Generated by XState Viz: https://xstate.js.org/viz

machine.js

function canTraverse (graph, start, end) {
  return Boolean(graph[start]?.[end]);
}

const questionsMachine = Machine({
  id: "questions",
  parallel: true,
  context: {
    routes: {
      home: {
        feed: true
      },
    },
    // history stack with initial route of one
    stack: ["home"]
  },
  states: {
    app: {
      initial: "home",
      states: {
        home: {},
        feed: {}
      }
    },
    router: {
      on: {
        ROUTER_SEND_TO: {
          actions: assign((ctx, e) => {
            const {stack} = ctx;
            
            if(!e.route || !canTraverse(ctx.routes, ctx.stack[ctx.stack.length - 1], e.route)) {
              return {
                stack
              }
            }
            
            
            return {
              stack: stack.concat(e.route) 
            }
          })
        },
        ROUTER_BACK: {
          actions: assign(ctx => {
            const { stack } = ctx;
            const newStack = stack.slice(0, stack.length - 1);
            const prev = stack[stack.length - 1];
            
            if(newStack.length === 0) {
              return {
                stack
              }
            }

            return {
              stack: newStack
            };
          }),
          cond: ctx => ctx.stack.length > 1
        },
        // ...
      }
    },
    // ...	
  }
});