query: expose query results as json-ld, if supported

go.mod

@@ -4,7 +4,7 @@ go 1.12
 
 require (
 	github.com/badgerodon/peg v0.0.0-20130729175151-9e5f7f4d07ca
-	github.com/cayleygraph/quad v1.0.0
+	github.com/cayleygraph/quad v1.1.0
 	github.com/cockroachdb/apd v1.1.0 // indirect
 	github.com/containerd/continuity v0.0.0-20190426062206-aaeac12a7ffc // indirect
 	github.com/coreos/bbolt v1.3.3 // indirect

go.sum

@@ -27,6 +27,8 @@ github.com/boltdb/bolt v1.3.1 h1:JQmyP4ZBrce+ZQu0dY660FMfatumYDLun9hBCUVIkF4=
 github.com/boltdb/bolt v1.3.1/go.mod h1:clJnj/oiGkjum5o1McbSZDSLxVThjynRyGBgiAx27Ps=
 github.com/cayleygraph/quad v1.0.0 h1:RhKzgiWK3I0ekgxVlwpwdM9Q/Rq3QA9bc9Mtw7x4pRs=
 github.com/cayleygraph/quad v1.0.0/go.mod h1:maWODEekEhrO0mdc9h5n/oP7cH1h/OTgqQ2qWbuI9M4=
+github.com/cayleygraph/quad v1.1.0 h1:w1nXAmn+nz07+qlw89dke9LwWkYpeX+OcvfTvGQRBpM=
+github.com/cayleygraph/quad v1.1.0/go.mod h1:maWODEekEhrO0mdc9h5n/oP7cH1h/OTgqQ2qWbuI9M4=
 github.com/cenkalti/backoff v2.1.1+incompatible h1:tKJnvO2kl0zmb/jA5UKAt4VoEVw1qxKWjE/Bpp46npY=
 github.com/cenkalti/backoff v2.1.1+incompatible/go.mod h1:90ReRw6GdpyfrHakVjL/QHaoyV4aDUVVkXQJJJ3NXXM=
 github.com/cespare/xxhash v1.1.0/go.mod h1:XrSqR1VqqWfGrhpAt58auRo0WTKS1nRRg3ghfAqPWnc=

query/gizmo/finals.go

@@ -209,14 +209,3 @@ func quadValueToString(v quad.Value) string {
 	}
 	return quad.StringOf(v)
 }
-
-func quadValueToNative(v quad.Value) interface{} {
-	if v == nil {
-		return nil
-	}
-	out := v.Native()
-	if nv, ok := out.(quad.Value); ok && v == nv {
-		return quad.StringOf(v)
-	}
-	return out
-}

query/gizmo/gizmo.go

@@ -93,6 +93,7 @@ type Session struct {
 	vm  *goja.Runtime
 	ns  voc.Namespaces
 	sch *schema.Config
+	col query.Collation
 
 	last string
 	p    *goja.Program
@@ -127,10 +128,24 @@ func (s *Session) buildEnv() error {
 	return nil
 }
 
+func (s *Session) quadValueToNative(v quad.Value) interface{} {
+	if v == nil {
+		return nil
+	}
+	if s.col == query.JSONLD {
+		return jsonld.FromValue(v)
+	}
+	out := v.Native()
+	if nv, ok := out.(quad.Value); ok && v == nv {
+		return quad.StringOf(v)
+	}
+	return out
+}
+
 func (s *Session) tagsToValueMap(m map[string]graph.Ref) map[string]interface{} {
 	outputMap := make(map[string]interface{})
 	for k, v := range m {
-		if o := jsonld.FromValue(s.qs.NameOf(v)); o != nil {
+		if o := s.quadValueToNative(s.qs.NameOf(v)); o != nil {
 			outputMap[k] = o
 		}
 	}
@@ -161,7 +176,7 @@ func (s *Session) runIteratorToArrayNoTags(it graph.Iterator, limit int) ([]inte
 
 	output := make([]interface{}, 0)
 	err := graph.Iterate(ctx, it).Paths(false).Limit(limit).EachValue(s.qs, func(v quad.Value) {
-		if o := jsonld.FromValue(v); o != nil {
+		if o := s.quadValueToNative(v); o != nil {
 			output = append(output, o)
 		}
 	})
@@ -282,7 +297,7 @@ func (s *Session) run() (goja.Value, error) {
 }
 func (s *Session) Execute(ctx context.Context, qu string, opt query.Options) (query.Iterator, error) {
 	switch opt.Collation {
-	case query.Raw, query.JSON, query.REPL:
+	case query.Raw, query.JSON, query.JSONLD, query.REPL:
 	default:
 		return nil, &query.ErrUnsupportedCollation{Collation: opt.Collation}
 	}
@@ -293,6 +308,7 @@ func (s *Session) Execute(ctx context.Context, qu string, opt query.Options) (qu
 	s.count = 0
 	ctx, cancel := context.WithCancel(context.Background())
 	s.ctx = ctx
+	s.col = opt.Collation
 	return &results{
 		col: opt.Collation,
 		s:   s,
@@ -362,17 +378,15 @@ func (it *results) Result() interface{} {
 	switch it.col {
 	case query.Raw:
 		return it.cur
-	case query.JSON:
-		return it.jsonResult(false)
-	case query.JSONLD:
-		return it.jsonResult(true)
+	case query.JSON, query.JSONLD:
+		return it.jsonResult()
 	case query.REPL:
 		return it.replResult()
 	}
 	return nil
 }
 
-func (it *results) jsonResult(ld bool) interface{} {
+func (it *results) jsonResult() interface{} {
 	data := it.cur
 	if data.Meta {
 		return nil
@@ -389,13 +403,7 @@ func (it *results) jsonResult(ld bool) interface{} {
 	sort.Strings(tagKeys)
 	for _, k := range tagKeys {
 		if name := it.s.qs.NameOf(tags[k]); name != nil {
-			var v interface{}
-			if ld {
-				v = jsonld.FromValue(v)
-			} else {
-				v = quadValueToNative(name)
-			}
-			obj[k] = v
+			obj[k] = it.s.quadValueToNative(name)
 		} else {
 			delete(obj, k)
 		}

query/session.go

@@ -59,6 +59,8 @@ const (
 	REPL = Collation(iota)
 	// JSON collates results as maps, arrays and values, that can be encoded to JSON.
 	JSON
+	// JSONLD collates results as maps, arrays and values compatible with JSON-LD spec.
+	JSONLD
 )
 
 // Options for the query execution.

server/http/api_v2.go

@@ -115,6 +115,7 @@ const (
 	hdrAccept          = "Accept"
 	hdrAcceptEncoding  = "Accept-Encoding"
 	contentTypeJSON    = "application/json"
+	contentTypeJSONLD  = "application/ld+json"
 )
 
 func getFormat(r *http.Request, formKey string, acceptName string) *quad.Format {
@@ -415,9 +416,11 @@ func defaultErrorFunc(w query.ResponseWriter, err error) {
 }
 
 func writeResults(w io.Writer, r interface{}) {
-	w.Write([]byte(`{"result": `))
-	json.NewEncoder(w).Encode(r)
-	w.Write([]byte("}\n"))
+	enc := json.NewEncoder(w)
+	enc.SetEscapeHTML(false)
+	enc.Encode(map[string]interface{}{
+		"result": r,
+	})
 }
 
 const maxQuerySize = 1024 * 1024 // 1 MB
@@ -488,10 +491,20 @@ func (api *APIv2) ServeQuery(w http.ResponseWriter, r *http.Request) {
 		clog.Infof("query: %s: %q", lang, qu)
 	}
 
-	it, err := ses.Execute(ctx, qu, query.Options{
-		Collation: query.JSON,
+	opt := query.Options{
+		Collation: query.JSON, // TODO: switch to JSON-LD by default when the time comes
 		Limit:     api.limit,
-	})
+	}
+	if specs := ParseAccept(r.Header, hdrAccept); len(specs) != 0 {
+		// TODO: sort by Q
+		switch specs[0].Value {
+		case contentTypeJSON:
+			opt.Collation = query.JSON
+		case contentTypeJSONLD:
+			opt.Collation = query.JSONLD
+		}
+	}
+	it, err := ses.Execute(ctx, qu, opt)
 	if err != nil {
 		errFunc(w, err)
 		return
@@ -506,5 +519,10 @@ func (api *APIv2) ServeQuery(w http.ResponseWriter, r *http.Request) {
 		errFunc(w, err)
 		return
 	}
+	if opt.Collation == query.JSONLD {
+		w.Header().Set(hdrContentType, contentTypeJSONLD)
+	} else {
+		w.Header().Set(hdrContentType, contentTypeJSON)
+	}
 	writeResults(w, out)
 }