/** Calls a cloud function and resolves its `result`. */
export type CloudbaseFunctionCaller = (name: string, data: Record<string, unknown>) => Promise<unknown>

interface CloudbaseApp {
  auth: (options?: { persistence: 'session' }) => unknown
  callFunction: (options: { name: string, data: Record<string, unknown> }) => Promise<{
    errCode?: number | string
    errMsg?: string
    result?: unknown
  } | undefined>
}

interface CloudbaseModule {
  default?: {
    init: (config: {
      auth: { detectSessionInUrl: false }
      env: string
      region: 'ap-shanghai'
    }) => CloudbaseApp
  }
  init?: (config: {
    auth: { detectSessionInUrl: false }
    env: string
    region: 'ap-shanghai'
  }) => CloudbaseApp
}

let cachedCloudbaseEnv = ''
let cachedCloudbaseApp: Promise<CloudbaseApp> | undefined

function getCloudbaseApp(env: string): Promise<CloudbaseApp> {
  if (cachedCloudbaseApp) {
    if (cachedCloudbaseEnv !== env)
      return Promise.reject(new Error('CloudBase environment cannot change at runtime'))
    return cachedCloudbaseApp
  }

  cachedCloudbaseEnv = env
  cachedCloudbaseApp = (async () => {
    const cloudbaseModule = await import('@cloudbase/js-sdk') as unknown as CloudbaseModule
    const cloudbase = cloudbaseModule.default ?? cloudbaseModule
    if (!cloudbase.init)
      throw new Error('@cloudbase/js-sdk does not expose init()')

    return cloudbase.init({
      auth: { detectSessionInUrl: false },
      env,
      region: 'ap-shanghai',
    })
  })()
  cachedCloudbaseApp.catch(() => {
    cachedCloudbaseApp = undefined
  })
  return cachedCloudbaseApp
}

/** Call a cloud function on the configured CloudBase environment. */
export async function callCloudbaseFunction(
  env: string,
  name: string,
  data: Record<string, unknown>,
): Promise<unknown> {
  const app = await getCloudbaseApp(env)
  // The auth client is created first so the call carries the app's session.
  app.auth({ persistence: 'session' })
  const response = await app.callFunction({ name, data })
  // A missing result means the call itself failed (not deployed, crashed, …).
  if (!response || response.result === undefined)
    throw new Error(`CloudBase function ${name} failed: ${response?.errCode ?? response?.errMsg ?? 'no result'}`)
  return response.result
}