feat: add projection layer to eventstore

pkg/set/set.go

@@ -0,0 +1,35 @@
+package set
+
+import (
+	"fmt"
+	"strings"
+)
+
+type Set[T comparable] map[T]struct{}
+
+func New[T comparable](items ...T) Set[T] {
+	s := make(map[T]struct{}, len(items))
+	for i := range items {
+		s[items[i]] = struct{}{}
+	}
+	return s
+}
+func (s Set[T]) Has(v T) bool {
+	_, ok := (s)[v]
+	return ok
+}
+func (s Set[T]) String() string {
+	if s == nil {
+		return "set(<nil>)"
+	}
+	lis := make([]string, 0, len(s))
+	for k := range s {
+		lis = append(lis, fmt.Sprint(k))
+	}
+
+	var b strings.Builder
+	b.WriteString("set(")
+	b.WriteString(strings.Join(lis, ","))
+	b.WriteString(")")
+	return b.String()
+}