feat(agentcompat): add scoped IO stream capabilities

Co-authored-by: naiba/CloudCode <hi+cloudcode@nai.ba>

service/rpc/io_stream_capability_state_agentcompat.go

@@ -0,0 +1,78 @@
+//go:build agentcompat
+
+package rpc
+
+import (
+	"crypto/rand"
+)
+
+type agentCompatCapabilityPhase uint8
+
+const (
+	agentCompatCapabilityRegistered agentCompatCapabilityPhase = iota + 1
+	agentCompatCapabilityConsumed
+	agentCompatCapabilityPublished
+)
+
+const (
+	agentCompatCapabilityMaxActivePerPAT = 16
+	agentCompatCapabilityMaxActiveGlobal = 128
+	agentCompatCapabilityMaxProcessMints = 4096
+)
+
+type agentCompatCapabilityRegistration struct {
+	registration AgentCompatCapabilityRegistration
+	phase        agentCompatCapabilityPhase
+	generation   uint64
+	streamID     string
+	stream       *ioStreamContext
+	notify       chan struct{}
+}
+
+type agentCompatCapabilityState struct {
+	active      map[string]*agentCompatCapabilityRegistration
+	activeByPAT map[uint64]uint16
+	// Used tokens are process-lifetime tombstones; deletion never makes a capability reusable.
+	used            map[string]struct{}
+	tokenSource     func([]byte) error
+	nextIdentity    uint64
+	waitObserver    func()
+	publishObserver func()
+}
+
+func (s *NezhaHandler) initializeAgentCompatCapabilities() {
+	s.agentCompatCapabilities.active = make(map[string]*agentCompatCapabilityRegistration)
+	s.agentCompatCapabilities.activeByPAT = make(map[uint64]uint16)
+	s.agentCompatCapabilities.used = make(map[string]struct{})
+	s.agentCompatCapabilities.tokenSource = func(destination []byte) error {
+		_, err := rand.Read(destination)
+		return err
+	}
+}
+
+func (s *NezhaHandler) setAgentCompatCapabilityTokenSourceForTest(source func([]byte) error) {
+	s.ioStreamMutex.Lock()
+	defer s.ioStreamMutex.Unlock()
+	s.agentCompatCapabilities.tokenSource = source
+}
+
+func (s *NezhaHandler) setAgentCompatCapabilityWaitObserverForTest(observer func()) {
+	s.ioStreamMutex.Lock()
+	defer s.ioStreamMutex.Unlock()
+	s.agentCompatCapabilities.waitObserver = observer
+}
+
+func (s *NezhaHandler) setAgentCompatCapabilityPublishObserverForTest(observer func()) {
+	s.ioStreamMutex.Lock()
+	defer s.ioStreamMutex.Unlock()
+	s.agentCompatCapabilities.publishObserver = observer
+}
+
+func (s *NezhaHandler) SetAgentCompatCapabilityPublishObserverForTest(observer func()) {
+	s.setAgentCompatCapabilityPublishObserverForTest(observer)
+}
+
+func (registration *agentCompatCapabilityRegistration) publishLocked() {
+	close(registration.notify)
+	registration.notify = make(chan struct{})
+}