// Copyright 2024 Matthew Rich <matthewrich.conf@gmail.com>. All rights reserved.
 
package machine

import (
  "fmt"
  "errors"
)

type Transitioner interface {
  Run(m Modeler) error
  Subscribe(s Subscriber)
}

type Transition struct {
  trigger string
  source State
  dest State
  subscriptions []Subscriber
}

func NewTransition(trigger string, source State, dest State) Transitioner {
  return &Transition{ trigger: trigger, source: source, dest: dest }
}

func (r *Transition) Run(m Modeler) error {
  currentState := m.InspectState()
  if currentState == r.source {
    res := m.ChangeState(r.dest)
    if res == currentState {
      r.Notify(EXITSTATEEVENT, currentState, r.dest)
      r.Notify(ENTERSTATEEVENT, currentState, r.dest)
      return nil
    }
  }
  return errors.New(fmt.Sprintf("Transition from %s to %s failed on model state %s", r.source, r.dest, currentState))
}

func (r *Transition) Subscribe(s Subscriber) {
  r.subscriptions = append(r.subscriptions, s)
}

func (r *Transition) Notify(on Eventtype, source State, dest State) {
  for _,s := range r.subscriptions {
    s.Notify(&EventMessage{ on: on, source: source, dest: dest})
  }
}