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..d062c3a3cbb82c7a31870a163a084e5a078cd4da
--- /dev/null
+++ b/third_party/WebKit/Source/devtools/front_end/workspace_diff/WorkspaceDiff.js
@@ -0,0 +1,119 @@
+// 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.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
+   */
+  unsubscribeFromDiffChange(uiSourceCode, callback, thisObj) {
+    this._uiSourceCodeDiff(uiSourceCode).off(WorkspaceDiff.DiffChangedEvent, callback, thisObj);
+  }
+
+  /**
+   * @param {!Workspace.UISourceCode} uiSourceCode
+   * @return {!WorkspaceDiff.WorkspaceDiff.UISourceCodeDiff}
+   */
+  _uiSourceCodeDiff(uiSourceCode) {
+    if (!this._uiSourceCodeDiffs.has(uiSourceCode))
+      this._uiSourceCodeDiffs.set(uiSourceCode, new WorkspaceDiff.WorkspaceDiff.UISourceCodeDiff(uiSourceCode));
+    return this._uiSourceCodeDiffs.get(uiSourceCode);
+  }
+};
+
+WorkspaceDiff.WorkspaceDiff.UISourceCodeDiff = class extends Common.Object {
+  /**
+   * @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);
+      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.WorkspaceDiff.UISourceCodeDiff}
+     */
+    function emitDiffChanged() {
+      this.emit(new WorkspaceDiff.DiffChangedEvent());
+      this._pendingChanges = null;
+    }
+  }
+
+  /**
+   * @return {!Promise<?Diff.Diff.DiffArray>}
+   */
+  requestDiff() {
+    if (!this._requestDiffPromise)
+      this._requestDiffPromise = this._innerRequestDiff();
+    return this._requestDiffPromise;
+  }
+
+  /**
+   * @return {!Promise<?Diff.Diff.DiffArray>}
+   */
+  async _innerRequestDiff() {
+    var current = this._uiSourceCode.workingCopy();
+    if (!current && !this._uiSourceCode.contentLoaded())
+      current = await this._uiSourceCode.requestContent();
+    var baseline = await this._uiSourceCode.requestOriginalContent();
+    if (current === null || baseline === null)
+      return null;
+    return Diff.Diff.lineDiff(baseline.split('\n'), current.split('\n'));
+  }
+};
+
+/**
+ * @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;