1 files changed, 69 insertions, 0 deletions
diff --git a/devtools/client/debugger/src/reducers/preview.js b/devtools/client/debugger/src/reducers/preview.js
new file mode 100644
index 0000000000..7b11d581b2
--- /dev/null
+++ b/devtools/client/debugger/src/reducers/preview.js
@@ -0,0 +1,69 @@
+/* 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/>. */
+
+// @flow
+
+import type { AstLocation } from "../workers/parser";
+
+import type { Action } from "../actions/types";
+import type { Grip, Exception, OINode } from "../types";
+
+export type Preview = {|
+  expression: string,
+  resultGrip: Grip | null,
+  root: OINode,
+  properties: Array<Grip>,
+  location: AstLocation,
+  cursorPos: any,
+  tokenPos: AstLocation,
+  target: HTMLDivElement,
+  exception: ?Exception,
+|};
+
+export type PreviewState = {
+  +preview: ?Preview,
+  previewCount: number,
+};
+
+export function initialPreviewState(): PreviewState {
+  return {
+    preview: null,
+    previewCount: 0,
+  };
+}
+
+function update(
+  state: PreviewState = initialPreviewState(),
+  action: Action
+): PreviewState {
+  switch (action.type) {
+    case "CLEAR_PREVIEW": {
+      return { ...state, preview: null };
+    }
+
+    case "START_PREVIEW": {
+      return { ...state, previewCount: state.previewCount + 1 };
+    }
+
+    case "SET_PREVIEW": {
+      return { ...state, preview: action.value };
+    }
+  }
+
+  return state;
+}
+
+// NOTE: we'd like to have the app state fully typed
+// https://github.com/firefox-devtools/debugger/blob/master/src/reducers/sources.js#L179-L185
+type OuterState = { preview: PreviewState };
+
+export function getPreview(state: OuterState): ?Preview {
+  return state.preview.preview;
+}
+
+export function getPreviewCount(state: OuterState): number {
+  return state.preview.previewCount;
+}
+
+export default update;