3 files changed, 155 insertions, 0 deletions
diff --git a/devtools/client/framework/reducers/dom-mutation-breakpoints.js b/devtools/client/framework/reducers/dom-mutation-breakpoints.js
new file mode 100644
index 0000000000..f5e9c63a2c
--- /dev/null
+++ b/devtools/client/framework/reducers/dom-mutation-breakpoints.js
@@ -0,0 +1,134 @@
+/* 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 initialReducerState = {
+  counter: 1,
+  breakpoints: [],
+};
+
+exports.reducer = domMutationBreakpointReducer;
+function domMutationBreakpointReducer(state = initialReducerState, action) {
+  switch (action.type) {
+    case "ADD_DOM_MUTATION_BREAKPOINT":
+      const hasExistingBp = state.breakpoints.some(
+        bp =>
+          bp.nodeFront === action.nodeFront &&
+          bp.mutationType === action.mutationType
+      );
+
+      if (hasExistingBp) {
+        break;
+      }
+
+      state = {
+        ...state,
+        counter: state.counter + 1,
+        breakpoints: [
+          ...state.breakpoints,
+          {
+            id: `${state.counter}`,
+            nodeFront: action.nodeFront,
+            targetFront: action.nodeFront.targetFront,
+            mutationType: action.mutationType,
+            enabled: true,
+          },
+        ],
+      };
+      break;
+    case "REMOVE_DOM_MUTATION_BREAKPOINT":
+      for (const [index, bp] of state.breakpoints.entries()) {
+        if (
+          bp.nodeFront === action.nodeFront &&
+          bp.mutationType === action.mutationType
+        ) {
+          state = {
+            ...state,
+            breakpoints: [
+              ...state.breakpoints.slice(0, index),
+              ...state.breakpoints.slice(index + 1),
+            ],
+          };
+          break;
+        }
+      }
+      break;
+    case "REMOVE_DOM_MUTATION_BREAKPOINTS_FOR_FRONTS": {
+      const { nodeFronts } = action;
+      const nodeFrontSet = new Set(nodeFronts);
+
+      const breakpoints = state.breakpoints.filter(
+        bp => !nodeFrontSet.has(bp.nodeFront)
+      );
+
+      // Since we might not have made any actual changes, we verify first
+      // to avoid unnecessary changes in the state.
+      if (state.breakpoints.length !== breakpoints.length) {
+        state = {
+          ...state,
+          breakpoints,
+        };
+      }
+      break;
+    }
+
+    case "REMOVE_TARGET": {
+      const { targetFront } = action;
+      // When a target is destroyed, remove breakpoints associated with it.
+      const breakpoints = state.breakpoints.filter(
+        bp => bp.targetFront !== targetFront
+      );
+
+      // Since we might not have made any actual changes, we verify first
+      // to avoid unnecessary changes in the state.
+      if (state.breakpoints.length !== breakpoints.length) {
+        state = {
+          ...state,
+          breakpoints,
+        };
+      }
+      break;
+    }
+
+    case "SET_DOM_MUTATION_BREAKPOINTS_ENABLED_STATE": {
+      const { enabledStates } = action;
+      const toUpdateById = new Map(enabledStates);
+
+      const breakpoints = state.breakpoints.map(bp => {
+        const newBpState = toUpdateById.get(bp.id);
+        if (typeof newBpState === "boolean" && newBpState !== bp.enabled) {
+          bp = {
+            ...bp,
+            enabled: newBpState,
+          };
+        }
+
+        return bp;
+      });
+
+      // Since we might not have made any actual changes, we verify first
+      // to avoid unnecessary changes in the state.
+      if (state.breakpoints.some((bp, i) => breakpoints[i] !== bp)) {
+        state = {
+          ...state,
+          breakpoints,
+        };
+      }
+      break;
+    }
+  }
+  return state;
+}
+
+exports.getDOMMutationBreakpoints = getDOMMutationBreakpoints;
+function getDOMMutationBreakpoints(state) {
+  return state.domMutationBreakpoints.breakpoints;
+}
+
+exports.getDOMMutationBreakpoint = getDOMMutationBreakpoint;
+function getDOMMutationBreakpoint(state, id) {
+  return (
+    state.domMutationBreakpoints.breakpoints.find(v => v.id === id) || null
+  );
+}
diff --git a/devtools/client/framework/reducers/index.js b/devtools/client/framework/reducers/index.js
new file mode 100644
index 0000000000..3ab06e349c
--- /dev/null
+++ b/devtools/client/framework/reducers/index.js
@@ -0,0 +1,10 @@
+/* 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";
+
+module.exports = {
+  domMutationBreakpoints:
+    require("resource://devtools/client/framework/reducers/dom-mutation-breakpoints.js")
+      .reducer,
+};
diff --git a/devtools/client/framework/reducers/moz.build b/devtools/client/framework/reducers/moz.build
new file mode 100644
index 0000000000..e77a7cc2cc
--- /dev/null
+++ b/devtools/client/framework/reducers/moz.build
@@ -0,0 +1,11 @@
+# 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/.
+
+DevToolsModules(
+    "dom-mutation-breakpoints.js",
+    "index.js",
+)
+
+with Files("**"):
+    BUG_COMPONENT = ("DevTools", "Framework")