Editing Openai/694ab010-3e7c-8000-b0e8-b98c22b7a063 (section)

=== ## ===

Folder

<syntaxhighlight>ml-chatbot-api/
  main.py
  requirements.txt
  Dockerfile

</syntaxhighlight>

===== <syntaxhighlight lang="python">import os =====
from pydantic import BaseModel
from fastapi import FastAPI, HTTPException
from fastapi.middleware.cors import CORSMiddleware

from langchain_openai import ChatOpenAI
from langchain_core.messages import SystemMessage, HumanMessage

APP_NAME = "ml-chatbot-api"

class ChatRequest(BaseModel):
    message: str

class ChatResponse(BaseModel):
    reply: str

def get_openai_key() -> str:
    # ECS Secrets Manager injection will set OPENAI_API_KEY env var at runtime
    key = os.getenv("OPENAI_API_KEY", "").strip()
    if not key:
        raise RuntimeError("OPENAI_API_KEY is missing (Secrets Manager injection likely not configured).")
    return key

app = FastAPI(title=APP_NAME)

=== CORS: allow Streamlit UI origin(s). For simplicity in early testing, allow all. ===
=== In production, set allow_origins=["https://YOUR_UI_DOMAIN"]. ===
app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=False,
    allow_methods=["*"],
    allow_headers=["*"],
)

@app.get("/api/health")
def health():
    return {"status": "ok"}

@app.post("/api/chat", response_model=ChatResponse)
def chat(req: ChatRequest):
    msg = (req.message or "").strip()
    if not msg:
        raise HTTPException(status_code=400, detail="message is required")

    try:
        api_key = get_openai_key()
        llm = ChatOpenAI(
            model="gpt-4o-mini",
            temperature=0.2,
            api_key=api_key,
        )
        messages = [
            SystemMessage(content="You are a helpful assistant. Answer clearly and concisely."),
            HumanMessage(content=msg),
        ]
        resp = llm.invoke(messages)
        return ChatResponse(reply=resp.content)
    except HTTPException:
        raise
    except Exception as e:
        raise HTTPException(status_code=500, detail=f"Chat failed: {str(e)}")

</syntaxhighlight>

===== <syntaxhighlight lang="txt">fastapi==0.115.6 =====
uvicorn[standard]==0.30.6
pydantic==2.9.2
langchain==0.2.16
langchain-openai==0.1.22

</syntaxhighlight>

===== <syntaxhighlight lang="dockerfile">FROM python:3.11-slim =====

WORKDIR /app

RUN apt-get update && apt-get install -y --no-install-recommends curl \
  && rm -rf /var/lib/apt/lists/*

COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt

COPY main.py .

EXPOSE 8000

CMD ["uvicorn", "main:app", "--host=0.0.0.0", "--port=8000"]

</syntaxhighlight>

==== Folder ====

<syntaxhighlight>ml-chatbot-ui/
  app.py
  requirements.txt
  Dockerfile

</syntaxhighlight>

===== <syntaxhighlight lang="python">import os =====
import requests
import streamlit as st

st.set_page_config(page_title="ML Chatbot UI", layout="centered")
st.title("ML Chatbot (Streamlit UI)")

API_BASE_URL = os.getenv("API_BASE_URL", "").rstrip("/")

if not API_BASE_URL:
    st.error("API_BASE_URL is not set. Set it to your API Gateway stage URL, e.g. https://XXXX.execute-api.REGION.amazonaws.com/prod")
    st.stop()

CHAT_URL = f"{API_BASE_URL}/api/chat"
HEALTH_URL = f"{API_BASE_URL}/api/health"

=== Basic health check ===
with st.expander("Backend status", expanded=False):
    try:
        r = requests.get(HEALTH_URL, timeout=5)
        st.write("Health:", r.status_code, r.text)
    except Exception as e:
        st.write("Health check failed:", str(e))

if "history" not in st.session_state:
    st.session_state.history = []  # list of (role, text)

prompt = st.chat_input("Ask something...")

if prompt:
    st.session_state.history.append(("user", prompt))

    try:
        resp = requests.post(CHAT_URL, json={"message": prompt}, timeout=60)
        if resp.status_code != 200:
            reply = f"API error {resp.status_code}: {resp.text}"
        else:
            reply = resp.json().get("reply", "")
            if not reply:
                reply = "Empty reply from API."
    except Exception as e:
        reply = f"Request failed: {str(e)}"

    st.session_state.history.append(("assistant", reply))

for role, text in st.session_state.history:
    with st.chat_message(role):
        st.write(text)

</syntaxhighlight>

===== <syntaxhighlight lang="txt">streamlit==1.39.0 =====
requests==2.32.3

</syntaxhighlight>

===== <syntaxhighlight lang="dockerfile">FROM python:3.11-slim =====

WORKDIR /app

RUN apt-get update && apt-get install -y --no-install-recommends curl \
  && rm -rf /var/lib/apt/lists/*

COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt

COPY app.py .

EXPOSE 8501

CMD ["streamlit", "run", "app.py", "--server.address=0.0.0.0", "--server.port=8501"]

</syntaxhighlight>