app.py

import os

import gradio as gr


def enable_second_task(secret):
    if secret == os.environ["SECRET_KEY"]:
        return [
            gr.Textbox.update(visible=False),
            gr.HTML.update(visible=False),
            gr.Button.update(visible=False),
            gr.Textbox.update(visible=True),
            gr.Textbox.update(visible=True),
            gr.Button.update(visible=True)                                                
        ]
    return [
        gr.Textbox.update(value="", visible=True),
        gr.HTML.update(visible=True),
        gr.Button.update(visible=True),
        gr.Textbox.update(visible=False),
        gr.Textbox.update(visible=False),
        gr.Button.update(visible=False)                                                
    ]

def greet(name):
    return "Hello " + name + "!!"

demo = gr.Blocks()
with demo:
    # Authentication
    secret_textbox = gr.Textbox(
        placeholder="Enter secret key", label="Secret", show_label=True,
        max_lines=1
    )    
    error_message = gr.HTML(
        "<span style=\"color: red;\">Wrong secret key. Please retry</span>",
        visible=False
    )
    secret_button = gr.Button("Submit")

    # Demo logic
    name_textbox = gr.Textbox(
        placeholder="Name", label="Name", show_label=True, visible=False
    )
    greet_textbox = gr.Textbox(
        placeholder="", label="Output", show_label=True, visible=False
    )    
    greet_button = gr.Button("Greet", visible=False)    
    
    # Event handling
    secret_textbox.submit(
        enable_second_task,
        secret_textbox,
        [secret_textbox, error_message, secret_button,
         name_textbox, greet_textbox, greet_button]        
    )
    secret_button.click(
        enable_second_task,
        secret_textbox,
        [secret_textbox, error_message, secret_button,
         name_textbox, greet_textbox, greet_button]
    )
    greet_button.click(greet, name_textbox, greet_textbox)    

demo.launch()