go project - add a migration and rename the dockerfiles so that Go is the primary

go/internal/store/heartbeat.go

@@ -0,0 +1,94 @@
+package store
+
+import (
+	"errors"
+	"sync"
+	"time"
+)
+
+// ErrOutOfSequence is returned when a heartbeat timestamp is earlier than
+// the latest accepted heartbeat for that device.
+var ErrOutOfSequence = errors.New("heartbeat out of sequence")
+
+// heartbeatHistory tracks one device's heartbeat timeline.
+// Unexported: only Store methods expose behavior.
+type heartbeatHistory struct {
+	mu    sync.Mutex
+	count int64
+	first time.Time
+	last  time.Time
+}
+
+func (h *heartbeatHistory) add(sentAt time.Time) error {
+	h.mu.Lock()
+	defer h.mu.Unlock()
+
+	if h.first.IsZero() {
+		h.first = sentAt
+		h.last = sentAt
+		h.count = 1
+		return nil
+	}
+
+	// Equal timestamps are allowed (matches C#: sentAt < LastHeartBeat only).
+	if sentAt.Before(h.last) {
+		return ErrOutOfSequence
+	}
+
+	h.last = sentAt
+	h.count++
+	return nil
+}
+
+func (h *heartbeatHistory) uptime() float64 {
+	h.mu.Lock()
+	defer h.mu.Unlock()
+
+	if h.first.IsZero() {
+		return 0
+	}
+
+	minutes := h.last.Sub(h.first).Minutes()
+	// Single heartbeat (or identical timestamps): treat span as one minute.
+	if minutes == 0 {
+		minutes = 1
+	}
+
+	return float64(h.count) / minutes * 100
+}
+
+// historyFor returns the per-device history, creating it if needed.
+// The store-level lock only covers map insert/lookup; callers then use
+// the history's own lock for mutations/reads.
+func (s *Store) historyFor(id DeviceID) *heartbeatHistory {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	h, ok := s.heartbeats[id]
+	if !ok {
+		h = &heartbeatHistory{}
+		s.heartbeats[id] = h
+	}
+	return h
+}
+
+// AddHeartbeat records a heartbeat for deviceID.
+// Returns ErrOutOfSequence if sentAt is earlier than the last accepted beat.
+func (s *Store) AddHeartbeat(deviceID DeviceID, sentAt time.Time) error {
+	return s.historyFor(deviceID).add(sentAt)
+}
+
+// Uptime returns uptime percent for deviceID:
+//
+//	(heartbeatCount / minutesBetweenFirstAndLast) * 100
+//
+// Unknown / never-seen devices return 0. A zero-length span is treated as 1 minute.
+func (s *Store) Uptime(deviceID DeviceID) float64 {
+	s.mu.Lock()
+	h, ok := s.heartbeats[deviceID]
+	s.mu.Unlock()
+	if !ok {
+		return 0
+	}
+	return h.uptime()
+}