import dynaop.Interceptor;
import dynaop.Invocation;

import java.lang.Package;
import java.lang.reflect.Method;
import java.util.HashMap;

public class CachingInterceptor implements Interceptor
{
  private HashMap cacheMap = new HashMap();

  public Object intercept(Invocation invocation)
    throws Throwable
  {
    Long cacheCode = calculateCacheCode(invocation);

    // Look for method result in cache.
    Object cachedResult = cacheMap.get(cacheCode);
    if (cachedResult != null)
    {
      // Log cache hit.
      String methodName = getFullMethodName(invocation);
      System.out.println("Returning cached result for: " + methodName);

      return cachedResult;
    }

    // Call intercepted method and cache its result.
    Object result = invocation.proceed();
    cacheMap.put(cacheCode, result);

    return result;
  }

  private Long calculateCacheCode(Invocation invocation)
  {
    return new Long(getFullMethodName(invocation).hashCode());
  }

  private static String getFullMethodName(Invocation invocation)
  {
    Method method = invocation.getMethod();
    StringBuffer methodName = new StringBuffer();

    // Add package name.
    Package pkg = method.getDeclaringClass().getPackage();
    if (pkg != null) {
      methodName.append(pkg.getName() + ".");
    }

    // Add class name.
    methodName.append(method.getDeclaringClass().getName());

    // Add method name.
    methodName.append("." + method.getName());

    // Add argument names.
    methodName.append("(");
    Class[] arguments = method.getParameterTypes();
    for (int i = 0; i < arguments.length; i++) {
      if (i > 0) {
      	methodName.append(",");
      }
      methodName.append(arguments[i].getName());
    }
    methodName.append(")");

    return methodName.toString();
  }
}