const express = require("express");
const axios = require("axios");
const config = require("../config/api");

const router = express.Router();

router.get("/", async (req, res) => {
  try {
    const { apiKey, baseUrl, city, units, language } = config.weather;
    if (!apiKey) {
      return res.status(400).json({ message: "OPENWEATHER_API_KEY is not set" });
    }

    const { q, lat, lon } = req.query;
    const params = {
      appid: apiKey,
      units,
      lang: language,
    };

    let currentResponse, forecastResponse, airResponse;

    if (lat && lon) {
      // 1. Parallel fetch for all 3 endpoints if coordinates are available
      [currentResponse, forecastResponse, airResponse] = await Promise.all([
        axios.get(`${baseUrl}/weather`, { params: { ...params, lat, lon } }),
        axios.get(`${baseUrl}/forecast`, { params: { ...params, lat, lon } }),
        axios.get(`${baseUrl}/air_pollution`, { params: { lat, lon, appid: apiKey } }),
      ]);
    } else {
      // 2. Sequential fallback if only city name is provided
      params.q = q || city;
      currentResponse = await axios.get(`${baseUrl}/weather`, { params });
      const { coord } = currentResponse.data;

      [forecastResponse, airResponse] = await Promise.all([
        axios.get(`${baseUrl}/forecast`, {
          params: { ...params, lat: coord.lat, lon: coord.lon },
        }),
        axios.get(`${baseUrl}/air_pollution`, {
          params: { lat: coord.lat, lon: coord.lon, appid: apiKey },
        }),
      ]);
    }

    const currentData = currentResponse.data;

    // 3. Process Forecast for Today's Min/Max (Seoul Time: UTC+9)
    // OpenWeatherMap returns timestamps in UTC.
    // Seoul is UTC+9.
    const SeoulOffset = 9 * 60 * 60 * 1000;
    const nowKST = new Date(Date.now() + SeoulOffset);
    const todayStr = nowKST.toISOString().split("T")[0]; // YYYY-MM-DD in KST

    const todayItems = forecastResponse.data.list.filter((item) => {
      const itemDateKST = new Date(item.dt * 1000 + SeoulOffset);
      const itemDateStr = itemDateKST.toISOString().split("T")[0];
      return itemDateStr === todayStr;
    });

    if (todayItems.length > 0) {
      // Find min and max from the 3-hour segments
      const minTemp = Math.min(...todayItems.map((item) => item.main.temp_min));
      const maxTemp = Math.max(...todayItems.map((item) => item.main.temp_max));

      // Update the response structure
      currentData.main.temp_min = minTemp;
      currentData.main.temp_max = maxTemp;
    }

    // 4. Attach Air Quality (AQI)
    // OpenWeatherMap AQI: 1 (Good) ... 5 (Very Poor)
    if (airResponse.data.list && airResponse.data.list.length > 0) {
      currentData.aqi = airResponse.data.list[0].main.aqi;
    }

    res.json(currentData);
  } catch (error) {
    console.error("Weather API Error:", error.message);
    if (error.response) {
      console.error("Data:", error.response.data);
    }
    res.status(500).json({ message: "Failed to fetch weather" });
  }
});

module.exports = router;