Module-uo/server/core.js

// ── Everything this module reaches in core ─────────────────────────────────
//
// `ctx` arrives once, as an argument to `register()` (MODULE_API.md §2.3). The
// code below it — models, utils, controllers — is ordinary Node that requires
// its dependencies at file scope, the way it did when it lived in core. This
// file is what lets both be true.
//
// **The shape is a lazy accessor, not a stored reference, and that is the whole
// point.** A ported file writes
//
//     const { query } = require('../../core')
//
// at require time, which is before `register()` has been called and therefore
// before any `ctx` exists. Handing out `ctx.db.query` there would hand out
// `undefined`, permanently, and the failure would surface much later as a
// TypeError inside a model. So every export here is a stable function that
// resolves `ctx` when it is CALLED. Require order stops mattering, and the port
// stays a one-line import change per file rather than a signature change per
// function.
//
// The other half of the same rule: nothing here may be destructured off `ctx`
// at init time either, for the same reason in the other direction — core is
// free to hand over a getter (`ctx.site.baseUrl` is one), and a value captured
// once is a value that cannot change.
//
// If `ctx` is missing, every accessor throws with the same message. That is
// deliberate: the only way to reach one before `register()` is a require cycle
// or a test that forgot to call `init`, and both want naming, not `undefined`.

let ctx = null

function need() {
  if (!ctx) {
    throw new Error('module-uo: core accessed before register() — see server/core.js')
  }
  return ctx
}

/** Called once, first thing in `register()`. */
function init(value) {
  ctx = value
}

/** Test seam. Nothing in the module calls this; there is no de-registration. */
function _reset() {
  ctx = null
}

// A logger that can be taken at require time and used after `register()`.
//
// Ported files write `const log = require('../core').logger('shard-ingest')` at
// file scope — the same shape as core's `require('./logger')('…')` — so the
// object returned has to exist before `ctx` does. It is a façade whose four
// methods each resolve the real logger on call. Core namespaces it with the
// module id, so these come out as `[uo:shard-ingest]`.
function logger(namespace) {
  const call = (level) => (message, meta) => need().log(namespace)[level](message, meta)
  return { error: call('error'), warn: call('warn'), info: call('info'), debug: call('debug') }
}

module.exports = {
  init,
  _reset,
  logger,

  // Shared server dependencies. Core owns exactly one express, as it owns
  // exactly one React on the client, and for the same reason: a second copy in
  // the process is a second Router prototype and a second set of instanceof
  // checks. A module lives outside core's `server/`, so it could not resolve
  // these for itself even if it were allowed to (§7.2).
  get express() { return need().express },
  get validator() { return need().validator },

  // Database. `query` is the one every `*.db.js` uses; `pool` is for the
  // streamed atlas import, which needs a connection it can hold.
  query: (...args) => need().db.query(...args),
  get pool() { return need().db.pool },

  // Core state a module may read or append to, each narrowed to what is
  // actually used (§2.3).
  settings: {
    get: (...args) => need().settings.get(...args),
    set: (...args) => need().settings.set(...args),
    getInstanceName: (...args) => need().settings.getInstanceName(...args),
  },
  activity: { log: (...args) => need().activity.log(...args) },
  users: { getById: (...args) => need().users.getById(...args) },
  posts: {
    listAll: (...args) => need().posts.listAll(...args),
    getById: (...args) => need().posts.getById(...args),
    linkAnnounceJob: (...args) => need().posts.linkAnnounceJob(...args),
    markAnnounced: (...args) => need().posts.markAnnounced(...args),
  },
  auth: { getUserFromRequest: (...args) => need().auth.getUserFromRequest(...args) },
  push: { publish: (...args) => need().push.publish(...args) },
  secretBox: {
    encrypt: (...args) => need().secretBox.encrypt(...args),
    decrypt: (...args) => need().secretBox.decrypt(...args),
  },
  get uploads() { return need().uploads },

  // Middleware. Taken as values rather than wrapped, because express stores the
  // function reference at mount time — a wrapper would be what ends up in the
  // stack, and `requireRole('admin')` returns a middleware rather than being
  // one. Routers are built inside `register()`, so `ctx` is set by then.
  get middleware() { return need().middleware },

  // Deployment facts.
  get baseUrl() { return need().site.baseUrl },
  get moduleRoot() { return need().paths.moduleRoot },
  get moduleId() { return need().moduleId },
}