package de.retest.recheck.ignore;

import java.io.IOException;
import java.io.Reader;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;

import javax.script.Invocable;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import de.retest.recheck.ui.descriptors.Element;
import de.retest.recheck.ui.diff.AttributeDifference;

public class JSShouldIgnoreImpl implements ShouldIgnore {

	private static final Logger logger = LoggerFactory.getLogger( JSShouldIgnoreImpl.class );

	private static final String JS_ENGINE_NAME = "JavaScript";

	private final ScriptEngine engine;

	public JSShouldIgnoreImpl( final Path ignoreFilePath ) {
		final ScriptEngineManager manager = new ScriptEngineManager();
		engine = manager.getEngineByName( JS_ENGINE_NAME );
		try {
			engine.eval( readScriptFile( ignoreFilePath ) );
		} catch ( final ScriptException e ) {
			throw new IllegalArgumentException( e );
		}
	}

	Reader readScriptFile( final Path ignoreFilePath ) {
		try {
			return Files.newBufferedReader( ignoreFilePath, StandardCharsets.UTF_8 );
		} catch ( final IOException e ) {
			throw new IllegalArgumentException( e );
		}
	}

	@Override
	public boolean shouldIgnoreElement( final Element element ) {
		return callBooleanJSFunction( "shouldIgnoreElement", element );
	}

	@Override
	public boolean shouldIgnoreAttributeDifference( final Element element,
			final AttributeDifference attributeDifference ) {
		return callBooleanJSFunction( "shouldIgnoreAttributeDifference", element, attributeDifference );
	}

	private boolean callBooleanJSFunction( final String functionName, final Object... args ) {
		final Invocable inv = (Invocable) engine;
		// call function from script file
		try {
			final Object callResult = inv.invokeFunction( functionName, args );
			if ( callResult == null ) {
				logger.warn( "{} returned 'null' instead of a boolean value. Interpreting that as 'false'.",
						functionName );
				return false;
			}
			if ( !(callResult instanceof Boolean) ) {
				throw new ClassCastException( "'" + callResult + "' of type " + callResult.getClass()
						+ " cannot be cast to java.lang.Boolean." );
			}
			return (boolean) callResult;
		} catch ( final ScriptException e ) {
			throw new IllegalArgumentException( "JS `" + functionName + "` method caused an exception: ", e );
		} catch ( final NoSuchMethodException e ) {
			logger.warn( "Specified JS ignore file has no '{}' function.", functionName );
		}
		return false;
	}
}

@@ -1123,16 +1123,91 @@
 %09%09try %7B%0A
+%09%09%09logger.info( %22Reading JS ignore rules file from %7B%7D.%22, ignoreFilePath );%0A
 %09%09%09retur

Improve logging, so we know which js file is actually used