feat: add library code for mapping HTTP response errors onto specific…

… error types

pkg/httperr/from_response.go

@@ -0,0 +1,16 @@
+package httperr
+
+import "net/http"
+
+// ErrFromResponse maps an HTTP response (with an error status code) to a (more
+// or less) specific error type.
+func ErrFromResponse(res *http.Response) error {
+	switch res.StatusCode {
+	case http.StatusNotFound:
+		return &ErrNotFound{Response: res}
+	case http.StatusForbidden:
+		return &ErrPermissionDenied{Response: res}
+	default:
+		return &ErrUnexpectedResponse{Response: res}
+	}
+}

pkg/httperr/not_found_error.go

@@ -0,0 +1,16 @@
+package httperr
+
+import (
+	"fmt"
+	"net/http"
+)
+
+// ErrNotFound represents the error of trying to access a resource that does
+// not exist.
+type ErrNotFound struct {
+	Response *http.Response
+}
+
+func (e *ErrNotFound) Error() string {
+	return fmt.Sprintf("resource not found: %s", e.Response.Request.URL)
+}

pkg/httperr/permission_denied_error.go

@@ -0,0 +1,16 @@
+package httperr
+
+import (
+	"fmt"
+	"net/http"
+)
+
+// ErrPermissionDenied represents the error of trying to access a resource that
+// the currently authenticated user is not authorized to access.
+type ErrPermissionDenied struct {
+	Response *http.Response
+}
+
+func (e *ErrPermissionDenied) Error() string {
+	return fmt.Sprintf("permission to resource denied: %s", e.Response.Request.URL)
+}