package entity

import (
	"regexp"
	"strings"
)

var digitsOnly = regexp.MustCompile(`^\d+$`)

// NormalizePhone returns E.164-style +86XXXXXXXXXXX for mainland mobile, or "" if invalid.
func NormalizePhone(raw string) string {
	s := strings.TrimSpace(raw)
	s = strings.ReplaceAll(s, " ", "")
	s = strings.ReplaceAll(s, "-", "")
	if s == "" {
		return ""
	}
	if strings.HasPrefix(s, "+86") {
		s = s[3:]
	} else if strings.HasPrefix(s, "86") && len(s) > 11 {
		s = s[2:]
	}
	if len(s) != 11 || s[0] != '1' || !digitsOnly.MatchString(s) {
		return ""
	}
	return "+86" + s
}

// DetectCarrier maps a normalized +86 number to an operator bucket.
func DetectCarrier(normalized string) Carrier {
	if len(normalized) < 4 {
		return CarrierUnknown
	}
	d := normalized
	d = strings.TrimPrefix(d, "+86")
	if len(d) < 3 {
		return CarrierUnknown
	}
	p3 := d[:3]
	switch p3 {
	case "134", "135", "136", "137", "138", "139", "147", "148", "150", "151", "152", "157", "158", "159",
		"172", "178", "182", "183", "184", "187", "188", "195", "197", "198":
		return CarrierMobile
	case "130", "131", "132", "145", "146", "155", "156", "166", "167", "171", "175", "176", "185", "186", "196":
		return CarrierUnicom
	case "133", "149", "153", "173", "174", "177", "180", "181", "189", "190", "191", "193", "199":
		return CarrierTelecom
	default:
		if strings.HasPrefix(p3, "14") || strings.HasPrefix(p3, "16") {
			return CarrierUnicom
		}
		return CarrierUnknown
	}
}