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

go/internal/store/store.go

@@ -0,0 +1,38 @@
+package store
+
+import "sync"
+
+// DeviceID is a typed device identifier.
+// Using a named type (instead of plain string) makes call sites clearer
+// and prevents accidentally mixing unrelated string values.
+type DeviceID string
+
+// Store holds in-memory fleet metrics for known devices.
+type Store struct {
+	known map[DeviceID]struct{}
+
+	// mu protects the heartbeats/uploads maps (insert/lookup of entries only).
+	// Each per-device history has its own mutex for mutations.
+	mu         sync.Mutex
+	heartbeats map[DeviceID]*heartbeatHistory
+	uploads    map[DeviceID]*uploadHistory
+}
+
+// New creates a Store seeded with the given known device IDs.
+func New(known []DeviceID) *Store {
+	m := make(map[DeviceID]struct{}, len(known))
+	for _, id := range known {
+		m[id] = struct{}{}
+	}
+	return &Store{
+		known:      m,
+		heartbeats: make(map[DeviceID]*heartbeatHistory),
+		uploads:    make(map[DeviceID]*uploadHistory),
+	}
+}
+
+// Known reports whether deviceID was present in the startup device list.
+func (s *Store) Known(deviceID DeviceID) bool {
+	_, ok := s.known[deviceID]
+	return ok
+}