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// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// the License.  You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
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package com.cloud.utils.fsm;

public interface StateListener<S, E, V> {
    /**
     * Event is triggered before state machine transition finished.
     * If you want to get the state of vm before state machine changed, you need to listen on this event
     * @param oldState VM's old state
     * @param event that triggered this VM state change
     * @param newState VM's new state
     * @param vo the VM instance
     * @param opaque host id
     * @param vmDao VM dao
     * @return
     */
    public boolean preStateTransitionEvent(S oldState, E event, S newState, V vo, boolean status, Object opaque);

    /**
     * Event is triggered after state machine transition finished
     * @param oldState VM's old state
     * @param event that triggered this VM state change
     * @param newState VM's new state
     * @param vo the VM instance
     * @param status the state transition is allowed or not
     * @return
     */
    public boolean postStateTransitionEvent(S oldState, E event, S newState, V vo, boolean status, Object opaque);
}
