Println("NULL")
					continue
				}
				fmt.Println(**v)
			}
		}
	}
	return nil
}