DevTools: Diff subsystem

third_party/WebKit/Source/devtools/front_end/workspace_diff/WorkspaceDiff.js

Index: third_party/WebKit/Source/devtools/front_end/workspace_diff/WorkspaceDiff.js
diff --git a/third_party/WebKit/Source/devtools/front_end/workspace_diff/WorkspaceDiff.js b/third_party/WebKit/Source/devtools/front_end/workspace_diff/WorkspaceDiff.js
new file mode 100644
index 0000000000000000000000000000000000000000..94d0b90fd95b3441be2892515ca6bc22f2c30606
--- /dev/null
+++ b/third_party/WebKit/Source/devtools/front_end/workspace_diff/WorkspaceDiff.js
@@ -0,0 +1,111 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+
+WorkspaceDiff.WorkspaceDiff = class {
+  constructor() {
+    /** @type {!WeakMap<!Workspace.UISourceCode, !WorkspaceDiff._UISourceCodeDiff>} */
+    this._uiSourceCodeDiffs = new WeakMap();
+  }
+
+  /**
+   * @param {!Workspace.UISourceCode} uiSourceCode
+   * @return {!Promise<!Diff.Diff.DiffArray>}
+   */
+  requestDiff(uiSourceCode) {
+    return this._uiSourceCodeDiff(uiSourceCode).requestDiff();
+  }
+
+  /**
+   * @param {!Workspace.UISourceCode} uiSourceCode
+   * @param {function(!WorkspaceDiff.DiffChangedEvent)} callback
+   * @param {!Object=} thisObj
+   */
+  subscribeToDiffChange(uiSourceCode, callback, thisObj) {
+    this._uiSourceCodeDiff(uiSourceCode).on(WorkspaceDiff.DiffChangedEvent, callback, thisObj);
+  }
+
+  /**
+   * @param {!Workspace.UISourceCode} uiSourceCode
+   * @param {function(!WorkspaceDiff.DiffChangedEvent)} callback
+   * @param {!Object=} thisObj
+   */
+  unsubscribeToDiffChange(uiSourceCode, callback, thisObj) {
+    this._uiSourceCodeDiff(uiSourceCode).off(WorkspaceDiff.DiffChangedEvent, callback, thisObj);
+  }
+
+  /**
+   * @param {!Workspace.UISourceCode} uiSourceCode
+   * @return {!WorkspaceDiff._UISourceCodeDiff}
+   */
+  _uiSourceCodeDiff(uiSourceCode) {
+    if (!this._uiSourceCodeDiffs.has(uiSourceCode))
+      this._uiSourceCodeDiffs.set(uiSourceCode, new WorkspaceDiff._UISourceCodeDiff(uiSourceCode));
+    return this._uiSourceCodeDiffs.get(uiSourceCode);

[lushnikov, 2017/03/10 01:17:04]

how does this compile without a cast?

[einbinder, 2017/03/13 17:47:57]

Closure trusts you on getting non-nullable values out of maps.

+  }
+};
+
+WorkspaceDiff._UISourceCodeDiff = class extends Common.Object {

[lushnikov, 2017/03/10 01:17:04]

WorkspaceDiff.WorkspaceDiff.UISourceCodeDiff

[einbinder, 2017/03/13 17:47:57]

WorkspaceDiff.WorkspaceDiff._UISourceCodeDiff

+  /**
+   * @param {!Workspace.UISourceCode} uiSourceCode
+   */
+  constructor(uiSourceCode) {
+    super();
+    this._uiSourceCode = uiSourceCode;
+    uiSourceCode.addEventListener(Workspace.UISourceCode.Events.WorkingCopyChanged, this._uiSourceCodeChanged, this);
+    uiSourceCode.addEventListener(Workspace.UISourceCode.Events.WorkingCopyCommitted, this._uiSourceCodeChanged, this);
+    this._requestDiffPromise = null;
+    this._pendingChanges = null;
+  }
+
+  _uiSourceCodeChanged() {
+    if (this._pendingChanges) {
+      clearTimeout(this._pendingChanges);

[lushnikov, 2017/03/10 01:17:04]

do you really want this logic? In case of continious stream of events about
UISourceCode change, the diff would feel like stale

[einbinder, 2017/03/13 17:47:57]

This is the current behavior. If the user is typing for a long time with no
breaks, we probably shouldn't interrupt them with a potentially expensive diff
operation. And they probably aren't looking at diff.

+      this._pendingChanges = null;
+    }
+    this._requestDiffPromise = null;
+
+    var content = this._uiSourceCode.content();
+    var delay = (!content || content.length < 65536) ? 0 : WorkspaceDiff.WorkspaceDiff.UpdateTimeout;
+    this._pendingChanges = setTimeout(emitDiffChanged.bind(this), delay);
+
+    /**
+     * @this {WorkspaceDiff._UISourceCodeDiff}
+     */
+    function emitDiffChanged() {
+      this.emit(new WorkspaceDiff.DiffChangedEvent());
+      this._pendingChanges = null;
+    }
+  }
+
+  /**
+   * @return {!Promise<!Diff.Diff.DiffArray>}
+   */
+  requestDiff() {
+    if (!this._requestDiffPromise) {
+      this._requestDiffPromise = this._uiSourceCode.requestOriginalContent().then(baseline => {
+        var current = this._uiSourceCode.workingCopy();
+        var diff = Diff.Diff.lineDiff(baseline.split('\n'), current.split('\n'));
+        return diff || [];
+      });
+    }
+    return this._requestDiffPromise;
+  }
+};
+
+/**
+ * @implements {Common.Emittable}
+ */
+WorkspaceDiff.DiffChangedEvent = class {};
+
+/**
+ * @return {!WorkspaceDiff.WorkspaceDiff}
+ */
+WorkspaceDiff.workspaceDiff = function() {
+  if (!WorkspaceDiff.WorkspaceDiff._instance)
+    WorkspaceDiff.WorkspaceDiff._instance = new WorkspaceDiff.WorkspaceDiff();
+  return WorkspaceDiff.WorkspaceDiff._instance;
+};
+
+WorkspaceDiff.WorkspaceDiff.UpdateTimeout = 200;