unify hinted content codec for Arrows & Combinators (#58)

* unify hinted content codec for Arrows & Combinators
* improve test coverage for http.IO

examples/http-response-image/main.go

@@ -19,38 +19,31 @@ import (
 	ø "github.com/fogfish/gurl/v2/http/send"
 )
 
-type Heap struct {
-	image image.Image
+type api struct {
+	http.Stack
 }
 
-// declares http I/O
-func (h *Heap) request() http.Arrow {
-	return http.GET(
-		// specify specify the request
-		ø.URI("https://avatars.githubusercontent.com/u/716093"),
-		ø.Accept.Set("image/*"),
-
-		// specify requirements to the response
-		ƒ.Status.OK,
-		ƒ.ContentType.Is("image/jpeg"),
-		ƒ.Body(&h.image),
+func (api api) request(ctx context.Context) (*image.Image, error) {
+	return http.IO[image.Image](api.WithContext(ctx),
+		http.GET(
+			ø.URI("https://avatars.githubusercontent.com/u/716093"),
+			ø.Accept.Set("image/*"),
+
+			ƒ.Status.OK,
+			ƒ.ContentType.Is("image/jpeg"),
+		),
 	)
 }
 
 func main() {
-	// instance of http stack
-	stack := http.New(http.WithDebugPayload())
-
-	// declares http i/o
-	heap := &Heap{}
-	lazy := heap.request()
+	api := api{
+		Stack: http.New(http.WithDebugPayload()),
+	}
 
-	// executes http I/O
-	err := stack.IO(context.Background(), lazy)
+	img, err := api.request(context.Background())
 	if err != nil {
 		panic(err)
 	}
 
-	// process image
-	jpeg.Encode(os.Stdout, heap.image, &jpeg.Options{Quality: 93})
+	jpeg.Encode(os.Stdout, *img, &jpeg.Options{Quality: 93})
 }

http/recv/arrows.go

@@ -12,13 +12,11 @@ package recv
 import (
 	"encoding/json"
 	"fmt"
-	"image"
 	"io"
 	"strconv"
 	"strings"
 	"time"
 
-	"github.com/ajg/form"
 	"github.com/fogfish/gurl/v2"
 	"github.com/fogfish/gurl/v2/http"
 	"github.com/google/go-cmp/cmp"
@@ -635,7 +633,7 @@ const (
 // Supply the pointer to data target data structure.
 func Body[T any](out *T) http.Arrow {
 	return func(cat *http.Context) error {
-		err := decode(
+		err := http.HintedContentCodec(
 			cat.Response.Header.Get("Content-Type"),
 			cat.Response.Body,
 			out,
@@ -655,7 +653,7 @@ func Recv[T any](out *T) http.Arrow {
 func Expect[T any](expect T) http.Arrow {
 	return func(cat *http.Context) error {
 		var actual T
-		err := decode(
+		err := http.HintedContentCodec(
 			cat.Response.Header.Get("Content-Type"),
 			cat.Response.Body,
 			&actual,
@@ -678,28 +676,6 @@ func Expect[T any](expect T) http.Arrow {
 	}
 }
 
-func decode[T any](content string, stream io.ReadCloser, data *T) error {
-	switch {
-	case strings.Contains(content, "json"):
-		return json.NewDecoder(stream).Decode(data)
-	case strings.Contains(content, "www-form"):
-		return form.NewDecoder(stream).Decode(data)
-	case strings.HasPrefix(content, "image/"):
-		img, _, err := image.Decode(stream)
-		if err == nil {
-			*data = img.(T)
-		}
-		return err
-	default:
-		return &gurl.NoMatch{
-			ID:       "http.Recv",
-			Diff:     fmt.Sprintf("- Content-Type: application/{json | www-form}\n+ Content-Type: %s", content),
-			Protocol: "codec",
-			Actual:   content,
-		}
-	}
-}
-
 // Bytes receive raw binary from HTTP response
 func Bytes(val *[]byte) http.Arrow {
 	return func(cat *http.Context) (err error) {
@@ -720,7 +696,7 @@ func Match(val string) http.Arrow {
 	return func(cat *http.Context) (err error) {
 		var val any
 
-		err = decode(
+		err = http.HintedContentCodec(
 			cat.Response.Header.Get("Content-Type"),
 			cat.Response.Body,
 			&val,

http/recv/arrows_test.go

@@ -329,7 +329,6 @@ func TestBodyImage(t *testing.T) {
 
 	it.Then(t).Should(
 		it.Nil(err),
-	// 	it.Equal(site.Site, "example.com"),
 	)
 }
 

http/types.go

@@ -11,6 +11,7 @@ package http
 import (
 	"encoding/json"
 	"fmt"
+	"image"
 	"io"
 	"net/http"
 	"strings"
@@ -116,7 +117,7 @@ func IO[T any](ctx *Context, arrows ...Arrow) (*T, error) {
 	defer ctx.Response.Body.Close()
 
 	var val T
-	err := decode(
+	err := HintedContentCodec(
 		ctx.Response.Header.Get("Content-Type"),
 		ctx.Response.Body,
 		&val,
@@ -128,16 +129,22 @@ func IO[T any](ctx *Context, arrows ...Arrow) (*T, error) {
 	return &val, nil
 }
 
-func decode[T any](content string, stream io.ReadCloser, data *T) error {
+func HintedContentCodec[T any](content string, stream io.ReadCloser, data *T) error {
 	switch {
 	case strings.Contains(content, "json"):
 		return json.NewDecoder(stream).Decode(data)
 	case strings.Contains(content, "www-form"):
 		return form.NewDecoder(stream).Decode(data)
+	case strings.HasPrefix(content, "image/"):
+		img, _, err := image.Decode(stream)
+		if err == nil {
+			*data = img.(T)
+		}
+		return err
 	default:
 		return &gurl.NoMatch{
 			ID:       "http.Recv",
-			Diff:     fmt.Sprintf("- Content-Type: application/{json | www-form}\n+ Content-Type: %s", content),
+			Diff:     fmt.Sprintf("- Content-Type: {json | www-form | image}\n+ Content-Type: %s", content),
 			Protocol: "codec",
 			Actual:   content,
 		}

http/types_test.go

@@ -10,9 +10,13 @@ package http_test
 
 import (
 	"context"
+	"encoding/base64"
 	"fmt"
+	"image"
+	_ "image/png"
 	"net/http"
 	"net/http/httptest"
+	"strings"
 	"testing"
 	"time"
 
@@ -231,6 +235,21 @@ func TestIO(t *testing.T) {
 		)
 	})
 
+	t.Run("Image", func(t *testing.T) {
+		val, err := µ.IO[image.Image](cat.WithContext(context.Background()),
+			µ.GET(
+				ø.URI("%s/image", ø.Authority(ts.URL)),
+				ƒ.Status.OK,
+				ƒ.ContentType.Is("image/png"),
+			),
+		)
+
+		it.Then(t).Should(
+			it.Nil(err),
+		).ShouldNot(
+			it.Nil(val),
+		)
+	})
 }
 
 func mock() *httptest.Server {
@@ -243,6 +262,13 @@ func mock() *httptest.Server {
 			case r.URL.Path == "/form":
 				w.Header().Add("Content-Type", "application/x-www-form-urlencoded")
 				w.Write([]byte("site=example.com"))
+			case strings.HasPrefix(r.URL.Path, "/image"):
+				w.Header().Add("Content-Type", "image/png")
+				dst, err := base64.StdEncoding.DecodeString("iVBORw0KGgoAAAANSUhEUgAAAAEAAAABAQMAAAAl21bKAAAAA1BMVEUAAACnej3aAAAAAXRSTlMAQObYZgAAAApJREFUCNdjYAAAAAIAAeIhvDMAAAAASUVORK5CYII=")
+				if err != nil {
+					panic(err)
+				}
+				w.Write(dst)
 			case r.URL.Path == "/ok":
 				w.WriteHeader(http.StatusOK)
 			case r.URL.Path == "/opts":