Begin working on the update checker

Also added a config for toggling internet capabilities

src/main/java/com/falsepattern/lib/updates/UpdateChecker.java

@@ -0,0 +1,85 @@
+package com.falsepattern.lib.updates;
+
+import com.falsepattern.lib.dependencies.DependencyLoader;
+import com.falsepattern.lib.dependencies.SemanticVersion;
+import com.falsepattern.lib.internal.FalsePatternLib;
+import com.falsepattern.lib.internal.LibraryConfig;
+import com.falsepattern.lib.internal.Tags;
+import lombok.val;
+import lombok.var;
+
+import java.io.BufferedOutputStream;
+import java.io.File;
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.URL;
+import java.nio.file.Files;
+import java.util.List;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+public class UpdateChecker {
+    private static AtomicBoolean jsonLibraryLoaded = new AtomicBoolean(false);
+    private static final ExecutorService asyncExecutor = Executors.newSingleThreadExecutor((runnable) -> {
+        Thread thread = new Thread(runnable);
+        thread.setDaemon(true);
+        thread.setName(Tags.MODNAME + " Asynchronous Update Check Thread");
+        return thread;
+    });
+    /**
+     * Same this as {@link #fetchUpdates(String)}, but defers the check to a different thread. Useful for asynchronous
+     * update checks, if you don't want to block loading.
+     * @param url The URL to check
+     * @return A future that will contain the update info about mods that were both available on the URL and installed
+     */
+    public static Future<List<ModUpdateInfo>> fetchUpdatesAsync(String url) {
+        return asyncExecutor.submit(() -> fetchUpdates(url));
+    }
+
+    /**
+     * Checks for updates. The URL should be a JSON file that contains a list of mods, each with a mod ID, one or more
+     * versions, and a URL for the user to check for updates in case the current and latest versions are different.
+     * The JSON file must have the following format:
+     * <pre>{@code
+     *  [
+     *      {
+     *          "modID": "modid",
+     *          "latestVersion": ["1.0.0", "1.0.0-foo"],
+     *          "updateURL": "https://example.com/mods/mymod"
+     *      },
+     *      {
+     *          "modID": "modid2",
+     *          "latestVersion": ["0.2.0", "0.3.0-alpha"],
+     *          "updateURL": "https://example.com/mods/mymod2"
+     *      },
+     *      ...etc, one json object per mod.
+     *  ]
+     * }</pre>
+     * @param url The URL to check
+     * @return A list of mods that were both available on the URL and installed
+     */
+    public static List<ModUpdateInfo> fetchUpdates(String url) {
+        if (!LibraryConfig.ENABLE_UPDATE_CHECKER) {
+            return null;
+        }
+        if (!jsonLibraryLoaded.get()) {
+            DependencyLoader.addMavenRepo("https://maven.falsepattern.com/");
+            try {
+                DependencyLoader.builder()
+                                .groupId("com.falsepattern")
+                                .artifactId("json")
+                        .minVersion(new SemanticVersion(0, 4, 0))
+                        .maxVersion(new SemanticVersion(0, Integer.MAX_VALUE, Integer.MAX_VALUE))
+                        .build();
+            } catch (Exception e) {
+                FalsePatternLib.getLog().error("Failed to load json library for update checker!", e);
+                return null;
+            }
+            jsonLibraryLoaded.set(true);
+        }
+        //TODO
+        return null;
+    }
+}