app.py

import streamlit as st
import google.generativeai as genai
import os

# -------------------------------------------------
# 1️⃣  UI – page setup
# -------------------------------------------------
st.set_page_config(page_title="Python Code Reviewer 🤖", layout="centered")
st.title("🐍 Python Code Reviewer 🤖")
st.markdown(
    "### Paste your code and a short prompt – the AI will review it for you!"
)

# -------------------------------------------------
# 2️⃣  Input fields
# -------------------------------------------------
# API key (optional – fallback to hard‑coded key)
api_key_input = st.text_input(
    "🔑 Google API Key (optional – leave blank to use the built‑in key)",
    type="password",
    help="Enter your own Gemini API key if you have one. Otherwise the app uses the default key."
)

# System prompt (optional – fallback to env var or default)
sys_prompt_input = st.text_input(
    "🗒️ System Prompt (optional)",
    placeholder="e.g., 'You are a friendly Python code reviewer.'",
    help="Custom instructions for the model. If left empty, the USER_PROMPT env var is used."
)

# Code to be reviewed
code_box = st.text_area(
    "💻 Your Python code:",
    height=200,
    placeholder="# Paste your Python code here"
)

# What the model should do with the code
prompt_box = st.text_area(
    "📝 What should the AI do with this code?",
    height=80,
    placeholder="e.g., 'Find bugs and suggest improvements.'"
)

# -------------------------------------------------
# 3️⃣  Main logic – run when button pressed
# -------------------------------------------------
if st.button("🚀 Review"):
    # ---- Validate input ----
    if not code_box.strip():
        st.warning("⚠️ Please paste some Python code.")
        st.stop()

    # ---- Choose API key ----
    # User‑provided key > hard‑coded fallback
    api_key = api_key_input.strip() or "AIzaSyBiAW2GQLid0HGe9Vs_ReKwkwsSVNegNzs"
    genai.configure(api_key=api_key)

    # ---- Choose system instruction ----
    # User input > env var > generic default
    system_instruction = (
        sys_prompt_input.strip()
        or os.getenv("USER_PROMPT")
        or "You are a helpful Python code reviewer."
    )

    # ---- Initialise model ----
    model = genai.GenerativeModel(
        model_name="models/gemini-2.5-flash",
        system_instruction=system_instruction,
    )

    # ---- Build the user message ----
    user_message = (
        f"Code:\n```python\n{code\_box}\n```\n\n"
        f"Task: {prompt_box or 'Review the code.'}"
    )

    # ---- Call Gemini ----
    with st.spinner("Analyzing your code... 🧐"):
        response = model.generate_content(user_message)

    # ---- Show result ----
    st.markdown("### 🤖 Response")
    st.success(response.text)

# -------------------------------------------------
# 4️⃣  Footer
# -------------------------------------------------
st.markdown("---")
st.markdown("🛠️ **Built with Streamlit & Google Gemini AI** | ❤️ _Happy Coding!_ 🐍")