package com.nailabs.abac.process;

import edu.stanford.peer.rbtm.credential.*;

public class AckFact {

    /**
     * This attribute defines the scope of the AckFact instance.
     */
    protected EntityExpression attribute;

    /**
     * Optional string meta-identifier for the value field.
     */
    protected String field;

    /**
     * Optional value corresponding to the named field.
     */
    protected Object value;

    /**
     * The credential role required to match with the requesting subject.
     */
    protected EntityExpression requirement;
    
    /**
     * A constant to represent a default value (aka a wildcard).
     */
    static final String DEFAULT = "default";

    /**
     * A true constant for denoting that no requirements are necessary. 
     * This can also be implicitly represented as a null requirement.
     */
    static final String TRUE = "true";

    /**
     * Basic constructor method. This method subtitutes a default key-value
     * pair.
     */
    public AckFact(EntityExpression attribute, EntityExpression req) {
	this(attribute, DEFAULT, DEFAULT, req);
    }

    /**
     * Explicit constructor method. This represents a fully expanded policy
     * fact.
     */
    public AckFact(EntityExpression attr,String key,Object val,EntityExpression req) {
	attribute = attr;
	field = key;
	value = val;
	requirement = req;
    }


    /**
     * An accessor method for the attribute which needs to be unlocked. 
     * <B> This is private policy information and should not be xmitted </B>
     */
    public RoleName getAttribute() { 
        if(attribute instanceof Role) {
            return ((Role)attribute).getName(); 
        }
        else if(attribute instanceof LinkedRole) {        
            return ((LinkedRole)attribute).getFirstRole().getName();
        }
        else {
            return null;
        }
    }

    /**
     * An accessor method for the optional special case meta-type.
     * <B> This is private policy information and should not be xmitted </B>
     */
    public String getField() { return field; }

    /**
     * An accessor method for the optional special case value.
     * <B> This is private policy information and should not be xmitted </B>
     */
    public Object getValue() { return value; }

    /**
     * An accessor method for an expression which can unlocked the attribute
     * if the expression is proved to be true.
     * <B> This is public policy information but if transmitted may indicate
     * that particular credential is possessed.</B>
     */
    public EntityExpression getRequirement() { return requirement; }

    /**
     * Unique hash function, which is based on the attribute's hash code.
     */
    public int hashCode() { return attribute.hashCode(); }

    /** 
     * Tabular printout of the fact in the following order: attribute,
     * field, value, and attribute expression. The list is comma delimited.
     */
    public String toString() {
	StringBuffer buff = new StringBuffer("[AckFact ");
	String separator = ", ";
	buff.append(attribute).append(separator);
	buff.append(field).append(separator);
	buff.append(value).append(separator);
	buff.append(requirement).append("]");
	return buff.toString();
    }

}