const express = require("express");
const axios = require("axios");
const OpenAI = require("openai");
const dotenv = require("dotenv");
dotenv.config();

const router = express.Router();

// Environment Variables
const {
  META_ACCESS_TOKEN,
  META_PHONE_NUMBER_ID,
  META_VERIFY_TOKEN,
  DEEPSEEK_API_KEY,
  PYTHON_API_BASE_URL, // e.g. http://localhost:8000
  NVIDIA_API_KEY,      // Your NVIDIA secret key for LLM fallback
} = process.env;

if (
  !META_ACCESS_TOKEN ||
  !META_PHONE_NUMBER_ID ||
  !META_VERIFY_TOKEN ||
  !DEEPSEEK_API_KEY ||
  !PYTHON_API_BASE_URL ||
  !NVIDIA_API_KEY
) {
  console.error("Missing environment variables. Please check your .env file.");
  process.exit(1);
}

// -----------------------------------------------------------------------------
// Set up the OpenAI client for NVIDIA LLM fallback using the new format
// -----------------------------------------------------------------------------
const openaiLLM = new OpenAI({
  apiKey: NVIDIA_API_KEY,
  baseURL: "https://integrate.api.nvidia.com/v1",
});

/**
 * Call the LLM fallback using the new syntax.
 * This function streams the response and returns the full text.
 */
async function callLLMFallback(message) {
  try {
    const completion = await openaiLLM.chat.completions.create({
      model: "meta/llama-3.1-405b-instruct",
      messages: [{ role: "user", content: message }],
      temperature: 0.2,
      top_p: 0.7,
      max_tokens: 1024,
      stream: true,
    });
    
    let fullText = "";
    for await (const chunk of completion) {
      fullText += chunk.choices[0]?.delta?.content || "";
    }
    return fullText;
  } catch (err) {
    console.error("LLM fallback error:", err);
    throw err;
  }
}

// -----------------------------------------------------------------------------
// Helper Functions for calling Python API endpoints
// -----------------------------------------------------------------------------
async function getPythonChatResponse(userId, message) {
  try {
    console.log("Forwarding chat request to Python API...");
    const response = await axios.post(`${PYTHON_API_BASE_URL}/chatbot`, {
      user_id: userId,
      message: message,
    });

    if (typeof response.data === "object" && response.data !== null) {
      let result = response.data.response || "";
      if (Array.isArray(response.data.menu)) {
        result += "\n\n*Menu:*\n";
        response.data.menu.forEach((item) => {
          result += `• *${item.name}* - ${item.description} - ₦${item.price}\n`;
        });
      }
      if (response.data.follow_up) {
        result += "\n" + response.data.follow_up;
      }
      return result;
    }
    return response.data.response || "I'm sorry, I didn't get a response.";
  } catch (error) {
    console.error("Error from Python API (chatbot):", error.message);
    return "I'm experiencing technical difficulties. Please try again later.";
  }
}

async function getPythonChatHistory(userId) {
  try {
    console.log("Requesting chat history from Python API...");
    const response = await axios.get(`${PYTHON_API_BASE_URL}/chat_history/${userId}`);
    return response.data;
  } catch (error) {
    console.error("Error from Python API (chat_history):", error.message);
    return null;
  }
}

async function getPythonOrderDetails(orderId) {
  try {
    console.log("Requesting order details from Python API...");
    const response = await axios.get(`${PYTHON_API_BASE_URL}/order/${orderId}`);
    return response.data;
  } catch (error) {
    console.error("Error from Python API (order details):", error.message);
    return null;
  }
}

async function getPythonUserProfile(userId) {
  try {
    console.log("Requesting user profile from Python API...");
    const response = await axios.get(`${PYTHON_API_BASE_URL}/user_profile/${userId}`);
    return response.data;
  } catch (error) {
    console.error("Error from Python API (user profile):", error.message);
    return null;
  }
}

async function getPythonAnalytics() {
  try {
    console.log("Requesting analytics from Python API...");
    const response = await axios.get(`${PYTHON_API_BASE_URL}/analytics`);
    return response.data;
  } catch (error) {
    console.error("Error from Python API (analytics):", error.message);
    return null;
  }
}

// -----------------------------------------------------------------------------
// Utility: Log chat history locally (for debugging purposes)
// -----------------------------------------------------------------------------
const chatHistories = {};
function logChat(userId, direction, message) {
  if (!chatHistories[userId]) {
    chatHistories[userId] = [];
  }
  chatHistories[userId].push({
    timestamp: new Date().toISOString(),
    direction,
    message,
  });
}

// -----------------------------------------------------------------------------
// Webhook Verification (GET)
// -----------------------------------------------------------------------------
router.get("/", (req, res) => {
  const {
    "hub.mode": mode,
    "hub.verify_token": token,
    "hub.challenge": challenge,
  } = req.query;
  if (mode === "subscribe" && token === META_VERIFY_TOKEN) {
    console.log("Webhook verified successfully.");
    return res.status(200).send(challenge);
  }
  console.error("Webhook verification failed.");
  res.sendStatus(403);
});

// -----------------------------------------------------------------------------
// WhatsApp Webhook Handler (POST)
// -----------------------------------------------------------------------------
router.post("/", async (req, res) => {
  try {
    const body = req.body;
    console.log("Webhook received:", JSON.stringify(body, null, 2));

    if (body.object === "whatsapp_business_account") {
      const changes = body.entry[0]?.changes[0]?.value;
      if (changes?.messages) {
        const messageObj = changes.messages[0];
        const { from, text } = messageObj;
        const userMessage = text?.body;
        console.log(`Message from ${from}: ${userMessage}`);
        logChat(from, "inbound", userMessage);
        
        // Generate response
        const botResponse = await generateResponse(userMessage, from);
        console.log("Bot response:", botResponse);
        logChat(from, "outbound", botResponse);
        
        // Send the response via WhatsApp API.
        await sendMessage(from, botResponse);
        return res.status(200).send("EVENT_RECEIVED");
      }
      if (changes?.statuses) {
        console.log("Status update received:", JSON.stringify(changes.statuses, null, 2));
        return res.status(200).send("EVENT_RECEIVED");
      }
    }
    console.log("No valid content found in webhook.");
    res.sendStatus(404);
  } catch (error) {
    console.error("Error handling webhook:", error.message);
    res.sendStatus(500);
  }
});

// -----------------------------------------------------------------------------
// Order Flow is delegated to the Python API entirely, so no local order flow
// -----------------------------------------------------------------------------

// -----------------------------------------------------------------------------
// Enhanced Response Generator
// -----------------------------------------------------------------------------
async function generateResponse(message, from) {
  const lowerMessage = message.toLowerCase();

  // 1. Welcome/Main Menu
  if (lowerMessage === "hi" || lowerMessage === "hello" || lowerMessage.includes("welcome")) {
    return `👋 Hi there! Welcome to *FoodieBot*! 🍔🍕\nPlease choose an option:\n1️⃣ *View Menu*\n2️⃣ *Place an Order*\n3️⃣ *Payment Status*\n4️⃣ *My Profile*\n5️⃣ *Chat History*\n6️⃣ *Help & Support*\nSimply type the number or the option name.`;
  }

  // 2. Menu Display – Option "1" or any message that includes "menu" (but not "order")
  if (lowerMessage === "1" || (lowerMessage.includes("menu") && !lowerMessage.includes("order"))) {
    return await getPythonChatResponse(from, "menu");
  }

  // 3. Order Flow – Trigger on multiple keywords: "2", "order", "buy", "food"
  if (
    lowerMessage === "2" ||
    lowerMessage.includes("order") ||
    lowerMessage.includes("buy") ||
    lowerMessage.includes("food")
  ) {
    // Check if the user's message includes a dish name from the menu.
    let selectedDish = null;
    for (let item of menu_items) { // Assumes menu_items is defined as an array of dish objects.
      if (lowerMessage.includes(item.name.toLowerCase())) {
        selectedDish = item.name;
        break;
      }
    }
    if (selectedDish) {
      // Prepend the dish name to the order command so the Python API can handle it.
      return await getPythonChatResponse(from, `order: ${selectedDish}`);
    }
    return await getPythonChatResponse(from, "order");
  }

  // 4. Payment Status – Option "3" or keyword "payment"
  if (lowerMessage === "3" || lowerMessage.includes("payment")) {
    return await getPythonChatResponse(from, "payment");
  }

  // 5. User Profile – Option "4" or keyword "profile"
  if (lowerMessage === "4" || lowerMessage.includes("profile")) {
    const profile = await getPythonUserProfile(from);
    if (profile) {
      return `👤 *Your Profile*\nName: ${profile.name}\nPhone: ${profile.phone_number}\nEmail: ${profile.email}\nPreferences: ${profile.preferences}\nLast Interaction: ${profile.last_interaction}`;
    } else {
      return "No profile information found.";
    }
  }

  // 6. Chat History – Option "5" or keyword "chat history"
  if (lowerMessage === "5" || lowerMessage.includes("chat history")) {
    const history = await getPythonChatHistory(from);
    if (history && history.length > 0) {
      let formattedHistory = "*Your Chat History:*\n";
      history.forEach((entry) => {
        formattedHistory += `[${entry.timestamp}] ${entry.direction}: ${entry.message}\n`;
      });
      return formattedHistory;
    } else {
      return "No chat history found for your account.";
    }
  }

  // 7. Help & Support – Option "6" or keyword "help" / "support"
  if (lowerMessage === "6" || lowerMessage.includes("help") || lowerMessage.includes("support")) {
    return `❓ *How can I help you?*\nType one of the following:\n- *Order Status* (e.g., "order tracking ORD-123456789")\n- *Contact Support*\n- *Main Menu* to see all options again.`;
  }

  // 8. Recommendations (Advanced Feature)
  if (lowerMessage.includes("recommendations")) {
    return await getPythonChatResponse(from, "recommendations");
  }

  // 9. Analytics (for admin use)
  if (lowerMessage.includes("analytics")) {
    const analytics = await getPythonAnalytics();
    if (analytics) {
      return `📊 *Analytics*\nTotal Messages: ${analytics.total_messages}\nTotal Orders: ${analytics.total_orders}\nAverage Sentiment: ${analytics.average_sentiment}`;
    } else {
      return "Analytics data is not available.";
    }
  }

  // 10. Fallback: Use NVIDIA LLM fallback
  try {
    const llmResponse = await callLLMFallback(message);
    return llmResponse;
  } catch (error) {
    console.error("LLM fallback error:", error);
    return "I'm sorry, I didn't get a response.";
  }
}

// -----------------------------------------------------------------------------
// Send Message to User via WhatsApp API
// -----------------------------------------------------------------------------
async function sendMessage(to, message) {
  try {
    const url = `https://graph.facebook.com/v16.0/${META_PHONE_NUMBER_ID}/messages`;
    const response = await axios.post(
      url,
      {
        messaging_product: "whatsapp",
        to,
        text: { body: message },
      },
      {
        headers: { Authorization: `Bearer ${META_ACCESS_TOKEN}` },
      }
    );
    console.log("Message sent successfully:", response.data);
  } catch (error) {
    if (error.response) {
      const { status } = error.response;
      console.error(`Error sending message: Status ${status}`);
      if (status === 401 || status === 403) {
        console.error(
          "[Token Issue Detected] The META_ACCESS_TOKEN may have expired or is invalid. Please refresh the token."
        );
      }
    } else {
      console.error("Error sending message:", error.message);
    }
  }
}

// -----------------------------------------------------------------------------
// Proactive Engagement: Send a greeting to inactive users
// -----------------------------------------------------------------------------
async function sendProactiveGreeting(userId) {
  const greeting = "👋 Hi again! We miss you. 😊\nWould you like to see our new menu items or get personalized recommendations? Type *'Menu'* or *'Recommendations'*.";
  await sendMessage(userId, greeting);
  return greeting;
}

module.exports = router;