app.py

from fastapi import FastAPI, HTTPException
from fastapi.middleware.cors import CORSMiddleware
from pydantic import BaseModel
import requests
import os  # for reading environment variables

app = FastAPI()

# Enable CORS
app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],  # Allow all origins, or replace with your frontend URL
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

# Read OpenRouter API key from environment variable (HF Secret)
OPENROUTER_API_KEY = os.environ.get("OPENROUTER_API_KEY")
if not OPENROUTER_API_KEY:
    raise RuntimeError("OPENROUTER_API_KEY environment variable not set!")

# Request schema
class ExplainRequest(BaseModel):
    message: str
    label: str  # "Phishing" or "Safe"

@app.post("/explain")
def explain(req: ExplainRequest):
    user_message = req.message.strip()
    label = req.label.strip()

    if not user_message or not label:
        raise HTTPException(status_code=400, detail="Missing message or label")

    # Updated system prompt with bullet-point format and language adaptation
    system_prompt = (
        f"You are a robot that identifies phishing and safe messages. "
        f"The message was classified as '{label}'. "
        "Explain why this decision was made and point out any words or patterns that led to it. "
        "No greetings, introductions, or closing remarks. "
        "Don't restate the message or its classification. "
        "Output only the explanation as bullet points. "
        "Limit each bullet to 1–2 sentences. "
        "Limit the number of bullets to 3-4 "
        f"Message:\n\n{user_message}"
        "Respond using the same language as the message."
    )

    url = "https://openrouter.ai/api/v1/chat/completions"
    headers = {
        "Authorization": f"Bearer {OPENROUTER_API_KEY}",
        "Content-Type": "application/json"
    }
    payload = {
        "model": "arcee-ai/trinity-large-preview:free",
        "messages": [
            {"role": "system", "content": system_prompt},
            {"role": "user", "content": user_message}
        ]
    }

    try:
        response = requests.post(url, headers=headers, json=payload, timeout=20)
        response.raise_for_status()
        result = response.json()
        reply = result.get("choices", [{}])[0].get("message", {}).get("content", "").strip()
        if not reply:
            reply = "[No explanation returned]"
        return {"reply": reply}
    except requests.RequestException as e:
        raise HTTPException(status_code=500, detail=f"Error contacting OpenRouter: {e}")