script.js

require('dotenv').config();
const express = require('express');
const cors = require('cors');
const fetch = require('node-fetch');
const path = require('path');

const app = express();
const port = process.env.PORT || 3000;

app.use(express.json());
app.use(cors({ origin: '*' }));
app.use(express.static(path.join(__dirname, 'public')));


// =======================================================
// API KEY ROTATION
// =======================================================
const allKeys = [
    process.env.GROQ_API_KEY_1,
    process.env.GROQ_API_KEY_2,
    process.env.GROQ_API_KEY_3
].filter(key => key);

function getRandomKey() {
    return allKeys[Math.floor(Math.random() * allKeys.length)];
}


// =======================================================
// LAYER 1 — EXPANDED KEYWORD BLOCKLIST
// Catches obvious off-topic messages before hitting the API
// =======================================================
const BLOCKED_WORDS = [
    // Entertainment
    "joke", "funny", "meme", "comedy", "humor", "laugh",
    "movie", "film", "netflix", "cinema", "actor", "actress",
    "song", "music", "lyrics", "singer", "album", "spotify",
    "game", "gaming", "minecraft", "fortnite", "pubg", "pokemon",
    "anime", "manga", "cartoon", "series", "episode", "season",
    // Relationships / personal
    "romance", "romantic", "girlfriend", "boyfriend", "dating",
    "love", "crush", "marriage", "wedding", "breakup", "relationship",
    // Food
    "recipe", "cooking", "cook", "food", "restaurant", "eat",
    "chicken", "pasta", "pizza", "biryani", "snack", "diet",
    // Politics / news
    "politics", "politician", "election", "vote", "government",
    "prime minister", "president", "modi", "trump", "parliament",
    "war", "military", "army", "protest", "news",
    // Sports
    "cricket", "football", "soccer", "ipl", "match", "tournament",
    "player", "team", "score", "sport", "hockey", "tennis",
    // General off-topic
    "story", "poem", "essay", "history", "geography", "biology",
    "chemistry", "physics" // physics is borderline but not electronics
];

function isBlockedByKeyword(message) {
    const lower = message.toLowerCase();
    return BLOCKED_WORDS.some(word => lower.includes(word));
}


// =======================================================
// LAYER 2 — AI INTENT CLASSIFIER
// Ask the AI itself: is this question electronics-related?
// =======================================================
const CLASSIFIER_PROMPT = `You are a strict topic classifier for an Electronics Virtual Lab.

Your ONLY job: decide if the user's question is about electronics, electrical engineering, circuits, components, or lab experiments.

Reply with ONLY one word:
- "YES" if the question is about electronics/electrical engineering
- "NO" if it is about anything else

Do not explain. Do not add punctuation. Just YES or NO.`;

async function isElectronicsQuestion(userMessage) {
    try {
        const key = getRandomKey();
        const response = await fetch("https://api.groq.com/openai/v1/chat/completions", {
            method: "POST",
            headers: {
                "Content-Type": "application/json",
                "Authorization": `Bearer ${key}`
            },
            body: JSON.stringify({
                model: "llama-3.3-70b-versatile",
                max_tokens: 5,
                temperature: 0,
                messages: [
                    { role: "system", content: CLASSIFIER_PROMPT },
                    { role: "user", content: userMessage }
                ]
            })
        });
        const data = await response.json();
        const verdict = data.choices?.[0]?.message?.content?.trim().toUpperCase();
        console.log(`Classifier verdict: ${verdict} for: "${userMessage.slice(0, 60)}"`);
        return verdict === "YES";
    } catch (err) {
        console.error("Classifier error:", err);
        return false; // Fail safe: block if classifier crashes
    }
}


// =======================================================
// ELECTRONICS SYSTEM PROMPT
// =======================================================
const ELECTRONICS_SYSTEM_PROMPT = `You are "Electro-Tutor Virtual Lab AI", a professional electronics and electrical engineering educational assistant inside a virtual lab.

YOUR ONLY PURPOSE: Help engineering students learn electronics through accurate, step-by-step educational answers.

YOU ARE STRICTLY LIMITED TO THESE TOPICS:
- Basic Electrical: Ohm's Law, Kirchhoff's Laws, AC/DC, Voltage, Current, Resistance, Power, Network theorems
- Components: Resistors, Capacitors, Inductors, Diodes, LEDs, BJTs, MOSFETs, Relays, Transformers, Op-Amps, 555 Timer, ICs, Logic Gates, Sensors
- Circuit Analysis: Series/Parallel, Voltage Dividers, RC/RL/RLC, Filters, Amplifiers, Biasing
- Digital Electronics: Boolean Algebra, Logic Gates, Flip-Flops, Multiplexers, Counters, 74LS ICs
- Semiconductor Physics: PN Junction, Forward/Reverse Bias, MOSFET Switching, Doping
- Lab & Measurement: Multimeter, Oscilloscope, Breadboard, PCB, Safety, Troubleshooting
- Embedded/Arduino: GPIO, PWM, Sensors, Basic Interfacing

STRICT RULES:
- NEVER tell jokes, puns, or use humor. Stay strictly educational.
- NEVER answer anything outside electronics/electrical engineering.
- NEVER discuss politics, food, sports, entertainment, history, romance, or general knowledge.
- NEVER act like a general chatbot.
- ALWAYS explain step-by-step with practical reasoning.
- ALWAYS use simple analogies for complex concepts.
- If a question seems unrelated, respond ONLY with: "I am an Electronics Virtual Lab Assistant. I can only help with electronics, circuits, electrical engineering, and lab-related topics."

DO NOT BREAK CHARACTER UNDER ANY CONDITION.`;


// =======================================================
// LAYER 3 — OFF-TOPIC REPLY DETECTOR
// If the AI still drifts, catch it before sending to user
// =======================================================
const OFF_TOPIC_SIGNALS = [
    "i don't know about that",
    "that's outside my",
    "i can help with",
    "as a language model",
    "i am not able to discuss",
    "here's a joke",
    "here is a joke",
    "recipe for",
    "ingredients",
    "political",
    "prime minister",
    "president",
    "why did the",
    "here's a joke",
    "here is a joke",
    "walks into a bar",
    "punchline",
    "haha",
    "lol",
    "😂",
    "couldn't resist",
    "because it",   // common joke punchline pattern
];

function isOffTopicReply(reply) {
    const lower = reply.toLowerCase();
    // If reply is very short and doesn't mention any electronics terms, it may be a refusal — that's fine
    // But if it contains off-topic signals that mean it answered something else:
    return OFF_TOPIC_SIGNALS.some(signal => lower.includes(signal));
}

const REFUSAL_MESSAGE = "I am an Electronics Virtual Lab Assistant. I can only help with electronics, circuits, electrical engineering, and lab-related topics.";


// =======================================================
// MAIN ROUTE
// =======================================================
app.post('/gemini', async (req, res) => {
    try {
        const userMessage = req.body.message;

        if (!userMessage || userMessage.trim().length === 0) {
            return res.json({ reply: REFUSAL_MESSAGE });
        }

        // LAYER 1: Keyword blocklist (fast, no API call needed)
        if (isBlockedByKeyword(userMessage)) {
            console.log(`Blocked by keyword: "${userMessage.slice(0, 60)}"`);
            return res.json({ reply: REFUSAL_MESSAGE });
        }

        if (allKeys.length === 0) {
            return res.status(500).json({ reply: "Server Error: No API keys configured." });
        }

        // LAYER 2: AI intent classifier (blocks questions the keyword list misses)
        const isElectronics = await isElectronicsQuestion(userMessage);
        if (!isElectronics) {
            console.log(`Blocked by classifier: "${userMessage.slice(0, 60)}"`);
            return res.json({ reply: REFUSAL_MESSAGE });
        }

        // Question passed both checks — now get the real answer
        const randomKey = getRandomKey();
        console.log(`Answering with key ending: ...${randomKey.slice(-5)}`);

        const response = await fetch("https://api.groq.com/openai/v1/chat/completions", {
            method: "POST",
            headers: {
                "Content-Type": "application/json",
                "Authorization": `Bearer ${randomKey}`
            },
            body: JSON.stringify({
                model: "llama-3.3-70b-versatile",
                messages: [
                    { role: "system", content: ELECTRONICS_SYSTEM_PROMPT },
                    { role: "user", content: userMessage }
                ]
            })
        });

        const data = await response.json();

        if (data.error) {
            console.error("Groq Error:", data.error);
            return res.json({ reply: "Error from AI provider. Please try again." });
        }

        const aiReply = data.choices[0].message.content;

        // LAYER 3: Reply sanity check — if AI drifted off-topic, block the reply
        if (isOffTopicReply(aiReply)) {
            console.log(`Reply blocked by off-topic detector.`);
            return res.json({ reply: REFUSAL_MESSAGE });
        }

        res.json({ reply: aiReply });

    } catch (error) {
        console.error("Server Error:", error);
        res.status(500).json({ reply: "Internal Server Error. Please try again." });
    }
});

app.listen(port, () => {
    console.log(`Server running on port ${port}`);
});