MUV sketch for Rust

muv.rs

use std::io::{self, Write};

// messages

struct MsgLogin(String);

struct MsgGreet;

struct MsgLogout;

// models

struct ModelLogouted;

struct ModelLogined(String);

// update

struct Update<ML, MG> {
    model: ML,
    msg: MG,
}

impl<ML, MG> Update<ML, MG> {
    fn new(model: ML, msg: MG) -> Update<ML, MG> {
        Update { model, msg, }
    }
}

impl Update<ModelLogouted, MsgLogin> {
    fn update(self) -> ModelLogined {
        ModelLogined(self.msg.0)
    }
}

impl Update<ModelLogined, MsgGreet> {
    fn update(self) -> ModelLogined {
        self.model
    }
}

impl Update<ModelLogined, MsgLogout> {
    fn update(self) -> ModelLogouted {
        ModelLogouted
    }
}

// view

impl ModelLogouted {
    fn view(self) {
        print!("Login: ");
        io::stdout().flush().unwrap();
        let login = getline().unwrap_or_else(|| "anon".to_string());
        let model = Update::new(self, MsgLogin(login)).update();
        model.view();
    }
}

impl ModelLogined {
    fn view(self) {
        println!("Hello, {}!", self.0);
        println!("Input empty string for logout or nonempty for greeting.");
        match getline() {
            None => {
                let model = Update::new(self, MsgLogout).update();
                model.view();
            },
            Some(..) => {
                let model = Update::new(self, MsgGreet).update();
                model.view();
            }
        }
    }
}

// util

fn getline() -> Option<String> {
    let mut input = String::new();
    io::stdin().read_line(&mut input).unwrap();
    let trimmed = input.trim();
    if trimmed.is_empty() { None } else { Some(trimmed.to_string()) }
}

// main

fn main() {
    let init_model = ModelLogouted;
    init_model.view();
}