package com.example.demo.config;

import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;
import java.nio.charset.StandardCharsets;
import java.util.Iterator;

import javax.servlet.http.HttpServletRequest;

import org.apache.commons.io.IOUtils;
import org.json.JSONObject;
import org.apache.commons.lang3.StringUtils;
import com.google.gson.Gson;

public class HttpUtil {

    /* ===================== GET ===================== */

    public static String sendGet(String url) {

        HttpURLConnection conn = null;

        try {
            URL u = new URL(url);
            conn = (HttpURLConnection) u.openConnection();
            conn.setRequestMethod("GET");
            conn.setConnectTimeout(3000);
            conn.setReadTimeout(3000);

            try (InputStream in = new BufferedInputStream(conn.getInputStream())) {
                return IOUtils.toString(in, StandardCharsets.UTF_8);
            }

        } catch (Exception e) {
            e.printStackTrace();
            return null;
        } finally {
            if (conn != null) conn.disconnect();
        }
    }

    /* ===================== POST JSON ===================== */

    public static String sendObject2Json(String url, Object object) {

        HttpURLConnection conn = null;

        try {
            URL u = new URL(url);
            conn = (HttpURLConnection) u.openConnection();

            conn.setRequestMethod("POST");
            conn.setRequestProperty("Content-Type", "application/json; charset=UTF-8");
            conn.setDoOutput(true);
            conn.setConnectTimeout(3000);
            conn.setReadTimeout(3000);

            String jsonStr = new Gson().toJson(object);

            try (OutputStream os = conn.getOutputStream()) {
                os.write(jsonStr.getBytes(StandardCharsets.UTF_8));
            }

            try (InputStream in = new BufferedInputStream(conn.getInputStream())) {
                return IOUtils.toString(in, StandardCharsets.UTF_8);
            }

        } catch (Exception e) {
            e.printStackTrace();
            return null;
        } finally {
            if (conn != null) conn.disconnect();
        }
    }

    /* ===================== POST FORM ===================== */

    public static String sendObject2Post(String url, Object object) {

        HttpURLConnection conn = null;

        try {
            URL u = new URL(url);
            conn = (HttpURLConnection) u.openConnection();

            conn.setRequestMethod("POST");
            conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded; charset=UTF-8");
            conn.setDoOutput(true);

            JSONObject json = new JSONObject(new Gson().toJson(object));
            StringBuilder sb = new StringBuilder();

            Iterator<String> keys = json.keys();
            while (keys.hasNext()) {
                String key = keys.next();
                sb.append(key)
                  .append("=")
                  .append(URLEncoder.encode(json.getString(key), "UTF-8"))
                  .append("&");
            }

            try (OutputStream os = conn.getOutputStream()) {
                os.write(sb.toString().getBytes(StandardCharsets.UTF_8));
            }

            try (InputStream in = new BufferedInputStream(conn.getInputStream())) {
                return IOUtils.toString(in, StandardCharsets.UTF_8);
            }

        } catch (Exception e) {
            e.printStackTrace();
            return null;
        } finally {
            if (conn != null) conn.disconnect();
        }
    }

    /* ===================== Client IP ===================== */

    public static String getClientIp(HttpServletRequest request) {
        String ip = request.getHeader("HTTP_X_FORWARDED_FOR");
        if (StringUtils.isBlank(ip)) {
            ip = request.getRemoteAddr();
        }
        return ip;
    }
}