refactor(slack): centralize target parsing

src/slack/targets.ts

@@ -0,0 +1,78 @@
+export type SlackTargetKind = "user" | "channel";
+
+export type SlackTarget = {
+  kind: SlackTargetKind;
+  id: string;
+  raw: string;
+  normalized: string;
+};
+
+type SlackTargetParseOptions = {
+  defaultKind?: SlackTargetKind;
+};
+
+function normalizeTargetId(kind: SlackTargetKind, id: string) {
+  return `${kind}:${id}`.toLowerCase();
+}
+
+function buildTarget(kind: SlackTargetKind, id: string, raw: string): SlackTarget {
+  return {
+    kind,
+    id,
+    raw,
+    normalized: normalizeTargetId(kind, id),
+  };
+}
+
+export function parseSlackTarget(
+  raw: string,
+  options: SlackTargetParseOptions = {},
+): SlackTarget | undefined {
+  const trimmed = raw.trim();
+  if (!trimmed) return undefined;
+  const mentionMatch = trimmed.match(/^<@([A-Z0-9]+)>$/i);
+  if (mentionMatch) {
+    return buildTarget("user", mentionMatch[1], trimmed);
+  }
+  if (trimmed.startsWith("user:")) {
+    const id = trimmed.slice("user:".length).trim();
+    return id ? buildTarget("user", id, trimmed) : undefined;
+  }
+  if (trimmed.startsWith("channel:")) {
+    const id = trimmed.slice("channel:".length).trim();
+    return id ? buildTarget("channel", id, trimmed) : undefined;
+  }
+  if (trimmed.startsWith("slack:")) {
+    const id = trimmed.slice("slack:".length).trim();
+    return id ? buildTarget("user", id, trimmed) : undefined;
+  }
+  if (trimmed.startsWith("@")) {
+    const candidate = trimmed.slice(1).trim();
+    if (!/^[A-Z0-9]+$/i.test(candidate)) {
+      throw new Error("Slack DMs require a user id (use user:<id> or <@id>)");
+    }
+    return buildTarget("user", candidate, trimmed);
+  }
+  if (trimmed.startsWith("#")) {
+    const candidate = trimmed.slice(1).trim();
+    if (!/^[A-Z0-9]+$/i.test(candidate)) {
+      throw new Error("Slack channels require a channel id (use channel:<id>)");
+    }
+    return buildTarget("channel", candidate, trimmed);
+  }
+  if (options.defaultKind) {
+    return buildTarget(options.defaultKind, trimmed, trimmed);
+  }
+  return buildTarget("channel", trimmed, trimmed);
+}
+
+export function resolveSlackChannelId(raw: string): string {
+  const target = parseSlackTarget(raw, { defaultKind: "channel" });
+  if (!target) {
+    throw new Error("Slack channel id is required.");
+  }
+  if (target.kind !== "channel") {
+    throw new Error("Slack channel id is required (use channel:<id>).");
+  }
+  return target.id;
+}