package ij.plugin;
import ij.*;
import ij.plugin.frame.Editor;
import javax.script.*;

/** Implements the macro editor's Macros/Evaluate JavaScript command 
    on systems running Java 1.6 or later. The JavaScript plugin at
    
    is used to evaluate JavaScript on systems running versions
    of Java earlier than 1.6. */
public class JavaScriptEvaluator implements PlugIn, Runnable  {
	private Thread thread;
	private String script;
	private Object result;

	// run script in separate thread
	public void run(String script) {
		if (script.equals("")) return;
		if (!IJ.isJava16()) {
			IJ.error("Java 1.6 or later required");
			return;
		}
		this.script = script;
		thread = new Thread(this, "JavaScript"); 
		thread.setPriority(Math.max(thread.getPriority()-2, Thread.MIN_PRIORITY));
		thread.start();
	}

	// run script in current thread
	public String run(String script, String arg) {
		this.script = script;
		run();
		return null;
	}

	public void run() {
		result = null;
		Thread.currentThread().setContextClassLoader(IJ.getClassLoader());
		if (IJ.isJava19())
			System.setProperty("nashorn.args", "--language=es6"); // Use ECMAScript 6 on Java 9
		try {
			ScriptEngineManager scriptEngineManager = new ScriptEngineManager();
			ScriptEngine engine = scriptEngineManager.getEngineByName("ECMAScript");
			if (engine == null) {
				IJ.error("Could not find JavaScript engine");
				return;
			}
			if (!IJ.isJava18()) {
				engine.eval("function load(path) {\n"
					+ "  importClass(Packages.sun.org.mozilla.javascript.internal.Context);\n"
					+ "  importClass(Packages.java.io.FileReader);\n"
					+ "  var cx = Context.getCurrentContext();\n"
					+ "  cx.evaluateReader(this, new FileReader(path), path, 1, null);\n"
					+ "}");
			}
			result = engine.eval(script);
		} catch(Throwable e) {
			String msg = e.getMessage();
			if (msg==null)
				msg = "";
			if (msg.startsWith("sun.org.mozilla.javascript.internal.EcmaError: "))
				msg = msg.substring(47, msg.length());
			if (msg.startsWith("sun.org.mozilla.javascript.internal.EvaluatorException"))
				msg = "Error"+msg.substring(54, msg.length());
			if (msg.length()>0 && !msg.contains("Macro canceled"))
				IJ.log(msg);
		}
	}
	
	public String toString() {
		return result!=null?""+result:"";
	}

}