DMDirc-Util/src/main/java/com/dmdirc/util/io/Downloader.java

/*
 * Copyright (c) 2006-2017 DMDirc Developers
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated
 * documentation files (the "Software"), to deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
 * WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS
 * OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

package com.dmdirc.util.io;

import com.dmdirc.util.collections.CollectionFunctions;

import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URL;
import java.net.URLConnection;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

/**
 * Allows easy downloading of files from HTTP sites.
 */
public class Downloader {

    /**
     * Retrieves the specified page.
     *
     * @param url The URL to retrieve
     * @return A list of lines received from the server
     * @throws IOException If there's an I/O error while downloading
     */
    public List<String> getPage(final String url) throws IOException {
        return getPage(url, "");
    }

    /**
     * Retrieves the specified page, sending the specified post data.
     *
     * @param url The URL to retrieve
     * @param postData The raw POST data to send
     * @return A list of lines received from the server
     * @throws IOException If there's an I/O error while downloading
     */
    public List<String> getPage(final String url, final String postData)
            throws IOException {
        final URLConnection urlConn = getConnection(url, postData);
        final List<String> res;
        try (BufferedReader in = new BufferedReader(new InputStreamReader(
                urlConn.getInputStream()))) {
            res = in.lines().collect(Collectors.toList());
        }
        return res;
    }

    /**
     * Retrieves the specified page, sending the specified post data.
     *
     * @param url The URL to retrieve
     * @param postData A map of post data that should be sent
     * @return A list of lines received from the server
     * @throws IOException If there's an I/O error while downloading
     */
    public List<String> getPage(final String url,
            final Map<String, String> postData) throws IOException {
        return getPage(url, postData.entrySet().stream()
                .flatMap(CollectionFunctions::flattenAndEncodeKeyPair)
                .collect(Collectors.joining("&")));
    }

    /**
     * Downloads the specified page to disk.
     *
     * @param url The URL to retrieve
     * @param file The file to save the page to
     * @throws IOException If there's an I/O error while downloading
     */
    public void downloadPage(final String url, final Path file)
            throws IOException {
        downloadPage(url, file, null);
    }

    /**
     * Downloads the specified page to disk.
     *
     * @param url The URL to retrieve
     * @param file The file to save the page to
     * @param listener The progress listener for this download
     * @throws IOException If there's an I/O error while downloading
     */
    public void downloadPage(final String url, final Path file, final DownloadListener listener)
            throws IOException {
        final URLConnection connection = getConnection(url, "");
        Files.copy(new ListenerInputStream(connection.getInputStream(), listener,
                        connection.getContentLength()), file);
    }

    /**
     * Creates an URL connection for the specified URL and data.
     *
     * @param url The URL to connect to
     * @param postData The POST data to pass to the URL
     * @return An URLConnection for the specified URL/data
     * @throws IOException If an I/O exception occurs while connecting
     */
    private URLConnection getConnection(final String url, final String postData)
            throws IOException {
        final URLConnection urlConn = getURLConnection(url);

        urlConn.setUseCaches(false);
        urlConn.setDoInput(true);
        urlConn.setDoOutput(!postData.isEmpty());
        urlConn.setConnectTimeout(10000);

        if (!postData.isEmpty()) {
            urlConn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");

            try (DataOutputStream out = new DataOutputStream(urlConn.getOutputStream())) {
                out.writeBytes(postData);
                out.flush();
            }
        }

        return urlConn;
    }

    protected URLConnection getURLConnection(final String url) throws IOException {
        final URL myUrl = new URL(url);
        return myUrl.openConnection();
    }

}