Main

import org.json.simple.JSONArray;
import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;

import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.URL;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.util.Scanner;

// retreive weather data from API - this backend logic will fetch the latest weather
// data from the external API and return it. The GUI will
// display this data to the user
public class WeatherApp1 {
    // fetch weather data for given location
    public static JSONObject getWeatherData(String locationName){
        // get location coordinates using the geolocation API
        JSONArray locationData = getLocationData(locationName);

        // extract latitude and longitude data
        JSONObject location = (JSONObject) locationData.get(0);
        double latitude = (double) location.get("latitude");
        double longitude = (double) location.get("longitude");

        // build API request URL with location coordinates
        String urlString = "https://api.open-meteo.com/v1/forecast?" +
                "latitude=" + latitude + "&longitude=" + longitude +
                "&hourly=temperature_2m,relativehumidity_2m,weathercode,windspeed_10m&timezone=America%2FLos_Angeles";

        try{
            // call api and get response
            HttpURLConnection conn = fetchApiResponse(urlString);

            // check for response status
            // 200 - means that the connection was a success
            if(conn.getResponseCode() != 200){
                System.out.println("Error: Could not connect to API");
                return null;
            }

            // store resulting json data
            StringBuilder resultJson = new StringBuilder();
            Scanner scanner = new Scanner(conn.getInputStream());
            while(scanner.hasNext()){
                // read and store into the string builder
                resultJson.append(scanner.nextLine());
            }

            // close scanner
            scanner.close();

            // close url connection
            conn.disconnect();

            // parse through our data
            JSONParser parser = new JSONParser();
            JSONObject resultJsonObj = (JSONObject) parser.parse(String.valueOf(resultJson));

            // retrieve hourly data
            JSONObject hourly = (JSONObject) resultJsonObj.get("hourly");

            // we want to get the current hour's data
            // so we need to get the index of our current hour
            JSONArray time = (JSONArray) hourly.get("time");
            int index = findIndexOfCurrentTime(time);

            // get temperature
            JSONArray temperatureData = (JSONArray) hourly.get("temperature_2m");
            double temperature = (double) temperatureData.get(index);

            // get weather code
            JSONArray weathercode = (JSONArray) hourly.get("weathercode");
            String weatherCondition = convertWeatherCode((long) weathercode.get(index));

            // get humidity
            JSONArray relativeHumidity = (JSONArray) hourly.get("relativehumidity_2m");
            long humidity = (long) relativeHumidity.get(index);

            // get windspeed
            JSONArray windspeedData = (JSONArray) hourly.get("windspeed_10m");
            double windspeed = (double) windspeedData.get(index);

            // build the weather json data object that we are going to access in our frontend
            JSONObject weatherData = new JSONObject();
            weatherData.put("temperature", temperature);
            weatherData.put("weather_condition", weatherCondition);
            weatherData.put("humidity", humidity);
            weatherData.put("windspeed", windspeed);

            return weatherData;
        }catch(Exception e){
            e.printStackTrace();
        }

        return null;
    }

    // retrieves geographic coordinates for given location name
    public static JSONArray getLocationData(String locationName){
        // replace any whitespace in location name to + to adhere to API's request format
        locationName = locationName.replaceAll(" ", "+");

        // build API url with location parameter
        String urlString = "https://geocoding-api.open-meteo.com/v1/search?name=" +
                locationName + "&count=10&language=en&format=json";

        try{
            // call api and get a response
            HttpURLConnection conn = fetchApiResponse(urlString);

            // check response status
            // 200 means successful connection
            if(conn.getResponseCode() != 200){
                System.out.println("Error: Could not connect to API");
                return null;
            }else{
                // store the API results
                StringBuilder resultJson = new StringBuilder();
                Scanner scanner = new Scanner(conn.getInputStream());

                // read and store the resulting json data into our string builder
                while(scanner.hasNext()){
                    resultJson.append(scanner.nextLine());
                }

                // close scanner
                scanner.close();

                // close url connection
                conn.disconnect();

                // parse the JSON string into a JSON obj
                JSONParser parser = new JSONParser();
                JSONObject resultsJsonObj = (JSONObject) parser.parse(String.valueOf(resultJson));

                // get the list of location data the API gtenerated from the lcoation name
                JSONArray locationData = (JSONArray) resultsJsonObj.get("results");
                return locationData;
            }

        }catch(Exception e){
            e.printStackTrace();
        }

        // couldn't find location
        return null;
    }

    private static HttpURLConnection fetchApiResponse(String urlString){
        try{
            // attempt to create connection
            URL url = new URL(urlString);
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();

            // set request method to get
            conn.setRequestMethod("GET");

            // connect to our API
            conn.connect();
            return conn;
        }catch(IOException e){
            e.printStackTrace();
        }

        // could not make connection
        return null;
    }

    private static int findIndexOfCurrentTime(JSONArray timeList){
        String currentTime = getCurrentTime();

        // iterate through the time list and see which one matches our current time
        for(int i = 0; i < timeList.size(); i++){
            String time = (String) timeList.get(i);
            if(time.equalsIgnoreCase(currentTime)){
                // return the index
                return i;
            }
        }

        return 0;
    }

    protected static String getCurrentTime(){
        // get current date and time
        LocalDateTime currentDateTime = LocalDateTime.now();

        // format date to be 2023-09-02T00:00 (this is how is is read in the API)
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH':00'");

        // format and print the current date and time
        String formattedDateTime = currentDateTime.format(formatter);

        return formattedDateTime;
    }

    // convert the weather code to something more readable
    private static String convertWeatherCode(long weathercode){
        String weatherCondition = "";
        if(weathercode == 0L){
            // clear
            weatherCondition = "Clear";
        }else if(weathercode > 0L && weathercode <= 3L){
            // cloudy
            weatherCondition = "Cloudy";
        }else if((weathercode >= 51L && weathercode <= 67L)
                || (weathercode >= 80L && weathercode <= 99L)){
            // rain
            weatherCondition = "Rain";
        }else if(weathercode >= 71L && weathercode <= 77L){
            // snow
            weatherCondition = "Snow";
        }

        return weatherCondition;
    }
}