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Common API to build HyperLap2D plugins
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package games.rednblack.h2d.common.network;

import games.rednblack.h2d.common.ProgressHandler;

import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;

/**
 * A utility that downloads a file from a URL.
 * @author www.codejava.net
 *
 */
public class HttpDownloadUtility {
    private static final int BUFFER_SIZE = 4096;

    /**
     * Downloads a file from a URL
     * @param fileURL HTTP URL of the file to be downloaded
     * @param saveDir path of the directory to save the file
     * @throws IOException
     */
    public static void downloadFile(String fileURL, String saveDir, ProgressHandler progressHandler)
            throws IOException {
        URL url = new URL(fileURL);
        HttpURLConnection httpConn = (HttpURLConnection) url.openConnection();
        httpConn.setInstanceFollowRedirects(true);
        int responseCode = httpConn.getResponseCode();

        // always check HTTP response code first
        if (responseCode == HttpURLConnection.HTTP_OK) {
            String fileName = "";
            String disposition = httpConn.getHeaderField("Content-Disposition");
            String contentType = httpConn.getContentType();
            int contentLength = httpConn.getContentLength();

            if (disposition != null) {
                // extracts file name from header field
                int index = disposition.indexOf("filename=");
                if (index > 0) {
                    fileName = disposition.substring(index + 9);
                }
            } else {
                // extracts file name from URL
                fileName = fileURL.substring(fileURL.lastIndexOf("/") + 1);
            }

            System.out.println("Content-Type = " + contentType);
            System.out.println("Content-Disposition = " + disposition);
            System.out.println("Content-Length = " + contentLength);
            System.out.println("fileName = " + fileName);

            // opens input stream from the HTTP connection
            InputStream inputStream = httpConn.getInputStream();
            String saveFilePath = saveDir + File.separator + fileName;

            // opens an output stream to save into file
            FileOutputStream outputStream = new FileOutputStream(saveFilePath);
            int currentBytes = 0;

            int bytesRead = -1;
            byte[] buffer = new byte[BUFFER_SIZE];
            while ((bytesRead = inputStream.read(buffer)) != -1) {
                currentBytes += bytesRead;
                progressHandler.progressChanged(currentBytes * 100f / contentLength);
                outputStream.write(buffer, 0, bytesRead);
            }

            outputStream.close();
            inputStream.close();

            progressHandler.progressComplete();
        } else {
            System.out.println("No file to download. Server replied HTTP code: " + responseCode);
            progressHandler.progressFailed();
        }

        httpConn.disconnect();
    }

    public static String downloadToString(String fileURL) throws IOException {
        URL url = new URL(fileURL);
        HttpURLConnection httpConn = (HttpURLConnection) url.openConnection();
        httpConn.setInstanceFollowRedirects(true);
        int responseCode = httpConn.getResponseCode();

        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();

        // always check HTTP response code first
        if (responseCode == HttpURLConnection.HTTP_OK) {
            String disposition = httpConn.getHeaderField("Content-Disposition");
            String contentType = httpConn.getContentType();
            int contentLength = httpConn.getContentLength();


            System.out.println("Content-Type = " + contentType);
            System.out.println("Content-Disposition = " + disposition);
            System.out.println("Content-Length = " + contentLength);

            // opens input stream from the HTTP connection
            InputStream inputStream = httpConn.getInputStream();

            int bytesRead = -1;
            byte[] buffer = new byte[BUFFER_SIZE];
            while ((bytesRead = inputStream.read(buffer)) != -1) {
                outputStream.write(buffer, 0, bytesRead);
            }

            outputStream.close();
            inputStream.close();
        } else {
            System.out.println("No file to download. Server replied HTTP code: " + responseCode);
        }
        httpConn.disconnect();

        return outputStream.toString("UTF-8");
    }
}