Changeset 0.15.0 (#71)

server/treepath/summary.go

@@ -0,0 +1,38 @@
+package treepath
+
+import "encoding/json"
+
+// IsSummaryMessage checks if a PathMessage has summary metadata
+// (metadata.type == "summary").
+func IsSummaryMessage(m *PathMessage) bool {
+	if m.Metadata == nil {
+		return false
+	}
+	meta := ParseMetadata(m)
+	return meta["type"] == "summary"
+}
+
+// ParseMetadata unmarshals the JSONB metadata on a PathMessage.
+// Returns an empty map on any error.
+func ParseMetadata(m *PathMessage) map[string]interface{} {
+	if m.Metadata == nil {
+		return map[string]interface{}{}
+	}
+	var meta map[string]interface{}
+	if err := json.Unmarshal(*m.Metadata, &meta); err != nil {
+		return map[string]interface{}{}
+	}
+	return meta
+}
+
+// FindSummaryBoundary returns the index of the most recent summary node
+// in a path, or -1 if no summary exists.
+func FindSummaryBoundary(path []PathMessage) int {
+	idx := -1
+	for i := range path {
+		if IsSummaryMessage(&path[i]) {
+			idx = i
+		}
+	}
+	return idx
+}