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machine.js

// Available variables:
// - Machine
// - interpret
// - assign
// - send
// - sendParent
// - spawn
// - raise
// - actions
// - XState (all XState exports)

const HEAT_CAPACITY_OF_WATER = 4180

const heatingDuration = ({
  power,
  efficiency,
  milliliter,
  waterTemp,
  targetTemp = 100
}) => {
  const effectivePower = power * (efficiency * 0.01)
  const heat = HEAT_CAPACITY_OF_WATER * (milliliter / 1000) * (targetTemp - waterTemp)
  return Math.round(heat / effectivePower)
}


const kettle = Machine({
  id: 'kettle',
  initial: 'idle',
  context: {
    temp: 10, // in °C
    amount: 100, // in millilitre
    power: 2000, // in Watts
    efficiency: 90,
    targetTemp: 100, // °C
    startTime: undefined
  },
  states: {
    idle: {
      on: {
        START: "heating"
      }
    },
    heating: {
      entry: {
        actions: "setStartTime"
      },
      after: {
        HEATING_TIME: "done",
        NEXT_TEMP_TIME: [{
          actions: "incTemp"
        }, {
          target: "done",
          cond: "targetTempReached",
        }]
      },
      on: {
        DISCONNECT: 'disconnected',
      }
    },
    disconnected: {
      on: {
        CONNECT: "heating"
      }
    },
    done: {
      type: "final"
    }
  }
}, {
  actions: {
    setStartTime: context => assign({ startTime: Date.now() }),
    incTemp: context => assign({ temp: context.temp + 1 })
  },
  delays: {
    NEXT_TEMP_TIME: (context, event) => {
      const time = heatingDuration({
        power: context.power,
        efficiency: context.efficiency,
        waterTemp: context.temp,
        milliliter: context.amount,
        targetTemp: context.temp + 1
      })
      console.log("heating time: " + time + " secs")
      return time
    },
    HEATING_TIME: (context, event) => {
      const time = heatingDuration({
        power: context.power,
        efficiency: context.efficiency,
        waterTemp: context.temp,
        milliliter: context.amount,
        targetTemp: context.targetTemp
      })
      console.log("heating time: " + time + " secs")
      return time * 1000
    }
  },
  guards: {
    targetTempReached: (context) => {
      return context.temp === context.targetTemp
    }
  }
});