1 files changed, 40 insertions, 0 deletions
diff --git a/app/assets/javascripts/content_editor/services/markdown_sourcemap.js b/app/assets/javascripts/content_editor/services/markdown_sourcemap.js
new file mode 100644
index 00000000000..a1199589c9b
--- /dev/null
+++ b/app/assets/javascripts/content_editor/services/markdown_sourcemap.js
@@ -0,0 +1,40 @@
+const getFullSource = (element) => {
+  const commentNode = element.ownerDocument.body.lastChild;
+
+  if (commentNode.nodeName === '#comment') {
+    return commentNode.textContent.split('\n');
+  }
+
+  return [];
+};
+
+const getRangeFromSourcePos = (sourcePos) => {
+  const [start, end] = sourcePos.split('-');
+  const [startRow, startCol] = start.split(':');
+  const [endRow, endCol] = end.split(':');
+
+  return {
+    start: { row: Number(startRow) - 1, col: Number(startCol) - 1 },
+    end: { row: Number(endRow) - 1, col: Number(endCol) - 1 },
+  };
+};
+
+export const getMarkdownSource = (element) => {
+  if (!element.dataset.sourcepos) return undefined;
+
+  const source = getFullSource(element);
+  const range = getRangeFromSourcePos(element.dataset.sourcepos);
+  let elSource = '';
+
+  for (let i = range.start.row; i <= range.end.row; i += 1) {
+    if (i === range.start.row) {
+      elSource += source[i]?.substring(range.start.col);
+    } else if (i === range.end.row) {
+      elSource += `\n${source[i]?.substring(0, range.start.col)}`;
+    } else {
+      elSource += `\n${source[i]}` || '';
+    }
+  }
+
+  return elSource.trim();
+};