refactor: simplify summary generation (resolve #68)

models/heartbeats.go

@@ -0,0 +1,38 @@
+package models
+
+import "sort"
+
+type Heartbeats []*Heartbeat
+
+func (h Heartbeats) Len() int {
+	return len(h)
+}
+
+func (h Heartbeats) Less(i, j int) bool {
+	return h[i].Time.T().Before(h[j].Time.T())
+}
+
+func (h Heartbeats) Swap(i, j int) {
+	h[i], h[j] = h[j], h[i]
+}
+
+func (h *Heartbeats) Sorted() *Heartbeats {
+	sort.Sort(h)
+	return h
+}
+
+func (h *Heartbeats) First() *Heartbeat {
+	// assumes slice to be sorted
+	if h.Len() == 0 {
+		return nil
+	}
+	return (*h)[0]
+}
+
+func (h *Heartbeats) Last() *Heartbeat {
+	// assumes slice to be sorted
+	if h.Len() == 0 {
+		return nil
+	}
+	return (*h)[h.Len()-1]
+}