property parser

src/shared/commands/properties.js

@@ -0,0 +1,31 @@
+const mustNumber = (v) => {
+  let num = Number(v);
+  if (isNaN(num)) {
+    throw new Error('Not number: ' + v);
+  }
+  return num;
+};
+
+const parseProperty = (word, types) => {
+  let [key, value] = word.split('=');
+  if (!value) {
+    value = !key.startsWith('no');
+    key = value ? key : key.slice(2);
+  }
+  let type = types[key];
+  if (!type) {
+    throw new Error('Unknown property: ' + key);
+  }
+  if (type === 'boolean' && typeof value !== 'boolean' ||
+       type !== 'boolean' && typeof value === 'boolean') {
+    throw new Error('Invalid argument: ' + word);
+  }
+
+  switch (type) {
+  case 'string': return [key, value];
+  case 'number': return [key, mustNumber(value)];
+  case 'boolean': return [key, value];
+  }
+};
+
+export { parseProperty };