Allow the update of a characteristic value to fail brutella/hc#163

README.md

@@ -36,9 +36,10 @@ If you want to support `hap`, please purchase Home from the [App Store][home-app
 This library is a rewrite of [hc](https://github.com/brutella/hc).
 If you want to migrate from `hc`, consider the following changes.
 
-- Instead of `hc.NewIPTransport(...)` you now call `hap.NewServer(...)` to create a server. 
-- You can provide your own persistent store by implementing the [Store](store.go) interface.
-- You can define your own http handlers. [hc#212](https://github.com/brutella/hc/issues/212)
+- Instead of `hc.NewIPTransport(...)` you now call [hap.NewServer(...)](https://pkg.go.dev/github.com/brutella/hap#NewServer) to create a server.
+- You can create your own persistent storage by implementing the [Store](store.go) interface.
+- Setting the value of a characteristic can now fail. Fixes [hc#163](https://github.com/brutella/hc/issues/163)
+- You can define custom http handlers. Fixes [hc#212](https://github.com/brutella/hc/issues/212)
 ```go
 server.ServeMux().HandleFunc("/ping", func(res http.ResponseWriter, req *http.Request) {
     res.Write([]byte("pong"))

characteristic/bool.go

@@ -23,7 +23,12 @@ func (c *Bool) SetValue(v bool) {
 
 // Value returns the value of c as bool.
 func (c *Bool) Value() bool {
-	return c.C.value(nil).(bool)
+	v, _ := c.C.valueRequest(nil)
+	if v == nil {
+		return false
+	}
+
+	return v.(bool)
 }
 
 // OnValueRemoteUpdate calls fn when the value of the characteristic was updated.

characteristic/bytes.go

@@ -23,7 +23,12 @@ func (c *Bytes) SetValue(v []byte) {
 
 // Value returns the value of c as byte array.
 func (c *Bytes) Value() []byte {
-	str := c.C.value(nil).(string)
+	v, _ := c.C.valueRequest(nil)
+	if v == nil {
+		return []byte{}
+	}
+
+	str := v.(string)
 	if b, err := base64.StdEncoding.DecodeString(str); err != nil {
 		return []byte{}
 	} else {

characteristic/c.go

@@ -79,10 +79,20 @@ type C struct {
 	// Stores which connected client has events enabled for this characteristic.
 	Events map[string]bool
 
-	// ValFunc returns the value of C.
-	// If no nil, the return value of this function is used instead of Val.
-	// req is non nil, if the value is requested from a request.
-	ValFunc func(req *http.Request) interface{}
+	// ValueRequestFunc is called when the value of C is requested.
+	// The http request is non-nil, if the value of C is requested.
+	// by an HTTP request coming from a paired controller.
+	// The first return value of this function is the value of C.
+	// If the second argument is non-zero, the server responds with the
+	// HTTP status code 500 Internal Server Error.
+	ValueRequestFunc func(request *http.Request) (interface{}, int)
+
+	// SetValueRequestFunc is called when the value of C is updated.
+	// The first argument "value" is the new value of C.
+	// The second argument "request" is non-nil, if the value of C is
+	// updated from an HTTP request coming from a paired controller.
+	// An error is inidcated if the return value is non-zero.
+	SetValueRequestFunc func(value interface{}, request *http.Request) int
 
 	// A list of update value functions.
 	// There are called when the value of the characteristic is updated.
@@ -110,14 +120,23 @@ func (c *C) OnCValueUpdate(fn ValueUpdateFunc) {
 
 // Sets the value of c to v.
 // The function is called if the value is updated from an http request.
-func (c *C) SetValueRequest(v interface{}, req *http.Request) {
+func (c *C) SetValueRequest(v interface{}, req *http.Request) int {
 	// check write permission
 	if !c.IsWritable() {
 		log.Info.Printf("writing %v by %s not allowed\n", v, req.RemoteAddr)
-		return
+		return -70404
+	}
+
+	if c.SetValueRequestFunc != nil {
+		if s := c.SetValueRequestFunc(v, req); s != 0 {
+			return s
+		}
 	}
 
 	c.setValue(v, req)
+
+	// no error
+	return 0
 }
 
 func (c *C) setValue(v interface{}, req *http.Request) {
@@ -148,25 +167,25 @@ func (c *C) setValue(v interface{}, req *http.Request) {
 	}
 }
 
-// ValueRequest returns the value of the characteristic for
-// a http request.
-func (c *C) ValueRequest(req *http.Request) interface{} {
+// ValueRequest returns the value of C and a status code.
+// if the characteristic is not readable, the status code -70405 is returned.
+func (c *C) ValueRequest(req *http.Request) (interface{}, int) {
 	// check write permission
 	if !c.IsReadable() {
 		log.Info.Printf("reading %d by %s not allowed\n", c.Id, req.RemoteAddr)
-		return nil
+		return nil, -70405
 	}
 
-	return c.value(req)
+	return c.valueRequest(req)
 }
 
-// value returns the value of the characteristic.
-func (c *C) value(req *http.Request) interface{} {
-	if c.ValFunc != nil {
-		return c.ValFunc(req)
+// value returns the value of C and a status code.
+func (c *C) valueRequest(req *http.Request) (interface{}, int) {
+	if c.ValueRequestFunc != nil {
+		return c.ValueRequestFunc(req)
 	}
 
-	return c.Val
+	return c.Val, 0
 }
 
 func (c *C) IsWritable() bool {
@@ -203,7 +222,7 @@ func (c *C) IsWriteOnly() bool {
 	return len(c.Permissions) == 1 && c.Permissions[0] == PermissionWrite
 }
 
-func (ch *C) MarshalJSON() ([]byte, error) {
+func (c *C) MarshalJSON() ([]byte, error) {
 	d := struct {
 		Id          uint64   `json:"iid"` // managed by accessory
 		Type        string   `json:"type"`
@@ -219,20 +238,22 @@ func (ch *C) MarshalJSON() ([]byte, error) {
 		MinValue  interface{} `json:"minValue,omitempty"`
 		StepValue interface{} `json:"minStep,omitempty"`
 	}{
-		Id:          ch.Id,
-		Type:        ch.Type,
-		Permissions: ch.Permissions,
-		Description: ch.Description,
-		Format:      ch.Format,
-		Unit:        ch.Unit,
-		MaxLen:      ch.MaxLen,
-		MaxValue:    ch.MaxVal,
-		MinValue:    ch.MinVal,
-		StepValue:   ch.StepVal,
+		Id:          c.Id,
+		Type:        c.Type,
+		Permissions: c.Permissions,
+		Description: c.Description,
+		Format:      c.Format,
+		Unit:        c.Unit,
+		MaxLen:      c.MaxLen,
+		MaxValue:    c.MaxVal,
+		MinValue:    c.MinVal,
+		StepValue:   c.StepVal,
 	}
 
-	if ch.IsReadable() {
-		d.Value = ch.value(nil)
+	if c.IsReadable() {
+		if v, _ := c.valueRequest(nil); v != nil {
+			d.Value = v
+		}
 	}
 
 	return json.Marshal(&d)

characteristic/c_test.go

@@ -11,9 +11,9 @@ func TestCharacteristicValue(t *testing.T) {
 	c.Val = 0
 
 	n := 0
-	c.ValFunc = func(*http.Request) interface{} {
+	c.ValueRequestFunc = func(*http.Request) (interface{}, int) {
 		n++
-		return n
+		return n, 0
 	}
 
 	if is, want := c.Value(), 1; is != want {
@@ -139,3 +139,25 @@ func TestReadOnly(t *testing.T) {
 		t.Fatalf("is=%v want=%v", is, want)
 	}
 }
+
+func TestSetValueRequestFunc(t *testing.T) {
+	c := NewBrightness()
+
+	c.SetValue(100)
+	c.SetValueRequestFunc = func(v interface{}, r *http.Request) int {
+		if r != nil {
+			return -70408
+		}
+
+		return 0
+	}
+
+	s := c.SetValueRequest(50, &http.Request{})
+	if is, want := s, -70408; is != want {
+		t.Fatalf("%v != %v", is, want)
+	}
+
+	if is, want := c.Value(), 100; is != want {
+		t.Fatalf("is=%v want=%v", is, want)
+	}
+}

characteristic/float.go

@@ -33,7 +33,12 @@ func (c *Float) SetStepValue(v float64) {
 
 // Value returns the value of c as float64.
 func (c *Float) Value() float64 {
-	return c.C.value(nil).(float64)
+	v, _ := c.C.valueRequest(nil)
+	if v == nil {
+		return 0
+	}
+
+	return v.(float64)
 }
 
 func (c *Float) MinValue() float64 {

characteristic/int.go

@@ -33,7 +33,12 @@ func (c *Int) SetStepValue(v int) {
 
 // Value returns the value of c as integer.
 func (c *Int) Value() int {
-	return c.C.value(nil).(int)
+	v, _ := c.C.valueRequest(nil)
+	if v == nil {
+		return 0
+	}
+
+	return v.(int)
 }
 
 func (c *Int) MinValue() int {

characteristic/string.go

@@ -23,7 +23,12 @@ func (c *String) SetValue(v string) {
 
 // Value returns the value of c as string.
 func (c *String) Value() string {
-	return c.C.value(nil).(string)
+	v, _ := c.C.valueRequest(nil)
+	if v == nil {
+		return ""
+	}
+
+	return v.(string)
 }
 
 // OnValueRemoteUpdate calls fn when the value of the characteristic was updated.

characteristics.go

@@ -72,7 +72,13 @@ func (srv *Server) getCharacteristics(res http.ResponseWriter, req *http.Request
 			continue
 		}
 
-		cdata.Value = c.ValueRequest(req)
+		v, s := c.ValueRequest(req)
+		if s != 0 {
+			err = true
+			cdata.Status = &s
+		} else {
+			cdata.Value = v
+		}
 
 		if meta {
 			cdata.Format = &c.Format
@@ -156,13 +162,19 @@ func (srv *Server) putCharacteristics(res http.ResponseWriter, req *http.Request
 			continue
 		}
 
-		if d.Response != nil {
-			cdata.Value = c.ValueRequest(req)
-			arr = append(arr, cdata)
+		if d.Value != nil {
+			s := c.SetValueRequest(d.Value, req)
+			if s != 0 {
+				cdata.Status = &s
+			}
 		}
 
-		if d.Value != nil {
-			c.SetValueRequest(d.Value, req)
+		if d.Response != nil {
+			if v, s := c.ValueRequest(req); s != 0 {
+				cdata.Status = &s
+			} else {
+				cdata.Value = v
+			}
 		}
 
 		if d.Events != nil {
@@ -174,6 +186,10 @@ func (srv *Server) putCharacteristics(res http.ResponseWriter, req *http.Request
 				c.Events[req.RemoteAddr] = *d.Events
 			}
 		}
+
+		if cdata.Status != nil || cdata.Value != nil {
+			arr = append(arr, cdata)
+		}
 	}
 
 	if len(arr) == 0 {

identify.go

@@ -6,7 +6,6 @@ import (
 
 func (srv *Server) identify(res http.ResponseWriter, req *http.Request) {
 	if srv.isPaired() {
-		res.WriteHeader(http.StatusBadRequest)
 		jsonError(res, JsonStatusInsufficientPrivileges)
 		return
 	}

json.go

@@ -41,6 +41,7 @@ func jsonError(res http.ResponseWriter, status int) error {
 		return err
 	}
 
+	res.WriteHeader(http.StatusBadRequest)
 	_, err = res.Write(b)
 	return err
 }