import java.io.*;
import java.lang.String;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;
import java.nio.charset.StandardCharsets;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ExecutionException;

import static javax.xml.bind.DatatypeConverter.parseHexBinary;

public class TwikeyAPI {

    public static final String UTF_8 = "UTF-8";

    //from_creditor_env
    private static final String TEMPLATE_ID = "**ct**";// id of contract template in https://www.twikey.com/r/admin#/c/template
    private static final String API_TOKEN = "**API_TOKEN**"; // found in https://www.twikey.com/r/admin#/c/settings/ei

    public static void main(String... args) throws GeneralSecurityException, ExecutionException, InterruptedException, IOException {

        String query = java.lang.String.format("apiToken=%s", API_TOKEN);

        URL myurl;
        HttpURLConnection con;
        DataOutputStream output;
        String sessionToken;

        // login
        {
            myurl = new URL("https://api.twikey.com/creditor");
            con = (HttpURLConnection)myurl.openConnection();
            con.setRequestMethod("POST");
            con.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
            con.setDoOutput(true);
            con.setDoInput(true);

            output = new DataOutputStream(con.getOutputStream());
            output.writeBytes(query);
            output.close();

            sessionToken = con.getHeaderField("Authorization");
            con.disconnect();
            System.out.println("Authorization:" + sessionToken);
        }

        // prepare new contract and redirect user
        if(sessionToken != null){
            Map<String,String> params = new HashMap<>();
            params.put("ct",TEMPLATE_ID);
            params.put("email","info@twikey.com");
            params.put("firstname","Info");
            params.put("lastname","Twikey");
            params.put("l","en");
            params.put("address","Abbey road");
            params.put("city","Liverpool");
            params.put("zip","1526");
            params.put("country","BE");
            params.put("mobile","");
            params.put("vatno","");
            params.put("iban","");
            params.put("bic","");
            params.put("mandateNumber","");
            params.put("contractNumber","");

            myurl = new URL("https://api.twikey.com/creditor/prepare");
            con = (HttpURLConnection)myurl.openConnection();
            con.setRequestMethod("POST");
            con.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
            con.setRequestProperty("Authorization", sessionToken);
            con.setDoOutput(true);
            con.setDoInput(true);

            output = new DataOutputStream(con.getOutputStream());
            output.writeBytes(getPostDataString(params));
            output.flush();
            output.close();

            int responseCode=con.getResponseCode();

            StringBuilder response = new StringBuilder();
            if (responseCode == HttpURLConnection.HTTP_OK) {
                String line;
                BufferedReader br=new BufferedReader(new InputStreamReader(con.getInputStream()));
                while ((line=br.readLine()) != null) {
                    response.append(line);
                }
            }

            con.disconnect();
            System.out.println("Url to redirect too:" + response);
        }
    }

    private static String getPostDataString(Map<String, String> params) throws UnsupportedEncodingException {
        StringBuilder result = new StringBuilder();
        boolean first = true;
        for(Map.Entry<String, String> entry : params.entrySet()){
            if (first)
                first = false;
            else
                result.append("&");

            result.append(URLEncoder.encode(entry.getKey(), UTF_8));
            result.append("=");
            result.append(URLEncoder.encode(entry.getValue(), UTF_8));
        }

        return result.toString();
    }
}