/**
 * 后端接口的客户端。
 *
 * 令牌存在 localStorage 里。它等同于密码，但这个页面本来就只有能访问 127.0.0.1
 * （或者持有 SSH 隧道）的人才打得开，存在浏览器里不额外扩大暴露面。
 */
import type { ConfigDiagnostic, ConfigObject } from '../vendor/config-editor/index.ts'

const TOKEN_KEY = 'patchbay.token'

export function getToken(): string {
  return localStorage.getItem(TOKEN_KEY) ?? ''
}

export function setToken(value: string): void {
  localStorage.setItem(TOKEN_KEY, value.trim())
}

export function clearToken(): void {
  localStorage.removeItem(TOKEN_KEY)
}

/** 接口报错时抛这个，界面据此决定是提示重填令牌还是显示错误内容。 */
export class ApiError extends Error {
  constructor(
    readonly status: number,
    readonly payload: Record<string, unknown>,
  ) {
    super(typeof payload.message === 'string' ? payload.message : `请求失败（${String(status)}）`)
    this.name = 'ApiError'
  }

  get unauthorized(): boolean {
    return this.status === 401
  }
}

async function request<T>(method: string, path: string, body?: unknown): Promise<T> {
  const res = await fetch(path, {
    method,
    headers: {
      Authorization: `Bearer ${getToken()}`,
      ...(body === undefined ? {} : { 'Content-Type': 'application/json' }),
    },
    body: body === undefined ? undefined : JSON.stringify(body),
  })
  const text = await res.text()
  const payload = text ? (JSON.parse(text) as Record<string, unknown>) : {}
  if (!res.ok) throw new ApiError(res.status, payload)
  return payload as T
}

export interface ConfigSnapshot {
  data: ConfigObject
  yaml: string
  revision: string
  diagnostics: ConfigDiagnostic[]
}

export interface ApplySuccess {
  ok: true
  snapshot: ConfigSnapshot
  reloaded: boolean
  reloadMessage: string
}

export interface ApplyFailure {
  ok: false
  stage: 'stale' | 'self-check' | 'kernel-check' | 'write' | 'reload'
  message: string
  hint: string
  restored: boolean
}

export const api = {
  readConfig: () => request<ConfigSnapshot>('GET', '/api/config'),

  applyConfig: (data: ConfigObject, baseRevision: string) =>
    request<ApplySuccess>('PUT', '/api/config', { data, baseRevision }),

  listBackups: () => request<{ backups: string[] }>('GET', '/api/config/backups'),

  restoreBackup: (name: string) =>
    request<ApplySuccess>('POST', `/api/config/backups/${encodeURIComponent(name)}/restore`),

  kernel: () => request<{ online: boolean; version?: string }>('GET', '/api/kernel'),

  /** 订阅里当前有哪些线路。配置文件给不出这个答案，只能问运行中的内核。 */
  providers: () =>
    request<{ providers: Record<string, { vehicleType: string; proxies: { name: string }[] }> }>(
      'GET',
      '/api/kernel/providers/proxies',
    ),
}