/*
Checks the hub makes on what passes through it to a server (stage 5): which `settings/set`
fields it will not forward, which values of `settings/get` a role may see, and which single
identifier of a write may go into the audit log.

Pure functions, so the tests feed them any input.
*/

/*
`settings/set` and the hub's own way in.

The hub reaches a server through that server's web service, with an API token. Changing the
service's bind addresses, ports, TLS or reverse-proxy settings from here can cut the hub off with
no way back except the server's own console, so the hub refuses a change to any `webService*`
field. The console sends the whole Web Service block with every save, unchanged values included,
so a field is refused only when its value DIFFERS from what the server holds now (see
`webServiceChanges`). Users, SSO and LDAP are not part of `settings/set`; a field that looks like
one (`user*`, `sso*`, `ldap*`, `auth*`) is refused outright, in case a server version adds it.
*/
export const WEB_SERVICE_MESSAGE = "Change the web service settings in that server's own console."

const FORBIDDEN_FIELD = /^(user|sso|ldap|auth)/i
const WEB_FIELD = /^webService/

/** True for a field the hub never forwards, whatever its value. */
export const isForbiddenSettingsField = (name: string): boolean => FORBIDDEN_FIELD.test(name)

/* A list as the console sends it (`a,b`, one per line, or `false` for none) or as the server holds it. */
function listOf(value: unknown): string[] {
  const items = Array.isArray(value) ? value.map(String) : String(value ?? '').split(/[,\n]/)
  return items.map((v) => v.trim()).filter((v) => v !== '' && v !== 'false')
}

/* Whether a submitted text means what the server holds. Booleans and numbers by value, lists as sets, text trimmed. */
function sameSetting(submitted: string, current: unknown): boolean {
  if (typeof current === 'boolean') return submitted.trim().toLowerCase() === String(current)
  if (typeof current === 'number') return submitted.trim() !== '' && Number(submitted) === current
  if (Array.isArray(current)) {
    const a = listOf(submitted).sort()
    const b = listOf(current).sort()
    return a.length === b.length && a.every((v, i) => v === b[i])
  }
  return submitted.trim() === String(current ?? '').trim()
}

/*
The `webService*` fields of a `settings/set` whose value differs from the server's current
settings (`settings/get`). A field the server does not report is not compared: it would be ignored
there too.
*/
export function webServiceChanges(submitted: Record<string, string>, current: unknown): string[] {
  const now = (current !== null && typeof current === 'object' ? current : {}) as Record<string, unknown>
  const changed: string[] = []
  for (const [name, value] of Object.entries(submitted)) {
    if (!WEB_FIELD.test(name) || !Object.hasOwn(now, name)) continue
    if (!sameSetting(value, now[name])) changed.push(name)
  }
  return changed
}

/*
`settings/get` carries secrets: the TSIG shared secrets, the forward proxy password and the two
certificate passwords. A role without `admin` gets a copy with those values blanked (a viewer
needs the screen, not the keys); an admin gets them, since saving the form sends them back. The
blanked copy is for display only and `settings/set` is `admin`-only, so a blank cannot be saved
over a real secret by someone who may not read it.
*/
export function redactSettings(response: unknown): unknown {
  if (response === null || typeof response !== 'object') return response
  const copy = { ...(response as Record<string, unknown>) }
  for (const key of ['webServiceTlsCertificatePassword', 'dnsTlsCertificatePassword']) {
    if (typeof copy[key] === 'string' && copy[key] !== '') copy[key] = ''
  }
  if (Array.isArray(copy.tsigKeys)) {
    copy.tsigKeys = copy.tsigKeys.map((k: unknown) => (k !== null && typeof k === 'object' ? { ...k, sharedSecret: '' } : k))
  }
  const proxy = copy.proxy
  if (proxy !== null && typeof proxy === 'object' && typeof (proxy as { password?: unknown }).password === 'string') {
    copy.proxy = { ...proxy, password: '' }
  }
  return copy
}

/*
The one identifier an audit line may carry for a write: a zone, a domain, a name or a scope. Never
the other parameters (records carry data, settings carry passwords and TSIG secrets). Cut short.
*/
const IDENTIFIERS = ['zone', 'domain', 'name', 'scope', 'zones']

export function safeTarget(params: Record<string, string>): string | undefined {
  for (const key of IDENTIFIERS) {
    const value = params[key]
    if (typeof value === 'string' && value.trim() !== '') return value.trim().slice(0, 120)
  }
  return undefined
}