const express = require("express");
const Todo = require("../models/Todo");

const router = express.Router();

// Get day range in Korea Standard Time (UTC+9)
const getDayRange = () => {
  const now = new Date();
  // Get current time in KST (UTC+9)
  const kstOffset = 9 * 60; // minutes
  const utcTime = now.getTime() + (now.getTimezoneOffset() * 60000);
  const kstTime = new Date(utcTime + (kstOffset * 60000));

  // Start of day in KST
  const startKst = new Date(kstTime);
  startKst.setHours(0, 0, 0, 0);

  // End of day in KST
  const endKst = new Date(kstTime);
  endKst.setHours(23, 59, 59, 999);

  // Convert back to UTC for MongoDB query
  const start = new Date(startKst.getTime() - (kstOffset * 60000));
  const end = new Date(endKst.getTime() - (kstOffset * 60000));

  return { start, end };
};

router.get("/", async (req, res) => {
  try {
    const todos = await Todo.find().sort({ dueDate: 1, createdAt: -1 });
    res.json(todos);
  } catch (error) {
    res.status(500).json({ message: "Failed to fetch todos" });
  }
});

router.get("/today", async (req, res) => {
  try {
    const { start, end } = getDayRange();
    // Include:
    // 1. Tasks due today
    // 2. Overdue tasks (due before today) that are not completed
    // 3. Tasks with no due date that are not completed
    const todos = await Todo.find({
      $or: [
        { dueDate: { $gte: start, $lte: end } },
        { dueDate: { $lt: start }, completed: false },
        { dueDate: { $exists: false }, completed: false },
        { dueDate: null, completed: false }
      ]
    }).sort({
      dueDate: 1,
      createdAt: -1,
    });
    res.json(todos);
  } catch (error) {
    res.status(500).json({ message: "Failed to fetch today todos" });
  }
});

router.post("/", async (req, res) => {
  try {
    const todo = await Todo.create(req.body);
    res.status(201).json(todo);
  } catch (error) {
    res.status(400).json({ message: "Failed to create todo" });
  }
});

router.get("/:id", async (req, res) => {
  try {
    const todo = await Todo.findById(req.params.id);
    if (!todo) {
      return res.status(404).json({ message: "Todo not found" });
    }
    res.json(todo);
  } catch (error) {
    res.status(400).json({ message: "Failed to fetch todo" });
  }
});

router.put("/:id", async (req, res) => {
  try {
    const todo = await Todo.findByIdAndUpdate(req.params.id, req.body, { new: true });
    if (!todo) {
      return res.status(404).json({ message: "Todo not found" });
    }
    res.json(todo);
  } catch (error) {
    res.status(400).json({ message: "Failed to update todo" });
  }
});

router.delete("/:id", async (req, res) => {
  try {
    const todo = await Todo.findByIdAndDelete(req.params.id);
    if (!todo) {
      return res.status(404).json({ message: "Todo not found" });
    }
    res.json({ ok: true });
  } catch (error) {
    res.status(400).json({ message: "Failed to delete todo" });
  }
});

module.exports = router;