From 6d0152cf703eec85d5241620a56d048567f3fd31 Mon Sep 17 00:00:00 2001
From: Jordan Eldredge <jordan@jordaneldredge.com>
Date: Mon, 18 Dec 2017 08:54:56 -0800
Subject: [PATCH] Fix shift-select

---
 js/reducers/playlist.js      |  7 ++++---
 js/reducers/playlist.test.js | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+), 3 deletions(-)
 create mode 100644 js/reducers/playlist.test.js

diff --git a/js/reducers/playlist.js b/js/reducers/playlist.js
index 5e47138a..661b457b 100644
--- a/js/reducers/playlist.js
+++ b/js/reducers/playlist.js
@@ -61,11 +61,12 @@ const playlist = (state = defaultPlaylistState, action) => {
       const clickedIndex = action.index;
       const start = Math.min(clickedIndex, state.lastSelectedIndex);
       const end = Math.max(clickedIndex, state.lastSelectedIndex);
+      const selected = new Set(state.trackOrder.slice(start, end + 1));
       return {
         ...state,
-        tracks: state.trackOrder.map((trackId, i) => ({
-          ...state.tracks[trackId],
-          selected: i >= start && i <= end
+        tracks: mapObject(state.tracks, (track, trackId) => ({
+          ...track,
+          selected: selected.has(Number(trackId))
         }))
       };
     case SELECT_ALL:
diff --git a/js/reducers/playlist.test.js b/js/reducers/playlist.test.js
new file mode 100644
index 00000000..d0a7bdd0
--- /dev/null
+++ b/js/reducers/playlist.test.js
@@ -0,0 +1,32 @@
+import reducer from "./playlist";
+import { SHIFT_CLICKED_TRACK } from "../actionTypes";
+
+describe("playlist reducer", () => {
+  it("can handle shift-click", () => {
+    const initialState = {
+      tracks: {
+        0: { selected: false },
+        1: { selected: false },
+        2: { selected: false },
+        3: { selected: false }
+      },
+      trackOrder: [3, 2, 1, 0],
+      lastSelectedIndex: 1
+    };
+
+    const nextState = reducer(initialState, {
+      type: SHIFT_CLICKED_TRACK,
+      index: 3
+    });
+    expect(nextState).toEqual({
+      lastSelectedIndex: 1,
+      tracks: {
+        0: { selected: true },
+        1: { selected: true },
+        2: { selected: true },
+        3: { selected: false }
+      },
+      trackOrder: [3, 2, 1, 0]
+    });
+  });
+});