app.py

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

# 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!")

# Inputs
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."
)

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_box = st.text_area(
    "💻 Your Python code:",
    height=200,
    placeholder="# Paste your Python code here"
)

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

if st.button("🚀 Review"):
    if not code_box.strip():
        st.warning("⚠️ Please paste some Python code.")
        st.stop()

    # Select API key (user-provided > fallback)
    api_key = api_key_input.strip() or "AIzaSyBiAW2GQLid0HGe9Vs_ReKwkwsSVNegNzs"
    genai.configure(api_key=api_key)

    # Select system instruction (user > env > default)
    system_instruction = (
        sys_prompt_input.strip()
        or os.getenv("USER_PROMPT")
        or "You are a helpful Python code reviewer."
    )

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

    # Build message WITHOUT triple-backtick fences to avoid backslash/escape issues
    separator = "\n---CODE START---\n"
    user_message = (
        "Please analyze the following Python code and perform the requested task.\n"
        + separator
        + code_box
        + "\n---CODE END---\n"
        + ("Task: " + (prompt_box.strip() or "Review the code."))
    )

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

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

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