import { isEmbeddedInWechatMiniProgram } from '@/utils/hostEnvironment'
import {
  buildWechatOpenLocationPageUrl,
  validateWechatOpenLocationTarget,
  type WechatOpenLocationTarget
} from '@/utils/wechatOpenLocationProtocol'

interface MiniProgramBridge {
  getEnv?: (callback: (result: { miniprogram?: boolean }) => void) => void
  navigateTo?: (options: { url: string; success?: () => void; fail?: (error: { errMsg?: string }) => void }) => void
  navigateBack?: (options: { delta: number; success?: () => void; fail?: (error: { errMsg?: string }) => void }) => void
  postMessage?: (options: { data: { type: string } }) => void
}

export type WechatMiniProgramBridgeResult =
  | { status: 'opened' }
  | { status: 'not-embedded' }
  | { status: 'failed'; reason: 'invalid-target' | 'bridge-unavailable' | 'not-in-mini-program' | 'navigation-failed' | 'page-not-found' | 'timeout' }

export type WechatMiniProgramReturnResult =
  | { status: 'returned' }
  | { status: 'not-embedded' }
  | { status: 'failed'; reason: 'bridge-unavailable' | 'not-in-mini-program' | 'navigation-failed' | 'timeout' }

const SDK_URL = 'https://res.wx.qq.com/open/js/jweixin-1.3.2.js'
export const MINI_PROGRAM_RETURN_MESSAGE = 'museum-guide:return'
const BRIDGE_WAIT_TIMEOUT = 2500
const BRIDGE_POLL_INTERVAL = 50
const GET_ENV_TIMEOUT = 1500
const NAVIGATION_TIMEOUT = 3000

let pendingNavigation: Promise<WechatMiniProgramBridgeResult> | null = null
let pendingReturn: Promise<WechatMiniProgramReturnResult> | null = null
let sdkLoadPromise: Promise<void> | null = null

const getBridge = (): MiniProgramBridge | null => {
  if (typeof window === 'undefined') return null
  return (window as Window & { wx?: { miniProgram?: MiniProgramBridge } }).wx?.miniProgram || null
}

const wait = (duration: number) => new Promise<void>((resolve) => setTimeout(resolve, duration))

const loadWechatJsSdk = () => {
  if (typeof document === 'undefined' || getBridge()) return Promise.resolve()
  if (sdkLoadPromise) return sdkLoadPromise
  sdkLoadPromise = new Promise<void>((resolve) => {
    const existing = document.querySelector<HTMLScriptElement>('script[data-wechat-js-sdk="true"]')
    if (existing) {
      existing.addEventListener('load', () => resolve(), { once: true })
      existing.addEventListener('error', () => resolve(), { once: true })
      return
    }
    const script = document.createElement('script')
    script.src = SDK_URL
    script.async = true
    script.dataset.wechatJsSdk = 'true'
    script.onload = () => resolve()
    script.onerror = () => { script.remove(); resolve() }
    document.head.appendChild(script)
  }).finally(() => { sdkLoadPromise = null })
  return sdkLoadPromise
}

const waitForBridge = async (): Promise<MiniProgramBridge | null> => {
  const immediate = getBridge()
  if (immediate) return immediate
  void loadWechatJsSdk()
  const deadline = Date.now() + BRIDGE_WAIT_TIMEOUT
  while (Date.now() < deadline) {
    await wait(BRIDGE_POLL_INTERVAL)
    const bridge = getBridge()
    if (bridge) return bridge
  }
  return null
}

const isMiniProgramWebView = (bridge: MiniProgramBridge) => new Promise<boolean>((resolve) => {
  if (!bridge.getEnv) return resolve(isEmbeddedInWechatMiniProgram())
  let settled = false
  const finish = (value: boolean) => {
    if (settled) return
    settled = true
    clearTimeout(timeout)
    resolve(value)
  }
  const timeout = setTimeout(() => finish(isEmbeddedInWechatMiniProgram()), GET_ENV_TIMEOUT)
  try {
    bridge.getEnv((result) => finish(Boolean(result?.miniprogram)))
  } catch (error) {
    console.error('微信小程序环境识别失败:', error)
    finish(false)
  }
})

const navigateToHostLocationPage = (bridge: MiniProgramBridge, target: WechatOpenLocationTarget) => new Promise<WechatMiniProgramBridgeResult>((resolve) => {
  if (!bridge.navigateTo) return resolve({ status: 'failed', reason: 'bridge-unavailable' })
  let settled = false
  const finish = (result: WechatMiniProgramBridgeResult) => {
    if (settled) return
    settled = true
    clearTimeout(timeout)
    resolve(result)
  }
  const timeout = setTimeout(() => finish({ status: 'failed', reason: 'timeout' }), NAVIGATION_TIMEOUT)
  try {
    bridge.navigateTo({
      url: buildWechatOpenLocationPageUrl(target),
      success: () => finish({ status: 'opened' }),
      fail: (error) => {
        console.error('跳转宿主地图页失败:', error)
        finish({ status: 'failed', reason: /page.*not found|not found.*page/i.test(error?.errMsg || '') ? 'page-not-found' : 'navigation-failed' })
      }
    })
  } catch (error) {
    console.error('调用微信小程序导航桥接失败:', error)
    finish({ status: 'failed', reason: 'navigation-failed' })
  }
})

const requestHostReturnFallback = (bridge: MiniProgramBridge) => {
  if (!bridge.postMessage) return false

  try {
    bridge.postMessage({ data: { type: MINI_PROGRAM_RETURN_MESSAGE } })
    return true
  } catch (error) {
    console.error('请求宿主小程序安全返回失败:', error)
    return false
  }
}

const navigateBackToHost = (bridge: MiniProgramBridge) => new Promise<WechatMiniProgramReturnResult>((resolve) => {
  if (!bridge.navigateBack) return resolve({ status: 'failed', reason: 'bridge-unavailable' })

  let settled = false
  const finish = (result: WechatMiniProgramReturnResult) => {
    if (settled) return
    settled = true
    clearTimeout(timeout)
    resolve(result)
  }
  const timeout = setTimeout(() => finish({ status: 'failed', reason: 'timeout' }), NAVIGATION_TIMEOUT)

  try {
    bridge.navigateBack({
      delta: 1,
      success: () => finish({ status: 'returned' }),
      fail: (error) => {
        console.error('返回宿主小程序失败:', error)
        finish({ status: 'failed', reason: 'navigation-failed' })
      }
    })
  } catch (error) {
    console.error('调用宿主小程序返回桥接失败:', error)
    finish({ status: 'failed', reason: 'navigation-failed' })
  }
})

const openOnce = async (target: WechatOpenLocationTarget): Promise<WechatMiniProgramBridgeResult> => {
  const validation = validateWechatOpenLocationTarget(target)
  if (!validation.ok) return { status: 'failed', reason: 'invalid-target' }
  if (!isEmbeddedInWechatMiniProgram()) return { status: 'not-embedded' }
  const bridge = await waitForBridge()
  if (!bridge) return { status: 'failed', reason: 'bridge-unavailable' }
  if (!await isMiniProgramWebView(bridge)) return { status: 'failed', reason: 'not-in-mini-program' }
  return navigateToHostLocationPage(bridge, validation.value)
}

export const openWechatMiniProgramLocation = (target: WechatOpenLocationTarget) => {
  if (pendingNavigation) return pendingNavigation
  pendingNavigation = openOnce(target).finally(() => { pendingNavigation = null })
  return pendingNavigation
}

const returnOnce = async (): Promise<WechatMiniProgramReturnResult> => {
  if (!isEmbeddedInWechatMiniProgram()) return { status: 'not-embedded' }

  const bridge = await waitForBridge()
  if (!bridge) return { status: 'failed', reason: 'bridge-unavailable' }
  if (!await isMiniProgramWebView(bridge)) return { status: 'failed', reason: 'not-in-mini-program' }

  const result = await navigateBackToHost(bridge)
  if (result.status === 'returned') return result

  // 宿主页可能由分享或冷启动直接打开，页面栈没有上一页时改由宿主执行安全回退。
  if (requestHostReturnFallback(bridge)) return { status: 'returned' }
  return result
}

export const returnToWechatMiniProgram = () => {
  if (pendingReturn) return pendingReturn
  pendingReturn = returnOnce().finally(() => { pendingReturn = null })
  return pendingReturn
}