Duplicate code in readMetadata.js & versionFallback.js #725 (#726)

* Duplicate code in readMetadata.js & versionFallback.js #725

* Putting back package-lock.json

* Rename lib/server/utilsMetadata.js -> lib/server/metadataUtils.js

* Update splitHeader + extractMetadata

* Update prettier

lib/server/metadataUtils.js

@@ -0,0 +1,66 @@
+/**
+ * Copyright (c) 2017-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+// split markdown header
+function splitHeader(content) {
+  // New line characters need to handle all operating systems.
+  const lines = content.split(/\r?\n/);
+  if (lines[0] !== '---') {
+    return {};
+  }
+  let i = 1;
+  for (; i < lines.length - 1; ++i) {
+    if (lines[i] === '---') {
+      break;
+    }
+  }
+  return {
+    header: lines.slice(1, i + 1).join('\n'),
+    content: lines.slice(i + 1).join('\n'),
+  };
+}
+
+// Extract markdown metadata header
+function extractMetadata(content) {
+  const metadata = {};
+  const both = splitHeader(content);
+
+  // if no content returned, then that means there was no header, and both.header is the content
+  if (!both.content) {
+    if (!both.header) {
+      // if no both returned, then that means there was no header and no content => we return the current content of the file
+      return {metadata, rawContent: content};
+    }
+    return {metadata, rawContent: both.header};
+  }
+
+  // New line characters => to handle all operating systems.
+  const lines = both.header.split(/\r?\n/);
+
+  // Loop that add to metadata the current content of the fields of the header
+  // Like the format:
+  // id:
+  // title:
+  // original_id:
+  for (let i = 0; i < lines.length - 1; ++i) {
+    const keyvalue = lines[i].split(':');
+    const key = keyvalue[0].trim();
+    let value = keyvalue
+      .slice(1)
+      .join(':')
+      .trim();
+    try {
+      value = JSON.parse(value);
+    } catch (e) {}
+    metadata[key] = value;
+  }
+  return {metadata, rawContent: both.content};
+}
+
+module.exports = {
+  extractMetadata,
+};