import type { ApiError } from './types'

let accessToken: string | null = null
let refreshInFlight: Promise<boolean> | null = null
let onUnauthorized: (() => void) | null = null

export function setAccessToken(token: string | null) {
  accessToken = token
}

export function getAccessToken() {
  return accessToken
}

/** Вызывается, когда refresh-токен недействителен — обычно очищает стор авторизации и шлёт на /login. */
export function setUnauthorizedHandler(handler: (() => void) | null) {
  onUnauthorized = handler
}

type RequestOptions = {
  method?: 'GET' | 'POST' | 'PUT' | 'PATCH' | 'DELETE'
  body?: unknown
  /** Не пытаться освежить токен на 401 (используется самим refresh-запросом, чтобы не зациклиться). */
  skipRefresh?: boolean
}

async function refreshAccessToken(): Promise<boolean> {
  if (!refreshInFlight) {
    refreshInFlight = (async () => {
      try {
        const response = await fetch('/api/auth/refresh', { method: 'POST', credentials: 'include' })
        if (!response.ok) return false
        const data = (await response.json()) as { accessToken: string }
        setAccessToken(data.accessToken)
        return true
      } catch {
        return false
      } finally {
        refreshInFlight = null
      }
    })()
  }
  return refreshInFlight
}

export class HttpError extends Error implements ApiError {
  title: string
  detail: string
  status: number

  constructor(problem: Partial<ApiError>, status: number) {
    super(problem.detail ?? problem.title ?? `HTTP ${status}`)
    this.title = problem.title ?? 'Error'
    this.detail = problem.detail ?? this.message
    this.status = status
  }
}

async function parseError(response: Response): Promise<HttpError> {
  try {
    const problem = (await response.json()) as Partial<ApiError>
    return new HttpError(problem, response.status)
  } catch {
    return new HttpError({ title: response.statusText }, response.status)
  }
}

export async function apiRequest<T>(path: string, options: RequestOptions = {}): Promise<T> {
  const headers: Record<string, string> = {}
  if (accessToken) headers.Authorization = `Bearer ${accessToken}`
  if (options.body !== undefined) headers['Content-Type'] = 'application/json'

  const response = await fetch(`/api${path}`, {
    method: options.method ?? 'GET',
    headers,
    credentials: 'include',
    body: options.body !== undefined ? JSON.stringify(options.body) : undefined,
  })

  if (response.status === 401 && !options.skipRefresh) {
    const refreshed = await refreshAccessToken()
    if (refreshed) return apiRequest<T>(path, { ...options, skipRefresh: true })
    onUnauthorized?.()
    throw await parseError(response)
  }

  if (!response.ok) throw await parseError(response)

  if (response.status === 204) return undefined as T

  const text = await response.text()
  return (text ? JSON.parse(text) : undefined) as T
}

type UploadOptions = {
  method?: 'POST' | 'PUT'
  skipRefresh?: boolean
}

/** Как apiRequest, но для multipart/form-data (вложения к тикетам) — без JSON.stringify и
 * без Content-Type (браузер сам проставляет boundary). */
export async function apiUpload<T>(path: string, formData: FormData, options: UploadOptions = {}): Promise<T> {
  const headers: Record<string, string> = {}
  if (accessToken) headers.Authorization = `Bearer ${accessToken}`

  const response = await fetch(`/api${path}`, {
    method: options.method ?? 'POST',
    headers,
    credentials: 'include',
    body: formData,
  })

  if (response.status === 401 && !options.skipRefresh) {
    const refreshed = await refreshAccessToken()
    if (refreshed) return apiUpload<T>(path, formData, { ...options, skipRefresh: true })
    onUnauthorized?.()
    throw await parseError(response)
  }

  if (!response.ok) throw await parseError(response)

  if (response.status === 204) return undefined as T

  const text = await response.text()
  return (text ? JSON.parse(text) : undefined) as T
}