1 files changed, 73 insertions, 0 deletions
diff --git a/app/assets/javascripts/static_site_editor/services/front_matterify.js b/app/assets/javascripts/static_site_editor/services/front_matterify.js
new file mode 100644
index 00000000000..cbf0fffd515
--- /dev/null
+++ b/app/assets/javascripts/static_site_editor/services/front_matterify.js
@@ -0,0 +1,73 @@
+import jsYaml from 'js-yaml';
+
+const NEW_LINE = '\n';
+
+const hasMatter = (firstThreeChars, fourthChar) => {
+  const isYamlDelimiter = firstThreeChars === '---';
+  const isFourthCharNewline = fourthChar === NEW_LINE;
+  return isYamlDelimiter && isFourthCharNewline;
+};
+
+export const frontMatterify = source => {
+  let index = 3;
+  let offset;
+  const delimiter = source.slice(0, index);
+  const type = 'yaml';
+  const NO_FRONTMATTER = {
+    source,
+    matter: null,
+    spacing: null,
+    content: source,
+    delimiter: null,
+    type: null,
+  };
+
+  if (!hasMatter(delimiter, source.charAt(index))) {
+    return NO_FRONTMATTER;
+  }
+
+  offset = source.indexOf(delimiter, index);
+
+  // Finds the end delimiter that starts at a new line
+  while (offset !== -1 && source.charAt(offset - 1) !== NEW_LINE) {
+    index = offset + delimiter.length;
+    offset = source.indexOf(delimiter, index);
+  }
+
+  if (offset === -1) {
+    return NO_FRONTMATTER;
+  }
+
+  const matterStr = source.slice(index, offset);
+  const matter = jsYaml.safeLoad(matterStr);
+
+  let content = source.slice(offset + delimiter.length);
+  let spacing = '';
+  let idx = 0;
+  while (content.charAt(idx).match(/(\s|\n)/)) {
+    spacing += content.charAt(idx);
+    idx += 1;
+  }
+  content = content.replace(spacing, '');
+
+  return {
+    source,
+    matter,
+    spacing,
+    content,
+    delimiter,
+    type,
+  };
+};
+
+export const stringify = ({ matter, spacing, content, delimiter }, newMatter) => {
+  const matterObj = newMatter || matter;
+
+  if (!matterObj) {
+    return content;
+  }
+
+  const header = `${delimiter}${NEW_LINE}${jsYaml.safeDump(matterObj)}${delimiter}`;
+  const body = `${spacing}${content}`;
+  return `${header}${body}`;
+};