feat: observer pattern for statistics

pkg/emitter/emitter.go

@@ -0,0 +1,54 @@
+package emitter
+
+import "git.maximhutz.com/max/lambda/pkg/set"
+
+type Observer[T any] struct {
+	fn      func(T)
+	message string
+	emitter *Emitter[T]
+}
+
+type Emitter[T any] struct {
+	listeners map[string]*set.Set[*Observer[T]]
+}
+
+func Ignore[T any](fn func()) func(T) {
+	return func(T) { fn() }
+}
+
+func (e *Emitter[T]) On(message string, fn func(T)) *Observer[T] {
+	observer := &Observer[T]{
+		fn:      fn,
+		message: message,
+		emitter: e,
+	}
+
+	if e.listeners == nil {
+		e.listeners = map[string]*set.Set[*Observer[T]]{}
+	}
+
+	if e.listeners[message] == nil {
+		e.listeners[message] = set.New[*Observer[T]]()
+	}
+
+	e.listeners[message].Add(observer)
+	return observer
+}
+
+func (o *Observer[T]) Off() {
+	if o.emitter.listeners[o.message] == nil {
+		return
+	}
+
+	o.emitter.listeners[o.message].Remove(o)
+}
+
+func (e *Emitter[T]) Emit(message string, value T) {
+	if e.listeners[message] == nil {
+		return
+	}
+
+	for listener := range *e.listeners[message] {
+		listener.fn(value)
+	}
+}

pkg/lambda/generate_name.go

@@ -6,7 +6,7 @@ import (
 	"git.maximhutz.com/max/lambda/pkg/set"
 )
 
-func GenerateFreshName(used set.Set[string]) string {
+func GenerateFreshName(used *set.Set[string]) string {
 	for i := uint64(0); ; i++ {
 		attempt := "_" + string(strconv.AppendUint(nil, i, 10))
 

pkg/lambda/get_free_variables.go

@@ -2,7 +2,7 @@ package lambda
 
 import "git.maximhutz.com/max/lambda/pkg/set"
 
-func GetFreeVariables(e Expression) set.Set[string] {
+func GetFreeVariables(e Expression) *set.Set[string] {
 	switch e := e.(type) {
 	case *Variable:
 		return set.New(e.Value)

pkg/set/set.go

@@ -18,8 +18,8 @@ func (s *Set[T]) Remove(items ...T) {
 	}
 }
 
-func (s *Set[T]) Merge(o Set[T]) {
-	for item := range o {
+func (s *Set[T]) Merge(o *Set[T]) {
+	for item := range *o {
 		s.Add(item)
 	}
 }
@@ -34,8 +34,8 @@ func (s Set[T]) ToList() []T {
 	return list
 }
 
-func New[T comparable](items ...T) Set[T] {
-	result := Set[T]{}
+func New[T comparable](items ...T) *Set[T] {
+	result := &Set[T]{}
 
 	for _, item := range items {
 		result.Add(item)