Disable buttons on the interface if a skin server doesn't support/permit that particular functionality

src/hdskins/java/com/minelittlepony/gui/Button.java

@@ -36,8 +36,14 @@ public class Button extends GuiButton implements IActionable, IGuiTooltipped<But
         return this;
     }
 
+    protected List<String> getTooltip() {
+        return tooltip;
+    }
+
     @Override
     public void renderToolTip(Minecraft mc, int mouseX, int mouseY) {
+        List<String> tooltip = getTooltip();
+
         if (visible && isMouseOver() && tooltip != null) {
             mc.currentScreen.drawHoveringText(tooltip, mouseX + tipX, mouseY + tipY);
         }

src/hdskins/java/com/voxelmodpack/hdskins/SkinUploader.java

@@ -15,6 +15,7 @@ import com.mojang.authlib.minecraft.MinecraftProfileTexture;
 import com.mojang.authlib.minecraft.MinecraftProfileTexture.Type;
 import com.mumfrey.liteloader.util.log.LiteLoaderLogger;
 import com.voxelmodpack.hdskins.gui.EntityPlayerModel;
+import com.voxelmodpack.hdskins.gui.Feature;
 import com.voxelmodpack.hdskins.resources.PreviewTextureManager;
 import com.voxelmodpack.hdskins.server.SkinServer;
 import com.voxelmodpack.hdskins.server.SkinUpload;
@@ -102,6 +103,10 @@ public class SkinUploader implements Closeable {
         return gateway == null ? "" : gateway.toString();
     }
 
+    public boolean supportsFeature(Feature feature) {
+        return gateway != null && gateway.supportsFeature(feature);
+    }
+
     protected void setError(String er) {
         status = er;
         sendingSkin = false;

src/hdskins/java/com/voxelmodpack/hdskins/gui/Feature.java

@@ -0,0 +1,50 @@
+package com.voxelmodpack.hdskins.gui;
+
+/**
+ * Represents the possible features that a skin server can implement.
+ */
+public enum Feature {
+    /**
+     * Whether a server has write access.
+     * i.e. If the server allows for users to upload a new skin.
+     */
+    UPLOAD_USER_SKIN,
+    /**
+     * Whether a server allows for downloading and saving a user's skin.
+     * Most servers should support this.
+     */
+    DOWNLOAD_USER_SKIN,
+    /**
+     * Whether a server has delete access.
+     * i.e. If the server allows a user to deleted a previously uploaded skin.
+     */
+    DELETE_USER_SKIN,
+    /**
+     * Whether a server can send a full list of skins for a given profile.
+     * Typically used for servers that keep a record of past uploads
+     * and/or allow for switching between past skins.
+     */
+    FETCH_SKIN_LIST,
+    /**
+     * Whether a server supports thin (Alex) skins or just default (Steve) skins.
+     * Servers without this will typically fall back to using the player's uuid on the client side.
+     *
+     * (unused)
+     */
+    MODEL_VARIANTS,
+    /**
+     * Whether a server allows for uploading alternative skin types. i.e. Cape, Elytra, Hats and wears.
+     */
+    MODEL_TYPES,
+    /**
+     * Whether a server will accept arbitrary extra metadata values with skin uploads.
+     *
+     * (unused)
+     */
+    MODEL_METADATA,
+    /**
+     * Whether a server can provide a link to view a user's profile online,
+     * typically through a web-portal.
+     */
+    LINK_PROFILE
+}

src/hdskins/java/com/voxelmodpack/hdskins/gui/GuiSkins.java

@@ -1,7 +1,9 @@
 package com.voxelmodpack.hdskins.gui;
 
+import com.google.common.base.Splitter;
 import com.minelittlepony.gui.Button;
 import com.minelittlepony.gui.GameGui;
+import com.minelittlepony.gui.IGuiAction;
 import com.minelittlepony.gui.IconicButton;
 import com.minelittlepony.gui.IconicToggle;
 import com.minelittlepony.gui.Label;
@@ -44,15 +46,15 @@ public class GuiSkins extends GameGui implements ISkinUploadHandler {
     private int updateCounter = 0;
 
     private Button btnBrowse;
-    private Button btnUpload;
-    private Button btnDownload;
-    private Button btnClear;
+    private FeatureButton btnUpload;
+    private FeatureButton btnDownload;
+    private FeatureButton btnClear;
 
-    private Button btnModeSteve;
-    private Button btnModeAlex;
+    private FeatureSwitch btnModeSteve;
+    private FeatureSwitch btnModeAlex;
 
-    private Button btnModeSkin;
-    private Button btnModeElytra;
+    private FeatureSwitch btnModeSkin;
+    private FeatureSwitch btnModeElytra;
 
     protected EntityPlayerModel localPlayer;
     protected EntityPlayerModel remotePlayer;
@@ -148,21 +150,21 @@ public class GuiSkins extends GameGui implements ISkinUploadHandler {
                     chooser.openBrowsePNG(mc, format("hdskins.open.title"))))
                 .setEnabled(!mc.isFullScreen());
 
-        addButton(btnUpload = new Button(width / 2 - 24, height / 2 - 20, 48, 20, "hdskins.options.chevy", sender -> {
+        addButton(btnUpload = new FeatureButton(width / 2 - 24, height / 2 - 20, 48, 20, "hdskins.options.chevy", sender -> {
             if (uploader.canUpload()) {
                 punchServer("hdskins.upload");
             }
         })).setEnabled(uploader.canUpload())
                 .setTooltip("hdskins.options.chevy.title");
 
-        addButton(btnDownload = new Button(width / 2 - 24, height / 2 + 20, 48, 20, "hdskins.options.download", sender -> {
+        addButton(btnDownload = new FeatureButton(width / 2 - 24, height / 2 + 20, 48, 20, "hdskins.options.download", sender -> {
             if (uploader.canClear()) {
                 chooser.openSavePNG(mc, format("hdskins.save.title"));
             }
         })).setEnabled(uploader.canClear())
                 .setTooltip("hdskins.options.download.title");
 
-        addButton(btnClear = new Button(width / 2 + 60, height - 27, 90, 20, "hdskins.options.clear", sender -> {
+        addButton(btnClear = new FeatureButton(width / 2 + 60, height - 27, 90, 20, "hdskins.options.clear", sender -> {
             if (uploader.canClear()) {
                 punchServer("hdskins.request");
             }
@@ -171,26 +173,26 @@ public class GuiSkins extends GameGui implements ISkinUploadHandler {
         addButton(new Button(width / 2 - 50, height - 25, 100, 20, "hdskins.options.close", sender ->
                     mc.displayGuiScreen(new GuiMainMenu())));
 
-        addButton(btnModeSteve = new IconicButton(width - 25, 32, sender -> switchSkinMode("default"))
-                .setIcon(new ItemStack(Items.LEATHER_LEGGINGS), 0x3c5dcb))
+        addButton(btnModeSteve = new FeatureSwitch(width - 25, 32, sender -> switchSkinMode("default")))
+                .setIcon(new ItemStack(Items.LEATHER_LEGGINGS), 0x3c5dcb)
                 .setEnabled("slim".equals(uploader.getMetadataField("model")))
                 .setTooltip("hdskins.mode.steve")
                 .setTooltipOffset(0, 10);
 
-        addButton(btnModeAlex = new IconicButton(width - 25, 51, sender -> switchSkinMode("slim"))
-                .setIcon(new ItemStack(Items.LEATHER_LEGGINGS), 0xfff500))
+        addButton(btnModeAlex = new FeatureSwitch(width - 25, 51, sender -> switchSkinMode("slim")))
+                .setIcon(new ItemStack(Items.LEATHER_LEGGINGS), 0xfff500)
                 .setEnabled("default".equals(uploader.getMetadataField("model")))
                 .setTooltip("hdskins.mode.alex")
                 .setTooltipOffset(0, 10);
 
-        addButton(btnModeSkin = new IconicButton(width - 25, 75, sender -> uploader.setSkinType(Type.SKIN))
-                .setIcon(new ItemStack(Items.LEATHER_CHESTPLATE)))
+        addButton(btnModeSkin = new FeatureSwitch(width - 25, 75, sender -> uploader.setSkinType(Type.SKIN)))
+                .setIcon(new ItemStack(Items.LEATHER_CHESTPLATE))
                 .setEnabled(uploader.getSkinType() == Type.ELYTRA)
                 .setTooltip(format("hdskins.mode.skin", toTitleCase(Type.SKIN.name())))
                 .setTooltipOffset(0, 10);
 
-        addButton(btnModeElytra = new IconicButton(width - 25, 94, sender -> uploader.setSkinType(Type.ELYTRA))
-                .setIcon(new ItemStack(Items.ELYTRA)))
+        addButton(btnModeElytra = new FeatureSwitch(width - 25, 94, sender -> uploader.setSkinType(Type.ELYTRA)))
+                .setIcon(new ItemStack(Items.ELYTRA))
                 .setEnabled(uploader.getSkinType() == Type.SKIN)
                 .setTooltip(format("hdskins.mode.skin", toTitleCase(Type.ELYTRA.name())))
                 .setTooltipOffset(0, 10);
@@ -506,8 +508,85 @@ public class GuiSkins extends GameGui implements ISkinUploadHandler {
 
     private void updateButtons() {
         btnClear.enabled = uploader.canClear();
-        btnUpload.enabled = uploader.canUpload();
+        btnUpload.enabled = uploader.canUpload() && uploader.supportsFeature(Feature.UPLOAD_USER_SKIN);
         btnDownload.enabled = uploader.canClear() && !chooser.pickingInProgress();
         btnBrowse.enabled = !chooser.pickingInProgress();
+
+        boolean types = !uploader.supportsFeature(Feature.MODEL_TYPES);
+        boolean variants = !uploader.supportsFeature(Feature.MODEL_VARIANTS);
+
+        btnModeSkin.setLocked(types);
+        btnModeElytra.setLocked(types);
+
+        btnModeSteve.setLocked(variants);
+        btnModeAlex.setLocked(variants);
+
+        btnClear.setLocked(!uploader.supportsFeature(Feature.DELETE_USER_SKIN));
+        btnUpload.setLocked(!uploader.supportsFeature(Feature.UPLOAD_USER_SKIN));
+        btnDownload.setLocked(!uploader.supportsFeature(Feature.DOWNLOAD_USER_SKIN));
+    }
+
+    protected class FeatureButton extends Button {
+        private List<String> disabledTooltip = Splitter.onPattern("\r?\n|\\\\n").splitToList(format("hdskins.warning.disabled.description"));
+
+        protected boolean locked;
+
+        public FeatureButton(int x, int y, int width, int height, String label, IGuiAction<? extends Button> callback) {
+            super(x, y, width, height, label, callback);
+        }
+
+        @Override
+        protected List<String> getTooltip() {
+            if (locked) {
+                return disabledTooltip;
+            }
+            return super.getTooltip();
+        }
+
+        @Override
+        public Button setTooltip(String tooltip) {
+            disabledTooltip = Splitter.onPattern("\r?\n|\\\\n").splitToList(
+                    format("hdskins.warning.disabled.title",
+                    format(tooltip),
+                    format("hdskins.warning.disabled.description")));
+            return super.setTooltip(tooltip);
+        }
+
+        public void setLocked(boolean lock) {
+            locked = lock;
+            enabled &= !lock;
+        }
+    }
+
+    protected class FeatureSwitch extends IconicButton {
+        private List<String> disabledTooltip = null;
+
+        protected boolean locked;
+
+        public FeatureSwitch(int x, int y, IGuiAction<? extends IconicButton> callback) {
+            super(x, y, callback);
+        }
+
+        @Override
+        protected List<String> getTooltip() {
+            if (locked) {
+                return disabledTooltip;
+            }
+            return super.getTooltip();
+        }
+
+        @Override
+        public Button setTooltip(String tooltip) {
+            disabledTooltip = Splitter.onPattern("\r?\n|\\\\n").splitToList(
+                    format("hdskins.warning.disabled.title",
+                    format(tooltip),
+                    format("hdskins.warning.disabled.description")));
+            return super.setTooltip(tooltip);
+        }
+
+        public void setLocked(boolean lock) {
+            locked = lock;
+            enabled &= !lock;
+        }
     }
 }

src/hdskins/java/com/voxelmodpack/hdskins/server/BethlehemSkinServer.java

@@ -7,6 +7,7 @@ import com.mojang.authlib.GameProfile;
 import com.mojang.authlib.exceptions.AuthenticationException;
 import com.mojang.authlib.yggdrasil.response.MinecraftTexturesPayload;
 import com.mojang.util.UUIDTypeAdapter;
+import com.voxelmodpack.hdskins.gui.Feature;
 import com.voxelmodpack.hdskins.util.IndentedToStringStyle;
 import com.voxelmodpack.hdskins.util.MoreHttpResponses;
 import com.voxelmodpack.hdskins.util.NetClient;
@@ -84,4 +85,17 @@ public class BethlehemSkinServer implements SkinServer {
                 .append("address", address)
                 .build();
     }
+
+    @Override
+    public boolean supportsFeature(Feature feature) {
+        switch (feature) {
+            case DOWNLOAD_USER_SKIN:
+            case UPLOAD_USER_SKIN:
+            case MODEL_VARIANTS:
+            case MODEL_TYPES:
+            case LINK_PROFILE:
+                return true;
+            default: return false;
+        }
+    }
 }

src/hdskins/java/com/voxelmodpack/hdskins/server/LegacySkinServer.java

@@ -10,6 +10,7 @@ import com.mojang.authlib.minecraft.MinecraftProfileTexture;
 import com.mojang.authlib.yggdrasil.response.MinecraftTexturesPayload;
 import com.mojang.util.UUIDTypeAdapter;
 import com.voxelmodpack.hdskins.HDSkinManager;
+import com.voxelmodpack.hdskins.gui.Feature;
 import com.voxelmodpack.hdskins.util.CallableFutures;
 import com.voxelmodpack.hdskins.util.IndentedToStringStyle;
 import com.voxelmodpack.hdskins.util.MoreHttpResponses;
@@ -164,6 +165,17 @@ public class LegacySkinServer implements SkinServer {
         return !Strings.isNullOrEmpty(gateway);
     }
 
+    @Override
+    public boolean supportsFeature(Feature feature) {
+        switch (feature) {
+            case DOWNLOAD_USER_SKIN:
+            case UPLOAD_USER_SKIN:
+            case DELETE_USER_SKIN:
+                return true;
+            default: return false;
+        }
+    }
+
     @Override
     public String toString() {
         return new IndentedToStringStyle.Builder(this)

src/hdskins/java/com/voxelmodpack/hdskins/server/ServerType.java

@@ -5,6 +5,14 @@ import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 
+/**
+ * The remote server API level that this skin server implements.
+ *
+ * Current values are:
+ *  - legacy
+ *  - valhalla
+ *  - bethlehem
+ */
 @Target(ElementType.TYPE)
 @Retention(RetentionPolicy.RUNTIME)
 public @interface ServerType {

src/hdskins/java/com/voxelmodpack/hdskins/server/SkinServer.java

@@ -10,6 +10,7 @@ import com.mojang.authlib.yggdrasil.response.MinecraftTexturesPayload;
 import com.mojang.util.UUIDTypeAdapter;
 import com.mumfrey.liteloader.modconfig.Exposable;
 import com.voxelmodpack.hdskins.HDSkinManager;
+import com.voxelmodpack.hdskins.gui.Feature;
 import com.voxelmodpack.hdskins.util.CallableFutures;
 import net.minecraft.client.Minecraft;
 import net.minecraft.util.Session;
@@ -30,22 +31,67 @@ public interface SkinServer extends Exposable {
             "http://skinmanager.voxelmodpack.com")
     );
 
+    /**
+     * Returns true for any features that this skin server supports.
+     */
+    boolean supportsFeature(Feature feature);
+
+    /**
+     * Synchronously loads texture information for the provided profile.
+     *
+     * @return The parsed server response as a textures payload.
+     *
+     * @throws IOException  If any authenticaiton or network error occurs.
+     */
     MinecraftTexturesPayload loadProfileData(GameProfile profile) throws IOException;
 
+    /**
+     * Synchronously uploads a skin to this server.
+     *
+     * @param upload The payload to send.
+     *
+     * @return A server response object.
+     *
+     * @throws IOException
+     * @throws AuthenticationException
+     */
     SkinUploadResponse performSkinUpload(SkinUpload upload) throws IOException, AuthenticationException;
 
+    /**
+     * Asynchronously uploads a skin to the server.
+     *
+     * Returns an incomplete future for chaining other actions to be performed after this method completes.
+     * Actions are dispatched to the default skinUploadExecutor
+     *
+     * @param upload The payload to send.
+     */
     default CompletableFuture<SkinUploadResponse> uploadSkin(SkinUpload upload) {
         return CallableFutures.asyncFailableFuture(() -> performSkinUpload(upload), HDSkinManager.skinUploadExecutor);
     }
 
+    /**
+     * Asynchronously loads texture information for the provided profile.
+     *
+     * Returns an incomplete future for chaining other actions to be performed after this method completes.
+     * Actions are dispatched to the default skinDownloadExecutor
+     */
     default CompletableFuture<MinecraftTexturesPayload> getPreviewTextures(GameProfile profile) {
         return CallableFutures.asyncFailableFuture(() -> loadProfileData(profile), HDSkinManager.skinDownloadExecutor);
     }
 
+    /**
+     * Called to validate this skin server's state.
+     * Any servers with an invalid gateway format will not be loaded and generate an exception.
+     */
     default boolean verifyGateway() {
         return true;
     }
 
+    /**
+     * Joins with the Mojang API to verify the current user's session.
+
+     * @throws AuthenticationException if authentication failed or the session is invalid.
+     */
     static void verifyServerConnection(Session session, String serverId) throws AuthenticationException {
         MinecraftSessionService service = Minecraft.getMinecraft().getSessionService();
         service.joinServer(session.getProfile(), session.getToken(), serverId);

src/hdskins/java/com/voxelmodpack/hdskins/server/ValhallaSkinServer.java

@@ -8,6 +8,7 @@ import com.mojang.authlib.minecraft.MinecraftProfileTexture;
 import com.mojang.authlib.yggdrasil.response.MinecraftTexturesPayload;
 import com.mojang.util.UUIDTypeAdapter;
 import com.voxelmodpack.hdskins.HDSkinManager;
+import com.voxelmodpack.hdskins.gui.Feature;
 import com.voxelmodpack.hdskins.util.IndentedToStringStyle;
 import com.voxelmodpack.hdskins.util.MoreHttpResponses;
 import net.minecraft.client.Minecraft;
@@ -176,6 +177,19 @@ public class ValhallaSkinServer implements SkinServer {
         return URI.create(String.format("%s/auth/response", this.address));
     }
 
+    @Override
+    public boolean supportsFeature(Feature feature) {
+        switch (feature) {
+            case DOWNLOAD_USER_SKIN:
+            case UPLOAD_USER_SKIN:
+            case DELETE_USER_SKIN:
+            case MODEL_VARIANTS:
+            case MODEL_TYPES:
+                return true;
+            default: return false;
+        }
+    }
+
     @Override
     public String toString() {
         return new IndentedToStringStyle.Builder(this)

src/hdskins/resources/assets/hdskins/lang/en_us.lang

@@ -25,7 +25,7 @@ hdskins.server=Server Skin
 hdskins.mode.steve=Steve Model
 hdskins.mode.alex=Alex Model
 
-hdskins.mode.skin=%s
+hdskins.mode.skin=%s Texture
 
 hdskins.mode.stand=Standing
 hdskins.mode.sleep=Sleeping
@@ -43,4 +43,6 @@ hdskins.options.browse=Browse
 hdskins.options.skindrops=Experimental Skin Drop
 hdskins.options.cache=Clear Skin Cache
 
-hdskins.warning.experimental=§6WARNING: This feature is §4experimental§6, meaning things may break or derp or even slurp. Enabling this means you accept responsibility for what may happen to your chickens.
+hdskins.warning.experimental=§6WARNING: This feature is §4experimental§6, meaning things may break or derp or even slurp. Enabling this means you accept responsibility for what may happen to your chickens.
+hdskins.warning.disabled.title=§c%s %s
+hdskins.warning.disabled.description=§4(DISABLED)\n§7This feature is not supported by your current skin server.\n§7Please choose a different one to proceed.