/*
The hub's configuration, read from the environment. `parseConfig` is pure so the
tests can feed it any environment; `loadConfig` is the one that reads `process.env`.
*/

export const HUB_VERSION = '1.0.0'

export interface HubServer {
  id: string
  url: string
  token: string
  /** Optional write-capable token (`<ID>_ADMIN_TOKEN`). Not used yet; never logged. */
  adminToken?: string
}

/** The single admin from HUB_USER and HUB_PASSWORD, used only while there is no users file. */
export interface Bootstrap {
  user: string
  password: string
}

export interface HubConfig {
  servers: HubServer[]
  /** From HUB_USER and HUB_PASSWORD; null when they are not set. Whether it is used depends on the users file. */
  bootstrap: Bootstrap | null
  /** Where users.json and audit.log live (HUB_DATA). */
  dataDir: string
  /** Believe the first X-Forwarded-For entry as the client address (HUB_TRUST_PROXY=1). */
  trustProxy: boolean
  port: number
  cacheSeconds: number
  /** How often the drift check runs (HUB_DRIFT_MINUTES); 0 turns it off. */
  driftMinutes: number
  timeoutMs: number
  /** Where drift and failed-write notices are POSTed (HUB_WEBHOOK_URL); null when not set. */
  webhookUrl: string | null
  /** Signs the notices with HMAC-SHA256 (HUB_WEBHOOK_SECRET); null when not set. Never logged. */
  webhookSecret: string | null
  /** Lets the block list counter fetch from private addresses (HUB_LISTS_ALLOW_PRIVATE=1), for lists kept on the LAN. */
  listsAllowPrivate: boolean
  /** Shown as `dnsServerDomain` (and `clusterDomain`) in the session. */
  domain: string
  /** The console's static build. */
  staticDir: string
}

type Env = Record<string, string | undefined>

/* `ndns` -> `NDNS_TOKEN`, `my-dns.1` -> `MY_DNS_1_TOKEN`. */
export function tokenVariable(id: string): string {
  return `${id.toUpperCase().replace(/[^A-Z0-9]/g, '_')}_TOKEN`
}

/* `ndns` -> `NDNS_ADMIN_TOKEN`. */
export function adminTokenVariable(id: string): string {
  return `${id.toUpperCase().replace(/[^A-Z0-9]/g, '_')}_ADMIN_TOKEN`
}

function number(env: Env, name: string, fallback: number, min: number): number {
  const raw = env[name]
  if (raw === undefined || raw.trim() === '') return fallback
  const value = Number(raw)
  if (!Number.isFinite(value) || value < min) throw new Error(`${name} must be a number of at least ${min}.`)
  return value
}

export function parseConfig(env: Env): HubConfig {
  // The users file decides whether these are needed; the config does not read the file.
  const user = env.HUB_USER ?? ''
  const password = env.HUB_PASSWORD ?? ''
  if ((user === '') !== (password === '')) throw new Error('HUB_USER and HUB_PASSWORD must be set together.')

  const servers: HubServer[] = []
  for (const part of (env.HUB_SERVERS ?? '').split(',')) {
    const entry = part.trim()
    if (entry === '') continue
    const at = entry.indexOf('=')
    const id = at < 0 ? '' : entry.slice(0, at).trim()
    const url = at < 0 ? '' : entry.slice(at + 1).trim().replace(/\/+$/, '')
    if (!/^[A-Za-z0-9._-]+$/.test(id) || id === 'cluster' || !/^https?:\/\/[^/]/.test(url)) {
      throw new Error(`HUB_SERVERS entry "${entry}" is not of the form id=https://host (id: letters, digits, . _ -).`)
    }
    if (servers.some((s) => s.id === id)) throw new Error(`HUB_SERVERS lists "${id}" twice.`)
    const variable = tokenVariable(id)
    const token = env[variable] ?? ''
    if (token === '') throw new Error(`${variable} is required for the server "${id}".`)
    const adminToken = env[adminTokenVariable(id)] ?? ''
    servers.push(adminToken === '' ? { id, url, token } : { id, url, token, adminToken })
  }
  if (servers.length === 0) {
    throw new Error('HUB_SERVERS is required, e.g. dns=https://dns.example.net,ndns=https://ndns.example.net.')
  }

  const webhookUrl = (env.HUB_WEBHOOK_URL ?? '').trim()
  if (webhookUrl !== '') {
    let ok = /^https?:\/\/[^/\s]/i.test(webhookUrl)
    try {
      new URL(webhookUrl)
    } catch {
      ok = false
    }
    if (!ok) throw new Error('HUB_WEBHOOK_URL must be an http or https address.')
  }

  return {
    servers,
    bootstrap: user === '' ? null : { user, password },
    dataDir: env.HUB_DATA?.trim() || '/data',
    trustProxy: ['1', 'true'].includes((env.HUB_TRUST_PROXY ?? '').trim().toLowerCase()),
    port: number(env, 'HUB_PORT', 8080, 0),
    cacheSeconds: number(env, 'HUB_CACHE_SECONDS', 15, 0),
    driftMinutes: number(env, 'HUB_DRIFT_MINUTES', 15, 0),
    timeoutMs: number(env, 'HUB_TIMEOUT_MS', 8000, 1),
    webhookUrl: webhookUrl === '' ? null : webhookUrl,
    webhookSecret: (env.HUB_WEBHOOK_SECRET ?? '') === '' ? null : (env.HUB_WEBHOOK_SECRET as string),
    listsAllowPrivate: ['1', 'true'].includes((env.HUB_LISTS_ALLOW_PRIVATE ?? '').trim().toLowerCase()),
    domain: env.HUB_DOMAIN?.trim() || 'hub',
    staticDir: env.HUB_STATIC?.trim() || './dist',
  }
}

export function loadConfig(): HubConfig {
  return parseConfig(process.env)
}