feat: add chain writer

chain.go

@@ -5,7 +5,7 @@ import "context"
 // Chain chains provided Processors.
 // When an error is returned by a Processor in chain, processing
 // stops and the error is retuned without running further stages.
-func Chain(processors ...Processor) Processor {
+func ChainProcessor(processors ...Processor) Processor {
 	return func(ctx context.Context, in []string) ([]string, error) {
 		var err error
 		for _, p := range processors {
@@ -21,3 +21,23 @@ func Chain(processors ...Processor) Processor {
 		return in, nil
 	}
 }
+
+type chainWriter struct {
+	w []Writer
+}
+
+func (c *chainWriter) Write(in []string) error {
+	for _, w := range c.w {
+		if err := w.Write(in); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func ChainWriter(writers ...Writer) Writer {
+	return &chainWriter{
+		w: writers,
+	}
+}

chain_processor_test.go

@@ -1,28 +0,0 @@
-package script
-
-import (
-	"context"
-	"slices"
-	"testing"
-)
-
-func TestChain(t *testing.T) {
-	p := func(_ context.Context, in []string) ([]string, error) {
-		in[0] = in[0] + in[0]
-		return in, nil
-	}
-
-	chain := Chain(p, p, p)
-
-	in := []string{"a"}
-	want := []string{"aaaaaaaa"}
-
-	res, err := chain(t.Context(), in)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	if !slices.Equal(res, want) {
-		t.Fatalf("slices are not equal, have: %+v, want: %+v", res, want)
-	}
-}

chain_test.go

@@ -0,0 +1,49 @@
+package script
+
+import (
+	"context"
+	"slices"
+	"testing"
+)
+
+func TestChainProcessor(t *testing.T) {
+	p := func(_ context.Context, in []string) ([]string, error) {
+		in[0] = in[0] + in[0]
+		return in, nil
+	}
+
+	chain := ChainProcessor(p, p, p)
+
+	in := []string{"a"}
+	want := []string{"aaaaaaaa"}
+
+	res, err := chain(t.Context(), in)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if !slices.Equal(res, want) {
+		t.Fatalf("slices are not equal, have: %+v, want: %+v", res, want)
+	}
+}
+
+func TestChainWriter(t *testing.T) {
+	w1 := NewMemWriter()
+	w2 := NewMemWriter()
+
+	w := ChainWriter(w1, w2)
+
+	in := []string{"a"}
+
+	if err := w.Write(in); err != nil {
+		t.Fatal(err)
+	}
+
+	if !slices.Equal(w1.Output()[0], in) {
+		t.Fatalf("w1 slices are not equal, have: %+v, want: %+v", w1.Output()[0], in)
+	}
+
+	if !slices.Equal(w2.Output()[0], in) {
+		t.Fatalf("w2 slices are not equal, have: %+v, want: %+v", w2.Output()[0], in)
+	}
+}