import { writeA7Payload } from '../core/packet'
import { waitForProtocolState } from '../core/stateWait'
import { parseDeviceInfo } from '../parsers'
import { BLE_STAGE } from '../core/state'

function generateRandomKey(length = 16) {
  const chars = 'ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnpqrstuvwxyz23456789'
  let result = ''

  for (let index = 0; index < length; index += 1) {
    const random = Math.floor(Math.random() * chars.length)
    result += chars[random]
  }

  return result
}

function normalizeMacForKey(macText = '') {
  return String(macText || '').replace(/[^0-9a-fA-F]/g, '').toUpperCase()
}

/**
 * 按协议约定生成设备密钥：MAC(去分隔符) + 固定后缀。
 * 默认后缀为 "0000"，对应 12 位 MAC + 4 位后缀 = 16 位密钥。
 */
export function buildKeyFromMac(macText, suffix = '0000', expectedLength = 16) {
  const normalizedMac = normalizeMacForKey(macText)
  const normalizedSuffix = String(suffix || '').trim()

  if (!normalizedSuffix) {
    throw new Error('密钥后缀不能为空')
  }

  const requiredMacLength = expectedLength - normalizedSuffix.length
  if (requiredMacLength <= 0) {
    throw new Error('密钥长度配置异常')
  }

  if (normalizedMac.length !== requiredMacLength) {
    throw new Error(`设备 MAC 长度异常，期望 ${requiredMacLength} 位，实际 ${normalizedMac.length} 位`)
  }

  return `${normalizedMac}${normalizedSuffix}`
}

async function writePacketsToKeyCharacteristic(ble, keyText) {
  const { key } = ble.getState().characteristics

  if (!key || !key.uuid) {
    throw new Error('未发现 UUID_KEY 特征值')
  }

  const profile = ble.getProfile()
  const keyValue = String(keyText || '').trim()

  if (keyValue.length !== profile.auth.keyLength) {
    throw new Error(`密钥长度必须为 ${profile.auth.keyLength}`)
  }

  await writeA7Payload(ble, key.uuid, keyValue, profile.packet)

  return keyValue
}

async function writeKeyAndExpectStates(ble, keyText, expectedStateCodes, options = {}) {
  const keyValue = await writePacketsToKeyCharacteristic(ble, keyText)

  const stateEvent = await waitForProtocolState(ble, {
    allowedCodes: expectedStateCodes,
    rejectOnUnexpected: true,
    timeout: options.timeout || 6000,
    timeoutMessage: '等待 UUID_STATE 超时',
    unexpectedMessage: '密钥流程状态异常'
  })

  const stateCode = Number(stateEvent.stateCode)

  ble.setStage(BLE_STAGE.AUTHORIZED)
  ble.setAuthState({
    keyMatched: true,
    lastStateCode: stateCode
  })

  return {
    success: true,
    stateCode,
    key: keyValue
  }
}

async function ensureAuthorizedWithDeviceInfo(ble, info, keyText, options = {}) {
  const bindStatus = Number(info.bindStatus)
  const profile = ble.getProfile()

  ble.setAuthState({
    bound: Number.isNaN(bindStatus) ? null : bindStatus,
    keyMatched: false
  })

  if (bindStatus === 0) {
    const keyToBind = String(keyText || '').trim() || generateRandomKey(profile.auth.keyLength)
    const authResult = await writeKeyAndExpectStates(ble, keyToBind, [5], options)

    return {
      mode: 'BIND',
      deviceInfo: info,
      authResult,
      key: keyToBind
    }
  }

  if (bindStatus === 1) {
    const keyToMatch = String(keyText || '').trim()
    if (!keyToMatch) {
      throw new Error('设备已绑定，必须提供已绑定密钥用于匹配')
    }

    const authResult = await writeKeyAndExpectStates(ble, keyToMatch, [7], options)

    return {
      mode: 'MATCH',
      deviceInfo: info,
      authResult,
      key: keyToMatch
    }
  }

  const fallbackKey = String(keyText || '').trim()
  if (!fallbackKey) {
    throw new Error(`无法识别的绑定状态: ${info.bindStatus}，且未提供密钥`)
  }

  const fallbackResult = await writeKeyAndExpectStates(ble, fallbackKey, [7, 5], options)

  return {
    mode: 'UNKNOWN_BIND_STATE_FALLBACK',
    deviceInfo: info,
    authResult: fallbackResult,
    key: fallbackKey
  }
}

export function createAuthModule(ble) {
  async function readDeviceInfo() {
    const { msg } = ble.getState().characteristics

    if (!msg || !msg.uuid) {
      throw new Error('未发现 UUID_MSG 特征值')
    }

    const valuePromise = new Promise((resolve) => {
      const off = ble.on('protocol:msg', (payload) => {
        off()
        resolve(payload)
      })
    })

    await ble.readCharacteristic(msg.uuid)
    const payload = await valuePromise

    return parseDeviceInfo(payload.value)
  }

  /**
   * 严格遵循协议1.2绑定流程：
   * 1) 读取 UUID_MSG 的 bindStatus；
   * 2) bindStatus=0 写随机/指定密钥并等待 STATE=5；
   * 3) bindStatus=1 写已知密钥并等待 STATE=7。
   */
  async function ensureAuthorized(keyText, options = {}) {
    ble.setStage(BLE_STAGE.AUTHORIZING)
    const info = await readDeviceInfo()
    return ensureAuthorizedWithDeviceInfo(ble, info, keyText, options)
  }

  /**
   * 固定规则鉴权：密钥 = 设备MAC(去分隔符) + "0000"。
   * 用于“先鉴权再进行 WiFi 配置”的页面流程。
   */
  async function ensureAuthorizedByMac(options = {}) {
    ble.setStage(BLE_STAGE.AUTHORIZING)

    const info = await readDeviceInfo()
    const profile = ble.getProfile()
    const keyByMac = buildKeyFromMac(info.mac, options.suffix || '0000', profile.auth.keyLength)

    const authResult = await ensureAuthorizedWithDeviceInfo(ble, info, keyByMac, options)

    return {
      ...authResult,
      key: keyByMac,
      keyRule: 'MAC+0000'
    }
  }

  return {
    readDeviceInfo,
    ensureAuthorized,
    ensureAuthorizedByMac,
    buildKeyFromMac,
    generateRandomKey
  }
}