Complete refactor to new grpc control plane and only http proxy for carts (#4)

Co-authored-by: matst80 <mats.tornberg@gmail.com>
Reviewed-on: https://git.tornberg.me/mats/go-cart-actor/pulls/4
Co-authored-by: Mats Törnberg <mats@tornberg.me>
Co-committed-by: Mats Törnberg <mats@tornberg.me>

pkg/discovery/discovery_mock.go

@@ -0,0 +1,102 @@
+package discovery
+
+import (
+	"context"
+	"sync"
+
+	"k8s.io/apimachinery/pkg/watch"
+)
+
+// MockDiscovery is an in-memory Discovery implementation for tests.
+// It allows deterministic injection of host additions/removals without
+// depending on Kubernetes API machinery.
+type MockDiscovery struct {
+	mu      sync.RWMutex
+	hosts   []string
+	events  chan HostChange
+	closed  bool
+	started bool
+}
+
+// NewMockDiscovery creates a mock discovery with an initial host list.
+func NewMockDiscovery(initial []string) *MockDiscovery {
+	cp := make([]string, len(initial))
+	copy(cp, initial)
+	return &MockDiscovery{
+		hosts:  cp,
+		events: make(chan HostChange, 32),
+	}
+}
+
+// Discover returns the current host snapshot.
+func (m *MockDiscovery) Discover() ([]string, error) {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+	cp := make([]string, len(m.hosts))
+	copy(cp, m.hosts)
+	return cp, nil
+}
+
+// Watch returns a channel that will receive HostChange events.
+// The channel is buffered; AddHost/RemoveHost push events non-blockingly.
+func (m *MockDiscovery) Watch() (<-chan HostChange, error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	if m.closed {
+		return nil, context.Canceled
+	}
+	m.started = true
+	return m.events, nil
+}
+
+// AddHost inserts a new host (if absent) and emits an Added event.
+func (m *MockDiscovery) AddHost(host string) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	if m.closed {
+		return
+	}
+	for _, h := range m.hosts {
+		if h == host {
+			return
+		}
+	}
+	m.hosts = append(m.hosts, host)
+	if m.started {
+		m.events <- HostChange{Host: host, Type: watch.Added}
+	}
+}
+
+// RemoveHost removes a host (if present) and emits a Deleted event.
+func (m *MockDiscovery) RemoveHost(host string) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	if m.closed {
+		return
+	}
+	idx := -1
+	for i, h := range m.hosts {
+		if h == host {
+			idx = i
+			break
+		}
+	}
+	if idx == -1 {
+		return
+	}
+	m.hosts = append(m.hosts[:idx], m.hosts[idx+1:]...)
+	if m.started {
+		m.events <- HostChange{Host: host, Type: watch.Deleted}
+	}
+}
+
+// Close closes the event channel (idempotent).
+func (m *MockDiscovery) Close() {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	if m.closed {
+		return
+	}
+	m.closed = true
+	close(m.events)
+}