// ── The logic half ────────────────────────────────────────────────────────
//
// Shapes what the database returned into what a client should see, and holds the
// one rule that matters most in this module: **what leaves this file is never the
// sidecar's credential.**
//
// It is a separate file from the SQL so that it is testable without a database,
// and the suite next door tests it that way.
//
// The other decision worth pointing at: **a module answers when the game is
// unreachable rather than failing.** The website is the internet-facing process
// and the game is not; a game being down, or a sidecar being mid-restart, is an
// ordinary Tuesday. A page that renders "offline, last seen 20 minutes ago" is
// right; a page that 500s because a socket is closed is a module that has made
// the site's availability depend on the game's.

const core = require('../../core')
const db = require('./servers.db')

const log = core.logger('servers')

// Past this, the last thing a server said stops being news and starts being
// history. Presentation, so the number lives with the code that shapes the
// response rather than in the client.
const STALE_AFTER_MS = 5 * 60 * 1000

/**
 * A configured server with its token decrypted, for this module's own use.
 *
 * **Never hand the result of this to a controller.** It is the input to
 * `sidecarClient`, and the only shape in this module that holds a plaintext
 * secret.
 *
 * A token that will not decrypt is returned as `null` rather than throwing: the
 * usual cause is a `SECRET_ENC_KEY` that changed, and the right behaviour is a
 * server that reports itself unconfigured with a line in the log — not a module
 * that fails to boot and takes every other server down with it.
 */
function withToken(row) {
  if (!row) return null

  let token = null
  if (row.sidecarTokenEnc) {
    try {
      token = core.secretBox().decrypt(row.sidecarTokenEnc)
    } catch (err) {
      log.error('could not decrypt a sidecar token', { server: row.id, error: err.message })
    }
  }

  return { id: row.id, name: row.name, baseUrl: row.sidecarBaseUrl, token, protocol: row.protocol }
}

/** Every enabled server, with tokens, for the poller. */
async function listForPolling() {
  const rows = await db.listServers({ enabledOnly: true })
  return rows.map(withToken)
}

/**
 * The public view: every enabled server and what it last said.
 *
 * Nothing here is conditional on who is asking, which is the point of it being
 * the public shape. What a *player* or an *admin* additionally sees is added by
 * their own tier's controller, never removed by this one.
 */
async function listPublic(now = Date.now()) {
  const [servers, states] = await Promise.all([db.listServers({ enabledOnly: true }), db.listState()])
  const byId = new Map(states.map((s) => [s.serverId, s]))

  return servers.map((row) => shapePublic(row, byId.get(row.id), now))
}

function shapePublic(row, state, now) {
  const updatedAt = state && state.updatedAt ? new Date(state.updatedAt) : null
  const lastSeenAt = state && state.lastSeenAt ? new Date(state.lastSeenAt) : null
  const stale = !updatedAt || now - updatedAt.getTime() > STALE_AFTER_MS

  return {
    id: row.id,
    name: row.name,
    // A stale row cannot claim a server is up. The row says what was true when it
    // was written, and nothing has written it since.
    online: Boolean(state && state.online) && !stale,
    players: stale ? 0 : Number(state && state.players) || 0,
    maxPlayers: Number(state && state.maxPlayers) || 0,
    hostname: (state && state.hostname) || null,
    level: (state && state.level) || null,
    worldSize: state && state.worldSize != null ? Number(state.worldSize) : null,
    seed: state && state.seed != null ? Number(state.seed) : null,
    // The CURRENT wipe, from the state row rather than from the newest row in
    // `rust_wipes`. The two usually agree and the state row is the one that is
    // right when they do not: a wipe list is derived from events that have been
    // ingested, so a server that has just wiped and said nothing since has a new
    // wipe id here and no row there at all.
    wipeId: (state && state.wipeId) || null,
    wipedAt: (state && state.saveCreatedAt) || null,
    // Two timestamps, because they are two facts. `lastSeenAt` is when a frame
    // last arrived and is what a page means by "last reported"; `updatedAt` is
    // when this module last wrote the row, and is what `stale` is computed from.
    // Reading the second as the first is what made an offline server claim it had
    // reported just now, on every failed poll, for as long as it stayed down.
    lastSeenAt: lastSeenAt ? lastSeenAt.toISOString() : null,
    updatedAt: updatedAt ? updatedAt.toISOString() : null,
    stale,
  }
}

/**
 * One enabled server, or `null`.
 *
 * It exists because `/rust/servers/:id` is a page and a page needs to be able to
 * 404. A detail view built by fetching the list and finding the row in it cannot
 * tell "no such server" from "a server that has said nothing" — both are an
 * absence — and renders an empty page under a heading for a server that does not
 * exist. Filtering happens here, where `enabled = 0` and "never configured" are
 * the same answer on purpose: a disabled server is not a 403, it is not there.
 */
async function getPublic(id, now = Date.now()) {
  if (!id) return null

  const row = await db.getServer(id)
  if (!row || !row.enabled) return null

  return shapePublic(row, await db.getState(row.id), now)
}

/**
 * The admin view: configuration plus reachability, and **no token**.
 *
 * `hasToken` rather than the token, because the credential is write-only in the
 * API: the admin form accepts a new value and never shows the stored one. An
 * operator still needs to know whether one is set — a blank field means both
 * "unset" and "set, and not being shown you" otherwise.
 */
async function listForAdmin(now = Date.now()) {
  const [servers, states] = await Promise.all([db.listServers(), db.listState()])
  const byId = new Map(states.map((s) => [s.serverId, s]))

  return servers.map((row) => {
    const state = byId.get(row.id)
    return {
      // The public shape first, so the admin-only fields below cannot be
      // overwritten by a key the public shape happens to share.
      ...shapePublic(row, state, now),
      sidecarBaseUrl: row.sidecarBaseUrl,
      hasToken: Boolean(row.sidecarTokenEnc),
      protocol: Number(row.protocol),
      enabled: Boolean(row.enabled),
      sortOrder: Number(row.sortOrder),
      reachable: Boolean(state && state.reachable),
      bootId: (state && state.bootId) || null,
      sidecarProtocol: state && state.protocol != null ? Number(state.protocol) : null,
    }
  })
}

/** Encrypt a token for storage. `null`/empty means "leave whatever is stored alone". */
function encryptToken(token) {
  if (token === null || token === undefined || token === '') return null
  return core.secretBox().encrypt(String(token))
}

module.exports = {
  STALE_AFTER_MS,
  withToken,
  listForPolling,
  listPublic,
  getPublic,
  listForAdmin,
  shapePublic,
  encryptToken,
}