Update app.py

app.py

@@ -1,40 +1,35 @@
-# -----------------------------------------------------------------------------
-# A basic example of dynamically re-rendering a Shiny Chat instance with different models.
-# To run it, you'll need an OpenAI API key.
-# To get one, follow the instructions at https://platform.openai.com/docs/quickstart
-# -----------------------------------------------------------------------------
-import os
-
-from langchain_openai import ChatOpenAI
-
-from shiny.express import input, render, ui
-
-ui.input_select("model", "Model", choices=["gpt-4o", "gpt-3.5-turbo"])
-
-
-@render.express
-def chat_ui():
-
-    chat = ui.Chat(
-        id="chat",
-        messages=[
-            {
-                "content": f"Hi! I'm a {input.model()} model. How can I help you today?",
-                "role": "assistant",
-            }
-        ],
-    )
-
-    chat.ui()
-
-    llm = ChatOpenAI(
-        model=input.model(),
-        # Provide your API key here (or set the environment variable)
-        api_key=os.environ.get("OPENAI_API_KEY"),  # type: ignore
-    )
-
-    @chat.on_user_submit
-    async def _():
-        messages = chat.messages(format="langchain")
-        response = llm.astream(messages)
-        await chat.append_message_stream(response)
+from shiny.express import ui
+
+# Set some Shiny page options
+ui.page_opts(
+    title="Hello Shiny Chat",
+    fillable=True,
+    fillable_mobile=True,
+)
+
+# Create a welcome message
+welcome = ui.markdown(
+    """
+    Hi! This is a simple Shiny `Chat` UI. Enter a message below and I will
+    simply repeat it back to you. For more examples, see this
+    [folder of examples](https://github.com/posit-dev/py-shiny/tree/main/examples/chat).
+    """
+)
+
+# Create a chat instance
+chat = ui.Chat(
+    id="chat",
+    messages=[welcome],
+)
+
+# Display it
+chat.ui()
+
+
+# Define a callback to run when the user submits a message
+@chat.on_user_submit
+async def _():
+    # Get the user's input
+    user = chat.user_input()
+    # Append a response to the chat
+    await chat.append_message(f"You said: {user}")