1 files changed, 135 insertions, 0 deletions

diff --git a/app/assets/javascripts/issues/show/utils.js b/app/assets/javascripts/issues/show/utils.js
index 05b06586362..7742a015836 100644
--- a/app/assets/javascripts/issues/show/utils.js
+++ b/app/assets/javascripts/issues/show/utils.js
@@ -1,4 +1,6 @@
+import { TITLE_LENGTH_MAX } from '~/issues/constants';
 import { COLON, HYPHEN, NEWLINE } from '~/lib/utils/text_utility';
+import { __ } from '~/locale';
 
 /**
  * Returns the start and end `sourcepos` rows, converted to zero-based numbering.
@@ -93,3 +95,136 @@ export const convertDescriptionWithNewSort = (description, list) => {
 
   return descriptionLines.join(NEWLINE);
 };
+
+const bulletTaskListItemRegex = /^\s*[-*]\s+\[.]\s+/;
+const numericalTaskListItemRegex = /^\s*[0-9]\.\s+\[.]\s+/;
+const codeMarkdownRegex = /^\s*`.*`\s*$/;
+const imageOrLinkMarkdownRegex = /^\s*!?\[.*\)\s*$/;
+
+/**
+ * Checks whether the line of markdown contains a task list item,
+ * i.e. `- [ ]`, `* [ ]`, or `1. [ ]`.
+ *
+ * @param {String} line A line of markdown
+ * @returns {boolean} `true` if the line contains a task list item, otherwise `false`
+ */
+const containsTaskListItem = (line) =>
+  bulletTaskListItemRegex.test(line) || numericalTaskListItemRegex.test(line);
+
+/**
+ * Deletes a task list item from the description.
+ *
+ * Starting from the task list item, it deletes each line until it hits a nested
+ * task list item and reduces the indentation of each line from this line onwards.
+ *
+ * For example, for a given description like:
+ *
+ * <pre>
+ * 1. [ ] item 1
+ *
+ *    paragraph text
+ *
+ *    1. [ ] item 2
+ *
+ *       paragraph text
+ *
+ *    1. [ ] item 3
+ * </pre>
+ *
+ * Then when prompted to delete item 1, this function will return:
+ *
+ * <pre>
+ * 1. [ ] item 2
+ *
+ *    paragraph text
+ *
+ * 1. [ ] item 3
+ * </pre>
+ *
+ * @param {String} description Description in markdown format
+ * @param {String} sourcepos Source position in format `23:3-23:14`
+ * @returns {{newDescription: String, taskDescription: String, taskTitle: String}} Object with:
+ *
+ * - `newDescription` property that contains markdown with the deleted task list item omitted
+ * - `taskDescription` property that contains the description of the deleted task list item
+ * - `taskTitle` property that contains the title of the deleted task list item
+ */
+export const deleteTaskListItem = (description, sourcepos) => {
+  const descriptionLines = description.split(NEWLINE);
+  const [startIndex, endIndex] = getSourceposRows(sourcepos);
+
+  const firstLine = descriptionLines[startIndex];
+  const firstLineIndentation = firstLine.length - firstLine.trimStart().length;
+
+  const taskTitle = firstLine
+    .replace(bulletTaskListItemRegex, '')
+    .replace(numericalTaskListItemRegex, '');
+  const taskDescription = [];
+
+  let indentation = 0;
+  let linesToDelete = 1;
+  let reduceIndentation = false;
+
+  for (let i = startIndex + 1; i <= endIndex; i += 1) {
+    if (reduceIndentation) {
+      descriptionLines[i] = descriptionLines[i].slice(indentation);
+    } else if (containsTaskListItem(descriptionLines[i])) {
+      reduceIndentation = true;
+      const currentLine = descriptionLines[i];
+      const currentLineIndentation = currentLine.length - currentLine.trimStart().length;
+      indentation = currentLineIndentation - firstLineIndentation;
+      descriptionLines[i] = descriptionLines[i].slice(indentation);
+    } else {
+      taskDescription.push(descriptionLines[i].trimStart());
+      linesToDelete += 1;
+    }
+  }
+
+  descriptionLines.splice(startIndex, linesToDelete);
+
+  return {
+    newDescription: descriptionLines.join(NEWLINE),
+    taskDescription: taskDescription.join(NEWLINE) || undefined,
+    taskTitle,
+  };
+};
+
+/**
+ * Given a title and description for a task:
+ *
+ * - Moves characters beyond the 255 character limit from the title to the description
+ * - Moves a pure markdown title to the description and gives the title the value `Untitled`
+ *
+ * @param {String} taskTitle The task title
+ * @param {String} taskDescription The task description
+ * @returns {{description: String, title: String}} An object with the formatted task title and description
+ */
+export const extractTaskTitleAndDescription = (taskTitle, taskDescription) => {
+  const isTitleOnlyMarkdown =
+    codeMarkdownRegex.test(taskTitle) || imageOrLinkMarkdownRegex.test(taskTitle);
+
+  if (isTitleOnlyMarkdown) {
+    return {
+      title: __('Untitled'),
+      description: taskDescription
+        ? taskTitle.concat(NEWLINE, NEWLINE, taskDescription)
+        : taskTitle,
+    };
+  }
+
+  const isTitleTooLong = taskTitle.length > TITLE_LENGTH_MAX;
+
+  if (isTitleTooLong) {
+    return {
+      title: taskTitle.slice(0, TITLE_LENGTH_MAX),
+      description: taskDescription
+        ? taskTitle.slice(TITLE_LENGTH_MAX).concat(NEWLINE, NEWLINE, taskDescription)
+        : taskTitle.slice(TITLE_LENGTH_MAX),
+    };
+  }
+
+  return {
+    title: taskTitle,
+    description: taskDescription,
+  };
+};