chore: import upstream snapshot with attribution

internal/event/source/source.go

@@ -0,0 +1,47 @@
+// Copyright (c) 2026 Lark Technologies Pte. Ltd.
+// SPDX-License-Identifier: MIT
+
+// Package source is a pluggable event source abstraction (separate package to keep
+// business registrations free of SDK transitive deps).
+package source
+
+import (
+	"context"
+	"sync"
+
+	"github.com/larksuite/cli/internal/event"
+)
+
+// StatusNotifier surfaces SourceState* lifecycle states; detail is free-form context.
+type StatusNotifier func(state, detail string)
+
+// Source produces events; emit MUST return quickly (anything slow stalls the SDK read loop).
+type Source interface {
+	Name() string
+	Start(ctx context.Context, eventTypes []string, emit func(*event.RawEvent), notify StatusNotifier) error
+}
+
+var (
+	registry   []Source
+	registryMu sync.Mutex
+)
+
+func Register(s Source) {
+	registryMu.Lock()
+	defer registryMu.Unlock()
+	registry = append(registry, s)
+}
+
+func All() []Source {
+	registryMu.Lock()
+	defer registryMu.Unlock()
+	out := make([]Source, len(registry))
+	copy(out, registry)
+	return out
+}
+
+func ResetForTest() {
+	registryMu.Lock()
+	defer registryMu.Unlock()
+	registry = nil
+}