export type ChatSenderType = 'STUDENT' | 'AI' | 'INSTRUCTOR' | 'SYSTEM' | string;

export type InstructorChatMessage = {
  id: string;
  senderType: ChatSenderType;
  senderName?: string;
  senderAvatarUrl?: string | null;
  content: string;
  createdAt?: string;
};

export type InstructorChatThread = {
  id: string;
  title: string;
  studentName: string;
  studentAvatarUrl?: string | null;
  groupName?: string;
  week?: number | string;
  status: string;
  lastMessage: string;
  lastMessageAt?: string;
  messages: InstructorChatMessage[];
};

const CHAT_API_BASE_URL = (import.meta.env.VITE_API_BASE_URL ?? 'http://localhost:4400/api').replace(/\/+$/, '');
export const CHAT_SOCKET_BASE_URL = CHAT_API_BASE_URL.replace(/\/api$/, '');

type ChatThreadsPayload = {
  threads?: unknown[];
  data?: unknown[];
};

export async function listInstructorChatThreads(accessToken: string, week?: number): Promise<InstructorChatThread[]> {
  const params = new URLSearchParams();
  if (week) params.set('week', String(week));
  const queryString = params.toString();

  const response = await fetch(`${CHAT_API_BASE_URL}/chat/instructor/threads${queryString ? `?${queryString}` : ''}`, {
    headers: {
      Authorization: `Bearer ${accessToken}`,
    },
  });

  if (!response.ok) {
    throw new Error(`강사 채팅 목록을 불러오지 못했습니다. (${response.status})`);
  }

  const payload = (await response.json()) as ChatThreadsPayload | unknown[];
  const items = Array.isArray(payload) ? payload : Array.isArray(payload?.threads) ? payload.threads : Array.isArray(payload?.data) ? payload.data : [];
  return items.map(normalizeThread).filter((thread): thread is InstructorChatThread => Boolean(thread));
}

export async function getInstructorChatThread(accessToken: string, threadId: string): Promise<InstructorChatThread> {
  const response = await fetch(`${CHAT_API_BASE_URL}/chat/instructor/threads/${threadId}`, {
    headers: {
      Authorization: `Bearer ${accessToken}`,
    },
  });

  if (!response.ok) {
    throw new Error(`강사 채팅방을 불러오지 못했습니다. (${response.status})`);
  }

  const payload = await response.json();
  const thread = normalizeThread(payload?.thread ?? payload);
  if (!thread) throw new Error('강사 채팅방 응답이 올바르지 않습니다.');

  return thread;
}

export async function createInstructorChatMessage(accessToken: string, threadId: string, content: string): Promise<InstructorChatThread> {
  const response = await fetch(`${CHAT_API_BASE_URL}/chat/instructor/threads/${threadId}/messages`, {
    method: 'POST',
    headers: {
      Authorization: `Bearer ${accessToken}`,
      'Content-Type': 'application/json',
    },
    body: JSON.stringify({ content }),
  });

  if (!response.ok) {
    throw new Error(`강사 답변을 저장하지 못했습니다. (${response.status})`);
  }

  const payload = await response.json();
  const thread = normalizeThread(payload?.thread ?? payload);
  if (!thread) throw new Error('강사 답변 응답이 올바르지 않습니다.');

  return thread;
}

function normalizeThread(raw: unknown): InstructorChatThread | null {
  if (!raw || typeof raw !== 'object') return null;
  const item = raw as Record<string, any>;

  const messages = Array.isArray(item.messages) ? item.messages.map(normalizeMessage).filter((message): message is InstructorChatMessage => Boolean(message)) : [];
  const lastMessageFromList = messages.length > 0 ? messages[messages.length - 1]?.content : undefined;
  const rawLastMessage = item.lastMessage?.content ?? item.lastMessageContent ?? item.lastMessage;
  const studentName = item.student?.name ?? item.studentName ?? item.student?.email ?? item.studentEmail ?? item.studentId ?? '수강생';
  const title = item.title ?? item.threadTitle ?? studentName;
  const weekValue = typeof item.week === 'object' && item.week ? item.week.week : item.week;

  return {
    id: String(item.id ?? item.threadId ?? title),
    title: String(title),
    studentName: String(studentName),
    studentAvatarUrl: typeof item.studentAvatarUrl === 'string' ? item.studentAvatarUrl : null,
    groupName: item.group?.name ?? item.groupName ?? item.metadata?.groupName,
    week: weekValue ?? item.weekId ?? item.metadata?.week,
    status: String(item.status ?? 'WAITING_INSTRUCTOR'),
    lastMessage: String(rawLastMessage ?? lastMessageFromList ?? '저장된 문의 내용을 확인해 주세요.'),
    lastMessageAt: item.lastMessageAt ?? item.updatedAt ?? item.createdAt,
    messages,
  };
}

function normalizeMessage(raw: unknown): InstructorChatMessage | null {
  if (!raw || typeof raw !== 'object') return null;
  const item = raw as Record<string, any>;

  return {
    id: String(item.id ?? `${item.senderType ?? 'MESSAGE'}-${item.createdAt ?? item.content ?? 'unknown'}`),
    senderType: String(item.senderType ?? 'STUDENT'),
    senderName: item.senderName ?? item.sender?.name,
    senderAvatarUrl: typeof item.senderAvatarUrl === 'string' ? item.senderAvatarUrl : null,
    content: String(item.content ?? ''),
    createdAt: item.createdAt,
  };
}