Preact Hook Finite State Machine

useFSM.tsx

import { useCallback, useEffect, useMemo, useState } from "preact/hooks"

class StateTransitionError extends Error {}

function useFSM<T extends string>(
  transitions: Record<T, T[]>,
  options: {
    throwOnTransitionError?: boolean
  } = { throwOnTransitionError: true },
) {
  const [startingState] = useMemo(
    () => Object.keys(transitions) as unknown as T[],
    [transitions],
  )
  const [currentState, setCurrentState] = useState<T>(startingState)

  const reset = useCallback(
    function () {
      setCurrentState(startingState)
    },
    [startingState],
  )

  const canGoToState = useCallback(
    function (state: T) {
      return transitions[currentState]?.includes(state)
    },
    [currentState, transitions],
  )

  const goToState = useCallback(
    function (state: T) {
      if (!canGoToState(state)) {
        if (options.throwOnTransitionError) {
          throw new StateTransitionError(
            `Cannot perform transition ${currentState} -> ${state}`,
          )
        }

        return false
      }

      console.log("[state transition]", currentState, "->", state)
      setCurrentState(state)
      return true
    },
    [canGoToState, currentState, options.throwOnTransitionError],
  )

  return {
    reset,
    goToState,
    canGoToState,
    state: currentState,
  }
}

export default useFSM