const AUTH_STORAGE_KEY = 'ten-minute-planner-auth'
const API_BASE_URL = import.meta.env.VITE_API_BASE_URL ?? 'http://localhost:3001'

function buildHeaders(token, extraHeaders = {}) {
  return {
    'Content-Type': 'application/json',
    ...(token ? { Authorization: `Bearer ${token}` } : {}),
    ...extraHeaders,
  }
}

async function request(path, { method = 'GET', token, body } = {}) {
  const response = await fetch(`${API_BASE_URL}${path}`, {
    method,
    headers: buildHeaders(token),
    body: body ? JSON.stringify(body) : undefined,
  })

  const data = await response.json().catch(() => ({}))

  if (!response.ok) {
    throw new Error(data.message || '요청 처리 중 문제가 발생했습니다.')
  }

  return data
}

export function readAuthState() {
  if (typeof window === 'undefined') {
    return { token: '', user: null }
  }

  try {
    return JSON.parse(window.localStorage.getItem(AUTH_STORAGE_KEY) ?? '{"token":"","user":null}')
  } catch (error) {
    console.warn('저장된 인증 상태를 불러오지 못했습니다.', error)
    return { token: '', user: null }
  }
}

export function persistAuthState({ token, user }) {
  if (typeof window === 'undefined') {
    return
  }

  window.localStorage.setItem(
    AUTH_STORAGE_KEY,
    JSON.stringify({
      token,
      user,
    }),
  )
}

export function clearAuthState() {
  if (typeof window === 'undefined') {
    return
  }

  window.localStorage.removeItem(AUTH_STORAGE_KEY)
}

export async function signup({ email, password, nickname }) {
  return request('/api/auth/signup', {
    method: 'POST',
    body: { email, password, nickname },
  })
}

export async function login({ email, password }) {
  return request('/api/auth/login', {
    method: 'POST',
    body: { email, password },
  })
}

export async function fetchCurrentUser(token) {
  return request('/api/auth/me', {
    token,
  })
}