com.alibaba.cola.statemachine.impl.EventTransitions Maven / Gradle / Ivy

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package com.alibaba.cola.statemachine.impl;

import com.alibaba.cola.statemachine.Transition;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

/**
 * EventTransitions
 *
 * 同一个Event可以触发多个Transitions，https://github.com/alibaba/COLA/pull/158
 *
 * @author Frank Zhang
 * @date 2021-05-28 5:17 PM
 */
public class EventTransitions {
    private HashMap>> eventTransitions;

    public EventTransitions(){
        eventTransitions = new HashMap<>();
    }

    public void put(E event, Transition transition){
        if(eventTransitions.get(event) == null){
            List> transitions = new ArrayList<>();
            transitions.add(transition);
            eventTransitions.put(event, transitions);
        }
        else{
            List existingTransitions = eventTransitions.get(event);
            verify(existingTransitions, transition);
            existingTransitions.add(transition);
        }
    }

    /**
     * Per one source and target state, there is only one transition is allowed
     * @param existingTransitions
     * @param newTransition
     */
    private void verify(List> existingTransitions, Transition newTransition) {
        for (Transition transition : existingTransitions) {
            if (transition.equals(newTransition)) {
                throw new StateMachineException(transition + " already Exist, you can not add another one");
            }
        }
    }

    public List> get(E event){
        return eventTransitions.get(event);
    }

    public List> allTransitions(){
        List> allTransitions = new ArrayList<>();
        for(List> transitions : eventTransitions.values()){
            allTransitions.addAll(transitions);
        }
        return allTransitions;
    }
}