fix: rework http support

Signed-off-by: Dr. Carsten Leue <carsten.leue@de.ibm.com>

http/utils.go

@@ -0,0 +1,79 @@
+package http
+
+import (
+	"fmt"
+	"io"
+	"mime"
+	H "net/http"
+	"regexp"
+
+	A "github.com/ibm/fp-go/array"
+	E "github.com/ibm/fp-go/either"
+	"github.com/ibm/fp-go/errors"
+	F "github.com/ibm/fp-go/function"
+	O "github.com/ibm/fp-go/option"
+	R "github.com/ibm/fp-go/record/generic"
+	T "github.com/ibm/fp-go/tuple"
+)
+
+type (
+	ParsedMediaType = T.Tuple2[string, map[string]string]
+)
+
+var (
+	// mime type to check if a media type matches
+	reJsonMimeType = regexp.MustCompile(`application/(?:\w+\+)?json`)
+	// ValidateResponse validates an HTTP response and returns an [E.Either] if the response is not a success
+	ValidateResponse = E.FromPredicate(isValidStatus, StatusCodeError)
+	// alidateJsonContentTypeString parses a content type a validates that it is valid JSON
+	validateJsonContentTypeString = F.Flow2(
+		ParseMediaType,
+		E.ChainFirst(F.Flow2(
+			T.First[string, map[string]string],
+			E.FromPredicate(reJsonMimeType.MatchString, func(mimeType string) error {
+				return fmt.Errorf("mimetype [%s] is not a valid JSON content type", mimeType)
+			}),
+		)),
+	)
+)
+
+const (
+	HeaderContentType = "Content-Type"
+)
+
+// ParseMediaType parses a media type into a tuple
+func ParseMediaType(mediaType string) E.Either[error, ParsedMediaType] {
+	return E.TryCatchError(func() (ParsedMediaType, error) {
+		m, p, err := mime.ParseMediaType(mediaType)
+		return T.MakeTuple2(m, p), err
+	})
+}
+
+func GetHeader(resp *H.Response) H.Header {
+	return resp.Header
+}
+
+func GetBody(resp *H.Response) io.ReadCloser {
+	return resp.Body
+}
+
+func isValidStatus(resp *H.Response) bool {
+	return resp.StatusCode >= H.StatusOK && resp.StatusCode < H.StatusMultipleChoices
+}
+
+func StatusCodeError(resp *H.Response) error {
+	return fmt.Errorf("invalid status code [%d] when accessing URL [%s]", resp.StatusCode, resp.Request.URL)
+}
+
+// ValidateJsonResponse checks if an HTTP response is a valid JSON response
+func ValidateJsonResponse(resp *H.Response) E.Either[error, *H.Response] {
+	return F.Pipe6(
+		resp,
+		GetHeader,
+		R.Lookup[H.Header](HeaderContentType),
+		O.Chain(A.First[string]),
+		E.FromOption[error, string](errors.OnNone("unable to access the [%s] header", HeaderContentType)),
+		E.ChainFirst(validateJsonContentTypeString),
+		E.MapTo[error, string](resp),
+	)
+}