// readAllStateCommon reads and unmarshals (given a function) all state into a
// list of core.State objects.
// XXX: move this to some common file
func readAllStateCommon(d core.StateDriver, baseKey string, sType core.State,
	unmarshal func([]byte, interface{}) error) ([]core.State, error) {
	stateType := reflect.TypeOf(sType)
	sliceType := reflect.SliceOf(stateType)
	values := reflect.MakeSlice(sliceType, 0, 1)

	byteValues, err := d.ReadAll(baseKey)
	if err != nil {
		return nil, err
	}
	for _, byteValue := range byteValues {
		value := reflect.New(stateType)
		err = unmarshal(byteValue, value.Interface())
		if err != nil {
			return nil, err
		}
		values = reflect.Append(values, value.Elem())
	}

	stateValues := []core.State{}
	for i := 0; i < values.Len(); i++ {
		// sanity checks
		if !values.Index(i).Elem().FieldByName("CommonState").IsValid() {
			return nil, core.Errorf("The state structure %v is missing core.CommonState",
				stateType)
		}
		//the following works as every core.State is expected to embed core.CommonState struct
		values.Index(i).Elem().FieldByName("CommonState").FieldByName("StateDriver").Set(reflect.ValueOf(d))
		stateValue := values.Index(i).Interface().(core.State)
		stateValues = append(stateValues, stateValue)
	}
	return stateValues, nil
}

func commonTestStateDriverWrite(t *testing.T, d core.StateDriver) {
	testBytes := []byte{0xb, 0xa, 0xd, 0xb, 0xa, 0xb, 0xe}
	key := "TestKeyRawWrite"

	err := d.Write(key, testBytes)
	if err != nil {
		t.Fatalf("failed to write bytes. Error: %s", err)
	}
}

func commonTestStateDriverWriteState(t *testing.T, d core.StateDriver) {
	state := &testState{IgnoredField: d, IntField: 1234,
		StrField: "testString"}
	key := "testKey"

	err := d.WriteState(key, state, json.Marshal)
	if err != nil {
		t.Fatalf("failed to write state. Error: %s", err)
	}
}

func commonTestStateDriverInitInvalidConfig(t *testing.T, d core.StateDriver) {
	config := &core.Config{}
	err := d.Init(config)
	if err == nil {
		t.Fatalf("d init succeeded, should have failed.")
	}

	err = d.Init(nil)
	if err == nil {
		t.Fatalf("d init succeeded, should have failed.")
	}
}

func commonTestStateDriverInitInvalidConfig(t *testing.T, d core.StateDriver) {
	instInfo := core.InstanceInfo{DbURL: "xyz://127.0.0.1:2379"}
	err := d.Init(&instInfo)
	if err == nil {
		t.Fatalf("d init succeeded, should have failed.")
	}

	err = d.Init(nil)
	if err == nil {
		t.Fatalf("d init succeeded, should have failed.")
	}
}

func commonTestStateDriverWatchAllStateModify(t *testing.T, d core.StateDriver) {
	state := &testState{IntField: 1234, StrField: "testString"}
	modState := &testState{IntField: 5678, StrField: "modString"}
	baseKey := "modify"
	key := baseKey + "/testKeyWatchAll"

	err := d.WriteState(key, state, json.Marshal)
	if err != nil {
		t.Fatalf("failed to write state. Error: %s", err)
	}
	defer func() {
		d.ClearState(key)
	}()

	recvErr := make(chan error, 1)
	stateCh := make(chan core.WatchState, 1)
	timer := time.After(waitTimeout)

	go func(rsps chan core.WatchState, retErr chan error) {
		err := d.WatchAllState(baseKey, state, json.Unmarshal, stateCh)
		if err != nil {
			retErr <- err
			return
		}
	}(stateCh, recvErr)

	// trigger modify after a slight pause to ensure that events are not missed
	time.Sleep(time.Second)
	err = d.WriteState(key, modState, json.Marshal)
	if err != nil {
		t.Fatalf("failed to write state. Error: %s", err)
	}

for_label:
	for {
		select {
		case watchState := <-stateCh:
			s := watchState.Curr.(*testState)
			if s.IntField != modState.IntField || s.StrField != modState.StrField {
				t.Fatalf("Watch state mismatch. Expctd: %+v, Rcvd: %+v", modState, s)
			}
			if watchState.Prev == nil {
				t.Fatalf("Received a modify event without previous state value set.")
			}
			s = watchState.Prev.(*testState)
			if s.IntField != state.IntField || s.StrField != state.StrField {
				t.Fatalf("Watch state mismatch. Expctd: %+v, Rcvd: %+v", state, s)
			}
			break for_label
		case err := <-recvErr:
			t.Fatalf("Watch failed. Error: %s", err)
			break for_label
		case <-timer:
			t.Fatalf("timed out waiting for events")
			break for_label
		}
	}
}

func commonTestStateDriverRead(t *testing.T, d core.StateDriver) {
	testBytes := []byte{0xb, 0xa, 0xd, 0xb, 0xa, 0xb, 0xe}
	key := "TestKeyRawRead"

	err := d.Write(key, testBytes)
	if err != nil {
		t.Fatalf("failed to write bytes. Error: %s", err)
	}

	readBytes, err := d.Read(key)
	if err != nil {
		t.Fatalf("failed to read bytes. Error: %s", err)
	}

	if !bytes.Equal(testBytes, readBytes) {
		t.Fatalf("read bytes don't match written bytes. Wrote: %v Read: %v",
			testBytes, readBytes)
	}
}

func commonTestStateDriverReadState(t *testing.T, d core.StateDriver) {
	state := &testState{IgnoredField: d, IntField: 1234,
		StrField: "testString"}
	key := "contiv/dir1/testKeyRead"

	err := d.WriteState(key, state, json.Marshal)
	if err != nil {
		t.Fatalf("failed to write state. Error: %s", err)
	}

	readState := &testState{}
	err = d.ReadState(key, readState, json.Unmarshal)
	if err != nil {
		t.Fatalf("failed to read state. Error: %s", err)
	}

	if readState.IntField != state.IntField || readState.StrField != state.StrField {
		t.Fatalf("Read state didn't match state written. Wrote: %v Read: %v",
			state, readState)
	}
}

func commonTestStateDriverReadStateAfterClear(t *testing.T, d core.StateDriver) {
	state := &testState{IntField: 1234, StrField: "testString"}
	key := "testKeyReadClear"

	err := d.WriteState(key, state, json.Marshal)
	if err != nil {
		t.Fatalf("failed to write state. Error: %s", err)
	}

	err = d.ClearState(key)
	if err != nil {
		t.Fatalf("failed to clear state. Error: %s", err)
	}

	readState := &testState{}
	err = d.ReadState(key, readState, json.Unmarshal)
	if err == nil {
		t.Fatalf("Able to read cleared state!. Key: %s, Value: %v",
			key, readState)
	}
}