Asynchronous on change handlers

spec/cursor_spec.ls

@@ -1,4 +1,4 @@
-require! '../src/cursor'
+require!  <[ ../src/cursor bluebird ]>
 
 {map} = require 'prelude-ls'
 
@@ -191,3 +191,69 @@ describe "cursor" (_) ->
 
       expect trace .to-equal [36, 36, 37, 37, 38, 38, 39, 39, 40, 40]
 
+  describe "update transactions", (_) ->
+    it "starts" ->
+      data = cursor raw-data
+      transaction = data.start-transaction!
+
+      expect transaction .not.to-be undefined
+
+    it "ends and returns a promise" ->
+      data = cursor raw-data
+
+      transaction = data.start-transaction!
+      promise = data.end-transaction transaction
+
+      expect promise .not.to-be undefined
+      expect promise.then .not.to-be undefined
+
+    it "throws when transaction isn't running" ->
+      data = cursor raw-data
+
+      expect(-> data.end-transaction "foo").to-throw new Error "Transaction isn't running"
+
+    it "waits for a promise returned by an on-change handler" (done) ->
+      data = cursor raw-data .get \person.first_name
+      log = []
+
+      data.on-change ->
+        log.push "first"
+        bluebird.delay 0
+        .then !->
+          log.push "second"
+
+      transaction = data.start-transaction!
+      data.update -> "Ringo"
+
+      data.end-transaction transaction
+      .then ->
+        expect log .to-equal ["first", "second"]
+      .finally done
+
+      expect log .to-equal ["first"]
+
+    it "waits for multiple promises returned by different on-change handlers" (done) ->
+      data = cursor raw-data .get \person.first_name
+      log = []
+
+      data.on-change ->
+        log.push "first"
+        bluebird.delay 0
+        .then !->
+          log.push "third"
+
+      data.on-change ->
+        log.push "second"
+        bluebird.delay 0
+        .then !->
+          log.push "fourth"
+
+      transaction = data.start-transaction!
+      data.update -> "Ringo"
+
+      data.end-transaction transaction
+      .then ->
+        expect log .to-equal ["first", "second", "third", "fourth"]
+      .finally done
+
+      expect log .to-equal ["first", "second"]

src/application.ls

@@ -30,7 +30,7 @@ module.exports =
         [route-component, context, _] = routes.resolve path, config.routes!
         root-element = app-component initial-state: initial-state, component: route-component, context: context
 
-        config.start initial-state, (->)
+        config.start initial-state
 
         root = React.render root-element, root-dom-node
 
@@ -40,29 +40,38 @@ module.exports =
       # render a particular route to string
       # returns a promise of [state, body]
       render: (path) ->
-        new bluebird (res, rej) ->
-          initial-state = cursor config.get-initial-state!
+        app-state = cursor config.get-initial-state!
 
-          [route-component, context, route-init] = routes.resolve path, config.routes!
-          root-element = app-component initial-state: initial-state, component: route-component, context: context
+        [route-component, context, route-init] = routes.resolve path, config.routes!
+        root-element = app-component initial-state: app-state, component: route-component, context: context
 
-          config.start initial-state, ->
-            return res [initial-state.deref!, React.render-to-string root-element] unless route-init
+        transaction = app-state.start-transaction!
 
-            route-init initial-state, context, ->
-              res [initial-state.deref!, React.render-to-string root-element]
+        config.start app-state
+        route-init app-state, context if route-init
+
+        app-state.end-transaction transaction
+        .then ->
+          [app-state.deref!, React.render-to-string root-element]
 
       # process a form from a particular route and render to string
       # returns a promise of [state, body, location]
       process-form: (path, post-data) ->
-        new bluebird (res, rej) ->
-          initial-state = cursor config.get-initial-state!
+        app-state = cursor config.get-initial-state!
+
+        [route-component, context, route-init] = routes.resolve path, config.routes!
+        root-element = app-component initial-state: app-state, component: route-component, context: context
+
+        transaction = app-state.start-transaction!
+
+        config.start app-state
+        route-init app-state, context if route-init
+
+        location = server-rendering.process-form root-element, app-state, post-data, path
 
-          [route-component, context, route-init] = routes.resolve path, config.routes!
-          root-element = app-component initial-state: initial-state, component: route-component, context: context
+        app-state.end-transaction transaction
+        .then ->
+          body = unless location then React.render-to-string root-element else null
 
-          config.start initial-state, ->
-            return res server-rendering.process-form root-element, initial-state, post-data, path unless route-init
+          [app-state.deref!, body, location]
 
-            route-init initial-state, context, ->
-              res server-rendering.process-form root-element, initial-state, post-data, path

src/cursor.ls

@@ -1,6 +1,14 @@
 Immutable = require 'immutable'
+require! 'bluebird'
+
 {map, take, reverse, each, join, split, is-type, empty} = require 'prelude-ls'
 
+UpdateTransaction = !->
+  @promises = []
+
+is-promise = ->
+  it and it.then and typeof! it.then is 'Function'
+
 # wraps array in a cursor
 array-cursor = (root, data, len, path) ->
   array = [0 til len] |> map ->
@@ -10,6 +18,7 @@ array-cursor = (root, data, len, path) ->
   array._root = root or this
   array._data = if data then Immutable.fromJS(data) else null
   array._listeners = {}
+  array._transactions = []
   array._updates = []
 
   # Support all the cursor API
@@ -20,7 +29,7 @@ array-cursor = (root, data, len, path) ->
 object-cursor = (root, data, path) ->
   new Cursor root, data, path
 
-notify-listeners = (listeners, path, new-data) !->
+notify-listeners = (listeners, transactions, path, new-data) !->
   paths = [0 to path.length]
   |> map (-> path |> take it)
   |> reverse
@@ -33,7 +42,10 @@ notify-listeners = (listeners, path, new-data) !->
       payload = new-data.get-in path
       payload .= toJS! if payload.toJS
 
-      it(payload)
+      maybe-promise = it(payload)
+
+      if is-promise maybe-promise
+        transactions |> each -> it.promises.push maybe-promise
 
 flush-updates = (updates) ->
   while updates.length > 0
@@ -60,13 +72,14 @@ perform-update = (cursor, update) ->
   cursor._root._swap new-data
 
   # Notify about the change
-  notify-listeners cursor._root._listeners, cursor._path, new-data
+  notify-listeners cursor._root._listeners, cursor._root._transactions, cursor._path, new-data
 
 Cursor = (root, data, path) ->
   @_path = path
   @_root = root or this
   @_data = if data then Immutable.fromJS(data) else null
   @_listeners = {}
+  @_transactions = []
   @_updates = []
 
   this
@@ -96,7 +109,7 @@ Cursor.prototype.update = (cbk) ->
   updates.push [this, cbk]
   return unless updates.length < 2
 
-  while updates.length > 0
+  until empty updates
     [cursor, update] = updates[0]
     perform-update cursor, update
 
@@ -112,6 +125,20 @@ Cursor.prototype.on-change = (cbk) ->
   @_root._listeners[key] ||= []
   @_root._listeners[key].push cbk
 
+Cursor.prototype.start-transaction = ->
+  t = new UpdateTransaction!
+  @_root._transactions.push t
+
+  t
+
+Cursor.prototype.end-transaction = (transaction) ->
+  i = @_root._transactions.index-of transaction
+  throw new Error "Transaction isn't running" if i < 0
+
+  return bluebird.resolve! if empty transaction.promises
+
+  bluebird.all transaction.promises
+
 module.exports = (data) ->
   if is-type 'Array', data
     array-cursor null, data, data.length, []

src/server-rendering.ls

@@ -72,6 +72,8 @@ submit-form = (form) ->
   form.props.on-submit fake-event form
   ReactUpdates.flushBatchedUpdates!
 
+# Processes a form server-side, returns a redirect location or null
+# FIXME should we deal with the redirect in application.ls?
 process-form = (root-element, initial-state, post-data, path) ->
   configure-react!
   reset-redirect!
@@ -88,20 +90,15 @@ process-form = (root-element, initial-state, post-data, path) ->
 
   [form, inputs] = extract-elements path, post-data, instance
 
-  # trigger on-change handlers
+  # trigger handlers
   change-inputs inputs, post-data
-
-  # trigger on-submit handler
   submit-form form
 
   # end of magic
 
-  return [null, null, that] if redirect-location
-
-  state = initial-state.deref!
-  body = React.render-to-string root-element
+  return that if redirect-location
 
-  [state, body, null]
+  null
 
 reset-redirect = ->
   redirect-location := null

src/server.ls

@@ -21,14 +21,14 @@ module.exports = (options=defaults) ->
   app = options.app or require options.paths.app.rel
 
   get = (req, res) ->
-    console.log "GET ", req.original-url
+    console.log "GET", req.original-url
     reflex-get app, req.original-url, options
     .then ->
       res.send it
 
   post = (req, res) ->
     post-data = req.body
-    console.log "POST ", req.original-url, post-data
+    console.log "POST", req.original-url, post-data
 
     reflex-post app, req.original-url, post-data, options
     .spread (status, headers, body) ->