状态模式

const readline = require('readline');
let rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout
})
let State = Object.freeze({
    offHook: '拿起座机手柄',
    connecting: '连接中',
    connected: '已连接',
    onHook: '放下座机手柄'
});
let Trigger = Object.freeze({
    callDialed: '拔号',
    hungUp: '挂断电话',
    callConnected: '打通电话',
    leftMessage: '留言'
});
let rules = {};
rules[State.offHook] = [
    {
        trigger: Trigger.callDialed,
        state: State.connecting
    }
];
rules[State.connecting] = [
    {
        trigger: Trigger.hungUp,
        state: State.onHook
    },
    {
        trigger: Trigger.callConnected,
        state: State.connected
    }
];
rules[State.connected] = [
    {
        trigger: Trigger.leftMessage,
        state: State.onHook
    },
    {
        trigger: Trigger.hungUp,
        state: State.onHook
    }
];
let state = State.offHook;
let exitState = State.onHook;
let getInput = function () {
    let prompt = [
        `当前电话正处于${state}`,
        `下一步：`
    ]
    for (let i = 0; i < rules[state].length; i++) {
        let trigger = rules[state][i].trigger;
        prompt.push(`${i}, ${trigger}`);
    }
    prompt.push('');
    rl.question(prompt.join('\n'), function (answer) {
        let input = parseInt(answer);
        state = rules[state][input].state;
        if (state !== exitState) {
            getInput();
        } else {
            console.log(`我们使用完了座机电话`);
            rl.close();
        }
    })
}
getInput();