Minecraft-Server-Launcher/src/main/java/net/knarcraft/minecraftserverlauncher/utility/Updater.java

package net.knarcraft.minecraftserverlauncher.utility;

import com.google.gson.JsonArray;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;
import net.knarcraft.minecraftserverlauncher.userinterface.GUI;

import javax.swing.*;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Scanner;

import static net.knarcraft.minecraftserverlauncher.Main.getApplicationWorkDirectory;
import static net.knarcraft.minecraftserverlauncher.utility.CommonFunctions.downloadFile;
import static net.knarcraft.minecraftserverlauncher.utility.CommonFunctions.getResourceAsScanner;
import static net.knarcraft.minecraftserverlauncher.utility.CommonFunctions.readFile;

/**
 * A utility used for updating the software
 */
public final class Updater {

    /**
     * Checks if a newer version is available
     *
     * @param updateURL     <p>The URL used for checking for updates</p>
     * @param updateChannel <p>The release channel to use</p>
     * @param gui           <p>The GUI to use for output</p>
     * @throws IOException <p>If the update data cannot be read</p>
     */
    public static void checkForUpdate(String updateURL, String updateChannel, GUI gui) throws IOException {
        Scanner file = getResourceAsScanner("currentversion.csv");
        if (!file.hasNextLine()) {
            throw new FileNotFoundException("File currentversion.csv is invalid");
        }
        String oldType = file.nextLine();
        if (!file.hasNextLine()) {
            throw new FileNotFoundException("File currentversion.csv is invalid");
        }
        String oldVer = file.nextLine();
        file.close();

        String data = readFile(updateURL);
        JsonObject jsonObject = new JsonParser().parse(data).getAsJsonObject();
        String latest = jsonObject.getAsJsonObject("latest").get(updateChannel).getAsString();

        if (!oldType.equals(updateChannel) || !oldVer.equals(latest)) {
            String dir = getApplicationWorkDirectory() + File.separator;
            JsonArray versionList = jsonObject.getAsJsonArray("versions");
            String url = "";
            for (JsonElement elem : versionList) {
                JsonObject obj = elem.getAsJsonObject();
                String ver = obj.get("id").getAsString();
                String type = obj.get("type").getAsString();
                if (ver.equals(latest) && type.equals(updateChannel)) {
                    url = obj.get("url").getAsString();
                }
            }
            if (downloadFile(url, new File(dir + "update.jar").toPath())) {
                doUpdate(dir, gui);
            } else {
                gui.showError("Update available",
                        "An update is available, but could not be downloaded.");
            }
        }
    }

    /**
     * Asks the user whether to update and downloads the new update
     *
     * @param dir <p>The directory to save the updated file to</p>
     * @param gui <p>The GUI to write output to</p>
     */
    public static void doUpdate(String dir, GUI gui) {
        int answer = JOptionPane.showConfirmDialog(
                null,
                "An update is available. Do you want to update?",
                "Update available",
                JOptionPane.YES_NO_OPTION
        );
        if (answer == JOptionPane.YES_NO_OPTION) {
            if (new File(dir + "Minecraft-Server-Launcher.jar").renameTo(new File(dir +
                    "Old.jar"))) {
                if (new File(dir + "update.jar").renameTo(new File(dir +
                        "Minecraft-Server-Launcher.jar"))) {
                    if (new File(dir + "Old.jar").delete()) {
                        gui.showMessage("Update complete",
                                "Update finished. Please run the software again.");
                        System.exit(0);
                    }
                } else {
                    if (!new File(dir + "Old.jar").renameTo(new File(dir +
                            "Minecraft-Server-Launcher.jar"))) {
                        System.out.println("Shit");
                    }
                }
            }
            gui.showError("Update failed",
                    "Could not replace the main .jar with the downloaded .jar.");
        }
    }
}