Generate Random Phone Numbers in Go

package main

import (
    "fmt"
    "math/rand"
    "regexp"
    "strings"
    "time"
)

func init() {
    rand.Seed(time.Now().UnixNano())
}

// Generate random US phone number (xxx) xxx-xxxx
func randomUsPhoneNumber() string {
    areaCode := rand.Intn(800) + 200
    exchange := rand.Intn(800) + 200
    lineNumber := rand.Intn(9000) + 1000
    return fmt.Sprintf("(%03d) %03d-%04d", areaCode, exchange, lineNumber)
}

// Generate random phone number with country code
func randomInternationalPhone(countryCode string) string {
    areaCode := rand.Intn(800) + 200
    exchange := rand.Intn(800) + 200
    lineNumber := rand.Intn(9000) + 1000
    return fmt.Sprintf("%s (%03d) %03d-%04d", countryCode, areaCode, exchange, lineNumber)
}

// Generate phone number without formatting
func randomPhoneDigits(length int) string {
    var sb strings.Builder
    for i := 0; i < length; i++ {
        sb.WriteString(fmt.Sprintf("%d", rand.Intn(10)))
    }
    return sb.String()
}

// Validate US phone number format
func isValidUsPhone(phone string) bool {
    pattern := `^\(\d{3}\) \d{3}-\d{4}$`
    matched, _ := regexp.MatchString(pattern, phone)
    return matched
}

// Generate multiple phone numbers
func generatePhoneNumbers(count int) []string {
    phones := make([]string, count)
    for i := 0; i < count; i++ {
        phones[i] = randomUsPhoneNumber()
    }
    return phones
}

func main() {
    fmt.Println("US Phone:", randomUsPhoneNumber())
    fmt.Println("International:", randomInternationalPhone("+44"))
    fmt.Println("Digits only:", randomPhoneDigits(10))
    fmt.Println("Valid:", isValidUsPhone("(555) 123-4567"))
    fmt.Println("Batch:", strings.Join(generatePhoneNumbers(3), ", "))
}