Replace history.invoke with event emissions

src/emitter.js

@@ -100,5 +100,23 @@ Emitter.prototype = {
     }
 
     return this
+  },
+
+  /**
+   * Remove all events for a given scope
+   */
+  _removeScope (scope) {
+    let i = 0
+    while (i < this._events.length) {
+      var cb = this._events[i]
+
+      if (scope === cb.scope) {
+        this._events.splice(i, 1)
+        continue
+      }
+
+      i += 1
+    }
   }
+
 }

src/history.js

@@ -21,7 +21,6 @@ export default function History (limit) {
 
   this.size = 0
   this.limit = Math.max(1, limit || 1)
-  this.repos = []
 
   this.begin()
 }
@@ -122,27 +121,6 @@ inherit(History, Emitter, {
     this.append(START, 'resolve')
   },
 
-  addRepo (repo) {
-    this.repos.push(repo)
-  },
-
-  removeRepo (repo) {
-    let index = this.repos.indexOf(repo)
-
-    if (~index) {
-      this.repos.splice(index, 1)
-    }
-  },
-
-  invoke (method, payload) {
-    let repos = this.repos
-
-    for (var i = 0; i < repos.length; i++) {
-      console.assert(repos[i], `Missing repo! Was it removed before it could run repo.${method}?`)
-      repos[i][method](payload)
-    }
-  },
-
   append (command, status) {
     let action = new Action(command, status)
 
@@ -159,12 +137,10 @@ inherit(History, Emitter, {
     this.head = action
     this.size += 1
 
-    this.invoke('createInitialSnapshot', action)
+    this._emit('append', action)
 
     action.on('change', this.reconcile, this)
 
-    this._emit('append', action)
-
     return this.head
   },
 
@@ -204,7 +180,8 @@ inherit(History, Emitter, {
    */
   clean (action) {
     this.size -= 1
-    this.invoke('removeSnapshot', action)
+
+    this._emit('remove', action)
 
     action.remove()
   },
@@ -216,7 +193,7 @@ inherit(History, Emitter, {
     let focus = action
 
     while (focus) {
-      this.invoke('reconcile', focus)
+      this._emit('update', focus)
 
       if (focus === this.head) {
         break
@@ -227,7 +204,9 @@ inherit(History, Emitter, {
 
     this.archive()
 
-    this.invoke('release', action)
+    this._emit('reconcile', action)
+
+    this._emit('release')
   },
 
   archive () {
@@ -236,7 +215,7 @@ inherit(History, Emitter, {
 
     while (size > this.limit && root.complete) {
       size -= 1
-      this.invoke('removeSnapshot', root.parent)
+      this._emit('remove', root.parent)
       root = root.next
     }
 

src/microcosm.js

@@ -31,16 +31,33 @@ function Microcosm (preOptions, state, deserialize)  {
   this.parent = options.parent
 
   this.history = this.parent ? this.parent.history : new History(options.maxHistory)
-  this.history.addRepo(this)
 
   this.archive = new Archive()
   this.domains = new DomainEngine(this)
   this.effects = new EffectEngine(this)
-  this.changes = new CompareTree(this.state)
+  this.changes = new CompareTree()
 
   this.initial = this.parent ? this.parent.initial : {}
   this.state = this.parent ? this.parent.state : this.initial
 
+  // History moves through a set lifecycle. As that lifecycle occurs,
+  // save snapshots of new state:
+
+  // When an action is first created
+  this.history.on('append', this.createSnapshot, this)
+
+  // When an action snapshot needs updating
+  this.history.on('update', this.updateSnapshot, this)
+
+  // When an action snapshot should be removed
+  this.history.on('remove', this.removeSnapshot, this)
+
+  // When an action changes, it causes a reconcilation
+  this.history.on('reconcile', this.dispatchEffect, this)
+
+  // A history is done reconciling and is ready for a release
+  this.history.on('release', this.release, this)
+
   // Microcosm is now ready. Call the setup lifecycle method
   this.setup(options)
 
@@ -83,27 +100,15 @@ inherit(Microcosm, Emitter, {
    * that, when rolling back to this action, it always has a state value.
    * @param {Action} action - The action to generate a snapshot for
    */
-  createInitialSnapshot (action) {
+  createSnapshot (action) {
     this.archive.create(action)
   },
 
   /**
    * Update the state snapshot for a given action
    * @param {Action} action - The action to update the snapshot for
    */
-  updateSnapshot (action, state) {
-    this.archive.set(action, state)
-  },
-
-  /**
-   * Remove the snapshot for a given action
-   * @param {Action} action - The action to remove the snapshot for
-   */
-  removeSnapshot (action) {
-    this.archive.remove(action)
-  },
-
-  reconcile (action) {
+  updateSnapshot (action) {
     let next = this.recall(action.parent, this.initial)
 
     if (this.parent) {
@@ -114,16 +119,27 @@ inherit(Microcosm, Emitter, {
       next = this.domains.dispatch(next, action)
     }
 
-    this.updateSnapshot(action, next)
+    this.archive.set(action, next)
 
     this.state = next
   },
 
-  release (action) {
-    this.changes.update(this.state)
+  /**
+   * Remove the snapshot for a given action
+   * @param {Action} action - The action to remove the snapshot for
+   */
+  removeSnapshot (action) {
+    this.archive.remove(action)
+  },
+
+  dispatchEffect (action) {
     this.effects.dispatch(action)
   },
 
+  release () {
+    this.changes.update(this.state)
+  },
+
   on (type, callback, scope) {
     let [event, meta=''] = type.split(':', 2)
 
@@ -253,8 +269,8 @@ inherit(Microcosm, Emitter, {
     // Trigger a teardown event before completely shutting down
     this._emit('teardown', this)
 
-    // Remove this repo from history
-    this.history.removeRepo(this)
+    // Stop tracking history
+    this.history._removeScope(this)
 
     // Remove all listeners
     this.removeAllListeners()