Merge pull request #424 from resin-io/improve-key-exchange

Improve key exchange by first checking if an existing device api key is valid.

src/bootstrap.coffee

@@ -35,17 +35,29 @@ loadPreloadedApps = ->
 	.catch (err) ->
 		utils.mixpanelTrack('Loading preloaded apps failed', { error: err })
 
-exchangeKey = ->
+fetchDevice = (apiKey) ->
 	resinApi.get
 		resource: 'device'
 		options:
 			filter:
 				uuid: userConfig.uuid
 		customOptions:
-			apikey: userConfig.apiKey
+			apikey: apiKey
-	.catchReturn([])
+	.get(0)
+	.catchReturn(null)
 	.timeout(config.apiTimeout)
-	.then ([ device ]) ->
+
+exchangeKey = ->
+	Promise.try ->
+		# If we have an existing device key we first check if it's valid, because if it is we can just use that
+		if userConfig.deviceApiKey?
+			fetchDevice(userConfig.deviceApiKey)
+	.then (device) ->
+		if device?
+			return device
+		# If it's not valid/doesn't exist then we try to use the user/provisioning api key for the exchange
+		fetchDevice(userConfig.apiKey)
+		.then (device) ->
 			if not device?
 				throw new ExchangeKeyError("Couldn't fetch device with provisioning key")
 			# We found the device, we can try to generate a working device key for it
@@ -73,28 +85,14 @@ bootstrap = ->
 		)
 		.timeout(config.apiTimeout)
 		.catch DuplicateUuidError, ->
-			console.log('UUID already registered, checking if our device key is valid for it')
+			console.log('UUID already registered, trying a key exchange')
-			resinApi.get
-				resource: 'device'
-				options:
-					filter:
-						uuid: userConfig.uuid
-				customOptions:
-					apikey: userConfig.deviceApiKey
-			.catchReturn([])
-			.timeout(config.apiTimeout)
-			.then ([ device ]) ->
-				if device?
-					console.log('Fetched device, all is good')
-					return device
-				# If we couldn't fetch with the device key then we can try to key exchange in case the provisioning key is an old 'user-api-key'
-				console.log("Couldn't fetch the device, trying to exchange for a valid key")
 			exchangeKey()
+			.tap ->
+				console.log('Key exchange succeeded, all good')
 			.tapCatch ExchangeKeyError, (err) ->
 				# If it fails we just have to reregister as a provisioning key doesn't have the ability to change existing devices
 				console.log('Exchanging key failed, having to reregister')
 				generateRegistration(true)
-				.then (device) ->
 		.then ({ id }) ->
 			userConfig.registered_at = Date.now()
 			userConfig.deviceId = id