rc: add NewJobFromBytes for reading jobs from non HTTP transactions

fs/rc/jobs/job.go

@@ -2,7 +2,9 @@
 package jobs
 
 import (
+	"bytes"
 	"context"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"net/http"
@@ -532,6 +534,32 @@ func NewJobFromParams(ctx context.Context, in rc.Params) (out rc.Params) {
 	return out
 }
 
+// NewJobFromBytes creates an rc job from a JSON blob as bytes.
+//
+// The JSON blob should contain a _path entry.
+//
+// It returns a JSON blob as output which may be an error.
+func NewJobFromBytes(ctx context.Context, inBuf []byte) (outBuf []byte) {
+	var in rc.Params
+	var out rc.Params
+
+	// Parse a JSON blob from the input
+	err := json.Unmarshal(inBuf, &in)
+	if err != nil {
+		out, _ = rc.Error("unknown", in, err, http.StatusBadRequest)
+	} else {
+		out = NewJobFromParams(ctx, in)
+	}
+
+	var w bytes.Buffer
+	err = rc.WriteJSON(&w, out)
+	if err != nil {
+		fs.Errorf(nil, "rc: NewJobFromBytes: failed to write JSON output: %v", err)
+		return []byte(`{"error":"failed to write JSON output"}`)
+	}
+	return w.Bytes()
+}
+
 func init() {
 	rc.Add(rc.Call{
 		Path:         "job/batch",

fs/rc/jobs/job_test.go

@@ -702,6 +702,58 @@ func TestNewJobFromParams(t *testing.T) {
 	}
 }
 
+func TestNewJobFromBytes(t *testing.T) {
+	ctx := context.Background()
+	for _, test := range []struct {
+		in   string
+		want string
+	}{{
+		in: `{
+			"_path": "rc/noop",
+			"a":     "potato"
+}`,
+		want: `{
+	"a": "potato"
+}
+`,
+	}, {
+		in: `{
+				"_path": "rc/error",
+				"e":     "sausage"
+			}`,
+		want: `{
+	"error": "arbitrary error on input map[e:sausage]",
+	"input": {
+		"e": "sausage"
+	},
+	"path": "rc/error",
+	"status": 500
+}
+`,
+	}, {
+		in: `parse error`,
+		want: `{
+	"error": "invalid character 'p' looking for beginning of value",
+	"input": null,
+	"path": "unknown",
+	"status": 400
+}
+`,
+	}, {
+		in: `"just a string"`,
+		want: `{
+	"error": "json: cannot unmarshal string into Go value of type rc.Params",
+	"input": null,
+	"path": "unknown",
+	"status": 400
+}
+`,
+	}} {
+		got := NewJobFromBytes(ctx, []byte(test.in))
+		assert.Equal(t, test.want, string(got))
+	}
+}
+
 func TestJobsBatch(t *testing.T) {
 	ctx := context.Background()