1 files changed, 114 insertions, 0 deletions
diff --git a/polygerrit-ui/app/embed/diff/gr-diff-highlight/gr-range-normalizer.ts b/polygerrit-ui/app/embed/diff/gr-diff-highlight/gr-range-normalizer.ts
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+++ b/polygerrit-ui/app/embed/diff/gr-diff-highlight/gr-range-normalizer.ts
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+/**
+ * @license
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the 'License');
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an 'AS IS' BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// Astral code point as per https://mathiasbynens.be/notes/javascript-unicode
+const REGEX_ASTRAL_SYMBOL = /[\uD800-\uDBFF][\uDC00-\uDFFF]/;
+
+export interface NormalizedRange {
+  endContainer: Node;
+  endOffset: number;
+  startContainer: Node;
+  startOffset: number;
+}
+
+/**
+ * Remap DOM range to whole lines of a diff if necessary. If the start or
+ * end containers are DOM elements that are singular pieces of syntax
+ * highlighting, the containers are remapped to the .contentText divs that
+ * contain the entire line of code.
+ *
+ * @param range - the standard DOM selector range.
+ * @return A modified version of the range that correctly accounts
+ *     for syntax highlighting.
+ */
+export function normalize(range: Range): NormalizedRange {
+  const startContainer = _getContentTextParent(range.startContainer);
+  const startOffset =
+    range.startOffset + _getTextOffset(startContainer, range.startContainer);
+  const endContainer = _getContentTextParent(range.endContainer);
+  const endOffset =
+    range.endOffset + _getTextOffset(endContainer, range.endContainer);
+  return {
+    startContainer,
+    startOffset,
+    endContainer,
+    endOffset,
+  };
+}
+
+function _getContentTextParent(target: Node): Node {
+  if (!target.parentElement) return target;
+
+  let element: Element | null;
+  if (target instanceof Element) {
+    element = target;
+  } else {
+    element = target.parentElement;
+  }
+
+  while (element && !element.classList.contains('contentText')) {
+    if (element.parentElement === null) {
+      return target;
+    }
+    element = element.parentElement;
+  }
+  return element ? element : target;
+}
+
+/**
+ * Gets the character offset of the child within the parent.
+ * Performs a synchronous in-order traversal from top to bottom of the node
+ * element, counting the length of the syntax until child is found.
+ *
+ * @param node The root DOM element to be searched through.
+ * @param child The child element being searched for.
+ */
+// TODO(TS): Only export for test.
+export function _getTextOffset(node: Node | null, child: Node): number {
+  let count = 0;
+  let stack = [node];
+  while (stack.length) {
+    const n = stack.pop();
+    if (n === child) {
+      break;
+    }
+    if (n?.childNodes && n.childNodes.length !== 0) {
+      const arr = [];
+      for (const childNode of n.childNodes) {
+        arr.push(childNode);
+      }
+      arr.reverse();
+      stack = stack.concat(arr);
+    } else {
+      count += _getLength(n);
+    }
+  }
+  return count;
+}
+
+/**
+ * The DOM API textContent.length calculation is broken when the text
+ * contains Unicode. See https://mathiasbynens.be/notes/javascript-unicode .
+ *
+ * @param node A text node.
+ * @return The length of the text.
+ */
+function _getLength(node?: Node | null) {
+  return node && node.textContent
+    ? node.textContent.replace(REGEX_ASTRAL_SYMBOL, '_').length
+    : 0;
+}