import { randomBytes } from 'node:crypto';
import type { ProvisionableUser } from 'officerdb';
import { authenticate, callUpstream, type UpstreamTarget } from './upstream';
import { planReconcile, describePlan, normalize, type JellyfinUser, type ReconcilePlan } from './reconcile';

// Carrying out the plan. `reconcile.ts` decides; this does, and does nothing else.
//
// ── Nobody is ever told their Jellyfin password ──
//
// The plan for this deployment is that Jellyfin's own web UI is never exposed: people reach their media
// through Officer, and Officer holds the credential. So the generated password is not a handover value —
// it is used once, immediately, to mint that person's own access token, and then discarded.
//
// That is what makes `USER_PROVISIONING.md` rule 3 survivable here. Jellyfin has no must-change-password
// flag (verified against its OpenAPI: `UserPolicy` has 44 properties and none of them is one), so a
// handed-over password would stay valid indefinitely. A password nobody ever learns cannot.
//
// It also means provisioning produces something immediately useful rather than a credential in an email:
// the account exists AND the person's Officer session can already read their library.
//
// ── Verify by using it, not by reading the 200 ──
//
// Rule 4. `POST /Users/New` returning a user object means a row was written, not that the account works —
// and here the sign-in is not merely a check, it is how the token is obtained. The verification and the
// useful work are the same call, which is the only reason it cannot be skipped when someone is in a hurry.

/** Long enough that it does not matter that it is never rotated, since nobody ever knows it. */
const generatePassword = (): string => randomBytes(32).toString('base64url');

export type ProvisionOutcome = {
  /** Officer user id → what happened. */
  linked: { userId: number; jellyfinUserId: string; username: string }[];
  created: { userId: number; jellyfinUserId: string; username: string; token: string }[];
  /** Left alone, reported so the owner can see accounts Officer does not manage. */
  untouched: JellyfinUser[];
  failed: { username: string; error: string }[];
  /** One line per decision, for the install log. */
  log: string[];
};

/** Everything Jellyfin knows about, as `GET /Users` reports it. */
export async function listJellyfinUsers(cfg: UpstreamTarget): Promise<JellyfinUser[]> {
  const res = await callUpstream(cfg, { path: '/Users' });
  if (!res.ok) throw new Error(`GET /Users → ${res.status}`);
  const body = (await res.json()) as { Id: string; Name: string }[];
  return body.map((u) => ({ Id: u.Id, Name: u.Name }));
}

/**
 * Create one account, then sign in as it.
 *
 * Two calls, not one — Jellyfin separates creation from everything else, and `POST /Users/New` is the
 * only one that takes a password. The sign-in that follows is both rule 4's verification and the way the
 * token is obtained; a create that cannot then authenticate is reported as a failure rather than a user.
 */
async function createOne(
  cfg: UpstreamTarget,
  user: ProvisionableUser,
): Promise<{ jellyfinUserId: string; token: string }> {
  const password = generatePassword();

  const res = await callUpstream(cfg, {
    method: 'POST',
    path: '/Users/New',
    contentType: 'application/json',
    body: JSON.stringify({ Name: user.username, Password: password }),
  });

  if (!res.ok) {
    // 400 here is most likely the name colliding on Jellyfin's uppercased `NormalizedUsername` index,
    // which the plan should have prevented — so the body is carried out rather than summarised.
    throw new Error(`POST /Users/New → ${res.status}: ${(await res.text()).slice(0, 200)}`);
  }

  const created = (await res.json()) as { Id?: string };
  if (!created.Id) throw new Error('POST /Users/New returned no Id');

  // Rule 4, and the token in one call. A per-user device id keeps this session distinct from the owner's
  // in Jellyfin's Devices screen, so revoking one does not sign out the other.
  const auth = await authenticate(cfg.base, `officer-${user.id}`, user.username!, password);
  return { jellyfinUserId: created.Id, token: auth.token };
}

/**
 * Reconcile Officer's accounts against Jellyfin's, and carry out what is missing.
 *
 * Idempotent: run it twice and the second does nothing, because `existing` grows and the plan shrinks. It
 * does not rely on Jellyfin rejecting a duplicate to stop — that would work, but it would also mean a
 * normal second run produced errors, and errors that are normal stop being read.
 *
 * Never deletes anything. A Jellyfin account with no Officer user is reported and left, because an
 * absence in Officer is indistinguishable from a list that has not been told about someone yet.
 */
export async function provision(params: {
  cfg: UpstreamTarget;
  users: ProvisionableUser[];
  existing: { userId: number; jellyfinUserId: string }[];
}): Promise<ProvisionOutcome> {
  const { cfg, users, existing } = params;

  const jellyfinUsers = await listJellyfinUsers(cfg);
  const plan: ReconcilePlan = planReconcile({ users, jellyfinUsers, existing });

  const outcome: ProvisionOutcome = {
    linked: [],
    created: [],
    untouched: plan.leave,
    failed: [],
    log: describePlan(plan),
  };

  // Adoptions first: they touch nothing upstream, so they cannot fail halfway and leave Jellyfin ahead of
  // the mapping. Doing them first also means a create that fails later does not strand a link that was
  // already safe to record.
  for (const { user, jellyfin } of plan.link) {
    outcome.linked.push({ userId: user.id, jellyfinUserId: jellyfin.Id, username: jellyfin.Name });
  }

  for (const user of plan.create) {
    try {
      const { jellyfinUserId, token } = await createOne(cfg, user);
      outcome.created.push({ userId: user.id, jellyfinUserId, username: user.username!, token });
    } catch (error) {
      // One person failing must not stop the rest. A partially provisioned server is recoverable by
      // running again; a run that aborts on the first error leaves everyone after them unprovisioned and
      // gives no clue which ones those were.
      outcome.failed.push({ username: user.username ?? String(user.id), error: error instanceof Error ? error.message : String(error) });
    }
  }

  return outcome;
}

export { normalize };