/**
 * Makes usernames and emails unique regardless of case. Usernames were unique
 * only as typed, so "Bob" and "bob" could both sign up, and a mention, which
 * looks names up in lower case, then reached one of them at random. Emails
 * had no constraint at all: two sign-ups racing past the service's check could
 * share an address, and password resets are looked up by address.
 *
 * @module
 */

import type { DatabaseSync } from "node:sqlite";

/**
 * Run once by `runMigrations`. It refuses to run, naming the clashes, when two
 * accounts already share a name or an address in some case: which one keeps
 * it is for whoever runs the site to decide, by editing one of them.
 */
export function up(db: DatabaseSync): void {
  for (const column of ["username", "email"]) {
    const clashes = db.prepare(
      `SELECT lower(${column}) AS value FROM users GROUP BY lower(${column}) HAVING COUNT(*) > 1;`,
    ).all() as { value: string }[];
    if (clashes.length > 0) {
      throw new Error(
        `Several accounts share a ${column} in different cases: ${
          clashes.map((c) => c.value).join(", ")
        }. Change all but one of each, then restart.`,
      );
    }
  }
  db.exec(`
    DROP INDEX IF EXISTS idx_users_username_lower;
    CREATE UNIQUE INDEX IF NOT EXISTS idx_users_username_lower ON users(lower(username));
    CREATE UNIQUE INDEX IF NOT EXISTS idx_users_email_lower    ON users(lower(email));
  `);
}