5 files changed, 203 insertions, 0 deletions
diff --git a/app/scripts/lib/observable/host.js b/app/scripts/lib/observable/host.js
new file mode 100644
index 000000000..d1b110503
--- /dev/null
+++ b/app/scripts/lib/observable/host.js
@@ -0,0 +1,50 @@
+const Dnode = require('dnode')
+const ObservableStore = require('./index')
+const endOfStream = require('end-of-stream')
+
+//
+// HostStore
+//
+// plays host to many RemoteStores and sends its state over a stream
+//
+
+class HostStore extends ObservableStore {
+
+  constructor (initState, opts) {
+    super(initState)
+    this._opts = opts || {}
+  }
+
+  createStream () {
+    const self = this
+    // setup remotely exposed api
+    let remoteApi = {}
+    if (!self._opts.readOnly) {
+      remoteApi.put = (newState) => self.put(newState)
+    }
+    // listen for connection to remote
+    const dnode = Dnode(remoteApi)
+    dnode.on('remote', (remote) => {
+      // setup update subscription lifecycle
+      const updateHandler = (state) => remote.put(state)
+      self._onConnect(updateHandler)
+      endOfStream(dnode, () => self._onDisconnect(updateHandler))
+    })
+    return dnode
+  }
+
+  _onConnect (updateHandler) {
+    // subscribe to updates
+    this.subscribe(updateHandler)
+    // send state immediately
+    updateHandler(this.get())
+  }
+
+  _onDisconnect (updateHandler) {
+    // unsubscribe to updates
+    this.unsubscribe(updateHandler)
+  }
+
+}
+
+module.exports = HostStore
diff --git a/app/scripts/lib/observable/index.js b/app/scripts/lib/observable/index.js
new file mode 100644
index 000000000..1ff112e95
--- /dev/null
+++ b/app/scripts/lib/observable/index.js
@@ -0,0 +1,41 @@
+const EventEmitter = require('events').EventEmitter
+
+class ObservableStore extends EventEmitter {
+
+  constructor (initialState) {
+    super()
+    this._state = initialState
+  }
+
+  // wrapper around internal get
+  get () {
+    return this._state
+  }
+  
+  // wrapper around internal put
+  put (newState) {
+    this._put(newState)
+  }
+
+  // subscribe to changes
+  subscribe (handler) {
+    this.on('update', handler)
+  }
+
+  // unsubscribe to changes
+  unsubscribe (handler) {
+    this.removeListener('update', handler)
+  }
+
+  //
+  // private
+  //
+
+  _put (newState) {
+    this._state = newState
+    this.emit('update', newState)
+  }
+
+}
+
+module.exports = ObservableStore
diff --git a/app/scripts/lib/observable/local-storage.js b/app/scripts/lib/observable/local-storage.js
new file mode 100644
index 000000000..6ed3860f6
--- /dev/null
+++ b/app/scripts/lib/observable/local-storage.js
@@ -0,0 +1,37 @@
+const ObservableStore = require('./index')
+
+//
+// LocalStorageStore
+//
+// uses localStorage instead of a cache
+//
+
+class LocalStorageStore extends ObservableStore {
+
+  constructor (opts) {
+    super()
+    delete this._state
+
+    this._opts = opts || {}
+    if (!this._opts.storageKey) {
+      throw new Error('LocalStorageStore - no "storageKey" specified')
+    }
+    this._storageKey = this._opts.storageKey
+  }
+
+  get() {
+    try {
+      return JSON.parse(global.localStorage[this._storageKey])
+    } catch (err) {
+      return undefined
+    }
+  }
+
+  _put(newState) {
+    global.localStorage[this._storageKey] = JSON.stringify(newState)
+    this.emit('update', newState)
+  }
+
+}
+
+module.exports = LocalStorageStore
diff --git a/app/scripts/lib/observable/remote.js b/app/scripts/lib/observable/remote.js
new file mode 100644
index 000000000..603f6f0b8
--- /dev/null
+++ b/app/scripts/lib/observable/remote.js
@@ -0,0 +1,51 @@
+const Dnode = require('dnode')
+const ObservableStore = require('./index')
+const endOfStream = require('end-of-stream')
+
+//
+// RemoteStore
+//
+// connects to a HostStore and receives its latest state 
+//
+
+class RemoteStore extends ObservableStore {
+
+  constructor (initState, opts) {
+    super(initState)
+    this._opts = opts || {}
+    this._remote = null
+  }
+
+  put (newState) {
+    if (!this._remote) throw new Error('RemoteStore - "put" called before connection to HostStore')
+    this._put(newState)
+    this._remote.put(newState)
+  }
+
+  createStream () {
+    const self = this
+    const dnode = Dnode({
+      put: (newState) => self._put(newState),
+    })
+    // listen for connection to remote
+    dnode.once('remote', (remote) => {
+      // setup connection lifecycle
+      self._onConnect(remote)
+      endOfStream(dnode, () => self._onDisconnect())
+    })
+    return dnode
+  }
+
+  _onConnect (remote) {
+    this._remote = remote
+    this.emit('connected')
+  }
+
+  _onDisconnect () {
+    this._remote = null
+    this.emit('disconnected')
+  }
+
+}
+
+module.exports = RemoteStore
+\ No newline at end of file
diff --git a/app/scripts/lib/observable/util/sync.js b/app/scripts/lib/observable/util/sync.js
new file mode 100644
index 000000000..c61feb02e
--- /dev/null
+++ b/app/scripts/lib/observable/util/sync.js
@@ -0,0 +1,24 @@
+
+//
+// synchronizeStore(inStore, outStore, stateTransform)
+//
+// keeps outStore synchronized with inStore, via an optional stateTransform
+//
+
+module.exports = synchronizeStore
+
+
+function synchronizeStore(inStore, outStore, stateTransform) {
+  stateTransform = stateTransform || transformNoop
+  const initState = stateTransform(inStore.get())
+  outStore.put(initState)
+  inStore.subscribe((inState) => {
+    const outState = stateTransform(inState)
+    outStore.put(outState)
+  })
+  return outStore
+}
+
+function transformNoop(state) {
+  return state
+}
+\ No newline at end of file