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package org.apache.taglibs.standard.lang.jstl;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

/**
 *
 * <p>Represents a function call.</p>
 * 
 * @author Shawn Bayern (in the style of Nathan's other classes)
 **/

public class FunctionInvocation
  extends Expression
{
  //-------------------------------------
  // Properties
  //-------------------------------------
  // property index

  private String functionName;
  private List argumentList;
  public String getFunctionName() { return functionName; }
  public void setFunctionName(String f) { functionName = f; }
  public List getArgumentList() { return argumentList; }
  public void setArgumentList(List l) { argumentList = l; }

  //-------------------------------------
  /**
   * Constructor
   **/
  public FunctionInvocation (String functionName, List argumentList)
  {
    this.functionName = functionName;
    this.argumentList = argumentList;
  }

  //-------------------------------------
  // Expression methods
  //-------------------------------------
  /**
   * Returns the expression in the expression language syntax
   **/
  public String getExpressionString ()
  {
    StringBuffer b = new StringBuffer();
    b.append(functionName);
    b.append("(");
    Iterator i = argumentList.iterator();
    while (i.hasNext()) {
      b.append(((Expression) i.next()).getExpressionString());
      if (i.hasNext())
        b.append(", ");
    }
    b.append(")");
    return b.toString();
  }


  //-------------------------------------
  /**
   *
   * Evaluates by looking up the name in the VariableResolver
   **/
  public Object evaluate (Object pContext,
                          VariableResolver pResolver,
			  Map functions,
			  String defaultPrefix,
                          Logger pLogger)
    throws ELException
  {

    // if the Map is null, then the function is invalid
    if (functions == null)
      pLogger.logError(Constants.UNKNOWN_FUNCTION, functionName);

    // normalize function name against default prefix
    String functionName = this.functionName;
    if (functionName.indexOf(":") == -1) {
      if (defaultPrefix == null)
        pLogger.logError(Constants.UNKNOWN_FUNCTION, functionName);
      functionName = defaultPrefix + ":" + functionName;
    }

    // ensure that the function's name is mapped
    Method target = (Method) functions.get(functionName);
    if (target == null)
      pLogger.logError(Constants.UNKNOWN_FUNCTION, functionName);

    // ensure that the number of arguments matches the number of parameters
    Class[] params = target.getParameterTypes();
    if (params.length != argumentList.size())
        pLogger.logError(Constants.INAPPROPRIATE_FUNCTION_ARG_COUNT,
                         Integer.valueOf(params.length),
                         Integer.valueOf(argumentList.size()));

    // now, walk through each parameter, evaluating and casting its argument
    Object[] arguments = new Object[argumentList.size()];
    for (int i = 0; i < params.length; i++) {
      // evaluate
      arguments[i] = ((Expression) argumentList.get(i)).evaluate(pContext,
								 pResolver,
								 functions,
								 defaultPrefix,
								 pLogger);
      // coerce
      arguments[i] = Coercions.coerce(arguments[i], params[i], pLogger);
    }

    // finally, invoke the target method, which we know to be static
    try {
      return (target.invoke(null, arguments));
    } catch (InvocationTargetException ex) {
      pLogger.logError(Constants.FUNCTION_INVOCATION_ERROR,
			ex.getTargetException(),
			functionName);
      return null;
    } catch (Exception ex) {
      pLogger.logError(Constants.FUNCTION_INVOCATION_ERROR, ex, functionName);
      return null;
    }
  }

  //-------------------------------------
}