A Nitro app with back button support and state handling

app.py

# ===
# About: Back button and state handling demo
# Author: Prithvi Prabhu <prithvi.prabhu@gmail.com>
# License: Apache-2.0
# Source: https://github.com/h2oai/nitro/py/examples
# Keywords: [basic, flask]
#
# Setup:
# FILE requirements.txt EOF
# flask
# simple-websocket
# h2o-nitro[web] >= 0.13
# EOF
# RUN python -m pip install -r requirements.txt
# ENV FLASK_APP hello.py
# ENV FLASK_ENV development
# START python -m flask run
# ===
import simple_websocket
from flask import Flask, request, send_from_directory

# ┌───────────────  Nitro app starts here ───────────────┐

from h2o_nitro import View, box, option
from h2o_nitro_web import web_directory


class Person:
    def __init__(self, first_name, last_name):
        self.first_name = first_name
        self.last_name = last_name


class State:
    def __init__(self):
        self.person = Person('Boaty', 'McBoatface')
        self.father = Person('Papa', 'McBoatface')
        self.mother = Person('Mama', 'McBoatface')


def ask_name(view: View):
    person: Person = view.context['state'].person
    person.first_name, person.last_name = view(
        f"# Step 1",
        box('Your first name?', value=person.first_name),
        box('Your last name?', value=person.last_name)
    )
    view.jump(ask_father_name)


def ask_father_name(view: View):
    father: Person = view.context['state'].father
    father.first_name, father.last_name = view(
        f"# Step 2",
        box("Father's first name?", value=father.first_name),
        box("Father's last name?", value=father.last_name)
    )
    view.jump(ask_mother_name)


def ask_mother_name(view: View):
    mother: Person = view.context['state'].mother
    mother.first_name, mother.last_name = view(
        f"# Step 3",
        box("Mother's first name?", value=mother.first_name),
        box("Mother's last name?", value=mother.last_name)
    )
    view.jump(show_results)


def show_results(view: View):
    state: State = view.context['state']
    view(
        f"# Results",
        f"Your name: {state.person.first_name} {state.person.last_name}.",
        f"Your father's name: {state.father.first_name} {state.father.last_name}.",
        f"Your mother's name: {state.mother.last_name} {state.mother.last_name}.",
        halt=True,
    )


def main(view: View):
    view.context['state'] = State()
    view(
        '# Welcome to the wizard!',
        'Use the back button, Luke!'
    )
    view.jump(ask_name)


nitro = View(
    main,
    title='Hello Nitro!',
    caption='v1.0',
    routes=[
        option(ask_name),
        option(ask_father_name),
        option(ask_mother_name),
        option(show_results),
    ],
)

# └─────────────── Nitro app ends here ───────────────┘

app = Flask(__name__, static_folder=web_directory, static_url_path='')


@app.route('/')
def home_page():
    return send_from_directory(web_directory, 'index.html')


@app.route('/nitro', websocket=True)
def socket():
    ws = simple_websocket.Server(request.environ)
    try:
        nitro.serve(ws.send, ws.receive)
    except simple_websocket.ConnectionClosed:
        pass
    return ''


if __name__ == '__main__':
    app.run()