framework/fsm/hook_example_test.go

// Copyright (C) 2016 The Android Open Source Project
//
// 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 fsm_test

import (
	"android.googlesource.com/platform/tools/gpu/framework/fsm"
	"android.googlesource.com/platform/tools/gpu/framework/log"
)

// This example shows how to use hooks to detect specific transitions.
func ExampleHook() {
	ctx := log.Background().PreFilter(log.NoLimit).Filter(log.Pass).Handler(log.Stdout(log.Normal))
	ctx = ctx.Enter("Example")
	count := 0
	err := fsm.Run(ctx, fsm.MustCompile(fsm.FSM{
		States: []fsm.State{
			{Name: "Init"},
			fsm.Do("Ping", func(ctx log.Context) error {
				count++
				ctx.Printf("Pinging %d", count)
				if count > 2 {
					fsm.Get(ctx).Trigger(ctx, "stop")
				}
				return nil
			}),
			fsm.Do("Pong", func(ctx log.Context) error {
				ctx.Print("Ponged")
				return nil
			}),
			fsm.Exit("Done"),
		},
		Transitions: []fsm.Transition{
			{From: "Init", To: "Ping"},
			{From: "Ping", To: "Pong"},
			{From: "Pong", To: "Ping"},
			{From: "Ping", Event: "stop", To: "Done"},
		},
		Hooks: []fsm.Hook{
			fsm.OnExit("Ping", func(ctx log.Context, fsm *fsm.Instance, from fsm.StateID, event fsm.Event) {
				ctx.Printf("Leaving %s to %s because %s", from, fsm.State(), event)
			}),
			fsm.OnEnter("Ping", func(ctx log.Context, fsm *fsm.Instance, from fsm.StateID, event fsm.Event) {
				ctx.Printf("Entering %s from %s because %s", fsm.State(), from, event)
			}),
			fsm.OnEvent("stop", func(ctx log.Context, fsm *fsm.Instance, from fsm.StateID, event fsm.Event) {
				ctx.Printf("%s in %s goes to %s", event, from, fsm.State())
			}),
		},
	}))
	if err != nil {
		ctx.Fail(err, "FSM failed")
		return
	}
	// Output:
	//Info:Example:Entering Ping from Init because next
	//Info:Example->Ping:Pinging 1
	//Info:Example:Leaving Ping to Pong because next
	//Info:Example->Pong:Ponged
	//Info:Example:Entering Ping from Pong because next
	//Info:Example->Ping:Pinging 2
	//Info:Example:Leaving Ping to Pong because next
	//Info:Example->Pong:Ponged
	//Info:Example:Entering Ping from Pong because next
	//Info:Example->Ping:Pinging 3
	//Info:Example:Leaving Ping to Done because stop
	//Info:Example:stop in Ping goes to Done
}