Type-Level State Machines

Since 1.4.0

State machine types for complex state modeling.

Basic Usage

StateMachine

Define a state machine with states and transitions.

import type { StateMachine } from 'uni-types'

type TrafficLight = StateMachine<{
  states: { red: {}; yellow: {}; green: {} }
  initial: 'red'
  transitions: {
    next: { red: 'green'; green: 'yellow'; yellow: 'red' }
  }
}>

State

Define a state with data.

import type { State } from 'uni-types'

type Loading = State<'loading', { progress: number }>
// { state: 'loading'; data: { progress: number } }

State Utilities

CurrentState

Get current state type.

import type { CurrentState } from 'uni-types'

type Current = CurrentState<TrafficLight>  // 'red'

NextState

Get next state after an event.

import type { NextState } from 'uni-types'

type Next = NextState<TrafficLight, 'next'>  // 'green'

ValidTransitions

Get all valid transitions from current state.

import type { ValidTransitions } from 'uni-types'

type Transitions = ValidTransitions<TrafficLight>  // 'next'

CanTransition

Check if a transition is valid.

import type { CanTransition } from 'uni-types'

type Can = CanTransition<TrafficLight, 'next'>  // true

IsTerminal

Check if current state is terminal.

import type { IsTerminal } from 'uni-types'

type Done = IsTerminal<{ current: 'done'; transitions: {} }>  // true

Building State Machines

BuildStateMachine

Build state machine from config.

import type { BuildStateMachine } from 'uni-types'

type SM = BuildStateMachine<{
  states: ['idle', 'running', 'stopped']
  initial: 'idle'
  transitions: {
    start: { idle: 'running' }
    stop: { running: 'stopped' }
  }
}>

SendEvent

Send event to state machine.

import type { SendEvent } from 'uni-types'

type NewState = SendEvent<TrafficLight, 'next'>
// { current: 'green'; ... }

Related

• Pattern Types - Pattern matching utilities
• Data Structures - Tree, Graph structures