import type { ProvisionableUser } from 'officerdb';

// Deciding what to do about each account, with no side effects.
//
// Separated from the doing on purpose. The execution talks to a live Immich and cannot be rehearsed; the
// decision is where every mistake that matters lives, and it can be checked against the real addresses on
// the real instance without creating anything.
//
// ── The outcomes, and why none of them is "delete" ──
//
//   LINK    an Officer user whose email already exists on Immich. Record the pairing; create nothing.
//   CREATE  an Officer user with no Immich account. Make one.
//   LEAVE   an Immich account with no Officer user. Do nothing at all, and say so.
//
// Deleting an Immich account because nobody holds a matching Officer login would destroy somebody's
// photographs on the strength of an absence — and an absence is exactly what an incomplete list looks
// like. So they are reported, never touched, and the report is the feature.
//
// ── Matching is on email, lowercased ──
//
// Immich identifies an account by email and stores it lowercased (`ZodEmail` with a transform on both the
// create and update DTOs). Officer's `users.email` is the same key, so pairing is exact rather than
// heuristic — a real simplification over the Jellyfin side, which has to match usernames through Jellyfin's
// uppercased `NormalizedUsername` index and cope with two Officer names colliding into one.
//
// ── The admin's own account is not "not an Officer account" ──
//
// `listProvisionableUsers` excludes the owner deliberately: they hold the admin account this whole flow
// authenticates as, and provisioning them would be a second admin nobody asked for. But that makes the
// owner's own Immich account look like it belongs to nobody. It is identified here from the key's own
// identity rather than matched by name, and reported as itself. The Jellyfin plugin shipped this bug and
// had to fix it in `591c0da`; there is no reason to ship it twice.

/** An Immich account as `GET /api/admin/users` reports it. Only the fields a decision needs. */
export type ImmichUser = { id: string; email: string; name: string };

/** An existing pairing, so a second run does not re-decide what is already recorded. */
export type ExistingLink = { userId: number; immichUserId: string };

export type ReconcilePlan = {
  /** Officer users whose Immich account already exists — record the pairing, create nothing. */
  link: { user: ProvisionableUser; immich: ImmichUser }[];
  /** Officer users with no Immich account. */
  create: ProvisionableUser[];
  /** Immich accounts with no Officer user. Reported, never touched. */
  leave: ImmichUser[];
  /** The account the API key itself belongs to — the owner. Neither provisioned nor unclaimed. */
  self: ImmichUser | null;
  /** Already linked, and still valid on both sides. Nothing to do. */
  unchanged: ExistingLink[];
  /**
   * Links whose Immich account has vanished — deleted in Immich's own UI, most likely.
   *
   * Separated from `create` even though the remedy is the same, because they are different events: one is a
   * new person, the other is someone's account disappearing behind Officer's back.
   */
  brokenLinks: ExistingLink[];
};

/** Immich's own rule, applied on this side so the two agree. */
export const normalize = (email: string): string => email.trim().toLowerCase();

/**
 * Work out what should happen. Nothing here talks to anything.
 *
 * `adminImmichUserId` is who the configured API key authenticates as, read from `/api/users/me` rather
 * than assumed — it is what keeps the owner out of `leave`.
 */
export function planReconcile(params: {
  users: ProvisionableUser[];
  immichUsers: ImmichUser[];
  existing: ExistingLink[];
  adminImmichUserId: string | null;
}): ReconcilePlan {
  const { users, immichUsers, existing, adminImmichUserId } = params;

  const immichByEmail = new Map(immichUsers.map((u) => [normalize(u.email), u]));
  const immichById = new Map(immichUsers.map((u) => [u.id, u]));
  const linkedUserIds = new Set(existing.map((e) => e.userId));
  /** Immich accounts spoken for — pre-existing links, plus anything claimed during this pass. */
  const claimed = new Set(existing.map((e) => e.immichUserId));

  const plan: ReconcilePlan = {
    link: [],
    create: [],
    leave: [],
    self: adminImmichUserId ? (immichById.get(adminImmichUserId) ?? null) : null,
    unchanged: [],
    brokenLinks: [],
  };

  for (const link of existing) {
    (immichById.has(link.immichUserId) ? plan.unchanged : plan.brokenLinks).push(link);
  }

  for (const user of users) {
    if (linkedUserIds.has(user.id)) continue; // already recorded — handled above

    // An Officer account with no email cannot be matched or created: Immich has no other identifier and
    // requires one on create. Skipped rather than invented from the username, which would claim an address
    // the person does not own.
    if (!user.email) continue;

    const match = immichByEmail.get(normalize(user.email));
    if (match && !claimed.has(match.id)) {
      plan.link.push({ user, immich: match });
      claimed.add(match.id);
    } else if (!match) {
      plan.create.push(user);
    }
    // A match already claimed falls through deliberately: it is neither this user's account to adopt nor
    // safe to duplicate, and `leave` below reports it for a human to settle.
  }

  for (const immich of immichUsers) {
    if (claimed.has(immich.id)) continue;
    if (immich.id === adminImmichUserId) continue; // the connection's own account, reported as `self`
    plan.leave.push(immich);
  }

  return plan;
}

/** One line per outcome, for the log and the panel. Says what will happen before it happens. */
export function describePlan(plan: ReconcilePlan): string[] {
  const lines: string[] = [];
  for (const { user, immich } of plan.link) lines.push(`link ${user.email} → existing Immich "${immich.email}"`);
  for (const user of plan.create) lines.push(`create ${user.email}`);
  for (const immich of plan.leave) lines.push(`leave "${immich.email}" alone — no Officer account`);
  for (const broken of plan.brokenLinks) lines.push(`link for user ${broken.userId} is broken — Immich account is gone`);
  if (plan.self) lines.push(`"${plan.self.email}" is the account Officer connects as`);
  if (plan.unchanged.length) lines.push(`${plan.unchanged.length} already linked`);
  return lines;
}