package camfish

import "iter"
import "slices"
import "context"

// actorSets stores a sorted set of all actors, as well as information about
// their state.
type actorSets struct {
	all             actorSet[Actor]
	inf             map[Actor] actorInfo
	nextOrder       int
	
	flagAdder       actorSet[FlagAdder]
	configProcessor actorSet[ConfigProcessor]
	configurable    actorSet[Configurable]
	initializable   actorSet[Initializable]
	runnable        actorSet[Runnable]
	runShutdownable actorSet[RunShutdownable]
	trimmable       actorSet[Trimmable]
}

// actorInfo holds information about a running actor.
type actorInfo struct {
	// ctx is the context of the actor. It is passed to the actor's Run
	// method.
	ctx context.Context
	// done is used to stop the actor. It is created when the actor is added
	// to the actorSets.
	done func()
	// stopped is closed once the actor's run method exits. If the actor
	// does not have a run method, it will be nil.
	stopped chan struct { }
	// order is the semantic order of the actor within the sets. This is
	// incremented automatically for each actor that is added. It is never
	// less than one.
	order int
}

// actorSetIface holds only the add/del/clear methods of actorSet.
type actorSetIface interface {
	add(actor Actor)
	del(actor Actor)
	clear()
}

// All returns an iterator over all sets in the collection.
func (sets *actorSets) All() iter.Seq[actorSetIface] {
	return func(yield func(actorSetIface) bool) {
		yield(&sets.all)
		yield(&sets.flagAdder)
		yield(&sets.configProcessor)
		yield(&sets.configurable)
		yield(&sets.initializable)
		yield(&sets.runnable)
		yield(&sets.runShutdownable)
		yield(&sets.trimmable)
	}
}

// add adds an actor under the given parent context. This is a write operation.
func (this *actorSets) add(ctx context.Context, actor Actor) {
	if this.inf == nil { this.inf = make(map[Actor] actorInfo)}
	actorCtx, done := context.WithCancel(ctx)
	this.nextOrder ++
	info := actorInfo {
		ctx:   actorCtx,
		done:  done,
		order: this.nextOrder,
	}
	_, isRunnable        := actor.(Runnable)
	_, isRunShutdownable := actor.(RunShutdownable)
	if isRunnable || isRunShutdownable {
		info.stopped = make(chan struct { })
	}
	this.inf[actor] = info
	for set := range this.All() {
		set.add(actor)
	}
}

// del removes an actor. This is a write operation.
func (this *actorSets) del(actor Actor) {
	delete(this.inf, actor)
	for set := range this.All() {
		set.del(actor)
	}
}

// clear removes all actors.
func (this *actorSets) clear() {
	clear(this.inf)
	for set := range this.All() {
		set.clear()
	}
}

// info gets information about an actor.
func (this *actorSets) info(actor Actor) actorInfo {
	if this.inf == nil { return actorInfo { } }
	return this.inf[actor]
}

// sortActors sorts actors according to the order in which they were added.
func sortActors[T comparable] (sets *actorSets, actors []T) []T {
	slices.SortFunc(actors, func (left, right T) int {
		// :3
		leftOrder  := sets.info(any(left).(Actor)).order
		rightOrder := sets.info(any(right).(Actor)).order
		if leftOrder < 1 || rightOrder < 1 {
			panic("could not sort actors, some were invalid")
		}
		switch {
		case leftOrder < rightOrder: return -1
		case rightOrder > leftOrder: return  1
		default:                     return  0
		}
	})
	return actors
}

// actorSet is a list that holds all actors of a type. it must not return any
// references to data that is referenced elsewehre, except for references to
// actors.
type actorSet[T comparable] struct {
	actors map[T] string
}

// add adds an actor, if it is of the set's type
func (this *actorSet[T]) add(actor Actor) {
	if this.actors == nil { this.actors = make(map[T] string) }
	if item, ok := actor.(T); ok {
		this.actors[item] = actor.Type()
	}
}

// add removes an actor, if it is of the set's type
func (this *actorSet[T]) del(actor Actor) {
	if this.actors == nil { return }
	if item, ok := actor.(T); ok {
		delete(this.actors, item)
	}
}

// clear removes all actors.
func (this *actorSet[T]) clear() {
	if this.actors == nil { return }
	clear(this.actors)
}

// find returns the first actor with the given type.
func (this *actorSet[T]) find(typ string) T {
	for actor, actorType := range this.actors {
		if actorType == typ { return actor }
	}
	var zero T
	return zero
}

// findAll returns all actors with the given type. This method allocates and
// returns a slice instead of an iterator for concurrency reasons.
func (this *actorSet[T]) findAll(typ string) []T {
	if this.actors == nil { return nil }
	slice := []T { }
	for actor, actorType := range this.actors {
		if actorType == typ {
			slice = append(slice, actor)
		}
	}
	return slice
}

// all returns all actors. This method allocates and returns a slice instead of
// an iterator for concurrency reasons.
func (this *actorSet[T]) all() []T {
	if this.actors == nil { return nil }
	slice := []T { }
	for actor := range this.actors {
		slice = append(slice, actor)
	}
	return slice
}