Refactored all device list components to its own module.

res/app/device-list/util/patch-array/index.js

@@ -0,0 +1,71 @@
+function existenceMap(array) {
+  var map = Object.create(null)
+  for (var i = 0, l = array.length; i < l; ++i) {
+    map[array[i]] = 1
+  }
+  return map
+}
+
+// Returns a list of operations to transform array a into array b. May not
+// return the optimal set of operations.
+module.exports = function patchArray(a, b) {
+  var ops = []
+
+  var workA = [].concat(a)
+    , inA = Object.create(null)
+    , itemA
+    , cursorA
+
+  var inB = existenceMap(b)
+    , posB = Object.create(null)
+    , itemB
+    , cursorB
+
+  // First, check what was removed from a.
+  for (cursorA = 0; cursorA < workA.length;) {
+    itemA = workA[cursorA]
+
+    // If b does not contain the item, surely it must have been removed.
+    if (!inB[itemA]) {
+      workA.splice(cursorA, 1)
+      ops.push(['remove', cursorA])
+    }
+    // Otherwise, the item is still alive.
+    else {
+      inA[itemA] = true
+      cursorA += 1
+    }
+  }
+
+  // Then, check what was inserted into b.
+  for (cursorB = 0; cursorB < b.length; ++cursorB) {
+    itemB = b[cursorB]
+
+    // If a does not contain the item, it must have been added.
+    if (!inA[itemB]) {
+      workA.splice(cursorB, 0, itemB)
+      ops.push(['insert', cursorB, itemB])
+    }
+
+    posB[itemB] = cursorB
+  }
+
+  // At this point, workA contains the same items as b, but swaps may
+  // be needed.
+  for (cursorA = 0; cursorA < workA.length;) {
+    itemA = workA[cursorA]
+    var posInB = posB[itemA]
+
+    if (posInB === cursorA) {
+      cursorA += 1
+    }
+    else {
+      var temp = workA[posInB]
+      workA[posInB] = itemA
+      workA[cursorA] = temp
+      ops.push(['swap', cursorA, posInB])
+    }
+  }
+
+  return ops
+}