/*******************************************************************************
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package at.gv.egiz.eaaf.core.impl.idp.process.spring;

import java.util.Objects;

import javax.annotation.PostConstruct;

import org.apache.commons.lang3.BooleanUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.context.expression.BeanFactoryResolver;
import org.springframework.expression.Expression;
import org.springframework.expression.ExpressionParser;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.expression.spel.support.StandardEvaluationContext;

import at.gv.egiz.eaaf.core.api.idp.process.ExpressionEvaluationContext;
import at.gv.egiz.eaaf.core.api.idp.process.ExpressionEvaluator;
import at.gv.egiz.eaaf.core.impl.idp.process.model.Transition;

/**
 * Expression evaluator for processing {@link Transition} conditions allowing to reference Spring beans from the
 * application context.
 * 
 * @author tknall
 * 
 */
public class SpringExpressionEvaluator implements ExpressionEvaluator {

	private Logger log = LoggerFactory.getLogger(getClass());
	private ExpressionParser parser = new SpelExpressionParser();
	private StandardEvaluationContext evaluationContext = new StandardEvaluationContext();

	@Autowired(required = false)
	private ApplicationContext ctx;

	@PostConstruct
	private void init() {
		if (ctx != null) {
			evaluationContext.setBeanResolver(new BeanFactoryResolver(ctx));
		}
	}

	@Override
	public boolean evaluate(ExpressionEvaluationContext expressionContext, String expression) {
		Objects.requireNonNull(expression, "Expression must not be null.");
		log.trace("Evaluating '{}'.", expression);

		Expression expr = parser.parseExpression(expression);
		Boolean result = expr.getValue(evaluationContext, expressionContext, Boolean.class);
		if (result == null) {
			log.warn("Evaluation of '{}' results in null-value.", expression);
		} else {
			log.debug("Expression '{}' -> {}", expression, result);
		}

		return BooleanUtils.isTrue(result);
	}

}