package api

import (
	"fmt"
	"strconv"
)

// intParam parses the query parameter text as an integer from low to high,
// or returns fallback if it is empty. Its error is meant for the client.
func intParam(text string, fallback, low, high int) (int, error) {
	if text == "" {
		return fallback, nil
	}

	number, err := strconv.Atoi(text)
	if err != nil || number < low || number > high {
		return 0, fmt.Errorf(
			"parameter must be an integer between %d and %d", low, high,
		)
	}

	return number, nil
}