const base = () => (process.env.TELEGRAM_GATEWAY_URL || 'http://host.docker.internal:3000/api').replace(/\/$/, '')

let gatewayToken = process.env.TELEGRAM_GATEWAY_TOKEN || ''
let refreshPromise

function tokenExpiresSoon(token) {
  try {
    const payload = JSON.parse(Buffer.from(token.split('.')[1], 'base64url').toString('utf8'))
    return !payload.exp || payload.exp * 1000 < Date.now() + 5 * 60 * 1000
  } catch {
    return true
  }
}

async function refreshGatewayToken() {
  if (refreshPromise) return refreshPromise
  refreshPromise = (async () => {
    const email = process.env.TELEGRAM_GATEWAY_SERVICE_EMAIL
    const password = process.env.TELEGRAM_GATEWAY_SERVICE_PASSWORD
    const tenantId = process.env.TELEGRAM_GATEWAY_TENANT_ID
    if (!email || !password || !tenantId) {
      throw Object.assign(new Error('Telegram 网关服务账号凭据尚未配置'), { status: 503 })
    }
    const response = await fetch(`${base()}/auth/login`, {
      method: 'POST',
      headers: { 'content-type': 'application/json' },
      body: JSON.stringify({ email, password, tenantId }),
    })
    const raw = await response.text()
    let result
    try { result = raw ? JSON.parse(raw) : null } catch { result = raw }
    const token = result?.data?.token || result?.token
    if (!response.ok || !token) {
      throw Object.assign(new Error(result?.message || 'Telegram 网关服务账号续签失败'), { status: response.status || 503 })
    }
    gatewayToken = token
    return token
  })().finally(() => { refreshPromise = undefined })
  return refreshPromise
}

export async function gatewayRequest(path, options = {}) {
  const tenantId = process.env.TELEGRAM_GATEWAY_TENANT_ID
  if (!tenantId) throw Object.assign(new Error('Telegram 网关租户尚未配置'), { status: 503 })
  if (!gatewayToken || tokenExpiresSoon(gatewayToken)) await refreshGatewayToken()
  const send = () => fetch(`${base()}${path}`, {
    ...options,
    headers: {
      ...(options.body instanceof FormData ? {} : { 'content-type': 'application/json' }),
      authorization: `Bearer ${gatewayToken}`,
      'x-tenant-id': tenantId,
      ...(options.headers || {}),
    },
  })
  let response = await send()
  if (response.status === 401) {
    await refreshGatewayToken()
    response = await send()
  }
  const raw = await response.text()
  let result
  try { result = raw ? JSON.parse(raw) : null } catch { result = raw }
  if (!response.ok) {
    throw Object.assign(new Error(result?.message || `Telegram 网关请求失败 (${response.status})`), { status: response.status })
  }
  return result?.data ?? result
}

export function postGateway(path, body) {
  return gatewayRequest(path, { method: 'POST', body: JSON.stringify(body) })
}

export function putGateway(path, body) {
  return gatewayRequest(path, { method: 'PUT', body: JSON.stringify(body) })
}

export function uploadGateway(path, formData) {
  return gatewayRequest(path, { method: 'POST', body: formData })
}