machine/machine.go

// 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) error
	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) error {
	return 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 nil
	}
	return errors.New("Transition does not exist")
}