1 files changed, 97 insertions, 0 deletions
diff --git a/app/assets/javascripts/editor/extensions/editor_markdown_ext.js b/app/assets/javascripts/editor/extensions/editor_markdown_ext.js
new file mode 100644
index 00000000000..2ce003753f7
--- /dev/null
+++ b/app/assets/javascripts/editor/extensions/editor_markdown_ext.js
@@ -0,0 +1,97 @@
+import { EditorLiteExtension } from './editor_lite_extension_base';
+
+export class EditorMarkdownExtension extends EditorLiteExtension {
+  getSelectedText(selection = this.getSelection()) {
+    const { startLineNumber, endLineNumber, startColumn, endColumn } = selection;
+    const valArray = this.getValue().split('\n');
+    let text = '';
+    if (startLineNumber === endLineNumber) {
+      text = valArray[startLineNumber - 1].slice(startColumn - 1, endColumn - 1);
+    } else {
+      const startLineText = valArray[startLineNumber - 1].slice(startColumn - 1);
+      const endLineText = valArray[endLineNumber - 1].slice(0, endColumn - 1);
+
+      for (let i = startLineNumber, k = endLineNumber - 1; i < k; i += 1) {
+        text += `${valArray[i]}`;
+        if (i !== k - 1) text += `\n`;
+      }
+      text = text
+        ? [startLineText, text, endLineText].join('\n')
+        : [startLineText, endLineText].join('\n');
+    }
+    return text;
+  }
+
+  replaceSelectedText(text, select = undefined) {
+    const forceMoveMarkers = !select;
+    this.executeEdits('', [{ range: this.getSelection(), text, forceMoveMarkers }]);
+  }
+
+  moveCursor(dx = 0, dy = 0) {
+    const pos = this.getPosition();
+    pos.column += dx;
+    pos.lineNumber += dy;
+    this.setPosition(pos);
+  }
+
+  /**
+   * Adjust existing selection to select text within the original selection.
+   * - If `selectedText` is not supplied, we fetch selected text with
+   *
+   * ALGORITHM:
+   *
+   * MULTI-LINE SELECTION
+   * 1. Find line that contains `toSelect` text.
+   * 2. Using the index of this line and the position of `toSelect` text in it,
+   * construct:
+   *   * newStartLineNumber
+   *   * newStartColumn
+   *
+   * SINGLE-LINE SELECTION
+   * 1. Use `startLineNumber` from the current selection as `newStartLineNumber`
+   * 2. Find the position of `toSelect` text in it to get `newStartColumn`
+   *
+   * 3. `newEndLineNumber` — Since this method is supposed to be used with
+   * markdown decorators that are pretty short, the `newEndLineNumber` is
+   * suggested to be assumed the same as the startLine.
+   * 4. `newEndColumn` — pretty obvious
+   * 5. Adjust the start and end positions of the current selection
+   * 6. Re-set selection on the instance
+   *
+   * @param {string} toSelect - New text to select within current selection.
+   * @param {string} selectedText - Currently selected text. It's just a
+   * shortcut: If it's not supplied, we fetch selected text from the instance
+   */
+  selectWithinSelection(toSelect, selectedText) {
+    const currentSelection = this.getSelection();
+    if (currentSelection.isEmpty() || !toSelect) {
+      return;
+    }
+    const text = selectedText || this.getSelectedText(currentSelection);
+    let lineShift;
+    let newStartLineNumber;
+    let newStartColumn;
+
+    const textLines = text.split('\n');
+
+    if (textLines.length > 1) {
+      // Multi-line selection
+      lineShift = textLines.findIndex((line) => line.indexOf(toSelect) !== -1);
+      newStartLineNumber = currentSelection.startLineNumber + lineShift;
+      newStartColumn = textLines[lineShift].indexOf(toSelect) + 1;
+    } else {
+      // Single-line selection
+      newStartLineNumber = currentSelection.startLineNumber;
+      newStartColumn = currentSelection.startColumn + text.indexOf(toSelect);
+    }
+
+    const newEndLineNumber = newStartLineNumber;
+    const newEndColumn = newStartColumn + toSelect.length;
+
+    const newSelection = currentSelection
+      .setStartPosition(newStartLineNumber, newStartColumn)
+      .setEndPosition(newEndLineNumber, newEndColumn);
+
+    this.setSelection(newSelection);
+  }
+}