Improve parsing of sgnl:// hrefs

ts/util/sgnlHref.ts

@@ -0,0 +1,42 @@
+import { LoggerType } from '../types/Logging';
+
+function parseUrl(value: unknown, logger: LoggerType): null | URL {
+  if (value instanceof URL) {
+    return value;
+  } else if (typeof value === 'string') {
+    try {
+      return new URL(value);
+    } catch (err) {
+      return null;
+    }
+  }
+  logger.warn('Tried to parse a sgnl:// URL but got an unexpected type');
+  return null;
+}
+
+export function isSgnlHref(value: string | URL, logger: LoggerType): boolean {
+  const url = parseUrl(value, logger);
+  return url !== null && url.protocol === 'sgnl:';
+}
+
+type ParsedSgnlHref =
+  | { command: null; args: Map<never, never> }
+  | { command: string; args: Map<string, string> };
+export function parseSgnlHref(
+  href: string,
+  logger: LoggerType
+): ParsedSgnlHref {
+  const url = parseUrl(href, logger);
+  if (!url || !isSgnlHref(url, logger)) {
+    return { command: null, args: new Map<never, never>() };
+  }
+
+  const args = new Map<string, string>();
+  url.searchParams.forEach((value, key) => {
+    if (!args.has(key)) {
+      args.set(key, value);
+    }
+  });
+
+  return { command: url.host, args };
+}