1 files changed, 87 insertions, 0 deletions
diff --git a/devtools/client/inspector/grids/reducers/grids.js b/devtools/client/inspector/grids/reducers/grids.js
new file mode 100644
index 0000000000..5ab8bb5060
--- /dev/null
+++ b/devtools/client/inspector/grids/reducers/grids.js
@@ -0,0 +1,87 @@
+/* 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";
+
+const {
+  UPDATE_GRID_COLOR,
+  UPDATE_GRID_HIGHLIGHTED,
+  UPDATE_GRIDS,
+} = require("resource://devtools/client/inspector/grids/actions/index.js");
+
+const INITIAL_GRIDS = [];
+
+const reducers = {
+  [UPDATE_GRID_COLOR](grids, { nodeFront, color }) {
+    const newGrids = grids.map(g => {
+      if (g.nodeFront === nodeFront) {
+        g = Object.assign({}, g, { color });
+      }
+
+      return g;
+    });
+
+    return newGrids;
+  },
+
+  [UPDATE_GRID_HIGHLIGHTED](grids, { nodeFront, highlighted }) {
+    const maxHighlighters = Services.prefs.getIntPref(
+      "devtools.gridinspector.maxHighlighters"
+    );
+    const highlightedNodeFronts = grids
+      .filter(g => g.highlighted)
+      .map(g => g.nodeFront);
+    let numHighlighted = highlightedNodeFronts.length;
+
+    // Get the total number of highlighted grids including the one that will be
+    // highlighted/unhighlighted.
+    if (!highlightedNodeFronts.includes(nodeFront) && highlighted) {
+      numHighlighted += 1;
+    } else if (highlightedNodeFronts.includes(nodeFront) && !highlighted) {
+      numHighlighted -= 1;
+    }
+
+    return grids.map(g => {
+      if (maxHighlighters === 1) {
+        // When there is only one grid highlighter available, only the given grid
+        // container nodeFront can be highlighted, and all the other grid containers
+        // are unhighlighted.
+        return Object.assign({}, g, {
+          highlighted: g.nodeFront === nodeFront && highlighted,
+        });
+      } else if (
+        numHighlighted === maxHighlighters &&
+        g.nodeFront !== nodeFront
+      ) {
+        // The maximum number of highlighted grids have been reached. Disable all the
+        // other non-highlighted grids.
+        return Object.assign({}, g, {
+          disabled: !g.highlighted,
+        });
+      } else if (g.nodeFront === nodeFront) {
+        // This is the provided grid nodeFront to highlight/unhighlight.
+        return Object.assign({}, g, {
+          disabled: false,
+          highlighted,
+        });
+      }
+
+      return Object.assign({}, g, {
+        disabled: false,
+      });
+    });
+  },
+
+  [UPDATE_GRIDS](_, { grids }) {
+    return grids;
+  },
+};
+
+module.exports = function (grids = INITIAL_GRIDS, action) {
+  const reducer = reducers[action.type];
+  if (!reducer) {
+    return grids;
+  }
+  return reducer(grids, action);
+};