package org.esigate.tags;
   
   import java.io.IOException;
   
   import org.esigate.aggregator.AggregationSyntaxException;
   import org.esigate.parser.Element;
   import org.esigate.parser.ElementType;
   import org.esigate.parser.ParserContext;
   
  class ParamElement implements Element {
      public static final ElementType TYPE = new ElementType() {
  
          @Override
          public boolean isStartTag(String tag) {
              return tag.startsWith("<!--$beginparam$");
          }
  
          @Override
          public boolean isEndTag(String tag) {
              return tag.startsWith("<!--$endparam$");
          }
  
          @Override
          public Element newInstance() {
              return new ParamElement();
          }
  
          @Override
          public boolean isSelfClosing(String tag) {
              return false;
          }
  
      };
  
      private Element parent;
      private boolean valueFound = false;
  
      @Override
      public boolean onError(Exception e, ParserContext ctx) {
          return false;
      }
  
      @Override
      public void onTagEnd(String tag, ParserContext ctx) {
          // Nothing to do
      }
  
      @Override
      public boolean onTagStart(String tag, ParserContext ctx) throws IOException {
          this.parent = ctx.getCurrent();
          String[] parameters = tag.split("\\$");
          if (parameters.length != 4) {
              throw new AggregationSyntaxException("Invalid syntax: " + tag);
          }
          String name = parameters[2];
          TemplateElement templateElement = ctx.findAncestor(TemplateElement.class);
          TemplateRenderer templateRenderer = ctx.findAncestor(TemplateRenderer.class);
          if (templateElement == null || templateElement.isNameMatches()) {
              String value = templateRenderer.getParam(name);
              if (value != null) {
                  parent.characters(value, 0, value.length());
                  valueFound = true;
              }
          }
          return true;
      }
  
      @Override
      public void characters(CharSequence csq, int start, int end) throws IOException {
          if (!valueFound) {
              parent.characters(csq, start, end);
          }
      }
  
  }