const express = require("express");
const bcrypt = require("bcryptjs");
const jwt = require("jsonwebtoken");
const { PrismaClient } = require("@prisma/client");
const crypto = require("crypto");
const cors = require("cors");
require("dotenv").config();

const prisma = new PrismaClient();
const app = express();
app.use(express.json());


app.use(cors({
  origin: "*", // Allow all origins
  methods: ["GET", "POST", "PUT", "DELETE"], // Allow all methods
}));

const JWT_SECRET = "your_jwt_secret"; // Replace with a secure secret

// Authentication Middleware
const authenticate = async (req, res, next) => {
  const token = req.header("Authorization")?.replace("Bearer ", "");
  if (!token) return res.status(401).send("Access denied");

  try {
    const decoded = jwt.verify(token, JWT_SECRET);
    req.user = decoded;
    next();
  } catch (err) {
    return res.status(401).send("Invalid token");
  }
};

// Register User
app.post("/register", async (req, res) => {
  const { email, username, password, pubKey } = req.body;

  const userExists = await prisma.user.findUnique({ where: { username } });
  if (userExists) return res.status(400).send("User already exists");

  const hashedPassword = await bcrypt.hash(password, 10);
  const user = await prisma.user.create({
    data: {
      email,
      username,
      password: hashedPassword,
      pubKey,
    },
  });

  const token = jwt.sign({ username: user.username }, JWT_SECRET, { expiresIn: "1h" });
  res.send({ token });
});

// Update Public Key
app.post("/user/updatePublicKey", authenticate, async (req, res) => {
  const { pubKey } = req.body;
  const username = req.user.username;

  if (!pubKey) return res.status(400).send("Public key is required");

  try {
    await prisma.user.update({
      where: { username },
      data: { pubKey },
    });

    res.send({ message: "Public key updated successfully" });
  } catch (error) {
    console.error("Error updating public key:", error);
    res.status(500).send({ error: "Failed to update public key" });
  }
});


// Login User
// Login User
app.post("/login", async (req, res) => {
  const { username, password } = req.body;

  const user = await prisma.user.findUnique({
    where: { username },
    select: { password: true, pubKey: true },
  });
  if (!user) return res.status(400).send("Invalid credentials");

  const isMatch = await bcrypt.compare(password, user.password);
  if (!isMatch) return res.status(400).send("Invalid credentials");

  const token = jwt.sign({ username }, JWT_SECRET, { expiresIn: "1h" });
  res.send({ token, pubKey: user.pubKey });
});


// Fetch pending friend requests sent to the authenticated user
app.get("/friend-requests/pending", authenticate, async (req, res) => {
  const username = req.user.username;

  try {
    const pendingRequests = await prisma.friendRequest.findMany({
      where: {
        receiverUsername: username,
        status: "pending",
      },
      include: {
        sender: {
          select: { username: true },
        },
      },
    });

    res.send(pendingRequests);
  } catch (err) {
    res.status(500).send({ error: "Failed to fetch pending friend requests" });
  }
});

// Send Friend Request
app.post("/friend-request", authenticate, async (req, res) => {
  const { receiverUsername } = req.body;
  const senderUsername = req.user.username;

  const receiver = await prisma.user.findUnique({ where: { username: receiverUsername } });
  if (!receiver) return res.status(404).send("User not found");

  const existingRequest = await prisma.friendRequest.findFirst({
    where: {
      OR: [
        { senderUsername, receiverUsername },
        { senderUsername: receiverUsername, receiverUsername: senderUsername },
      ],
    },
  });

  if (existingRequest) return res.status(400).send("Friend request already exists");

  const request = await prisma.friendRequest.create({
    data: {
      senderUsername,
      receiverUsername,
      status: "pending",
    },
  });

  res.send(request);
});

// Respond to Friend Request
app.post("/friend-request/respond", authenticate, async (req, res) => {
  const { requestId, response } = req.body;
  const username = req.user.username;

  const request = await prisma.friendRequest.findUnique({ where: { id: requestId } });
  if (!request || request.receiverUsername !== username)
    return res.status(403).send("You cannot respond to this request");

  const status = response === "accepted" ? "accepted" : "rejected";

  await prisma.friendRequest.update({
    where: { id: requestId },
    data: { status },
  });

  res.send("Response recorded");
});

// Fetch Friends
app.get("/friends", authenticate, async (req, res) => {
  const username = req.user.username;

  try {
    const friends = await prisma.friendRequest.findMany({
      where: {
        OR: [
          { senderUsername: username, status: "accepted" },
          { receiverUsername: username, status: "accepted" },
        ],
      },
      include: {
        sender: { select: { username: true, email: true } },
        receiver: { select: { username: true, email: true } },
      },
    });

    const friendList = friends.map((f) => ({
      username: f.senderUsername === username ? f.receiver.username : f.sender.username,
      email: f.senderUsername === username ? f.receiver.email : f.sender.email,
    }));

    res.send(friendList);
  } catch (err) {
    res.status(500).send({ error: "Failed to fetch friends" });
  }
});

// Fetch Messages Between Two Users
app.get("/messages", authenticate, async (req, res) => {
  const { receiverUsername } = req.query;
  const username = req.user.username;

  if (!receiverUsername) {
    return res.status(400).send("Receiver username is required");
  }

  const messages = await prisma.message.findMany({
    where: {
      OR: [
        { senderUsername: username, receiverUsername },
        { senderUsername: receiverUsername, receiverUsername: username },
      ],
    },
    orderBy: { createdAt: "asc" },
  });

  res.send(messages);
});


// Send a Message
app.post("/messages", authenticate, async (req, res) => {
  const senderUsername = req.user.username;
  const { encrypted, nonce, pubKey, receiverUsername } = req.body;
  console.log(encrypted)
  if (!encrypted || !nonce || !pubKey || !receiverUsername) {
    return res.status(400).send("Missing required fields (encrypted, nonce, pubKey, receiverUsername)");
  }

  const receiver = await prisma.user.findUnique({ where: { username: receiverUsername } });
  if (!receiver) return res.status(404).send("Receiver not found");

  const isFriend = await prisma.friendRequest.findFirst({
    where: {
      OR: [
        { senderUsername, receiverUsername, status: "accepted" },
        { senderUsername: receiverUsername, receiverUsername: senderUsername, status: "accepted" },
      ],
    },
  });

  if (!isFriend) return res.status(403).send("You can only message friends");

  const message = await prisma.message.create({
    data: {
      content: encrypted,
      senderUsername,
      receiverUsername,
      nonce: nonce,
      pubKey: pubKey,
    },
  });

  res.send(message);
});

app.get("/test" , async(req,res) => {
  const messages = await prisma.message.findMany()
  res.send(messages)
})


// Get User Public Key if they are friends
app.get("/user/pubkey", authenticate, async (req, res) => {
  const { username: friendUsername } = req.query; // Username of the requested friend
  const username = req.user.username; // Authenticated user's username

  try {
    // Check if the user exists
    const user = await prisma.user.findUnique({
      where: { username: friendUsername },
      select: { pubKey: true }, // Only select the public key
    });

    if (!user) {
      return res.status(404).send("User not found");
    }

    // Check if the authenticated user is friends with the requested user
    const isFriend = await prisma.friendRequest.findFirst({
      where: {
        OR: [
          { senderUsername: username, receiverUsername: friendUsername, status: "accepted" },
          { senderUsername: friendUsername, receiverUsername: username, status: "accepted" },
        ],
      },
    });

    if (!isFriend) {
      return res.status(403).send("You can only fetch the public key of your friends");
    }

    // Return the public key
    res.send({ pubKey: user.pubKey });
  } catch (err) {
    res.status(500).send({ error: "Failed to fetch the public key" });
  }
});


// Delete Message
app.delete("/messages/:id", authenticate, async (req, res) => {
  const { id } = req.params;
  const username = req.user.username;

  const message = await prisma.message.findUnique({ where: { id: parseInt(id) } });
  if (!message || message.senderUsername !== username)
    return res.status(403).send("You can only delete your own messages");

  await prisma.message.delete({ where: { id: parseInt(id) } });
  res.send("Message deleted successfully");
});

app.listen(4000, () => {
  console.log("Server running on http://localhost:4000");
});