package org.jscsi.target.settings.entry;

 import org.jscsi.parser.ProtocolDataUnit;

 import org.jscsi.parser.login.LoginStage;

 import org.jscsi.target.connection.stage.fullfeature.TextNegotiationStage;

 import org.jscsi.target.connection.stage.login.LoginOperationalParameterNegotiationStage;

 /**

  * Instances of this class are used by {@link Entry} objects to determine during which circumstances a parameter may be

  * negotiated or declared.

  * <p>

  * The factors to consider are:

  * <ul>

  * <li>the current stage of the connection</li>

  * <li>whether that connection is the leading connection, i.e. the initial connection in the enclosing session.</li>

  * <li>if the <i>key-value</i> pair relating to the parameter was part of the first {@link ProtocolDataUnit} sent over

  * the connection</i>

  * </ul>

  * 

  * @author Andreas Ergenzinger

  */

 public enum Use {

     /**

      * The parameter may be negotiated by a leading connection in the {@link LoginOperationalParameterNegotiationStage}

      * only.

      */

     LEADING_LOPNS,

     /**

      * The parameter may be negotiated by any connection in the {@link LoginOperationalParameterNegotiationStage}.

      */

     LOPNS,

     /**

      * The parameter may be negotiated by any connection in the {@link LoginOperationalParameterNegotiationStage} or in

      * the Full Feature Phase (specifically the {@link TextNegotiationStage}).

      */

     LOPNS_AND_FFP,

     /**

      * The parameter may be negotiated by any connection in the Full Feature Phase (specifically the

      * {@link TextNegotiationStage}).

      */

     FFP,

     /**

      * The parameter may only be declared in the initial {@link ProtocolDataUnit}.

      */

     INITIAL,

     /**

      * The parameter may only be declared in the initial {@link ProtocolDataUnit} or by any PDU sent as part of the

      * {@link TextNegotiationStage} in the Full Feature Phase.

      */

     INITIAL_AND_FFP;

     /**

      * This method can be used for checking if a specified {@link Use} permits negotiating its associated parameter

      * given a situation described by several parameters.

      * 

      * @param use describes the conditions

      * @param loginStage specifies the stage of phase

      * @param leadingConnection <code>true</code> if and only if the connection is the leading connection of its session

      * @param initialPdu <code>true</code> if and only if the {@link ProtocolDataUnit} is the first PDU sent over the

      *            connection

      * @return <code>true</code> if and only if all requirements of the <i>use</i> parameter have been met

      */

     private static boolean checkUse (final Use use, final LoginStage loginStage, final boolean leadingConnection, final boolean initialPdu) {

         switch (use) {

             case LEADING_LOPNS :

                 if (leadingConnection && loginStage == LoginStage.LOGIN_OPERATIONAL_NEGOTIATION) return true;

                 return false;

             case LOPNS :

                 if (loginStage == LoginStage.LOGIN_OPERATIONAL_NEGOTIATION) return true;

                 return false;

             case LOPNS_AND_FFP :

                 if (loginStage == LoginStage.LOGIN_OPERATIONAL_NEGOTIATION || loginStage == LoginStage.FULL_FEATURE_PHASE) return true;

                 return false;

             case FFP :

                 if (loginStage == LoginStage.FULL_FEATURE_PHASE) return true;

                 return false;

             case INITIAL_AND_FFP :

                 if (initialPdu && loginStage == LoginStage.FULL_FEATURE_PHASE) return true;

                 // fall through

             case INITIAL :

                 if (initialPdu && (loginStage == LoginStage.SECURITY_NEGOTIATION || loginStage == LoginStage.LOGIN_OPERATIONAL_NEGOTIATION)) return true;

                 return false;

             default :

                 return false;// unreachable

         }

     }

     /**

      * This method can be used for checking if this {@link Use} instance permits negotiating its associated parameter

      * given a situation described by the passed parameters.

      * 

      * @param loginStage specifies the stage of phase

      * @param leadingConnection <code>true</code> if and only if the connection is the leading connection of its session

      * @param initialPdu <code>true</code> if and only if the {@link ProtocolDataUnit} is the first PDU sent over the

      *            connection

      * @return <code>true</code> if and only if all requirements of this {@link Use} instance have been met

      */

     public boolean checkUse (final LoginStage loginStage, final boolean leadingConnection, final boolean initialPdu) {

         return checkUse(this, loginStage, leadingConnection, initialPdu);

     }

 }