Add relay switching (on/off) actions

errors.go

@@ -5,4 +5,6 @@ import "errors"
 var (
 	// ErrRelayNotFound is returned when Relay is not found.
 	ErrRelayNotFound = errors.New("relay not found")
+	// ErrStateChangeFailed is returned if state change fails.
+	ErrStateChangeFailed = errors.New("state change failed")
 )

handlers.go

@@ -6,6 +6,7 @@ import (
 	"net/http"
 
 	"github.com/julienschmidt/httprouter"
+	"github.com/nathan-osman/go-rpigpio"
 )
 
 // Index handles the default route (GET /).
@@ -33,6 +34,18 @@ func RelayShow(w http.ResponseWriter, r *http.Request, params httprouter.Params)
 	writeResponse(w, http.StatusOK, &JsonResponse{Data: relay})
 }
 
+// RelayOn handles the relays on action (GET /relays/:id/on).
+func RelayOn(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
+	id := params.ByName("id")
+	switchRelay(w, id, true, rpi.LOW)
+}
+
+// RelayOff handles the relays off action (GET /relays/:id/off).
+func RelayOff(w http.ResponseWriter, r *http.Request, params httprouter.Params) {
+	id := params.ByName("id")
+	switchRelay(w, id, false, rpi.HIGH)
+}
+
 // findRelay locates Relay with the given ID on the module.
 func findRelay(id string) (*Relay, error) {
 	relay, ok := module[id]
@@ -43,6 +56,30 @@ func findRelay(id string) (*Relay, error) {
 	return relay, nil
 }
 
+// switchRelay provides unified wrapper for Relay On/Off actions.
+func switchRelay(w http.ResponseWriter, id string, state bool, pinState rpi.Value) {
+	relay, err := findRelay(id)
+	if err != nil {
+		writeError(w, http.StatusNotFound, err.Error())
+		return
+	}
+	if err := setState(id, state, pinState); err != nil {
+		writeError(w, http.StatusServiceUnavailable, err.Error())
+		return
+	}
+	writeResponse(w, http.StatusOK, &JsonResponse{Data: relay})
+}
+
+// setState switches given pin to requested state.
+func setState(id string, state bool, pinState rpi.Value) error {
+	if err := pins[id].Write(pinState); err != nil {
+		// Writing requested state to the given pin failed
+		return ErrStateChangeFailed
+	}
+	module[id].State = state
+	return nil
+}
+
 // writeError wraps writing API error response.
 func writeError(w http.ResponseWriter, status int, title string) {
 	apiError := &ApiError{Status: status, Title: title}

routes.go

@@ -19,6 +19,8 @@ func AllRoutes() Routes {
 		Route{"Index", "GET", "/", Index},
 		Route{"RelayIndex", "GET", "/relays", RelayIndex},
 		Route{"RelayShow", "GET", "/relays/:id", RelayShow},
+		Route{"RelayOn", "GET", "/relays/:id/on", RelayOn},
+		Route{"RelayOff", "GET", "/relays/:id/off", RelayOff},
 	}
 	return routes
 }