import { randomBytes } from "node:crypto";
import { APIErrorCode, APIException } from "../model/interfaces.ts";
import { db, isInviteRow } from "../model/db.ts";
import { UNUSED_INVITES_RETENTION_DAYS } from "../config.ts";

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

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). Returns the inviterId on success;
 * throws APIException otherwise.
 *
 * 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.
 */
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;
}

/**
 * Marks the token as used. Call this only after the user has been created.
 */
export function redeemInvite(token: string): void {
  db.prepare(
    `UPDATE invites SET used_at = ? WHERE token = ?;`,
  ).run(new Date().toISOString(), token);
}