/** Server 内部消息统一信封；字段同时满足幂等、版本演进和跨进程链路追踪。 */
export interface MessageEnvelope<TPayload> {
  eventId: string;
  eventType: string;
  schemaVersion: 1;
  idempotencyKey: string;
  occurredAt: string;
  tradeDate: string;
  traceId: string;
  payload: TPayload;
}

type MessageEnvelopeInput<TPayload> = Omit<MessageEnvelope<TPayload>, 'schemaVersion'> & {
  schemaVersion: number;
};

function deepFreeze<TValue>(value: TValue): Readonly<TValue> {
  if (value && typeof value === 'object' && !Object.isFrozen(value)) {
    for (const child of Object.values(value as Record<string, unknown>)) deepFreeze(child);
    Object.freeze(value);
  }
  return value;
}

/** 校验、规范化并深冻结消息信封，防止投递后字段被异步处理链路改写。 */
export function createMessageEnvelope<TPayload>(
  input: MessageEnvelopeInput<TPayload>,
): Readonly<MessageEnvelope<TPayload>> {
  if (!input.eventId.trim()) throw new Error('eventId 不能为空');
  if (!input.eventType.trim()) throw new Error('eventType 不能为空');
  if (input.schemaVersion !== 1) throw new Error('schemaVersion 只支持 1');
  if (!input.idempotencyKey.trim()) throw new Error('idempotencyKey 不能为空');
  if (!input.occurredAt.trim() || Number.isNaN(Date.parse(input.occurredAt))) {
    throw new Error('occurredAt 必须为合法 ISO 时间');
  }
  if (!/^\d{4}-\d{2}-\d{2}$/.test(input.tradeDate)) {
    throw new Error('tradeDate 必须为合法 YYYY-MM-DD 日期');
  }
  const [year, month, day] = input.tradeDate.split('-').map(Number);
  const parsedTradeDate = new Date(Date.UTC(year, month - 1, day));
  if (parsedTradeDate.toISOString().slice(0, 10) !== input.tradeDate) {
    throw new Error('tradeDate 必须为合法 YYYY-MM-DD 日期');
  }
  if (!input.traceId.trim()) throw new Error('traceId 不能为空');
  if (input.payload === undefined) throw new Error('payload 不能为空');

  return deepFreeze({
    eventId: input.eventId.trim(),
    eventType: input.eventType.trim(),
    schemaVersion: 1,
    idempotencyKey: input.idempotencyKey.trim(),
    occurredAt: new Date(input.occurredAt).toISOString(),
    tradeDate: input.tradeDate,
    traceId: input.traceId.trim(),
    payload: input.payload,
  }) as Readonly<MessageEnvelope<TPayload>>;
}