Improve the skin fix code

- Spoof 404 instead of keeping original URL.
- Move JsonParseException to the package.
- Pass proxy as null to reduce code duplication.

Signed-off-by: TheKodeToad <TheKodeToad@proton.me>

libraries/launcher/CMakeLists.txt

@@ -23,7 +23,8 @@ set(SRC
     org/prismlauncher/utils/JsonParser.java
     org/prismlauncher/utils/Parameters.java
     org/prismlauncher/utils/ReflectionUtils.java
-    org/prismlauncher/utils/UrlUtils.java
+    org/prismlauncher/utils/url/NullConnection.java
+    org/prismlauncher/utils/url/UrlUtils.java
     org/prismlauncher/utils/logging/Level.java
     org/prismlauncher/utils/logging/Log.java
     net/minecraft/Launcher.java

libraries/launcher/org/prismlauncher/exception/JsonParseException.java

@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: GPL-3.0-only
+/*
+ *  Prism Launcher - Minecraft Launcher
+ *  Copyright (C) 2022 TheKodeToad <TheKodeToad@proton.me>
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, version 3.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  Linking this library statically or dynamically with other modules is
+ *  making a combined work based on this library. Thus, the terms and
+ *  conditions of the GNU General Public License cover the whole
+ *  combination.
+ *
+ *  As a special exception, the copyright holders of this library give
+ *  you permission to link this library with independent modules to
+ *  produce an executable, regardless of the license terms of these
+ *  independent modules, and to copy and distribute the resulting
+ *  executable under terms of your choice, provided that you also meet,
+ *  for each linked independent module, the terms and conditions of the
+ *  license of that module. An independent module is a module which is
+ *  not derived from or based on this library. If you modify this
+ *  library, you may extend this exception to your version of the
+ *  library, but you are not obliged to do so. If you do not wish to do
+ *  so, delete this exception statement from your version.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package org.prismlauncher.exception;
+
+import java.io.IOException;
+
+public class JsonParseException extends IOException {
+
+    private static final long serialVersionUID = 1L;
+
+    public JsonParseException(String message) {
+        super(message);
+    }
+
+}

libraries/launcher/org/prismlauncher/fix/Fixes.java

@@ -45,11 +45,11 @@ public final class Fixes {
 
     private static final Fix[] FIXES = { new SkinFix() };
 
-    public static void apply(Parameters parameters) {
+    public static void apply(Parameters params) {
-        List<String> fixes = parameters.getList("fixes", Collections.<String>emptyList());
+        List<String> fixes = params.getList("fixes", Collections.<String>emptyList());
 
         for (Fix fix : FIXES)
-            if (fixes.contains(fix.getName()) && fix.isApplicable(parameters))
+            if (fixes.contains(fix.getName()) && fix.isApplicable(params))
                 fix.apply();
     }
 

libraries/launcher/org/prismlauncher/fix/skins/Handler.java

@@ -45,61 +45,51 @@ import java.util.Map;
 
 import org.prismlauncher.utils.Base64;
 import org.prismlauncher.utils.JsonParser;
-import org.prismlauncher.utils.UrlUtils;
+import org.prismlauncher.utils.url.NullConnection;
+import org.prismlauncher.utils.url.UrlUtils;
 
 @SuppressWarnings("unchecked")
 final class Handler extends URLStreamHandler {
 
     private URL redirect(URL address) throws IOException {
         String skinOwner = findSkinOwner(address);
-
         if (skinOwner != null)
-            return convertSkin(address, skinOwner);
+            return convert(skinOwner, "SKIN");
 
         String capeOwner = findCapeOwner(address);
-
         if (capeOwner != null)
-            return convertCape(address, capeOwner);
+            return convert(capeOwner, "CAPE");
 
         return address;
     }
 
     @Override
     protected URLConnection openConnection(URL address) throws IOException {
-        address = redirect(address);
+        return openConnection(address, null);
-        return UrlUtils.openHttpConnection(address);
     }
 
     @Override
     protected URLConnection openConnection(URL address, Proxy proxy) throws IOException {
         address = redirect(address);
+
+        if (address == null)
+            return NullConnection.INSTANCE;
+
         return UrlUtils.openHttpConnection(address, proxy);
     }
 
-    private URL convertSkin(URL defaultUrl, String owner) throws IOException {
+    private URL convert(String owner, String name) throws IOException {
         Map<String, Object> textures = getTextures(owner);
 
         if (textures != null) {
-            textures = (Map<String, Object>) textures.get("SKIN");
+            textures = (Map<String, Object>) textures.get(name);
-            return new URL((String) textures.get("url"));
-        }
-
-        return defaultUrl;
-    }
-
-    private URL convertCape(URL defaultUrl, String owner) throws IOException {
-        Map<String, Object> textures = getTextures(owner);
-
-        if (textures != null) {
-            textures = (Map<String, Object>) textures.get("CAPE");
-
             if (textures == null)
-                return defaultUrl;
+                return null;
 
             return new URL((String) textures.get("url"));
         }
 
-        return defaultUrl;
+        return null;
     }
 
     private static Map<String, Object> getTextures(String owner) throws IOException {
@@ -116,6 +106,7 @@ final class Handler extends URLStreamHandler {
                         Map<String, Object> result = (Map<String, Object>) JsonParser
                                 .parse(new String(Base64.decode((String) property.get("value"))));
                         result = (Map<String, Object>) result.get("textures");
+
                         return result;
                     }
                 }
@@ -128,11 +119,11 @@ final class Handler extends URLStreamHandler {
     private static String findSkinOwner(URL address) {
         switch (address.getHost()) {
             case "www.minecraft.net":
-                return stripPng(strip(address.getPath(), "/skin/"));
+                return stripIfPrefixed(address.getPath(), "/skin/");
 
             case "s3.amazonaws.com":
             case "skins.minecraft.net":
-                return stripPng(strip(address.getPath(), "/MinecraftSkins/"));
+                return stripIfPrefixed(address.getPath(), "/MinecraftSkins/");
         }
 
         return null;
@@ -141,26 +132,25 @@ final class Handler extends URLStreamHandler {
     private static String findCapeOwner(URL address) {
         switch (address.getHost()) {
             case "www.minecraft.net":
-                return stripPng(strip(address.getQuery(), "user="));
+                return stripIfPrefixed(address.getQuery(), "user=");
 
             case "s3.amazonaws.com":
             case "skins.minecraft.net":
-                return stripPng(strip(address.getPath(), "/MinecraftCloaks/"));
+                return stripIfPrefixed(address.getPath(), "/MinecraftCloaks/");
         }
 
         return null;
     }
 
-    private static String stripPng(String string) {
+    private static String stripIfPrefixed(String string, String prefix) {
-        if (string != null && string.endsWith(".png"))
+        if (string != null && string.startsWith(prefix)) {
-            return string.substring(0, string.lastIndexOf('.'));
+            string = string.substring(prefix.length());
 
-        return string;
+            if (string.endsWith(".png"))
-    }
+                string = string.substring(0, string.lastIndexOf('.'));
 
-    private static String strip(String string, String prefix) {
+            return string;
-        if (string != null && string.startsWith(prefix))
+        }
-            return string.substring(prefix.length());
 
         return null;
     }

libraries/launcher/org/prismlauncher/fix/skins/SkinFix.java

@@ -41,8 +41,8 @@ import java.net.URLStreamHandlerFactory;
 
 import org.prismlauncher.fix.Fix;
 import org.prismlauncher.utils.Parameters;
-import org.prismlauncher.utils.UrlUtils;
 import org.prismlauncher.utils.logging.Log;
+import org.prismlauncher.utils.url.UrlUtils;
 
 /**
  * Fixes skins by redirecting to other URLs.

libraries/launcher/org/prismlauncher/utils/JsonParser.java

@@ -59,6 +59,8 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
+import org.prismlauncher.exception.JsonParseException;
+
 /**
  * Single-file JSON parser to allow for usage in versions without GSON.
  */
@@ -420,14 +422,4 @@ public final class JsonParser {
         return character() == 'n' && read() == 'u' && read() == 'l' && read() == 'l';
     }
 
-    public static class JsonParseException extends IOException {
-
-        private static final long serialVersionUID = 1L;
-
-        public JsonParseException(String message) {
-            super(message);
-        }
-
-    }
-
 }

libraries/launcher/org/prismlauncher/utils/url/NullConnection.java

@@ -0,0 +1,66 @@
+// SPDX-License-Identifier: GPL-3.0-only
+/*
+ *  Prism Launcher - Minecraft Launcher
+ *  Copyright (C) 2022 TheKodeToad <TheKodeToad@proton.me>
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, version 3.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  Linking this library statically or dynamically with other modules is
+ *  making a combined work based on this library. Thus, the terms and
+ *  conditions of the GNU General Public License cover the whole
+ *  combination.
+ *
+ *  As a special exception, the copyright holders of this library give
+ *  you permission to link this library with independent modules to
+ *  produce an executable, regardless of the license terms of these
+ *  independent modules, and to copy and distribute the resulting
+ *  executable under terms of your choice, provided that you also meet,
+ *  for each linked independent module, the terms and conditions of the
+ *  license of that module. An independent module is a module which is
+ *  not derived from or based on this library. If you modify this
+ *  library, you may extend this exception to your version of the
+ *  library, but you are not obliged to do so. If you do not wish to do
+ *  so, delete this exception statement from your version.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package org.prismlauncher.utils.url;
+
+import java.io.IOException;
+import java.net.HttpURLConnection;
+
+/**
+ * Spoof 404 response from server to avoid unnecessary requests.
+ */
+public final class NullConnection extends HttpURLConnection {
+
+    public static final NullConnection INSTANCE = new NullConnection();
+
+    public NullConnection() {
+        super(null);
+    }
+
+    @Override
+    public void connect() throws IOException {
+        responseCode = 404;
+    }
+
+    @Override
+    public void disconnect() {
+    }
+
+    @Override
+    public boolean usingProxy() {
+        return false;
+    }
+
+}

libraries/launcher/org/prismlauncher/utils/url/UrlUtils.java

@@ -33,7 +33,7 @@
  *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
-package org.prismlauncher.utils;
+package org.prismlauncher.utils.url;
 
 import java.io.IOException;
 import java.lang.invoke.MethodHandle;
@@ -54,7 +54,6 @@ public final class UrlUtils {
 
     private static URLStreamHandler http;
     private static MethodHandle openConnection;
-    private static MethodHandle openConnectionProxied;
 
     static {
         try {
@@ -64,18 +63,10 @@ public final class UrlUtils {
             getURLStreamHandler.setAccessible(true);
             http = (URLStreamHandler) getURLStreamHandler.invoke(null, "http");
 
-            // reflection is required due to not having access
+            Method openConnectionReflect = URLStreamHandler.class.getDeclaredMethod("openConnection", URL.class,
-            // unreflect is used due to the potential frequency of calls
+                    Proxy.class);
-            Method openConnectionReflect = URLStreamHandler.class.getDeclaredMethod("openConnection", URL.class);
             openConnectionReflect.setAccessible(true);
             openConnection = MethodHandles.lookup().unreflect(openConnectionReflect);
-
-            // a second method which takes in a proxy is required for a fully-functional
-            // URLStreamHandler
-            Method openConnectionReflectProxied = URLStreamHandler.class.getDeclaredMethod("openConnection", URL.class,
-                    Proxy.class);
-            openConnectionReflectProxied.setAccessible(true);
-            openConnectionProxied = MethodHandles.lookup().unreflect(openConnectionReflectProxied);
         } catch (Throwable e) {
             Log.error("URL reflection failed - some features may not work", e);
         }
@@ -87,20 +78,16 @@ public final class UrlUtils {
      * @return <code>true</code> if all features can be used
      */
     public static boolean isSupported() {
-        return http != null && openConnection != null && openConnectionProxied != null;
+        return http != null && openConnection != null;
-    }
-
-    public static URLConnection openHttpConnection(URL url) throws IOException {
-        return openConnection(http, url);
     }
 
     public static URLConnection openHttpConnection(URL url, Proxy proxy) throws IOException {
         return openConnection(http, url, proxy);
     }
 
-    public static URLConnection openConnection(URLStreamHandler handler, URL url) throws IOException {
+    public static URLConnection openConnection(URLStreamHandler handler, URL url, Proxy proxy) throws IOException {
         try {
-            return (URLConnection) openConnection.invokeExact(handler, url);
+            return (URLConnection) openConnection.invokeExact(handler, url, proxy);
         } catch (IOException | Error | RuntimeException e) {
             throw e; // rethrow if possible
         } catch (Throwable e) {
@@ -108,14 +95,4 @@ public final class UrlUtils {
         }
     }
 
-    public static URLConnection openConnection(URLStreamHandler handler, URL url, Proxy proxy) throws IOException {
-        try {
-            return (URLConnection) openConnectionProxied.invokeExact(handler, url, proxy);
-        } catch (IOException | Error | RuntimeException e) {
-            throw e;
-        } catch (Throwable e) {
-            throw new Error(e);
-        }
-    }
-
 }