Begin working on the update checker

Also added a config for toggling internet capabilities

src/main/java/com/falsepattern/lib/internal/FalsePatternLib.java

@@ -1,14 +1,20 @@
 package com.falsepattern.lib.internal;
 
+import com.falsepattern.lib.config.ConfigException;
 import com.falsepattern.lib.config.ConfigurationManager;
 import com.falsepattern.lib.util.ResourceUtil;
 import com.google.common.eventbus.EventBus;
 import com.google.common.eventbus.Subscribe;
 import cpw.mods.fml.common.DummyModContainer;
 import cpw.mods.fml.common.LoadController;
+import cpw.mods.fml.common.Loader;
 import cpw.mods.fml.common.MetadataCollection;
 import cpw.mods.fml.common.event.FMLConstructionEvent;
+import cpw.mods.fml.common.event.FMLInterModComms;
+import cpw.mods.fml.common.event.FMLPostInitializationEvent;
+import cpw.mods.fml.common.event.FMLPreInitializationEvent;
 import lombok.Getter;
+import lombok.SneakyThrows;
 import net.minecraft.launchwrapper.Launch;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
@@ -17,6 +23,7 @@ import org.apache.logging.log4j.Logger;
  * Utility class used by FalsePatternLib's internal code. This can change between versions without notice, so do not use
  * this in your code!
  */
+@SuppressWarnings("UnstableApiUsage")
 public class FalsePatternLib extends DummyModContainer {
     @Getter private static final Logger log = LogManager.getLogger(Tags.MODNAME);
 
@@ -33,6 +40,16 @@ public class FalsePatternLib extends DummyModContainer {
     @Subscribe
     public void construct(FMLConstructionEvent e) {
         ConfigurationManager.init();
+        try {
+            ConfigurationManager.registerConfig(LibraryConfig.class);
+        } catch (ConfigException ex) {
+            getLog().error("Failed to register " + Tags.MODNAME + " config!", ex);
+        }
+    }
+
+    @Subscribe
+    public void postInit(FMLPostInitializationEvent e) {
+
     }
 
     @SuppressWarnings("UnstableApiUsage")

src/main/java/com/falsepattern/lib/internal/LibraryConfig.java

@@ -0,0 +1,18 @@
+package com.falsepattern.lib.internal;
+
+import com.falsepattern.lib.config.Config;
+
+@Config(modid = Tags.MODID)
+public class LibraryConfig {
+    @Config.Comment({"Used to control whether FalsePatternLib should check for outdated mods.",
+                    "If you're building a public modpack, you should turn this off so that your users don't " +
+                    "get nagged about outdated mods."})
+    @Config.LangKey("config.falsepatternlib.updatecheck")
+    public static boolean ENABLE_UPDATE_CHECKER = true;
+
+    @Config.Comment({"Used to control whether FalsePatternLib should be allowed to use the internet.",
+                    "If this is enabled, library downloads will be blocked.",
+                    "Note that if a mod tries to download a library that is not downloaded yet, the game will crash."})
+    @Config.LangKey("config.falsepatternlib.disableinternet")
+    public static boolean ENABLE_LIBRARY_DOWNLOADS = true;
+}

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

@@ -0,0 +1,11 @@
+package com.falsepattern.lib.updates;
+
+import lombok.Data;
+
+@Data
+public class ModUpdateInfo {
+    public final String modID;
+    public final String currentVersion;
+    public final String latestVersion;
+    public final String updateURL;
+}

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;
+    }
+}