Support JNBT string encoding as an option

Fixes #9

gradle/libs.versions.toml

@@ -13,6 +13,7 @@ ikonli-fontawesome5.module = "org.kordamp.ikonli:ikonli-fontawesome5-pack"
 junit-bom = "org.junit:junit-bom:5.10.3"
 junit-jupiter-api.module = "org.junit.jupiter:junit-jupiter-api"
 junit-jupiter-engine.module = "org.junit.jupiter:junit-jupiter-engine"
+junit-jupiter-params.module = "org.junit.jupiter:junit-jupiter-params"
 truth = "com.google.truth:truth:1.4.4"
 
 [libraries.tinylog-api]

gui/src/main/java/org/enginehub/linbus/gui/javafx/MainSceneSetup.java

@@ -47,12 +47,14 @@
 import javafx.stage.Stage;
 import org.enginehub.linbus.gui.LinBusGui;
 import org.enginehub.linbus.gui.util.ErrorReporter;
+import org.enginehub.linbus.stream.LinReadOptions;
 import org.jspecify.annotations.Nullable;
 import org.kordamp.ikonli.fontawesome5.FontAwesomeSolid;
 import org.kordamp.ikonli.javafx.FontIcon;
 
 import java.io.File;
 import java.io.IOException;
+import java.io.UTFDataFormatException;
 import java.nio.file.Path;
 import java.util.Optional;
 import java.util.concurrent.ExecutorService;
@@ -106,28 +108,7 @@ private MenuItem openFile(Stage stage, ExecutorService backgroundExecutor) {
                 return;
             }
             Path path = file.toPath();
-            backgroundExecutor.submit(new Task<TreeItem<NbtTreeView.TagEntry>>() {
-
-                @Override
-                protected TreeItem<NbtTreeView.TagEntry> call() throws Exception {
-                    return NbtTreeView.loadTreeItem(path);
-                }
-
-                @Override
-                protected void succeeded() {
-                    openPath.set(path);
-                    TreeItem<NbtTreeView.TagEntry> value = getValue();
-                    originalTag.set(value.getValue());
-                    treeTableView.setRoot(value);
-                }
-
-                @Override
-                protected void failed() {
-                    ErrorReporter.reportError(
-                        ErrorReporter.Level.INFORM, "Failed to open file " + path, getException()
-                    );
-                }
-            });
+            backgroundExecutor.submit(new LoadTreeItemTask(path, backgroundExecutor, false));
         });
         return openFile;
     }
@@ -239,15 +220,6 @@ private Button moveEntryDown() {
     public final Scene mainScene;
 
     public MainSceneSetup(Stage stage, ExecutorService backgroundExecutor) {
-        openPath.addListener((__, oldPath, newPath) -> {
-            if (newPath != null) {
-                try {
-                    treeTableView.setRoot(NbtTreeView.loadTreeItem(newPath));
-                } catch (IOException e) {
-                    ErrorReporter.reportError(ErrorReporter.Level.INFORM, "Failed to open file " + newPath, e);
-                }
-            }
-        });
         ObservableValue<NbtTreeView.TagEntry> rootTagEntry = treeTableView.rootProperty().flatMap(TreeItem::valueProperty);
         isModified = originalTag.isNotEqualTo(
             // Promote ObservableValue to ObjectBinding
@@ -267,4 +239,65 @@ public MainSceneSetup(Stage stage, ExecutorService backgroundExecutor) {
         VBox.setVgrow(treeTableView, Priority.ALWAYS);
         mainScene = new Scene(mainPane, 900, 600);
     }
+
+    private class LoadTreeItemTask extends Task<TreeItem<NbtTreeView.TagEntry>> {
+
+        private final Path path;
+        private final ExecutorService backgroundExecutor;
+        private final boolean tryingLegacyCompat;
+
+        public LoadTreeItemTask(Path path, ExecutorService backgroundExecutor, boolean tryingLegacyCompat) {
+            this.path = path;
+            this.backgroundExecutor = backgroundExecutor;
+            this.tryingLegacyCompat = tryingLegacyCompat;
+        }
+
+        @Override
+        protected TreeItem<NbtTreeView.TagEntry> call() throws Exception {
+            LinReadOptions.Builder options = LinReadOptions.builder();
+            if (tryingLegacyCompat) {
+                options.allowJnbtStringEncoding(true);
+            }
+            return NbtTreeView.loadTreeItem(path, options.build());
+        }
+
+        @Override
+        protected void succeeded() {
+            TreeItem<NbtTreeView.TagEntry> value = getValue();
+            openPath.set(path);
+            originalTag.set(value.getValue());
+            treeTableView.setRoot(value);
+        }
+
+        @Override
+        protected void failed() {
+            Throwable ex = getException();
+            if (ex instanceof UTFDataFormatException && !tryingLegacyCompat) {
+                Alert alert = createUtfAlert();
+                Optional<ButtonType> result = alert.showAndWait();
+                if (result.isPresent() && result.get() == ButtonType.YES) {
+                    backgroundExecutor.submit(new LoadTreeItemTask(path, backgroundExecutor, true));
+                    return;
+                }
+            }
+            ErrorReporter.reportError(
+                ErrorReporter.Level.INFORM, "Failed to open file " + path, getException()
+            );
+        }
+
+        private static Alert createUtfAlert() {
+            Alert alert = new Alert(Alert.AlertType.WARNING);
+            alert.setTitle(LinBusGui.TITLE_BASE + " - Invalid File");
+            alert.setHeaderText("File contained invalid modified UTF-8");
+            alert.setContentText("The file you tried to open contained invalid modified UTF-8, " +
+                "but may be a legacy JNBT file. Would you like to try opening it with JNBT compatibility?\n" +
+                "Saving the file will convert it to standard NBT format.");
+            alert.getButtonTypes().setAll(
+                ButtonType.YES,
+                ButtonType.NO
+            );
+            return alert;
+        }
+    }
+
 }

gui/src/main/java/org/enginehub/linbus/gui/javafx/NbtTreeView.java

@@ -26,6 +26,7 @@
 import javafx.scene.control.TreeTableRow;
 import javafx.scene.control.TreeTableView;
 import org.enginehub.linbus.stream.LinBinaryIO;
+import org.enginehub.linbus.stream.LinReadOptions;
 import org.enginehub.linbus.tree.LinCompoundTag;
 import org.enginehub.linbus.tree.LinListTag;
 import org.enginehub.linbus.tree.LinRootEntry;
@@ -97,10 +98,10 @@ private static TreeTableColumn<TagEntry, TagEntry> createValueColumn() {
         return valueCol;
     }
 
-    public static TreeItem<TagEntry> loadTreeItem(Path file) throws IOException {
+    public static TreeItem<TagEntry> loadTreeItem(Path file, LinReadOptions options) throws IOException {
         LinRootEntry root;
         try (var dataInput = new DataInputStream(new GZIPInputStream(Files.newInputStream(file)))) {
-            root = LinBinaryIO.readUsing(dataInput, LinRootEntry::readFrom);
+            root = LinBinaryIO.readUsing(dataInput, options, LinRootEntry::readFrom);
         }
         assert root != null;
         return new TagEntryTreeItem(root.name(), root.value());

stream/build.gradle.kts

@@ -12,6 +12,7 @@ dependencies {
 
     testImplementation(platform(libs.junit.bom))
     testImplementation(libs.junit.jupiter.api)
+    testImplementation(libs.junit.jupiter.params)
     testRuntimeOnly(libs.junit.jupiter.engine)
 
     testImplementation(libs.truth) {

stream/src/main/java/org/enginehub/linbus/stream/LinBinaryIO.java

@@ -50,7 +50,22 @@ public class LinBinaryIO {
      * @return the stream of NBT tokens
      */
     public static LinStream read(DataInput input) {
-        return new LinNbtReader(input);
+        return read(input, LinReadOptions.builder().build());
+    }
+
+    /**
+     * Read a stream of NBT tokens from a {@link DataInput}.
+     *
+     * <p>
+     * The input will not be closed by the iterator. The caller is responsible for managing the lifetime of the input.
+     * </p>
+     *
+     * @param input the input to read from
+     * @param options the options for reading
+     * @return the stream of NBT tokens
+     */
+    public static LinStream read(DataInput input, LinReadOptions options) {
+        return new LinNbtReader(input, options);
     }
 
     /**
@@ -71,6 +86,25 @@ public static LinStream read(DataInput input) {
         return transform.apply(read(input));
     }
 
+    /**
+     * Read a result using a stream of NBT tokens from a {@link DataInput}.
+     *
+     * <p>
+     * The input will not be closed by this method. The caller is responsible for managing the lifetime of the input.
+     * </p>
+     *
+     * @param input the input to read from
+     * @param options the options for reading
+     * @param transform the function to transform the stream of NBT tokens into the result
+     * @param <R> the type of the result
+     * @return the result
+     * @throws IOException if an I/O error occurs ({@link UncheckedIOException} is unwrapped)
+     */
+    public static <R extends @Nullable Object> R readUsing(DataInput input, LinReadOptions options, IOFunction<? super LinStream, ? extends R> transform)
+        throws IOException {
+        return transform.apply(read(input, options));
+    }
+
     /**
      * Write a stream of NBT tokens to a {@link DataOutput}.
      *

stream/src/main/java/org/enginehub/linbus/stream/LinReadOptions.java

@@ -0,0 +1,102 @@
+/*
+ * Copyright (c) EngineHub <https://enginehub.org>
+ * Copyright (c) contributors
+ *
+ * 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, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * 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.
+ *
+ * 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.enginehub.linbus.stream;
+
+
+/**
+ * Options for reading NBT streams.
+ */
+public final class LinReadOptions {
+
+    /**
+     * Create a new builder.
+     *
+     * @return a new builder
+     */
+    public static Builder builder() {
+        return new Builder();
+    }
+
+    /**
+     * Builder for {@link LinReadOptions}.
+     */
+    public static final class Builder {
+        private boolean allowJnbtStringEncoding = false;
+
+        private Builder() {
+        }
+
+        /**
+         * Set whether to allow the string encoding used by JNBT. It is not compliant with the NBT specification and
+         * uses normal UTF-8 encoding instead of the modified UTF-8 encoding of {@link java.io.DataInput}.
+         *
+         * <p>
+         * Note that this option will force checking the bytes to select the correct encoding, which will be slower.
+         * </p>
+         *
+         * @param allowJnbtStringEncoding whether to allow the string encoding used by JNBT
+         * @return this builder
+         */
+        public Builder allowJnbtStringEncoding(boolean allowJnbtStringEncoding) {
+            this.allowJnbtStringEncoding = allowJnbtStringEncoding;
+            return this;
+        }
+
+        /**
+         * Build the options.
+         *
+         * @return the options
+         */
+        public LinReadOptions build() {
+            return new LinReadOptions(this);
+        }
+
+        @Override
+        public String toString() {
+            return "LinReadOptions.Builder{" +
+                "allowJnbtStringEncoding=" + allowJnbtStringEncoding +
+                '}';
+        }
+    }
+
+    private final boolean allowJnbtStringEncoding;
+
+    private LinReadOptions(Builder builder) {
+        this.allowJnbtStringEncoding = builder.allowJnbtStringEncoding;
+    }
+
+    /**
+     * {@return whether to allow the string encoding used by JNBT} It is not compliant with the NBT specification and
+     * uses normal UTF-8 encoding instead of the modified UTF-8 encoding of {@link java.io.DataInput}.
+     *
+     * <p>
+     * Note that this option will force checking the bytes to select the correct encoding, which will be slower.
+     * </p>
+     */
+    public boolean allowJnbtStringEncoding() {
+        return allowJnbtStringEncoding;
+    }
+
+    @Override
+    public String toString() {
+        return "LinReadOptions{" +
+            "allowJnbtStringEncoding=" + allowJnbtStringEncoding +
+            '}';
+    }
+}