package api

import (
	"fmt"
	"strconv"
	"time"
)

// 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
}

// timeParam parses the query parameter name's text as an RFC 3339 time, or
// returns the zero time if it is empty. Its error is meant for the client.
func timeParam(name, text string) (time.Time, error) {
	if text == "" {
		return time.Time{}, nil
	}

	when, err := time.Parse(time.RFC3339, text)
	if err != nil {
		return time.Time{}, fmt.Errorf(
			"%s must be an RFC 3339 date and time, e.g. 2026-10-12T00:00:00+01:00",
			name,
		)
	}

	return when, nil
}