export const initialBindingState = () => ({
  ready: false, enabled: false, bound: false, subscribed: false, busy: false,
  sessionId: '', sessionStatus: '', sessionSubscribed: false, verificationCode: '', error: ''
})

export function createWechatBindingFlow({ state, api, getSessionKey, isActive, openAuthorization }) {
  let owner = '', revision = 0
  const cancel = () => { revision++; state.busy = false }
  const clearSession = () => {
    state.sessionId = ''; state.sessionStatus = ''; state.sessionSubscribed = false; state.verificationCode = ''
  }
  const run = async (operation) => {
    const key = getSessionKey()
    if (owner !== key) {
      cancel()
      Object.assign(state, initialBindingState())
      owner = key
    }
    if (!key || !isActive() || state.busy) return
    const version = ++revision
    const current = () => version === revision && isActive() && getSessionKey() === key
    state.busy = true
    state.error = ''
    try { await operation(current) } catch (error) {
      if (current()) state.error = error?.message || '绑定操作失败，请重试'
    } finally {
      if (current()) state.busy = false
    }
  }
  const refresh = () => run(async (current) => {
    state.ready = false
    const status = await api.status()
    if (!current()) return
    Object.assign(state, status, { ready: true })
    if (!status.enabled || status.bound) { clearSession(); return }
    if (!state.sessionId) return
    const session = await api.session(state.sessionId)
    if (!current()) return
    if (session.status === 'expired') {
      clearSession()
      state.error = '授权会话已过期，请重新绑定'
      return
    }
    state.sessionStatus = session.status
    state.sessionSubscribed = session.subscribed
    state.verificationCode = session.verificationCode || ''
    if (session.status !== 'scanned') return
    if (!session.subscribed) {
      state.error = '请先关注服务号，再重新授权绑定'
      return
    }
    // 仅确认本页面由当前登录用户主动发起的会话；回调网页不持有登录令牌。
    const result = await api.confirm(state.sessionId)
    if (!current()) return
    if (!result.bound || !result.subscribed) throw new Error('绑定未完成，请刷新状态后重试')
    Object.assign(state, result)
    clearSession()
  })
  const start = () => run(async (current) => {
    if (!state.ready || !state.enabled || state.bound) return
    clearSession()
    const session = await api.start()
    if (!current()) return
    state.sessionId = session.sessionId
    state.sessionStatus = 'waiting'
    await openAuthorization(session.authorizeUrl)
  })
  return { refresh, start, cancel }
}