Implemented device event watcher and improved errors.

cmd/demo/demo.go

@@ -6,8 +6,10 @@ import (
 	"fmt"
 	"io/ioutil"
 	"log"
+	"time"
 
 	adb "github.com/zach-klippenstein/goadb"
+	"github.com/zach-klippenstein/goadb/util"
 )
 
 var port = flag.Int("p", adb.AdbPort, "")
@@ -47,10 +49,33 @@ func main() {
 		PrintDeviceInfoAndError(adb.DeviceWithSerial(serial))
 	}
 
+	fmt.Println()
+	fmt.Println("Watching for device state changes.")
+	watcher, err := adb.NewDeviceWatcher(adb.ClientConfig{})
+	for event := range watcher.C() {
+		fmt.Printf("\t[%s]%+v\n", time.Now(), event)
+	}
+	if watcher.Err() != nil {
+		printErr(watcher.Err())
+	}
+
 	//fmt.Println("Killing server…")
 	//client.KillServer()
 }
 
+func printErr(err error) {
+	switch err := err.(type) {
+	case *util.Err:
+		fmt.Println(err.Error())
+		if err.Cause != nil {
+			fmt.Print("caused by ")
+			printErr(err.Cause)
+		}
+	default:
+		fmt.Println("error:", err)
+	}
+}
+
 func PrintDeviceInfoAndError(descriptor adb.DeviceDescriptor) {
 	device := adb.NewDeviceClient(adb.ClientConfig{}, descriptor)
 	if err := PrintDeviceInfo(device); err != nil {

device_watcher.go

@@ -0,0 +1,214 @@
+package goadb
+
+import (
+	"log"
+	"runtime"
+	"strings"
+	"sync/atomic"
+
+	"github.com/zach-klippenstein/goadb/util"
+	"github.com/zach-klippenstein/goadb/wire"
+)
+
+/*
+DeviceWatcher publishes device status change events.
+If the server dies while listening for events, it restarts the server.
+*/
+type DeviceWatcher struct {
+	*deviceWatcherImpl
+}
+
+type DeviceStateChangedEvent struct {
+	Serial   string
+	OldState string
+	NewState string
+}
+
+type deviceWatcherImpl struct {
+	config ClientConfig
+
+	// If an error occurs, it is stored here and eventChan is close immediately after.
+	err atomic.Value
+
+	eventChan chan DeviceStateChangedEvent
+
+	// Function to start the server if it's not running or dies.
+	startServer func() error
+}
+
+func NewDeviceWatcher(config ClientConfig) (*DeviceWatcher, error) {
+	watcher := &DeviceWatcher{&deviceWatcherImpl{
+		config:      config.sanitized(),
+		eventChan:   make(chan DeviceStateChangedEvent),
+		startServer: StartServer,
+	}}
+
+	runtime.SetFinalizer(watcher, func(watcher *DeviceWatcher) {
+		watcher.Shutdown()
+	})
+
+	go publishDevices(watcher.deviceWatcherImpl)
+
+	return watcher, nil
+}
+
+/*
+C returns a channel than can be received on to get events.
+If an unrecoverable error occurs, or Shutdown is called, the channel will be closed.
+*/
+func (w *DeviceWatcher) C() <-chan DeviceStateChangedEvent {
+	return w.eventChan
+}
+
+// Err returns the error that caused the channel returned by C to be closed, if C is closed.
+// If C is not closed, its return value is undefined.
+func (w *DeviceWatcher) Err() error {
+	if err, ok := w.err.Load().(error); ok {
+		return err
+	}
+	return nil
+}
+
+// Shutdown stops the watcher from listening for events and closes the channel returned
+// from C.
+func (w *DeviceWatcher) Shutdown() {
+	// TODO(z): Implement.
+}
+
+func (w *deviceWatcherImpl) reportErr(err error) {
+	w.err.Store(err)
+}
+
+/*
+publishDevices reads device lists from scanner, calculates diffs, and publishes events on
+eventChan.
+Returns when scanner returns an error.
+Doesn't refer directly to a *DeviceWatcher so it can be GCed (which will,
+in turn, close Scanner and stop this goroutine).
+
+TODO: to support shutdown, spawn a new goroutine each time a server connection is established.
+This goroutine should read messages and send them to a message channel. Can write errors directly
+to errVal. publisHDevicesUntilError should take the msg chan and the scanner and select on the msg chan and stop chan, and if the stop
+chan sends, close the scanner and return true. If the msg chan closes, just return false.
+publishDevices can look at ret val: if false and err == EOF, reconnect. If false and other error, report err
+and abort. If true, report no error and stop.
+*/
+func publishDevices(watcher *deviceWatcherImpl) {
+	defer close(watcher.eventChan)
+
+	var lastKnownStates map[string]string
+	finished := false
+
+	for {
+		scanner, err := connectToTrackDevices(watcher.config.Dialer)
+		if err != nil {
+			watcher.reportErr(err)
+			return
+		}
+
+		finished, err = publishDevicesUntilError(scanner, watcher.eventChan, &lastKnownStates)
+
+		if finished {
+			scanner.Close()
+			return
+		}
+
+		if util.HasErrCode(err, util.ConnectionResetError) {
+			// The server died, restart and reconnect.
+			log.Println("[DeviceWatcher] server died, restarting…")
+			if err := watcher.startServer(); err != nil {
+				log.Println("[DeviceWatcher] error restarting server, giving up")
+				watcher.reportErr(err)
+				return
+			} // Else server should be running, continue listening.
+		} else {
+			// Unknown error, don't retry.
+			watcher.reportErr(err)
+			return
+		}
+	}
+}
+
+func connectToTrackDevices(dialer Dialer) (wire.Scanner, error) {
+	conn, err := dialer.Dial()
+	if err != nil {
+		return nil, err
+	}
+
+	if err := wire.SendMessageString(conn, "host:track-devices"); err != nil {
+		conn.Close()
+		return nil, err
+	}
+
+	if err := wire.ReadStatusFailureAsError(conn, "host:track-devices"); err != nil {
+		conn.Close()
+		return nil, err
+	}
+
+	return conn, nil
+}
+
+func publishDevicesUntilError(scanner wire.Scanner, eventChan chan<- DeviceStateChangedEvent, lastKnownStates *map[string]string) (finished bool, err error) {
+	for {
+		msg, err := scanner.ReadMessage()
+		if err != nil {
+			return false, err
+		}
+
+		deviceStates, err := parseDeviceStates(string(msg))
+		if err != nil {
+			return false, err
+		}
+
+		for _, event := range calculateStateDiffs(*lastKnownStates, deviceStates) {
+			eventChan <- event
+		}
+		*lastKnownStates = deviceStates
+	}
+}
+
+func parseDeviceStates(msg string) (states map[string]string, err error) {
+	states = make(map[string]string)
+
+	for lineNum, line := range strings.Split(msg, "\n") {
+		if len(line) == 0 {
+			continue
+		}
+
+		fields := strings.Split(line, "\t")
+		if len(fields) != 2 {
+			err = util.Errorf(util.ParseError, "invalid device state line %d: %s", lineNum, line)
+			return
+		}
+
+		serial, state := fields[0], fields[1]
+		states[serial] = state
+	}
+
+	return
+}
+
+func calculateStateDiffs(oldStates, newStates map[string]string) (events []DeviceStateChangedEvent) {
+	for serial, oldState := range oldStates {
+		newState, ok := newStates[serial]
+
+		if oldState != newState {
+			if ok {
+				// Device present in both lists: state changed.
+				events = append(events, DeviceStateChangedEvent{serial, oldState, newState})
+			} else {
+				// Device only present in old list: device removed.
+				events = append(events, DeviceStateChangedEvent{serial, oldState, ""})
+			}
+		}
+	}
+
+	for serial, newState := range newStates {
+		if _, ok := oldStates[serial]; !ok {
+			// Device only present in new list: device added.
+			events = append(events, DeviceStateChangedEvent{serial, "", newState})
+		}
+	}
+
+	return events
+}

device_watcher_test.go

@@ -0,0 +1,232 @@
+package goadb
+
+import (
+	"log"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/zach-klippenstein/goadb/util"
+	"github.com/zach-klippenstein/goadb/wire"
+)
+
+func TestParseDeviceStatesSingle(t *testing.T) {
+	states, err := parseDeviceStates(`192.168.56.101:5555	emulator-state
+`)
+
+	assert.NoError(t, err)
+	assert.Len(t, states, 1)
+	assert.Equal(t, "emulator-state", states["192.168.56.101:5555"])
+}
+
+func TestParseDeviceStatesMultiple(t *testing.T) {
+	states, err := parseDeviceStates(`192.168.56.101:5555	emulator-state
+0x0x0x0x	usb-state
+`)
+
+	assert.NoError(t, err)
+	assert.Len(t, states, 2)
+	assert.Equal(t, "emulator-state", states["192.168.56.101:5555"])
+	assert.Equal(t, "usb-state", states["0x0x0x0x"])
+}
+
+func TestParseDeviceStatesMalformed(t *testing.T) {
+	_, err := parseDeviceStates(`192.168.56.101:5555	emulator-state
+0x0x0x0x
+`)
+
+	assert.True(t, util.HasErrCode(err, util.ParseError))
+	assert.Equal(t, "invalid device state line 1: 0x0x0x0x", err.(*util.Err).Message)
+}
+
+func TestCalculateStateDiffsUnchangedEmpty(t *testing.T) {
+	oldStates := map[string]string{}
+	newStates := map[string]string{}
+
+	diffs := calculateStateDiffs(oldStates, newStates)
+
+	assert.Empty(t, diffs)
+}
+
+func TestCalculateStateDiffsUnchangedNonEmpty(t *testing.T) {
+	oldStates := map[string]string{
+		"1": "device",
+		"2": "device",
+	}
+	newStates := map[string]string{
+		"1": "device",
+		"2": "device",
+	}
+
+	diffs := calculateStateDiffs(oldStates, newStates)
+
+	assert.Empty(t, diffs)
+}
+
+func TestCalculateStateDiffsOneAdded(t *testing.T) {
+	oldStates := map[string]string{}
+	newStates := map[string]string{
+		"serial": "added",
+	}
+
+	diffs := calculateStateDiffs(oldStates, newStates)
+
+	assert.Equal(t, []DeviceStateChangedEvent{
+		DeviceStateChangedEvent{"serial", "", "added"},
+	}, diffs)
+}
+
+func TestCalculateStateDiffsOneRemoved(t *testing.T) {
+	oldStates := map[string]string{
+		"serial": "removed",
+	}
+	newStates := map[string]string{}
+
+	diffs := calculateStateDiffs(oldStates, newStates)
+
+	assert.Equal(t, []DeviceStateChangedEvent{
+		DeviceStateChangedEvent{"serial", "removed", ""},
+	}, diffs)
+}
+
+func TestCalculateStateDiffsOneAddedOneUnchanged(t *testing.T) {
+	oldStates := map[string]string{
+		"1": "device",
+	}
+	newStates := map[string]string{
+		"1": "device",
+		"2": "added",
+	}
+
+	diffs := calculateStateDiffs(oldStates, newStates)
+
+	assert.Equal(t, []DeviceStateChangedEvent{
+		DeviceStateChangedEvent{"2", "", "added"},
+	}, diffs)
+}
+
+func TestCalculateStateDiffsOneRemovedOneUnchanged(t *testing.T) {
+	oldStates := map[string]string{
+		"1": "removed",
+		"2": "device",
+	}
+	newStates := map[string]string{
+		"2": "device",
+	}
+
+	diffs := calculateStateDiffs(oldStates, newStates)
+
+	assert.Equal(t, []DeviceStateChangedEvent{
+		DeviceStateChangedEvent{"1", "removed", ""},
+	}, diffs)
+}
+
+func TestCalculateStateDiffsOneAddedOneRemoved(t *testing.T) {
+	oldStates := map[string]string{
+		"1": "removed",
+	}
+	newStates := map[string]string{
+		"2": "added",
+	}
+
+	diffs := calculateStateDiffs(oldStates, newStates)
+
+	assert.Equal(t, []DeviceStateChangedEvent{
+		DeviceStateChangedEvent{"1", "removed", ""},
+		DeviceStateChangedEvent{"2", "", "added"},
+	}, diffs)
+}
+
+func TestCalculateStateDiffsOneChangedOneUnchanged(t *testing.T) {
+	oldStates := map[string]string{
+		"1": "oldState",
+		"2": "device",
+	}
+	newStates := map[string]string{
+		"1": "newState",
+		"2": "device",
+	}
+
+	diffs := calculateStateDiffs(oldStates, newStates)
+
+	assert.Equal(t, []DeviceStateChangedEvent{
+		DeviceStateChangedEvent{"1", "oldState", "newState"},
+	}, diffs)
+}
+
+func TestCalculateStateDiffsMultipleChangedMultipleUnchanged(t *testing.T) {
+	oldStates := map[string]string{
+		"1": "oldState",
+		"2": "oldState",
+	}
+	newStates := map[string]string{
+		"1": "newState",
+		"2": "newState",
+	}
+
+	diffs := calculateStateDiffs(oldStates, newStates)
+
+	assert.Equal(t, []DeviceStateChangedEvent{
+		DeviceStateChangedEvent{"1", "oldState", "newState"},
+		DeviceStateChangedEvent{"2", "oldState", "newState"},
+	}, diffs)
+}
+
+func TestCalculateStateDiffsOneAddedOneRemovedOneChanged(t *testing.T) {
+	oldStates := map[string]string{
+		"1": "oldState",
+		"2": "removed",
+	}
+	newStates := map[string]string{
+		"1": "newState",
+		"3": "added",
+	}
+
+	diffs := calculateStateDiffs(oldStates, newStates)
+
+	assert.Equal(t, []DeviceStateChangedEvent{
+		DeviceStateChangedEvent{"1", "oldState", "newState"},
+		DeviceStateChangedEvent{"2", "removed", ""},
+		DeviceStateChangedEvent{"3", "", "added"},
+	}, diffs)
+}
+
+func TestPublishDevicesRestartsServer(t *testing.T) {
+	starter := &MockServerStarter{}
+	dialer := &MockServer{
+		Status: wire.StatusSuccess,
+		Errs: []error{
+			nil, nil, nil, // Successful dial.
+			util.Errorf(util.ConnectionResetError, "failed first read"),
+			util.Errorf(util.ServerNotAvailable, "failed redial"),
+		},
+	}
+	watcher := deviceWatcherImpl{
+		config:      ClientConfig{dialer},
+		eventChan:   make(chan DeviceStateChangedEvent),
+		startServer: starter.StartServer,
+	}
+
+	publishDevices(&watcher)
+
+	assert.Empty(t, dialer.Errs)
+	assert.Equal(t, []string{"host:track-devices"}, dialer.Requests)
+	assert.Equal(t, []string{"Dial", "SendMessage", "ReadStatus", "ReadMessage", "Dial"}, dialer.Trace)
+	err := watcher.err.Load().(*util.Err)
+	assert.Equal(t, util.ServerNotAvailable, err.Code)
+	assert.Equal(t, 1, starter.startCount)
+}
+
+type MockServerStarter struct {
+	startCount int
+	err        error
+}
+
+func (s *MockServerStarter) StartServer() error {
+	log.Printf("Starting mock server")
+	if s.err == nil {
+		s.startCount += 1
+		return nil
+	} else {
+		return s.err
+	}
+}

dialer.go

@@ -54,7 +54,7 @@ func (d *netDialer) Dial() (*wire.Conn, error) {
 	address := fmt.Sprintf("%s:%d", host, port)
 	netConn, err := net.Dial("tcp", address)
 	if err != nil {
-		return nil, util.WrapErrorf(err, util.NetworkError, "error dialing %s", address)
+		return nil, util.WrapErrorf(err, util.ServerNotAvailable, "error dialing %s", address)
 	}
 
 	conn := &wire.Conn{

host_client.go

@@ -1,4 +1,3 @@
-// TODO(z): Implement TrackDevices.
 package goadb
 
 import (

host_client_test.go

@@ -25,27 +25,47 @@ func TestGetServerVersion(t *testing.T) {
 	assert.Equal(t, 10, v)
 }
 
+// MockServer implements Dialer, Scanner, and Sender.
 type MockServer struct {
+	// Each time an operation is performed, if this slice is non-empty, the head element
+	// of this slice is returned and removed from the slice. If the head is nil, it is removed
+	// but not returned.
+	Errs []error
+
 	Status wire.StatusCode
 
-	// Messages are sent in order, each preceded by a length header.
-	Messages []string
+	// Messages are returned from read calls in order, each preceded by a length header.
+	Messages     []string
+	nextMsgIndex int
 
-	// Each request is appended to this slice.
+	// Each message passed to a send call is appended to this slice.
 	Requests []string
 
-	nextMsgIndex int
+	// Each time an operaiton is performed, its name is appended to this slice.
+	Trace []string
 }
 
 func (s *MockServer) Dial() (*wire.Conn, error) {
+	s.logMethod("Dial")
+	if err := s.getNextErrToReturn(); err != nil {
+		return nil, err
+	}
 	return wire.NewConn(s, s), nil
 }
 
 func (s *MockServer) ReadStatus() (wire.StatusCode, error) {
+	s.logMethod("ReadStatus")
+	if err := s.getNextErrToReturn(); err != nil {
+		return "", err
+	}
 	return s.Status, nil
 }
 
 func (s *MockServer) ReadMessage() ([]byte, error) {
+	s.logMethod("ReadMessage")
+	if err := s.getNextErrToReturn(); err != nil {
+		return nil, err
+	}
 	if s.nextMsgIndex >= len(s.Messages) {
 		return nil, util.WrapErrorf(io.EOF, util.NetworkError, "")
 	}
@@ -55,6 +75,11 @@ func (s *MockServer) ReadMessage() ([]byte, error) {
 }
 
 func (s *MockServer) ReadUntilEof() ([]byte, error) {
+	s.logMethod("ReadUntilEof")
+	if err := s.getNextErrToReturn(); err != nil {
+		return nil, err
+	}
+
 	var data []string
 	for ; s.nextMsgIndex < len(s.Messages); s.nextMsgIndex++ {
 		data = append(data, s.Messages[s.nextMsgIndex])
@@ -63,18 +88,40 @@ func (s *MockServer) ReadUntilEof() ([]byte, error) {
 }
 
 func (s *MockServer) SendMessage(msg []byte) error {
+	s.logMethod("SendMessage")
+	if err := s.getNextErrToReturn(); err != nil {
+		return err
+	}
 	s.Requests = append(s.Requests, string(msg))
 	return nil
 }
 
 func (s *MockServer) NewSyncScanner() wire.SyncScanner {
+	s.logMethod("NewSyncScanner")
 	return nil
 }
 
 func (s *MockServer) NewSyncSender() wire.SyncSender {
+	s.logMethod("NewSyncSender")
 	return nil
 }
 
 func (s *MockServer) Close() error {
+	s.logMethod("Close")
+	if err := s.getNextErrToReturn(); err != nil {
+		return err
+	}
 	return nil
 }
+
+func (s *MockServer) getNextErrToReturn() (err error) {
+	if len(s.Errs) > 0 {
+		err = s.Errs[0]
+		s.Errs = s.Errs[1:]
+	}
+	return
+}
+
+func (s *MockServer) logMethod(name string) {
+	s.Trace = append(s.Trace, name)
+}

server_controller.go

@@ -8,9 +8,6 @@ import (
 
 /*
 StartServer ensures there is a server running.
-
-Currently implemented by just running
-	adb start-server
 */
 func StartServer() error {
 	cmd := exec.Command("adb", "start-server")

util/doc.go

@@ -0,0 +1,4 @@
+/*
+Contains code shared between the different sub-packages in this project.
+*/
+package util

util/errcode_string.go

@@ -4,9 +4,9 @@ package util
 
 import "fmt"
 
-const _ErrCode_name = "AssertionErrorParseErrorServerNotAvailableNetworkErrorAdbErrorDeviceNotFoundFileNoExistError"
+const _ErrCode_name = "AssertionErrorParseErrorServerNotAvailableNetworkErrorConnectionResetErrorAdbErrorDeviceNotFoundFileNoExistError"
 
-var _ErrCode_index = [...]uint8{0, 14, 24, 42, 54, 62, 76, 92}
+var _ErrCode_index = [...]uint8{0, 14, 24, 42, 54, 74, 82, 96, 112}
 
 func (i ErrCode) String() string {
 	if i+1 >= ErrCode(len(_ErrCode_index)) {

util/error.go

@@ -2,7 +2,19 @@ package util
 
 import "fmt"
 
-// Err is the implementation of error that all goadb functions return.
+/*
+Err is the implementation of error that all goadb functions return.
+
+Best Practice
+
+External errors should be wrapped using WrapErrorf, as soon as they are known about.
+
+Intermediate code should pass *Errs up until they will be returned outside the library.
+Errors should *not* be wrapped at every return site.
+
+Just before returning an *Err outside the library, it can be wrapped again, preserving the
+ErrCode (e.g. with WrapErrf).
+*/
 type Err struct {
 	// Code is the high-level "type" of error.
 	Code ErrCode
@@ -22,10 +34,12 @@ type ErrCode byte
 const (
 	AssertionError ErrCode = iota
 	ParseError     ErrCode = iota
-	// The server was not available on the request port and could not be started.
+	// The server was not available on the requested port.
 	ServerNotAvailable ErrCode = iota
 	// General network error communicating with the server.
 	NetworkError ErrCode = iota
+	// The connection to the server was reset in the middle of an operation. Server probably died.
+	ConnectionResetError ErrCode = iota
 	// The server returned an error message, but we couldn't parse it.
 	AdbError ErrCode = iota
 	// The server returned a "device not found" error.

wire/conn.go

@@ -20,7 +20,11 @@ For most cases, usage looks something like:
 
 For some messages, the server will return more than one message (but still a single
 status). Generally, after calling ReadStatus once, you should call ReadMessage until
-it returns an io.EOF error.
+it returns an io.EOF error. Note: the protocol docs seem to suggest that connections will be
+kept open for multiple commands, but this is not the case. The official client closes
+a connection immediately after its read the response, in most cases. The docs might be
+referring to the connection between the adb server and the device, but I haven't confirmed
+that.
 
 For most commands, the server will close the connection after sending the response.
 You should still always call Close() when you're done with the connection.

wire/scanner.go

@@ -8,6 +8,8 @@ import (
 	"github.com/zach-klippenstein/goadb/util"
 )
 
+// TODO(zach): All EOF errors returned from networoking calls should use ConnectionResetError.
+
 // StatusCodes are returned by the server. If the code indicates failure, the
 // next message will be the error.
 type StatusCode string
@@ -70,7 +72,7 @@ func (s *realScanner) ReadMessage() ([]byte, error) {
 
 	length, err := s.readLength()
 	if err != nil {
-		return nil, util.WrapErrorf(err, util.NetworkError, "error reading message length")
+		return nil, err
 	}
 
 	data := make([]byte, length)
@@ -103,9 +105,7 @@ func (s *realScanner) Close() error {
 func (s *realScanner) readLength() (int, error) {
 	lengthHex := make([]byte, 4)
 	n, err := io.ReadFull(s.reader, lengthHex)
-	if err != nil && err != io.ErrUnexpectedEOF {
-		return 0, util.WrapErrorf(err, util.NetworkError, "error reading length")
-	} else if err == io.ErrUnexpectedEOF {
+	if err != nil {
 		return 0, errIncompleteMessage("length", n, 4)
 	}
 

wire/scanner_test.go

@@ -98,7 +98,7 @@ func NewEofBuffer(str string) *TestReader {
 
 func assertEof(t *testing.T, s *realScanner) {
 	msg, err := s.ReadMessage()
-	assert.True(t, util.HasErrCode(err, util.NetworkError))
+	assert.True(t, util.HasErrCode(err, util.ConnectionResetError))
 	assert.Nil(t, msg)
 }
 

wire/util.go

@@ -60,7 +60,7 @@ func adbServerError(request string, serverMsg string) error {
 
 func errIncompleteMessage(description string, actual int, expected int) error {
 	return &util.Err{
-		Code:    util.NetworkError,
+		Code:    util.ConnectionResetError,
 		Message: fmt.Sprintf("incomplete %s: read %d bytes, expecting %d", description, actual, expected),
 		Details: struct {
 			ActualReadBytes int