stream support fold

examples/stream/fold/main.go

@@ -0,0 +1,17 @@
+package main
+
+import (
+	"fmt"
+
+	"github.com/azihsoyn/gollection"
+)
+
+func main() {
+	arr := []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
+
+	res, _ := gollection.NewStream(arr).Fold(100, func(v1, v2 int) int {
+		return v1 + v2
+	}).Result()
+	fmt.Println("origin : ", arr)
+	fmt.Println("ret    : ", res)
+}

fold.go

@@ -10,6 +10,14 @@ func (g *gollection) Fold(v0 interface{}, f interface{}) *gollection {
 		return &gollection{err: g.err}
 	}
 
+	if g.ch != nil {
+		return g.foldStream(v0, f)
+	}
+
+	return g.fold(v0, f)
+}
+
+func (g *gollection) fold(v0 interface{}, f interface{}) *gollection {
 	sv := reflect.ValueOf(g.slice)
 	if sv.Kind() != reflect.Slice {
 		return &gollection{
@@ -43,4 +51,43 @@ func (g *gollection) Fold(v0 interface{}, f interface{}) *gollection {
 	return &gollection{
 		val: ret,
 	}
+
+}
+
+func (g *gollection) foldStream(v0 interface{}, f interface{}) *gollection {
+	next := &gollection{
+		ch: make(chan interface{}),
+	}
+
+	funcValue := reflect.ValueOf(f)
+	funcType := funcValue.Type()
+	if funcType.Kind() != reflect.Func || funcType.NumIn() != 2 || funcType.NumOut() != 1 {
+		return &gollection{
+			slice: nil,
+			err:   fmt.Errorf("gollection.Reduce called with invalid func. required func(in1, in2 <T>) out <T> but supplied %v", g.slice),
+		}
+	}
+
+	go func() {
+		ret := v0
+
+		for {
+			select {
+			case v, ok := <-g.ch:
+				if ok {
+					v1 := reflect.ValueOf(ret)
+					v2 := reflect.ValueOf(v)
+					ret = funcValue.Call([]reflect.Value{v1, v2})[0].Interface()
+				} else {
+					next.ch <- ret
+					close(next.ch)
+					return
+				}
+			default:
+				continue
+			}
+		}
+	}()
+	return next
+
 }