bind interface{ Arrow() Arrow }

http/types.go

@@ -49,6 +49,22 @@ func Join(arrows ...Arrow) Arrow {
 	}
 }
 
+// Bind composes HTTP arrows to high-order function
+// In contrast with Join, input is arrow builders
+// (a ⟼ b, b ⟼ c, c ⟼ d) ⤇ a ⟼ d
+func Bind(arrows ...interface{ Arrow() Arrow }) Arrow {
+	return func(cat *Context) error {
+		for _, arrow := range arrows {
+			f := arrow.Arrow()
+			if err := f(cat); err != nil {
+				return err
+			}
+		}
+
+		return nil
+	}
+}
+
 // GET composes HTTP arrows to high-order function for HTTP GET request
 // (a ⟼ b, b ⟼ c, c ⟼ d) ⤇ a ⟼ d
 func GET(arrows ...Arrow) Arrow { return method(http.MethodGet, arrows) }

http/types_test.go

@@ -10,6 +10,7 @@ package http_test
 
 import (
 	"context"
+	"fmt"
 	"net/http"
 	"net/http/httptest"
 	"testing"
@@ -67,8 +68,13 @@ func TestJoin(t *testing.T) {
 	defer ts.Close()
 
 	req := µ.GET(
-		ø.URI("%s/ok", ø.Authority(ts.URL)),
+		ø.URI("%s/opts", ø.Authority(ts.URL)),
+		µ.Join(
+			ø.Param("a", "1"),
+			ø.Param("b", "2"),
+		),
 		ƒ.Code(µ.StatusOK),
+		ƒ.Match(`{"opts": "a=1&b=2"}`),
 	)
 	cat := µ.New()
 	err := cat.IO(context.Background(), req)
@@ -100,6 +106,56 @@ func TestJoinCats(t *testing.T) {
 	)
 }
 
+type opt struct{ key, val string }
+
+func (opt opt) Arrow() µ.Arrow { return ø.Param(opt.key, opt.val) }
+
+type err string
+
+func (err err) Arrow() µ.Arrow { return func(ctx *µ.Context) error { return fmt.Errorf("%s", err) } }
+
+func TestBind(t *testing.T) {
+	ts := mock()
+	defer ts.Close()
+
+	req := µ.GET(
+		ø.URI("%s/opts", ø.Authority(ts.URL)),
+		µ.Bind(
+			opt{"a", "1"},
+			opt{"b", "2"},
+		),
+		ƒ.Code(µ.StatusOK),
+		ƒ.Match(`{"opts": "a=1&b=2"}`),
+	)
+	cat := µ.New()
+	err := cat.IO(context.Background(), req)
+
+	it.Then(t).Should(
+		it.Nil(err),
+	)
+}
+
+func TestBindFailed(t *testing.T) {
+	ts := mock()
+	defer ts.Close()
+
+	req := µ.GET(
+		ø.URI("%s/opts", ø.Authority(ts.URL)),
+		µ.Bind(
+			opt{"a", "1"},
+			err("failed"),
+		),
+		ƒ.Code(µ.StatusOK),
+		ƒ.Match(`{"opts": "a=1&b=2"}`),
+	)
+	cat := µ.New()
+	err := cat.IO(context.Background(), req)
+
+	it.Then(t).ShouldNot(
+		it.Nil(err),
+	)
+}
+
 func TestIOWithContext(t *testing.T) {
 	ts := mock()
 	defer ts.Close()
@@ -189,6 +245,9 @@ func mock() *httptest.Server {
 				w.Write([]byte("site=example.com"))
 			case r.URL.Path == "/ok":
 				w.WriteHeader(http.StatusOK)
+			case r.URL.Path == "/opts":
+				w.Header().Add("Content-Type", "application/json")
+				w.Write([]byte(`{"opts": "` + r.URL.RawQuery + `"}`))
 			default:
 				w.WriteHeader(http.StatusBadRequest)
 			}