1 files changed, 55 insertions, 0 deletions
diff --git a/app/assets/javascripts/static_site_editor/services/parse_source_file.js b/app/assets/javascripts/static_site_editor/services/parse_source_file.js
new file mode 100644
index 00000000000..f32c693411f
--- /dev/null
+++ b/app/assets/javascripts/static_site_editor/services/parse_source_file.js
@@ -0,0 +1,55 @@
+const parseSourceFile = raw => {
+  const frontMatterRegex = /(^---$[\s\S]*?^---$)/m;
+  const preGroupedRegex = /([\s\S]*?)(^---$[\s\S]*?^---$)(\s*)([\s\S]*)/m; // preFrontMatter, frontMatter, spacing, and content
+  let initial;
+  let editable;
+
+  const hasFrontMatter = source => frontMatterRegex.test(source);
+
+  const buildPayload = (source, header, spacing, body) => {
+    return { raw: source, header, spacing, body };
+  };
+
+  const parse = source => {
+    if (hasFrontMatter(source)) {
+      const match = source.match(preGroupedRegex);
+      const [, preFrontMatter, frontMatter, spacing, content] = match;
+      const header = preFrontMatter + frontMatter;
+
+      return buildPayload(source, header, spacing, content);
+    }
+
+    return buildPayload(source, '', '', source);
+  };
+
+  const computedRaw = () => `${editable.header}${editable.spacing}${editable.body}`;
+
+  const syncBody = () => {
+    /*
+    We re-parse as markdown editing could have added non-body changes (preFrontMatter, frontMatter, or spacing).
+    Re-parsing additionally gets us the desired body that was extracted from the mutated editable.raw
+    Additionally we intentionally mutate the existing editable's key values as opposed to reassigning the object itself so consumers of the potentially reactive property stay in sync.
+    */
+    Object.assign(editable, parse(editable.raw));
+  };
+
+  const syncRaw = () => {
+    editable.raw = computedRaw();
+  };
+
+  const isModifiedRaw = () => initial.raw !== editable.raw;
+  const isModifiedBody = () => initial.raw !== computedRaw();
+
+  initial = parse(raw);
+  editable = parse(raw);
+
+  return {
+    editable,
+    isModifiedRaw,
+    isModifiedBody,
+    syncRaw,
+    syncBody,
+  };
+};
+
+export default parseSourceFile;