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

import (
  "errors"
)

type State string

type Stater interface {
  AddStates(name ...State)
  GetState(name string) State
  AddTransition(trigger string, source State, dest State)
  AddSubscription(transition string, subscription Subscriber) error
  AddModel(m Modeler)
  Trigger(transition string)
  CurrentState() State
}

type Definition struct {
  states []State
  triggers map[string]Transitioner
  model Modeler
}

func New(initial State) Stater {
  return &Definition{ model: NewModel(initial), triggers: make(map[string]Transitioner) }
}

func (d *Definition) AddStates(name ...State) {
  d.states = append(d.states, name...) 
}

func (d *Definition) AddTransition(trigger string, source State, dest State) {
  d.triggers[trigger] = NewTransition(trigger, source, dest) 
}

func (d *Definition) GetState(name string) State {
  var r State
  for _,s := range(d.states) {
    if string(s) == name {
      return s
    }
  }
  return r
}

func (d *Definition) AddModel(m Modeler) {
  d.model = m
}

func (d *Definition) Trigger(transition string) {
  d.triggers[transition].Run(d.model)
}

func (d *Definition) CurrentState() State {
  return d.model.InspectState()
}

func (d *Definition) AddSubscription(transition string, subscription Subscriber) error {
  if t,ok := d.triggers[transition]; ok {
    t.Subscribe(subscription)
  }
  return errors.New("Transition does not exist")
}