import type { ChatMessage } from '@/types';

export function messageFingerprint(msg: ChatMessage): string {
  const attachmentKey = (msg.attachments ?? [])
    .map((a) => `${a.file_id ?? ''}:${a.name}:${a.content_type}:${a.size ?? ''}`)
    .join('|');
  return `${msg.role}::${String(msg.content)}::${attachmentKey}`;
}

export function mergeServerWithPendingUsers(serverMessages: ChatMessage[], localMessages: ChatMessage[]): ChatMessage[] {
  const counts = new Map<string, number>();
  for (const message of serverMessages) {
    const key = messageFingerprint(message);
    counts.set(key, (counts.get(key) ?? 0) + 1);
  }

  const pendingUsers: ChatMessage[] = [];
  for (const message of localMessages) {
    const key = messageFingerprint(message);
    const count = counts.get(key) ?? 0;
    if (count > 0) {
      counts.set(key, count - 1);
      continue;
    }
    if (message.role === 'user') {
      pendingUsers.push(message);
    }
  }

  return [...serverMessages, ...pendingUsers];
}

export function getTaskCardMessageIndexes(messages: ChatMessage[]): Set<number> {
  const latestByTask = new Map<string, number>();

  messages.forEach((message, index) => {
    if (message.role !== 'assistant' || !message.task_id) {
      return;
    }
    latestByTask.set(message.task_id, index);
  });

  return new Set(latestByTask.values());
}