Introduce renderers; allow them to recurse.

app/api_topologies.go

@@ -37,7 +37,7 @@ func makeTopologyList(rep Reporter) func(w http.ResponseWriter, r *http.Request)
 					subTopologies = append(subTopologies, APITopologyDesc{
 						Name:  subDef.human,
 						URL:   "/api/topology/" + subName,
-						Stats: stats(render(rpt, subDef.maps)),
+						Stats: stats(subDef.renderer.Render(rpt)),
 					})
 				}
 			}
@@ -45,7 +45,7 @@ func makeTopologyList(rep Reporter) func(w http.ResponseWriter, r *http.Request)
 				Name:          def.human,
 				URL:           "/api/topology/" + name,
 				SubTopologies: subTopologies,
-				Stats:         stats(render(rpt, def.maps)),
+				Stats:         stats(def.renderer.Render(rpt)),
 			})
 		}
 		respondWith(w, http.StatusOK, topologies)

app/api_topology.go

@@ -30,19 +30,10 @@ type APIEdge struct {
 	Metadata report.AggregateMetadata `json:"metadata"`
 }
 
-func render(rpt report.Report, maps []topologyMapper) report.RenderableNodes {
-	result := report.RenderableNodes{}
-	for _, m := range maps {
-		rns := m.selector(rpt).RenderBy(m.mapper, m.pseudo)
-		result.Merge(rns)
-	}
-	return result
-}
-
 // Full topology.
 func handleTopology(rep Reporter, t topologyView, w http.ResponseWriter, r *http.Request) {
 	respondWith(w, http.StatusOK, APITopology{
-		Nodes: render(rep.Report(), t.maps),
+		Nodes: t.renderer.Render(rep.Report()),
 	})
 }
 
@@ -69,7 +60,7 @@ func handleNode(rep Reporter, t topologyView, w http.ResponseWriter, r *http.Req
 		vars     = mux.Vars(r)
 		nodeID   = vars["id"]
 		rpt      = rep.Report()
-		node, ok = render(rpt, t.maps)[nodeID]
+		node, ok = t.renderer.Render(rep.Report())[nodeID]
 	)
 	if !ok {
 		http.NotFound(w, r)
@@ -85,13 +76,9 @@ func handleEdge(rep Reporter, t topologyView, w http.ResponseWriter, r *http.Req
 		localID  = vars["local"]
 		remoteID = vars["remote"]
 		rpt      = rep.Report()
-		metadata = report.AggregateMetadata{}
+		metadata = t.renderer.AggregateMetadata(rpt, localID, remoteID)
 	)
 
-	for _, m := range t.maps {
-		metadata.Merge(m.selector(rpt).EdgeMetadata(m.mapper, localID, remoteID).Transform())
-	}
-
 	respondWith(w, http.StatusOK, APIEdge{Metadata: metadata})
 }
 
@@ -128,7 +115,7 @@ func handleWebsocket(
 		tick         = time.Tick(loop)
 	)
 	for {
-		newTopo := render(rep.Report(), t.maps)
+		newTopo := t.renderer.Render(rep.Report())
 		diff := report.TopoDiff(previousTopo, newTopo)
 		previousTopo = newTopo
 

app/router.go

@@ -5,6 +5,7 @@ import (
 
 	"github.com/gorilla/mux"
 
+	"github.com/weaveworks/scope/render"
 	"github.com/weaveworks/scope/report"
 )
 
@@ -47,51 +48,37 @@ func apiHandler(w http.ResponseWriter, r *http.Request) {
 
 var topologyRegistry = map[string]topologyView{
 	"applications": {
-		human:  "Applications",
-		parent: "",
-		maps: []topologyMapper{
-			{report.SelectEndpoint, report.ProcessPID, report.GenericPseudoNode},
-		},
+		human:    "Applications",
+		parent:   "",
+		renderer: render.Map{Selector: report.SelectEndpoint, Mapper: report.ProcessPID, Pseudo: report.GenericPseudoNode},
 	},
 	"applications-by-name": {
-		human:  "by name",
-		parent: "applications",
-		maps: []topologyMapper{
-			{report.SelectEndpoint, report.ProcessName, report.GenericGroupedPseudoNode},
-		},
+		human:    "by name",
+		parent:   "applications",
+		renderer: render.Map{Selector: report.SelectEndpoint, Mapper: report.ProcessName, Pseudo: report.GenericGroupedPseudoNode},
 	},
 	"containers": {
 		human:  "Containers",
 		parent: "",
-		maps: []topologyMapper{
-			{report.SelectEndpoint, report.MapEndpoint2Container, report.InternetOnlyPseudoNode},
-			{report.SelectContainer, report.MapContainerIdentity, report.InternetOnlyPseudoNode},
-		},
+		renderer: render.Reduce([]render.Renderer{
+			render.Map{Selector: report.SelectEndpoint, Mapper: report.MapEndpoint2Container, Pseudo: report.InternetOnlyPseudoNode},
+			render.Map{Selector: report.SelectContainer, Mapper: report.MapContainerIdentity, Pseudo: report.InternetOnlyPseudoNode},
+		}),
 	},
 	"containers-by-image": {
-		human:  "by image",
-		parent: "containers",
-		maps: []topologyMapper{
-			{report.SelectEndpoint, report.ProcessContainerImage, report.InternetOnlyPseudoNode},
-		},
+		human:    "by image",
+		parent:   "containers",
+		renderer: render.Map{Selector: report.SelectEndpoint, Mapper: report.ProcessContainerImage, Pseudo: report.InternetOnlyPseudoNode},
 	},
 	"hosts": {
-		human:  "Hosts",
-		parent: "",
-		maps: []topologyMapper{
-			{report.SelectAddress, report.NetworkHostname, report.GenericPseudoNode},
-		},
+		human:    "Hosts",
+		parent:   "",
+		renderer: render.Map{Selector: report.SelectAddress, Mapper: report.NetworkHostname, Pseudo: report.GenericPseudoNode},
 	},
 }
 
 type topologyView struct {
-	human  string
-	parent string
-	maps   []topologyMapper
-}
-
-type topologyMapper struct {
-	selector report.TopologySelector
-	mapper   report.MapFunc
-	pseudo   report.PseudoFunc
+	human    string
+	parent   string
+	renderer render.Renderer
 }