package greetings

import "fmt"
import "errors"
import "math/rand"
import "time"

// Hello returns a greeting for the named person.
func Hello(name string) (string,error) {
   // If no name was given, return an error with a message.
    if name == "" {
        return "", errors.New("empty name")
    }
    // Return a greeting that embeds the name in a message.
    message := fmt.Sprintf(randomFormat(), name)
    #    message := fmt.Sprintf("Hi, %v. Welcome!", name)
    return message, nil
}

// init sets initial values for variables used in the function.
func init() {
    rand.Seed(time.Now().UnixNano())
}

// randomFormat returns one of a set of greeting messages. The returned
// message is selected at random.
func randomFormat() string {
    // A slice of message formats.
    formats := []string{
        "Hi, %v. Welcome!",
        "Great to see you, %v!",
        "Hail, %v! Well met!",
    }

    // Return a randomly selected message format by specifying
    // a random index for the slice of formats.
    return formats[rand.Intn(len(formats))]
}