Add ability for browser to receiver updates to already discovered ser…

…vices. (#19)

I was looking at adding the ability to automatically detect changes to
accessories and bridges, and needed the capability to receive TXT record
updates. The existing Browser implementation just ignores them, so this
pull request adds another event that will emit when a new message is
received for an already discovered service.

This change is 100% backwards compatible with existing implementations.

README.md

@@ -112,6 +112,10 @@ Options are the same as given in the `browser.find` function.
 
 Emitted every time a new service is found that matches the browser.
 
+#### `Event: update`
+
+Emitted every time an update is received for existing service is found that matches the browser.
+
 #### `Event: down`
 
 Emitted every time an existing service emmits a goodbye message.
@@ -136,7 +140,7 @@ Broadcast the query again.
 
 #### `Event: up`
 
-Emitted when the service is up.
+Emitted when the service is up, and if the txt record of the service is updated `service.updateTxt(object)`.
 
 #### `Event: error`
 

lib/Browser.js

@@ -82,8 +82,11 @@ Browser.prototype.start = function () {
       if (matches.length === 0) return
 
       matches.forEach(function (service) {
-        if (self._serviceMap[service.fqdn]) return // ignore already registered services
-        self._addService(service)
+        if (self._serviceMap[service.fqdn]) {
+          self._updateService(service)
+        } else {
+          self._addService(service)
+        }
       })
     })
   }
@@ -109,6 +112,21 @@ Browser.prototype._addService = function (service) {
   this.emit('up', service)
 }
 
+Browser.prototype._updateService = function (service) {
+  let cachedService, index
+  this.services.some(function (s, i) {
+    if (dnsEqual(s.fqdn, service.fqdn)) {
+      cachedService = s
+      index = i
+      return true
+    }
+    return false
+  })
+  if (!cachedService) return
+  this.services[index] = service
+  this.emit('update', service)
+}
+
 Browser.prototype._removeService = function (fqdn) {
   let service, index
   this.services.some(function (s, i) {

test/bonjour.js

@@ -118,32 +118,58 @@ test('bonjour.find', function (bonjour, t) {
   bonjour.publish({ name: 'Baz', type: 'test', port: 3000, txt: { foo: 'bar' } }).on('up', next())
 })
 
-test('bonjour.change', function (bonjour, t) {
-  const data = { init: true, found: false, timer: null }
-  const service = bonjour.publish({ name: 'Baz', type: 'test', port: 3000, txt: { foo: 'bar' } }).on('up', function () {
-    const browser = bonjour.find({ type: 'test' })
-    browser.on('up', function (s) {
-      data.browserData = s
+test('bonjour.change and up event', function (bonjour, t) {
+  const data = { updateTxtSent: false, found: false, timer: null, serviceUp: false }
+  data.timer = setTimeout(function () {
+    t.equal(data.found, true)
+    bonjour.destroy()
+    t.end()
+  }, 3000) // Wait 3000 ms for any additional up messages when the updateTxt is sent
+  const service = bonjour.publish({ name: 'Baz', type: 'test', port: 3000, txt: { foo: 'originalUp' } }).on('up', function () {
+    if (!data.serviceUp) { // Workaround for Service.up firing when service.updateTxt is used
+      data.serviceUp = true
+      const browser = bonjour.find({ type: 'test' })
+      browser.on('up', function (s) {
+        t.equal(s.txt.foo, 'originalUp')
+        data.found = true
+        if (!data.updateTxtSent) {
+          data.updateTxtSent = true
+          service.updateTxt({ foo: 'updateUp' })
+        }
+      })
+    }
+  })
+})
+
+test('bonjour.change and update event', function (bonjour, t) {
+  const data = { updateTxtSent: false, success: false, timer: null, serviceUp: false }
+  data.timer = setTimeout(function () {
+    t.equal(data.success, true)
+    bonjour.destroy()
+    t.end()
+  }, 3000) // Wait for the record to update maximum 3000 ms
+  const service = bonjour.publish({ name: 'Baz', type: 'test', port: 3000, txt: { foo: 'original' } }).on('up', function () {
+    if (!data.serviceUp) { // Workaround for Service.up firing when service.updateTxt is used
+      data.serviceUp = true
+      const browser = bonjour.find({ type: 'test' })
+      browser.on('up', function (s) {
+        t.equal(s.txt.foo, 'original')
+        if (!data.updateTxtSent) {
+          data.updateTxtSent = true
+          service.updateTxt({ foo: 'update' })
+        }
+      })
 
-      if (data.init) {
-        t.equal(s.txt.foo, 'bar')
-        data.timer = setTimeout(function () {
-          t.equal(s.txt.foo, 'baz')
+      browser.on('update', function (s) {
+        if (s.txt.foo === 'update') { // Ignore updates that we are not interested in, have seen updates of just address information
+          t.equal(s.txt.foo, 'update')
+          data.success = true
+          clearTimeout(data.timer)
           bonjour.destroy()
           t.end()
-        }, 3000) // Wait for the record to update maximum 3000 ms
-        data.init = false
-        service.updateTxt({ foo: 'baz' })
-      }
-
-      if (!data.init && !data.found && s.txt.foo === 'baz') {
-        data.found = true
-        clearTimeout(data.timer)
-        t.equal(s.txt.foo, 'baz')
-        bonjour.destroy()
-        t.end()
-      }
-    })
+        }
+      })
+    }
   })
 })