package com.github.mygreen.supercsv.expression;
   
   import java.util.Map;
   import java.util.Objects;
   
   import org.apache.commons.jexl2.Expression;
   import org.apache.commons.jexl2.JexlEngine;
   import org.apache.commons.jexl2.MapContext;
   import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  
  /**
   * 式言語<a href="http://commons.apache.org/proper/commons-jexl/" target="_blank">JEXL(Java Expression Language)</a>の実装。
   * <p>利用する際には、JEXL2.1のライブラリが必要です。
   *
   * @version 2.3
   * @since 2.0
   * @author T.TSUCHIE
   *
   */
  public class ExpressionLanguageJEXLImpl implements ExpressionLanguage {
      
      private static final Logger logger = LoggerFactory.getLogger(ExpressionLanguageJEXLImpl.class);
      
      private final JexlEngine jexlEngine;
      
      private final ObjectCache<String, Expression> expressionCache = new ObjectCache<>();
      
      public ExpressionLanguageJEXLImpl() {
          JexlEngine engine = new JexlEngine();
          engine.setSilent(true);
          this.jexlEngine = engine;
      }
      
      /**
       * {@link JexlEngine}を指定するコンストラクタ。
       * @param jexlEngine JEXLの処理エンジン。
       */
      public ExpressionLanguageJEXLImpl(final JexlEngine jexlEngine) {
          this.jexlEngine = jexlEngine;
      }
      
      @Override
      public Object evaluate(final String expression, final Map<String, Object> values) {
          
          Objects.requireNonNull(expression, "expression shoud not be null.");
          Objects.requireNonNull(values, "values shoud not be null.");
          
          if(logger.isDebugEnabled()) {
              logger.debug("Evaluating JEXL expression: {}", expression);
          }
          
          try {
              Expression expr = expressionCache.get(expression);
              if (expr == null) {
                  expr = jexlEngine.createExpression(expression);
                  expressionCache.put(expression, expr);
              }
              
              return expr.evaluate(new MapContext((Map<String, Object>) values));
              
          } catch(Exception ex) {
              throw new ExpressionEvaluationException(String.format("Evaluating [%s] script with JEXL failed.", expression), ex,
                      expression, values);
          }
      }
      
      /**
       * {@link JexlEngine}を取得する。
       * @return
       */
      public JexlEngine getJexlEngine() {
          return jexlEngine;
      }
      
  }