Implement assistant-ui issue chat thread

Co-Authored-By: Paperclip <noreply@paperclip.ing>

ui/src/hooks/usePaperclipIssueRuntime.ts

@@ -0,0 +1,68 @@
+import { useExternalStoreRuntime, type ThreadMessage, type AppendMessage } from "@assistant-ui/react";
+
+export interface PaperclipIssueRuntimeReassignment {
+  assigneeAgentId: string | null;
+  assigneeUserId: string | null;
+}
+
+export interface PaperclipIssueRuntimeSendOptions {
+  body: string;
+  reopen?: boolean;
+  reassignment?: PaperclipIssueRuntimeReassignment;
+}
+
+interface UsePaperclipIssueRuntimeOptions {
+  messages: readonly ThreadMessage[];
+  isRunning: boolean;
+  onSend: (options: PaperclipIssueRuntimeSendOptions) => Promise<void>;
+  onCancel?: (() => Promise<void>) | undefined;
+}
+
+function asRecord(value: unknown): Record<string, unknown> | null {
+  if (typeof value !== "object" || value === null || Array.isArray(value)) return null;
+  return value as Record<string, unknown>;
+}
+
+function readTextContent(message: AppendMessage) {
+  return message.content
+    .filter((part): part is Extract<(typeof message.content)[number], { type: "text" }> => part.type === "text")
+    .map((part) => part.text)
+    .join("")
+    .trim();
+}
+
+export function usePaperclipIssueRuntime({
+  messages,
+  isRunning,
+  onSend,
+  onCancel,
+}: UsePaperclipIssueRuntimeOptions) {
+  return useExternalStoreRuntime({
+    messages,
+    isRunning,
+    onNew: async (message) => {
+      const body = readTextContent(message);
+      if (!body) return;
+
+      const custom = asRecord(message.runConfig?.custom);
+      const reassignmentRecord = asRecord(custom?.reassignment);
+      const reassignment =
+        reassignmentRecord &&
+        ("assigneeAgentId" in reassignmentRecord || "assigneeUserId" in reassignmentRecord)
+          ? {
+              assigneeAgentId:
+                typeof reassignmentRecord.assigneeAgentId === "string" ? reassignmentRecord.assigneeAgentId : null,
+              assigneeUserId:
+                typeof reassignmentRecord.assigneeUserId === "string" ? reassignmentRecord.assigneeUserId : null,
+            }
+          : undefined;
+
+      await onSend({
+        body,
+        reopen: custom?.reopen === true ? true : undefined,
+        reassignment,
+      });
+    },
+    ...(onCancel ? { onCancel } : {}),
+  });
+}