console-info-gather-example.ts

interface IValidQuestionValidation {
    success: true;
    value: string;
}

interface IInvalidQuestionValidation {
    success: false;
    message: string;
}

type IQuestionValidation = IInvalidQuestionValidation | IValidQuestionValidation;


declare function writeln(message: string): any;
declare function ioQuestion(message: string): Promise<string>;

async function question(
    message: string,
    validator: ((input: string) => IQuestionValidation | Promise<IQuestionValidation>),
    options?: {
        maxTries?: number,
        overtryMessage?: string,
    },
) {
    options = options || {};
    let tries = 0;
    const maxTries = options.maxTries || 3;

    while (tries <= maxTries) {
        tries++;

        const value = await ioQuestion(message);
        const validation = await Promise.resolve(validator(value));

        if (!validation.success) {
            writeln(`OOPS! ${validation.message}`);
        } else {
            return validation.value;
        }
    }

    throw new Error(options.overtryMessage || "Try again!");
}

async function getName<T extends object>(previousData: T) {
    const name = await question('What is your name?', value => {
        const minLength = 8;

        if (!value) {
            return {
                success: false,
                message: "Please provide a name.",
            };
        }

        if (value.length <= minLength) {
            return {
                success: false,
                message: `Your name must have at least ${minLength} character(s).`,
            };
        }

        return {
            success: true,
            value,
        };
    });

    return {
        ...previousData,
        name,
    };
}

async function getAge<T extends object>(previousData: T) {
    const age = await question('What is your age?', value => {
        if (!value) {
            return {
                success: false,
                message: "Please inform your age.",
            };
        }

        if (/\d+/.test(value)) {
            return {
                success: false,
                message: "Please inform a valid age.",
            };
        }

        return {
            success: true,
            value,
        };
    });

    return {
        ...previousData,
        age: parseInt(age, 10),
    };
}

async function main() {
    const data = await Promise.resolve({})
        .then(getAge)
        .then(getName);

    if (data.age < 18) {
        writeln(`Hello, ${data.name}! It seems you're too young to proceed.`);
    } else {
        writeln(`Welcome, ${data.name}! Have your beer! C[¨]`);
    }
}