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vendor/github.com/projectcalico/libcalico-go/lib/watch/interface.go

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+// Copyright (c) 2016-2017 Tigera, Inc. All rights reserved.
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package watch
+
+import (
+	"k8s.io/apimachinery/pkg/runtime"
+)
+
+// Interface can be implemented by anything that knows how to watch and report changes.
+type Interface interface {
+	// Stops watching. Will close the channel returned by ResultChan(). Releases
+	// any resources used by the watch.
+	Stop()
+
+	// Returns a chan which will receive all the events. If an error occurs
+	// or Stop() is called, this channel will be closed, in which case the
+	// watch should be completely cleaned up.
+	ResultChan() <-chan Event
+}
+
+// EventType defines the possible types of events.
+type EventType string
+
+const (
+	// Event type:
+	// Added
+	// * a new Object has been added.  If the Watcher does not have a specific
+	//   ResourceVersion to watch from, existing entries will first be listed
+	//   and propagated as "Added" events.
+	// Modified
+	// * an Object has been modified.
+	// Deleted
+	// * an Object has been deleted
+	// Error
+	// * an error has occurred.  If the error is terminating, the results channel
+	//   will be closed.
+	Added    EventType = "ADDED"
+	Modified EventType = "MODIFIED"
+	Deleted  EventType = "DELETED"
+	Error    EventType = "ERROR"
+
+	DefaultChanSize int32 = 100
+)
+
+// Event represents a single event to a watched resource.
+type Event struct {
+	Type EventType
+
+	// Previous is:
+	// * If Type is Added, Error or Synced: nil
+	// * If Type is Modified or Deleted: the previous state of the object
+	// Object is:
+	//  * If Type is Added or Modified: the new state of the object.
+	//  * If Type is Deleted, Error or Synced: nil
+	Previous runtime.Object
+	Object   runtime.Object
+
+	// The error, if EventType is Error.
+	Error error
+}