import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.nio.charset.StandardCharsets;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;

public class TestReadAPI {

    public static void main(String[] args) throws InvalidKeyException, NoSuchAlgorithmException {
        System.out.println("Start API Call ...");
        System.out.println("--------------------");

        // Set the timezone to UTC for 1WorldSync API call
        TimeZone timeZone = TimeZone.getTimeZone("UTC");
        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'");
        dateFormat.setTimeZone(timeZone);
        String timeStamp = dateFormat.format(new Date());
        System.out.println("Current DateTime: [" + timeStamp + "]");

        String appID = "abc123xy"; // Please update with your APP ID here (8 characters)
        System.out.println("AppID: [" + appID + "]");

        String secretKey = "qwertyuiopasdfghjklzxcvbnm123456"; // Please update with your Secret Key here (32 characters)
        String gln = "1234567890123"; // Please update with your 13-digit GLN here (13 digits)
        System.out.println("GLN: [" + gln + "]");

        String uri = "/V1/product/fetch?timestamp=" + timeStamp + "&pageSize=1";

        String hashInBase64 = generateHash(uri, secretKey);
        String hashInBase64URIencoded = urlencode(hashInBase64);

        String apiUrl = "https://content1-api.1worldsync.com" + uri;
        System.out.println("URL: [" + apiUrl + "]");
        System.out.println("--------------------");

        try {
            URL url = new URL(apiUrl);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("POST");
            connection.setRequestProperty("Content-Type", "application/json");
            connection.setRequestProperty("appId", appID);
            connection.setRequestProperty("hashcode", hashInBase64);
            connection.setDoOutput(true);

            String postData = "{}";
            try (OutputStream os = connection.getOutputStream()) {
                byte[] input = postData.getBytes(StandardCharsets.UTF_8);
                os.write(input, 0, input.length);
            }

            try (BufferedReader br = new BufferedReader(new InputStreamReader(connection.getInputStream()))) {
                String line;
                StringBuilder response = new StringBuilder();
                while ((line = br.readLine()) != null) {
                    response.append(line);
                }
                System.out.println("API Response: [" + response.toString() + "]");
            }

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

        System.out.println("--------------------");
        System.out.println("End API Call");
    }

    private static String generateHash(String data, String secretKey) throws NoSuchAlgorithmException, InvalidKeyException {
        Mac sha256Hmac = Mac.getInstance("HmacSHA256");
        SecretKeySpec secretKeySpec = new SecretKeySpec(secretKey.getBytes(StandardCharsets.UTF_8), "HmacSHA256");
        sha256Hmac.init(secretKeySpec);

        byte[] hash = sha256Hmac.doFinal(data.getBytes(StandardCharsets.UTF_8));
        return java.util.Base64.getEncoder().encodeToString(hash);
    }

    private static String urlencode(String value) {
        try {
            return java.net.URLEncoder.encode(value, StandardCharsets.UTF_8.toString());
        } catch (java.io.UnsupportedEncodingException ex) {
            throw new RuntimeException(ex.getCause());
        }
    }
}

// SAMPLE OUTPUT
// Start API Call ...
// --------------------
// Current DateTime: [2023-12-19T20:15:08Z]
// AppID: [abc123xy]
// GLN: [1234567890123]
// URL: [https://content1-api.1worldsync.com/V1/product/fetch?timestamp=2023-12-19T20:15:08Z&pageSize=1]
// --------------------
// API Response: [{"items":[{"objId":"123456","gln":"1234567890123","item":{ etc.....
// --------------------
// End API Call