grokify/mogo

package phonenumber

import (
    "regexp"
    "strconv"
    "strings"
)

const numbers = "2ABC3DEF4GHI5JKL6MNO7PQRS8TUV9WXYZ"

func LetterToNumberMap() map[string]int {
    rx := regexp.MustCompile(`(\d)([A-Z]+)`)
    m := rx.FindAllStringSubmatch(numbers, -1)

    l2n := map[string]int{}

    for _, m2 := range m {
        if len(m2) > 0 {
            num, err := strconv.Atoi(m2[1])
            if err != nil {
                panic(err)
            }

            letters := strings.Split(m2[2], "")

            for _, item := range letters {
                l2n[item] = num
            }
        }
    }

    return l2n
}

func StringToNumbers(s string) string {
    conv := []string{}
    arr := strings.Split(s, "")
    l2n := LetterToNumberMap()
    for _, letter := range arr {
        letter = strings.ToUpper(letter)
        if num, ok := l2n[letter]; ok {
            conv = append(conv, strconv.Itoa(num))
        } else {
            conv = append(conv, letter)
        }
    }
    return strings.Join(conv, "")
}