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#// Usage: jjs -fx filebrowser.js -- <start_dir>

// Uses -fx and javafx TreeView to visualize directories
if (!$OPTIONS._fx) {
    print("Usage: jjs -fx filebrowser.js -- <start_dir>");
    exit(1);
}

// Java classes used
var File = Java.type("java.io.File");
var Files = Java.type("java.nio.file.Files");

// check directory argument, if passed
var dir = arguments.length > 0? new File(arguments[0]) : new File(".");
if (! dir.isDirectory()) {
    print(dir + " is not a directory!");
    exit(2);
}

// JavaFX classes used
var FXCollections = Java.type("javafx.collections.FXCollections");
var Scene     = Java.type("javafx.scene.Scene");
var TreeItem  = Java.type("javafx.scene.control.TreeItem");
var TreeView  = Java.type("javafx.scene.control.TreeView");

// create a subclass of JavaFX TreeItem class
var LazyTreeItem = Java.extend(TreeItem);

// lazily filling children of a directory LazyTreeItem
function buildChildren(dir) {
    var children = FXCollections.observableArrayList();
    var stream = Files.list(dir.toPath());
    stream.forEach(function(path) {
        var file = path.toFile();
        var item = file.isDirectory()?
            makeLazyTreeItem(file) : new TreeItem(file.name);
        children.add(item);
    });
    stream.close();
    return children;
}

// create an instance LazyTreeItem with override methods
function makeLazyTreeItem(dir) {
    var item = new LazyTreeItem(dir.name) {
        expanded: false,
        isLeaf: function() false,
        getChildren: function() {
            if (! this.expanded) {
                // call super class (TreeItem) method
                Java.super(item).getChildren().setAll(buildChildren(dir));
                this.expanded = true;
            }
            // call super class (TreeItem) method
            return Java.super(item).getChildren();
        }
    }
    return item;
}

// JavaFX start method
function start(stage) {
    stage.title = dir.absolutePath;
    var rootItem = makeLazyTreeItem(dir);
    rootItem.expanded = true;
    var tree = new TreeView(rootItem);
    stage.scene = new Scene(tree, 300, 450);
    stage.show();
}