import { States, PickState } from 'class-states'

type SomeConnectionState =
  {
    state: 'DISCONNECTED'    
  } | {
    state: 'CONNECTING',
    transition: Promise<
      PickState<SomeConnectionState, 'CONNECTED' | 'DISCONNECTED'>
    >
  } | {
    state: 'CONNECTED',
    connection: Connection
  }

class SomeConnection {
  state: States<SomeConnectionState>
  constructor() {
    this.state = new States({
        state: 'DISCONNECTED'
    })
    this.state.onTransition((state, prevState) => {})
    this.state.onTransition('DISCONNECTED', (disconnectedState, prevState) => {})
  }
  private _connect() {
    return this.state.set({
      state: 'CONNECTING',
      transition: someConnectionCreator()
        .then((connection) => ({
          state: 'CONNECTED',
          connection
        }))
        .catch(() => ({
          state: 'DISCONNECTED'
        }))
    })
  }
  async connect() {
    // We first narrow down to a possible "CONNECTED" or "DISCONNECTED"
    // state
    const connectState =  await this.state.matches({
      DISCONNECTED: () => this._connect().transition,
      CONNECTING: ({ transition }) => transition,
      CONNECTED: (state) => state
    })
    
    // Then we use the narrowed state to evaluate what this method
    // returns
    return this.state.matches(connectState, {
      CONNECTED: ({ connection }) => connection,
      DISCONNECTED: () => {
        throw new Error("Could not connect")
      }
    })
  }
  disconnect() {
      this.state.matches({
          CONNECTED: ({ connection }) => {
              connection.dispose()
          },
          _: () => {
              // Do nothing
          }
      })
  }
}