import { api } from './client'
import type { LoginResponse, PasskeyCreationOptionsDto, PasskeyDto, PasskeyRequestOptionsDto, SignedStatementDto } from './types'

/** 浏览器是否支持在输入框的自动填充里列出 passkey（conditional UI）。 */
export async function conditionalSupported(): Promise<boolean> {
  try {
    return passkeySupported() && (await PublicKeyCredential.isConditionalMediationAvailable?.()) === true
  } catch {
    return false
  }
}

/**
 * passkey 保存在哪里：浏览器和系统决定具体用谁的密码管理器，网站只能给提示。
 * `device`：此设备或浏览器账户（Chrome 里是 Google 密码管理工具，也可以是 Windows Hello、iCloud 钥匙串）；
 * `external`：安全密钥，或者用手机扫码。
 */
export type PasskeyPlace = 'device' | 'external'

/** 浏览器是否支持 WebAuthn（passkey）。 */
export function passkeySupported(): boolean {
  return typeof window !== 'undefined' && !!window.PublicKeyCredential && !!navigator.credentials
}

function toBytes(text: string): Uint8Array<ArrayBuffer> {
  const padded = text.replace(/-/g, '+').replace(/_/g, '/').padEnd(Math.ceil(text.length / 4) * 4, '=')
  const binary = atob(padded)
  const out = new Uint8Array(binary.length)
  for (let i = 0; i < binary.length; i++) out[i] = binary.charCodeAt(i)
  return out
}

function toText(buffer: ArrayBuffer): string {
  let binary = ''
  for (const byte of new Uint8Array(buffer)) binary += String.fromCharCode(byte)
  return btoa(binary).replace(/\+/g, '-').replace(/\//g, '_').replace(/=+$/, '')
}

/**
 * 用 passkey 登录（可发现凭证：不需要用户名）。服务端设了会话 Cookie；返回登录响应。
 * passkey 绑定在后端的域名上：只有和后端同站的页面能用，所以其他后端（跨域）不显示这个入口。
 */
export async function signInWithPasskey(opts: { conditional?: boolean; signal?: AbortSignal } = {}): Promise<LoginResponse> {
  const options = await api.post<PasskeyRequestOptionsDto>('/api/admin/auth/passkey/options')
  const credential = (await navigator.credentials.get({
    // conditional：不弹窗，浏览器在用户名输入框的自动填充里列出已保存的 passkey（Chrome 里就是 Google 密码管理工具里的）
    mediation: opts.conditional ? 'conditional' : undefined,
    signal: opts.signal,
    publicKey: { challenge: toBytes(options.challenge), rpId: options.rp_id, timeout: opts.conditional ? undefined : options.timeout_ms, userVerification: 'required' },
  })) as PublicKeyCredential | null
  if (!credential) throw new Error('没有选择 passkey')
  const response = credential.response as AuthenticatorAssertionResponse
  return api.post<LoginResponse>('/api/admin/auth/passkey/login', {
    credential_id: credential.id,
    authenticator_data: toText(response.authenticatorData),
    client_data_json: toText(response.clientDataJSON),
    signature: toText(response.signature),
  })
}

/**
 * 用 passkey 对一段文本签名（挑战是文本的 SHA-256）：操作员集合、加入码的委托都是这样签出来的，节点自己验。
 * 浏览器会让用户从这个站点的 passkey 里选一个；面板再检查它是不是操作员集合里的凭证。
 */
export async function signStatement(statement: string): Promise<SignedStatementDto> {
  const challenge = new Uint8Array(await crypto.subtle.digest('SHA-256', new TextEncoder().encode(statement)))
  let credential: PublicKeyCredential | null
  try {
    credential = (await navigator.credentials.get({ publicKey: { challenge, userVerification: 'required', timeout: 120_000 } })) as PublicKeyCredential | null
  } catch (e) {
    if (e instanceof DOMException && (e.name === 'NotAllowedError' || e.name === 'AbortError')) throw new Error('已取消')
    throw e
  }
  if (!credential) throw new Error('没有选择 passkey')
  const response = credential.response as AuthenticatorAssertionResponse
  return {
    statement,
    credential_id: credential.id,
    authenticator_data: toText(response.authenticatorData),
    client_data_json: toText(response.clientDataJSON),
    signature: toText(response.signature),
  }
}

/** 给当前登录的用户注册一个新 passkey（要求用户验证，ES256）。 */
export async function registerPasskey(name: string, place: PasskeyPlace = 'device'): Promise<PasskeyDto> {
  const options = await api.post<PasskeyCreationOptionsDto>('/api/admin/auth/passkeys/options')
  const credential = (await navigator.credentials.create({
    publicKey: {
      challenge: toBytes(options.challenge),
      rp: { id: options.rp_id, name: options.rp_name },
      user: { id: toBytes(options.user_id), name: options.user_name, displayName: options.user_name },
      pubKeyCredParams: [{ type: 'public-key', alg: -7 }],
      excludeCredentials: options.exclude_credentials.map((id) => ({ type: 'public-key' as const, id: toBytes(id) })),
      authenticatorSelection: { authenticatorAttachment: place === 'device' ? 'platform' : 'cross-platform', residentKey: 'required', requireResidentKey: true, userVerification: 'required' },
      attestation: 'none',
      timeout: options.timeout_ms,
      // 给浏览器的提示（Chrome 128+）：优先用设备自带的（含 Google 密码管理工具），或者安全密钥和手机
      hints: place === 'device' ? ['client-device'] : ['security-key', 'hybrid'],
    } as PublicKeyCredentialCreationOptions,
  })) as PublicKeyCredential | null
  if (!credential) throw new Error('没有创建 passkey')
  const response = credential.response as AuthenticatorAttestationResponse
  return api.post<PasskeyDto>('/api/admin/auth/passkeys', {
    name,
    credential_id: credential.id,
    attestation_object: toText(response.attestationObject),
    client_data_json: toText(response.clientDataJSON),
    transports: response.getTransports?.() ?? [],
  })
}