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

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package com.alibaba.cola.statemachine.impl;

import com.alibaba.cola.statemachine.State;
import com.alibaba.cola.statemachine.StateMachine;
import com.alibaba.cola.statemachine.Transition;
import com.alibaba.cola.statemachine.Visitor;

import java.util.List;
import java.util.Map;

/**
 * For performance consideration,
 * The state machine is made "stateless" on purpose.
 * Once it's built, it can be shared by multi-thread
 * 
 * One side effect is since the state machine is stateless, we can not get current state from State Machine.
 *
 * @author Frank Zhang
 * @date 2020-02-07 5:40 PM
 */
public class StateMachineImpl implements StateMachine {

    private String machineId;

    private final Map> stateMap;

    private boolean ready;

    public StateMachineImpl(Map> stateMap) {
        this.stateMap = stateMap;
    }

    @Override
    public S fireEvent(S sourceStateId, E event, C ctx) {
        isReady();
        Transition transition = routeTransition(sourceStateId, event, ctx);

        if (transition == null) {
            Debugger.debug("There is no Transition for " + event);
            return sourceStateId;
        }

        return transition.transit(ctx).getId();
    }

    private Transition routeTransition(S sourceStateId, E event, C ctx) {
        State sourceState = getState(sourceStateId);

        List> transitions = sourceState.getEventTransitions(event);

        if (transitions == null || transitions.size() == 0) {
            return null;
        }

        Transition transit = null;
        for (Transition transition : transitions) {
            if (transition.getCondition() == null) {
                transit = transition;
            } else if (transition.getCondition().isSatisfied(ctx)) {
                transit = transition;
                break;
            }
        }

        return transit;
    }

    private State getState(S currentStateId) {
        State state = StateHelper.getState(stateMap, currentStateId);
        if (state == null) {
            showStateMachine();
            throw new StateMachineException(currentStateId + " is not found, please check state machine");
        }
        return state;
    }

    private void isReady() {
        if (!ready) {
            throw new StateMachineException("State machine is not built yet, can not work");
        }
    }

    @Override
    public String accept(Visitor visitor) {
        StringBuilder sb = new StringBuilder();
        sb.append(visitor.visitOnEntry(this));
        for (State state : stateMap.values()) {
            sb.append(state.accept(visitor));
        }
        sb.append(visitor.visitOnExit(this));
        return sb.toString();
    }

    @Override
    public void showStateMachine() {
        SysOutVisitor sysOutVisitor = new SysOutVisitor();
        accept(sysOutVisitor);
    }

    @Override
    public String generatePlantUML() {
        PlantUMLVisitor plantUMLVisitor = new PlantUMLVisitor();
        return accept(plantUMLVisitor);
    }

    @Override
    public String getMachineId() {
        return machineId;
    }

    public void setMachineId(String machineId) {
        this.machineId = machineId;
    }

    public void setReady(boolean ready) {
        this.ready = ready;
    }
}