package util

import (
	"errors"
	"regexp"
	"strings"
)

// ErrInvalidPhoneNumber means a phone number is not an Indonesian mobile number.
var ErrInvalidPhoneNumber = errors.New("invalid phone number format")

// customerPhonePattern is an Indonesian mobile number in its stored form: 62, then the
// number without its leading 0 (628…, 10 to 14 digits in all).
var customerPhonePattern = regexp.MustCompile(`^628\d{7,11}$`)

// NormalizePhoneNumber turns a customer's phone number into the one form it is stored
// and looked up in, 62…: "0812-3456-1234", "+62 812 3456 1234", "62812…" and "812…"
// all become "6281234561234". Spaces, dashes, dots and parentheses are dropped.
func NormalizePhoneNumber(raw string) (string, error) {
	digits := strings.Map(func(r rune) rune {
		switch r {
		case ' ', '-', '.', '(', ')':
			return -1
		}
		return r
	}, strings.TrimSpace(raw))
	digits = strings.TrimPrefix(digits, "+")
	switch {
	case strings.HasPrefix(digits, "620"):
		// +62 typed in front of a number that kept its 0.
		digits = "62" + digits[3:]
	case strings.HasPrefix(digits, "0"):
		digits = "62" + digits[1:]
	case strings.HasPrefix(digits, "8"):
		digits = "62" + digits
	}
	if !customerPhonePattern.MatchString(digits) {
		return "", ErrInvalidPhoneNumber
	}
	return digits, nil
}