refactor(channels): unify target parsing

src/channels/targets.ts

@@ -0,0 +1,56 @@
+export type MessagingTargetKind = "user" | "channel";
+
+export type MessagingTarget = {
+  kind: MessagingTargetKind;
+  id: string;
+  raw: string;
+  normalized: string;
+};
+
+export type MessagingTargetParseOptions = {
+  defaultKind?: MessagingTargetKind;
+  ambiguousMessage?: string;
+};
+
+export function normalizeTargetId(kind: MessagingTargetKind, id: string): string {
+  return `${kind}:${id}`.toLowerCase();
+}
+
+export function buildMessagingTarget(
+  kind: MessagingTargetKind,
+  id: string,
+  raw: string,
+): MessagingTarget {
+  return {
+    kind,
+    id,
+    raw,
+    normalized: normalizeTargetId(kind, id),
+  };
+}
+
+export function ensureTargetId(params: {
+  candidate: string;
+  pattern: RegExp;
+  errorMessage: string;
+}): string {
+  if (!params.pattern.test(params.candidate)) {
+    throw new Error(params.errorMessage);
+  }
+  return params.candidate;
+}
+
+export function requireTargetKind(params: {
+  platform: string;
+  target: MessagingTarget | undefined;
+  kind: MessagingTargetKind;
+}): string {
+  const kindLabel = params.kind;
+  if (!params.target) {
+    throw new Error(`${params.platform} ${kindLabel} id is required.`);
+  }
+  if (params.target.kind !== params.kind) {
+    throw new Error(`${params.platform} ${kindLabel} id is required (use ${kindLabel}:<id>).`);
+  }
+  return params.target.id;
+}