StateMachineService.java

package org.entrego.lms.api.service;

import static guru.nidi.graphviz.model.Factory.mutGraph;
import static guru.nidi.graphviz.model.Factory.node;
import static guru.nidi.graphviz.model.Link.to;

import guru.nidi.graphviz.attribute.Label;
import guru.nidi.graphviz.attribute.Shape;
import guru.nidi.graphviz.engine.Format;
import guru.nidi.graphviz.engine.Graphviz;
import guru.nidi.graphviz.model.MutableGraph;
import guru.nidi.graphviz.model.Node;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import javax.annotation.PostConstruct;
import lombok.Data;
import org.entrego.lms.api.config.fsm.Events;
import org.entrego.lms.api.config.fsm.States;
import org.springframework.http.MediaType;
import org.springframework.statemachine.StateMachine;
import org.springframework.statemachine.config.StateMachineFactory;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class DemoService {

  private final StateMachineFactory<States, Events> stateMachineFactory;
  private Graphviz graphviz;

  public DemoService(
    StateMachineFactory<States, Events> stateMachineFactory) {
    this.stateMachineFactory = stateMachineFactory;
  }

  @PostConstruct
  public void init() throws Exception {
    StateMachine<States, Events> stateMachine = stateMachineFactory.getStateMachine();
    MutableGraph graph = mutGraph("Order State Machine").setDirected(true);

    Map<String, Set<GraphVizLink>> graphMap = new HashMap<>();
    stateMachine.getStates().forEach(
      s -> graphMap.put(s.getId().name(), new HashSet<>())
    );

    stateMachine.getTransitions().forEach(t -> {
      graphMap.get(t.getSource().getId().name()).add(
        new GraphVizLink(t.getTarget().getId().name(), t.getTrigger().getEvent().name())
      );
    });

    graphMap.forEach((key, targetSet) -> {
      Node node = node(key).with(Shape.RECTANGLE);
      targetSet.forEach(l -> graph.add(
        node.link(to(node(l.getTarget())).with(Label.of(l.getLabel().toLowerCase())))
      ));
    });

    this.graphviz = Graphviz.fromGraph(graph);
  }

  @ResponseBody
  @RequestMapping(value = "/visualize", consumes = MediaType.ALL_VALUE, produces = "image/svg+xml")
  public String renderSVG() {
    return graphviz.render(Format.SVG).toString();
  }

  @Data
  private static class GraphVizLink {

    private final String target;
    private final String label;
  }

}