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

machine.js

  // Available variables:
  // - Machine
  // - interpret
  // - assign
  // - send
  // - sendParent
  // - spawn
  // - raise
  // - actions
  // - XState (all XState exports)
  
  function getClosest(isUp, floor) {
    const outsideQueue = isUp ? ctx.upRequests : ctx.downRequests
    const requests = { ...ctx.floorRequests, ...outsideQueue }
    const closestFloor = Object.keys(requests)
      .map(floor => parseInt(floor, 10))
      .filter(v => requests[v])
      .sort((a, b) => (isUp ? a - b : b - a))
      .find(r => (isUp ? floor <= r : floor >= r))
    return closestFloor
  }
  
  
  const elevatorMachine = Machine({
    id: 'elevator',
    initial: 'idle',
    context: {
      currentFloor: 0,
      maxFloor: 10,
      floorRequests: {},
      upRequests: {},
      downRequests: {}
    },
    on: {
      FLOOR: {
        actions: assign({ floorRequests: (ctx, ev) => ({ ...ctx.floorRequests, [ev.number]: true }) })
      },
      UP: {
        actions: assign({ upRequests: (ctx, ev) => ({ ...ctx.upRequests, [ev.number]: true }) })
      },
      DOWN: {
        actions: assign({ downRequests: (ctx, ev) => ({ ...ctx.downRequests, [ev.number]: true }) })
      }
    },
    states: {
      idle: {
        on: {
          '': [
            {
              target: 'moving_up',
              cond: 'hasUpRequests'
            },
            {
              target: 'moving_down',
              cond: 'hasDownRequests'
            }
          ]
        }
      },
      moving_up: {
        entry: [
          assign({
            currentFloor: 0
          })
        ],
        invoke: {
          id: 'moving_up',
          src: (context, event) => (callback, onEvent) => {
            // This will send the 'MOVED_UP' event to the parent every second
            const id = setInterval(() => callback('MOVED_UP'), 1000)

            // Perform cleanup
            return () => clearInterval(id)
          }
        },
        on: {
          MOVED_UP: {
            actions: [
              assign({ currentFloor: (ctx) => ctx.currentFloor + 1 }),
              assign({
                upRequests: (ctx) => {
                  const reqs = {
                    ...ctx.upRequests
                  };
                  delete reqs[ctx.currentFloor];
                  return reqs;
                }
              }),
              assign({
                floorRequests: (ctx) => {
                  const reqs = {
                    ...ctx.floorRequests
                  };
                  delete reqs[ctx.currentFloor];
                  return reqs;
                }
              })
            ]
         },
         '': [
           { target: 'moving_down', cond: (ctx) => ctx.currentFloor === ctx.maxFloor }
          ]
        }
      },
      moving_down: {
        entry: [
          assign({
            currentFloor: (ctx) => ctx.maxFloor
          })
        ],
        invoke: {
          id: 'moving_down',
          src: (context, event) => (callback, onEvent) => {
            // This will send the 'MOVED_UP' event to the parent every second
            const id = setInterval(() => callback('MOVED_DOWN'), 1000)

            // Perform cleanup
            return () => clearInterval(id)
          }
        },
        on: {
          MOVED_DOWN: {
            actions: [
              assign({ currentFloor: (ctx) => ctx.currentFloor - 1 }),
              assign({
                downRequests: (ctx) => {
                  const reqs = {
                    ...ctx.downRequests
                  };
                  delete reqs[ctx.currentFloor];
                  return reqs;
                }
              }),
              assign({
                floorRequests: (ctx) => {
                  const reqs = {
                    ...ctx.floorRequests
                  };
                  delete reqs[ctx.currentFloor];
                  return reqs;
                }
              })
            ]
         },
         '': [
           { target: 'idle', cond: (ctx) => ctx.currentFloor === 0 }
          ]
        }
      }
    }
  }, {
    guards: {
      hasDownRequests: (ctx) => !!Object.keys(ctx.downRequests).length,
      hasUpRequests: (ctx) => !!Object.keys(ctx.upRequests).length,
      noRequests: (ctx) => !Object.keys(ctx.downRequests)
    }
  });
  
  
  // IUR - inside up request
  // IDR - inside down request
  //