chore: import upstream snapshot with attribution

apps/sim/lib/copilot/request/session/event.ts

@@ -0,0 +1,74 @@
+import {
+  type PersistedStreamEventEnvelope,
+  parsePersistedStreamEventEnvelope,
+  type SessionStreamEvent,
+} from './contract'
+
+type CreateEventBase = {
+  chatId?: string
+  cursor: string
+  requestId: string
+  seq: number
+  streamId: string
+  ts?: string
+}
+
+type CreateEventVariant<TEvent extends SessionStreamEvent> = CreateEventBase &
+  Pick<TEvent, 'type' | 'payload' | 'scope'>
+
+export type CreateEventInput = SessionStreamEvent extends infer TEvent
+  ? TEvent extends SessionStreamEvent
+    ? CreateEventVariant<TEvent>
+    : never
+  : never
+
+type CreateEventResult<TInput extends CreateEventInput> = Extract<
+  PersistedStreamEventEnvelope,
+  { type: TInput['type']; payload: TInput['payload'] }
+>
+
+type StreamEventFromEnvelope<TEnvelope extends PersistedStreamEventEnvelope> = Extract<
+  SessionStreamEvent,
+  { type: TEnvelope['type']; payload: TEnvelope['payload'] }
+>
+
+export const TOOL_CALL_STATUS = {
+  generating: 'generating',
+} as const
+
+export function createEvent<TInput extends CreateEventInput>(
+  input: TInput
+): CreateEventResult<TInput> {
+  const { streamId, chatId, cursor, seq, requestId, type, payload, scope, ts } = input
+
+  return {
+    v: 1,
+    type,
+    seq,
+    ts: ts ?? new Date().toISOString(),
+    stream: {
+      streamId,
+      ...(chatId ? { chatId } : {}),
+      cursor,
+    },
+    trace: {
+      requestId,
+    },
+    ...(scope ? { scope } : {}),
+    payload,
+  } as CreateEventResult<TInput>
+}
+
+export function isEventRecord(value: unknown): value is PersistedStreamEventEnvelope {
+  return parsePersistedStreamEventEnvelope(value).ok
+}
+
+export function eventToStreamEvent<TEnvelope extends PersistedStreamEventEnvelope>(
+  envelope: TEnvelope
+): StreamEventFromEnvelope<TEnvelope> {
+  return {
+    type: envelope.type,
+    payload: envelope.payload,
+    ...(envelope.scope ? { scope: envelope.scope } : {}),
+  } as StreamEventFromEnvelope<TEnvelope>
+}