package org.pojomatic.internal;
   
   import java.util.Collections;
   import java.util.Set;
   
   import org.pojomatic.annotations.DefaultPojomaticPolicy;
   import org.pojomatic.annotations.PojomaticPolicy;
   
   public class PropertyFilter {
    private PropertyFilter() {}
  
    /**
     * Get the roles specified by a property policy and class policy.
     * @param elementPolicy the policy on the property ({@code null} if unspecified)
     * @param classPolicy the policy on the class ({@code null} if unspecified).
     * @return the roles specified by the policies.
     * @throws IllegalArgumentException if both {@code elementPolicy} and {@code classPolicy} are
     * {@code null}.
     */
    public static Set<PropertyRole> getRoles(
      PojomaticPolicy elementPolicy, DefaultPojomaticPolicy classPolicy) {
      if (elementPolicy != null) {
        Set<PropertyRole> roles = elementPolicy.getRoles();
        if (roles == null) { // this will be the case for PojomaticPolicy.DEFAULT
            return classPolicy != null ? classPolicy.getRoles() : PojomaticPolicy.ALL.getRoles();
        }
        else {
          return roles;
        }
      }
      else if(classPolicy != null) {
        return classPolicy.getRoles();
      }
      else {
        return Collections.emptySet();
      }
    }
  }