/**
 * Invites: making them, and checking and claiming one on registration.
 *
 * @module
 */

import { randomBytes } from "node:crypto";
import { APIErrorCode } from "../../shared/api.ts";
import { APIException } from "../lib/api-exception.ts";
import { db } from "../db/connection.ts";
import { isInviteRow } from "../model/invite.ts";
import { UNUSED_INVITES_RETENTION_DAYS } from "../config.ts";

/**
 * Returns a short, opaque, URL-safe invite token (128 bits of entropy → 22
 * chars).
 */
function generateInviteToken(): string {
  return randomBytes(16).toString("base64url");
}

/** Makes an invite from `inviterId` and returns its token. */
export function createInvite(inviterId: string): string {
  const token = generateInviteToken();
  db.prepare(
    `INSERT INTO invites (token, inviter_id, created_at) VALUES (?, ?, ?);`,
  ).run(token, inviterId, new Date().toISOString());
  return token;
}

/**
 * Looks the token up, checks it has not been used and has not expired (same
 * 7-day window as the startup cleanup), and returns the inviter's id.
 *
 * Tokens are opaque random strings stored as the row's primary key. Invites
 * created before this scheme (full JWTs) are still stored verbatim in the
 * token column, so they continue to validate by direct lookup.
 *
 * @throws {APIException} 404 when the invite doesn't exist or has expired,
 * 409 when it has been used.
 */
export function validateInvite(token: string): string {
  const row = db.prepare(
    `SELECT token, inviter_id, used_at, created_at FROM invites WHERE token = ?;`,
  ).get(token);

  if (!row || !isInviteRow(row)) {
    throw new APIException(
      APIErrorCode.NOT_FOUND,
      404,
      "Invalid or expired invite",
    );
  }

  if (row.used_at !== null) {
    throw new APIException(
      APIErrorCode.VALIDATION_ERROR,
      409,
      "Invite already used",
    );
  }

  const expiresAt = new Date(row.created_at).getTime() +
    UNUSED_INVITES_RETENTION_DAYS * 24 * 60 * 60 * 1000;
  if (Date.now() > expiresAt) {
    throw new APIException(
      APIErrorCode.NOT_FOUND,
      404,
      "Invalid or expired invite",
    );
  }

  return row.inviter_id;
}

/**
 * Validates the token and marks it used in one step, returning the inviter's
 * id.
 * Claim before the (async) account creation, not after: checking first and
 * marking later lets parallel registrations all pass the check on one invite.
 *
 * @throws {APIException} 404 when the invite doesn't exist or has expired,
 * 409 when it has been used.
 */
export function claimInvite(token: string): string {
  const inviterId = validateInvite(token);
  const result = db.prepare(
    `UPDATE invites SET used_at = ? WHERE token = ? AND used_at IS NULL;`,
  ).run(new Date().toISOString(), token);
  if (result.changes === 0) {
    throw new APIException(
      APIErrorCode.VALIDATION_ERROR,
      409,
      "Invite already used",
    );
  }
  return inviterId;
}

/** Hands a claimed invite back when the account it was claimed for failed. */
export function releaseInvite(token: string): void {
  db.prepare(`UPDATE invites SET used_at = NULL WHERE token = ?;`).run(token);
}