/*
Actions on several servers at once, outside Apps (stage 6): Blocked and Allowed, the temporary
blocking switch, the block lists, and the cache. One endpoint, `hub/servers/run`, takes a fixed
`action` and the action's own parameters, checks them HERE, and runs the one matching Technitium
call on every chosen server, in parallel, with that server's admin token.

  * `planAction` is pure: the allowlist, the validation, and the path and parameters to send.
  * `ServersRunner` runs a plan on targets. A server that is unknown or has no admin token fails
    on its own; the others still run. The answer is one result per server, never a bare "ok".

The block list URLs are part of blocking, so `blocking.setListUrls` needs `operate` like the rest,
not `admin` like the per-server `settings/set`. Only `blockListUrls` is sent, so nothing else of
the server's settings is touched, and the plan still goes through the checks of guards.ts.
*/
import type { HubConfig } from './config.ts'
import { isForbiddenSettingsField } from './guards.ts'
import { Upstream } from './upstream.ts'

export const SERVER_ACTIONS = [
  'blocked.add',
  'blocked.delete',
  'allowed.add',
  'allowed.delete',
  'blocking.disable',
  'blocking.enable',
  'blocking.updateLists',
  'blocking.setListUrls',
  'cache.flush',
  'cache.delete',
] as const

export type ServerAction = (typeof SERVER_ACTIONS)[number]

export interface TargetResult {
  server: string
  ok: boolean
  message?: string
}

export interface Plan {
  action: ServerAction
  /* The Technitium endpoint. */
  path: string
  /* Exactly what is sent (a form body). */
  params: Record<string, string>
  /* What the audit line may say about it: a domain, `minutes=15`, `urls=3`. Never the URLs. */
  target?: string
  /* The sentence for a server where it worked. */
  done: string
}

export const MAX_MINUTES = 1440
const MAX_URL_LENGTH = 2000

const LABEL = '[a-z0-9_](?:[a-z0-9_-]{0,61}[a-z0-9_])?'
const DOMAIN = new RegExp(`^(?:\\*\\.)?(?:${LABEL}\\.)*${LABEL}$`, 'i')

/* A domain as the hub accepts it (a trailing dot is dropped), or null. */
export function cleanDomain(value: string | undefined): string | null {
  const domain = (value ?? '').trim().replace(/\.$/, '')
  return domain.length > 0 && domain.length <= 253 && DOMAIN.test(domain) ? domain : null
}

/*
The lines of a block list request, one per line, in the grammar of the servers and of the console's
Lists tab (src/screens/blocking/list-lines.ts): `<url>` a block list, `!<url>` an allow list,
`#...` a switched-off list or a comment (a group heading), free text. Each URL is http, https or
file. Blank lines go. They travel as the console's own Settings save sends them: joined with a
comma. A comma cannot be told from the separator, so a line that has one is refused, not split.
*/
export const MAX_LINES = 300
export const MAX_COMMENT = 200
const SCHEMES = new Set(['http:', 'https:', 'file:'])

export function cleanUrls(value: string | undefined): { urls: string[] } | { error: string } {
  const lines = (value ?? '')
    .split(/\r?\n/)
    .map((l) => l.trim())
    .filter((l) => l !== '')
  if (lines.length === 0) return { error: 'Give at least one block list URL.' }
  if (lines.length > MAX_LINES) return { error: `At most ${MAX_LINES} lines.` }
  for (const line of lines) {
    if (line.includes(',')) return { error: `A line cannot contain a comma: ${line.slice(0, 60)}` }
    if (line.startsWith('#')) {
      if (line.length > MAX_COMMENT) return { error: 'A comment line is too long.' }
      continue
    }
    if (line.length > MAX_URL_LENGTH) return { error: 'A block list URL is too long.' }
    const text = line.startsWith('!') ? line.slice(1).trim() : line
    let url: URL
    try {
      url = new URL(text)
    } catch {
      return { error: `Not a valid http, https or file address: ${line.slice(0, 60)}` }
    }
    if (!SCHEMES.has(url.protocol) || /\s/.test(text)) return { error: `Not a valid http, https or file address: ${line.slice(0, 60)}` }
  }
  return { urls: lines }
}

export function planAction(action: string | undefined, raw: Record<string, string | undefined>): { error: string } | { plan: Plan } {
  if (action === undefined || !(SERVER_ACTIONS as readonly string[]).includes(action)) {
    return { error: `action must be one of: ${SERVER_ACTIONS.join(', ')}.` }
  }
  const kind = action as ServerAction
  switch (kind) {
    case 'blocked.add':
    case 'blocked.delete':
    case 'allowed.add':
    case 'allowed.delete':
    case 'cache.delete': {
      const domain = cleanDomain(raw.domain)
      if (domain === null) return { error: 'A valid domain name is required.' }
      const [list, verb] = kind.split('.')
      const path = list === 'cache' ? 'cache/delete' : `${list}/${verb}`
      const done =
        kind === 'cache.delete' ? 'Deleted from the cache.' : `${verb === 'add' ? 'Added to' : 'Removed from'} ${list === 'blocked' ? 'Blocked' : 'Allowed'}.`
      return { plan: { action: kind, path, params: { domain }, target: domain, done } }
    }
    case 'blocking.disable': {
      const text = (raw.minutes ?? '').trim()
      const minutes = /^\d{1,5}$/.test(text) ? Number(text) : 0
      if (minutes < 1 || minutes > MAX_MINUTES) return { error: `minutes must be a whole number from 1 to ${MAX_MINUTES}.` }
      return {
        plan: { action: kind, path: 'settings/temporaryDisableBlocking', params: { minutes: String(minutes) }, target: `minutes=${minutes}`, done: `Blocking disabled for ${minutes} minute(s).` },
      }
    }
    case 'blocking.enable':
      return settingsPlan(kind, { enableBlocking: 'true' }, undefined, 'Blocking enabled.')
    case 'blocking.setListUrls': {
      const cleaned = cleanUrls(raw.urls)
      if ('error' in cleaned) return cleaned
      return settingsPlan(kind, { blockListUrls: cleaned.urls.join(',') }, `urls=${cleaned.urls.length}`, `Block list URLs replaced (${cleaned.urls.length} line(s)).`)
    }
    case 'blocking.updateLists':
      return { plan: { action: kind, path: 'settings/forceUpdateBlockLists', params: {}, done: 'Block list update started.' } }
    case 'cache.flush':
      return { plan: { action: kind, path: 'cache/flush', params: {}, done: 'Cache flushed.' } }
  }
}

/* A `settings/set` of one field. The same checks as the per-server route, applied to what the hub itself builds. */
function settingsPlan(action: ServerAction, params: Record<string, string>, target: string | undefined, done: string): { error: string } | { plan: Plan } {
  if (Object.keys(params).some((k) => isForbiddenSettingsField(k) || k.startsWith('webService'))) return { error: 'That setting is not changed from the hub.' }
  return { plan: { action, path: 'settings/set', params, target, done } }
}

const reason = (e: unknown): string => (e instanceof Error ? e.message : 'failed')

export class ServersRunner {
  #config: HubConfig
  #upstream: Upstream

  constructor(config: HubConfig, upstream: Upstream) {
    this.#config = config
    this.#upstream = upstream
  }

  /*
  The plan on every target, in parallel. Returns `{ error }` when the request itself is refused
  (no targets, an unknown server), else one result per target.
  */
  async run(plan: Plan, targets: string[]): Promise<{ error: string } | { results: TargetResult[] }> {
    const known = new Map(this.#config.servers.map((s) => [s.id, s]))
    const unique = [...new Set(targets)]
    if (unique.length === 0) return { error: 'Choose at least one server.' }
    const unknown = unique.filter((t) => !known.has(t))
    if (unknown.length > 0) return { error: `Unknown server: ${unknown.join(', ')}.` }
    const results = await Promise.all(
      unique.map(async (id): Promise<TargetResult> => {
        const server = known.get(id)!
        if (server.adminToken === undefined) return { server: id, ok: false, message: 'no admin token configured' }
        try {
          await this.#upstream.write(server, plan.path, plan.params)
          return { server: id, ok: true, message: plan.done }
        } catch (e) {
          return { server: id, ok: false, message: reason(e) }
        }
      }),
    )
    return { results }
  }
}