1 files changed, 182 insertions, 0 deletions
diff --git a/toolkit/jetpack/sdk/ui/component.js b/toolkit/jetpack/sdk/ui/component.js
new file mode 100644
index 000000000..d1f12c95e
--- /dev/null
+++ b/toolkit/jetpack/sdk/ui/component.js
@@ -0,0 +1,182 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+// Internal properties not exposed to the public.
+const cache = Symbol("component/cache");
+const writer = Symbol("component/writer");
+const isFirstWrite = Symbol("component/writer/first-write?");
+const currentState = Symbol("component/state/current");
+const pendingState = Symbol("component/state/pending");
+const isWriting = Symbol("component/writing?");
+
+const isntNull = x => x !== null;
+
+const Component = function(options, children) {
+  this[currentState] = null;
+  this[pendingState] = null;
+  this[writer] = null;
+  this[cache] = null;
+  this[isFirstWrite] = true;
+
+  this[Component.construct](options, children);
+}
+Component.Component = Component;
+// Constructs component.
+Component.construct = Symbol("component/construct");
+// Called with `options` and `children` and must return
+// initial state back.
+Component.initial = Symbol("component/initial");
+
+// Function patches current `state` with a given update.
+Component.patch = Symbol("component/patch");
+// Function that replaces current `state` with a passed state.
+Component.reset = Symbol("component/reset");
+
+// Function that must return render tree from passed state.
+Component.render = Symbol("component/render");
+
+// Path of the component with in the mount point.
+Component.path = Symbol("component/path");
+
+Component.isMounted = component => !!component[writer];
+Component.isWriting = component => !!component[isWriting];
+
+// Internal method that mounts component to a writer.
+// Mounts component to a writer.
+Component.mount = (component, write) => {
+  if (Component.isMounted(component)) {
+    throw Error("Can not mount already mounted component");
+  }
+
+  component[writer] = write;
+  Component.write(component);
+
+  if (component[Component.mounted]) {
+    component[Component.mounted]();
+  }
+}
+
+// Unmounts component from a writer.
+Component.unmount = (component) => {
+  if (Component.isMounted(component)) {
+    component[writer] = null;
+    if (component[Component.unmounted]) {
+      component[Component.unmounted]();
+    }
+  } else {
+    console.warn("Unmounting component that is not mounted is redundant");
+  }
+};
+ // Method invoked once after inital write occurs.
+Component.mounted = Symbol("component/mounted");
+// Internal method that unmounts component from the writer.
+Component.unmounted = Symbol("component/unmounted");
+// Function that must return true if component is changed
+Component.isUpdated = Symbol("component/updated?");
+Component.update = Symbol("component/update");
+Component.updated = Symbol("component/updated");
+
+const writeChild = base => (child, index) => Component.write(child, base, index)
+Component.write = (component, base, index) => {
+  if (component === null) {
+    return component;
+  }
+
+  if (!(component instanceof Component)) {
+    const path = base ? `${base}${component.key || index}/` : `/`;
+    return Object.assign({}, component, {
+      [Component.path]: path,
+      children: component.children && component.children.
+                                        map(writeChild(path)).
+                                        filter(isntNull)
+    });
+  }
+
+  component[isWriting] = true;
+
+  try {
+
+    const current = component[currentState];
+    const pending = component[pendingState] || current;
+    const isUpdated = component[Component.isUpdated];
+    const isInitial = component[isFirstWrite];
+
+    if (isUpdated(current, pending) || isInitial) {
+      if (!isInitial && component[Component.update]) {
+        component[Component.update](pending, current)
+      }
+
+      // Note: [Component.update] could have caused more updates so can't use
+      // `pending` as `component[pendingState]` may have changed.
+      component[currentState] = component[pendingState] || current;
+      component[pendingState] = null;
+
+      const tree = component[Component.render](component[currentState]);
+      component[cache] = Component.write(tree, base, index);
+      if (component[writer]) {
+        component[writer].call(null, component[cache]);
+      }
+
+      if (!isInitial && component[Component.updated]) {
+        component[Component.updated](current, pending);
+      }
+    }
+
+    component[isFirstWrite] = false;
+
+    return component[cache];
+  } finally {
+    component[isWriting] = false;
+  }
+};
+
+Component.prototype = Object.freeze({
+  constructor: Component,
+
+  [Component.mounted]: null,
+  [Component.unmounted]: null,
+  [Component.update]: null,
+  [Component.updated]: null,
+
+  get state() {
+    return this[pendingState] || this[currentState];
+  },
+
+
+  [Component.construct](settings, items) {
+    const initial = this[Component.initial];
+    const base = initial(settings, items);
+    const options = Object.assign(Object.create(null), base.options, settings);
+    const children = base.children || items || null;
+    const state = Object.assign(Object.create(null), base, {options, children});
+    this[currentState] = state;
+
+    if (this.setup) {
+      this.setup(state);
+    }
+  },
+  [Component.initial](options, children) {
+    return Object.create(null);
+  },
+  [Component.patch](update) {
+    this[Component.reset](Object.assign({}, this.state, update));
+  },
+  [Component.reset](state) {
+    this[pendingState] = state;
+    if (Component.isMounted(this) && !Component.isWriting(this)) {
+      Component.write(this);
+    }
+  },
+
+  [Component.isUpdated](before, after) {
+    return before != after
+  },
+
+  [Component.render](state) {
+    throw Error("Component must implement [Component.render] member");
+  }
+});
+
+module.exports = Component;