/**
 * Prepares the chat's `@everyone`: it adds `chat_messages.mentions_everyone`,
 * and frees the name `everyone`, which no account may have any more.
 *
 * @module
 */

import type { DatabaseSync } from "node:sqlite";
import { EVERYONE, mentionsEveryone } from "../../../shared/mention.ts";
import { ROLE_PERMISSIONS } from "../../../shared/permissions.ts";

/**
 * Run once by `runMigrations`. The messages that a moderator or an admin
 * already sent with `@everyone` get the flag, so that editing one later
 * doesn't notify everyone of an old message; none is notified now. A user
 * named `everyone`, in any case, is renamed to the first free `everyone_2`,
 * `everyone_3`…, with no alias left behind, and an alias `everyone` is
 * dropped. Both are logged.
 */
export function up(db: DatabaseSync): void {
  const cols = db.prepare(`PRAGMA table_info(chat_messages);`).all() as {
    name: string;
  }[];
  if (!cols.some((c) => c.name === "mentions_everyone")) {
    db.exec(
      `ALTER TABLE chat_messages ADD COLUMN mentions_everyone INTEGER NOT NULL DEFAULT 0;`,
    );
  }

  const roles = Object.entries(ROLE_PERMISSIONS)
    .filter(([, perms]) => perms.includes("chat:everyone"))
    .map(([role]) => role);
  const messages = db.prepare(
    `SELECT m.id, m.body FROM chat_messages m JOIN users u ON u.id = m.user_id
      WHERE m.mentions_everyone = 0
        AND u.role IN (${roles.map(() => "?").join(", ")})
        AND m.body LIKE '%@%';`,
  ).all(...roles) as { id: string; body: string }[];
  const flag = db.prepare(
    `UPDATE chat_messages SET mentions_everyone = 1 WHERE id = ?;`,
  );
  for (const m of messages) {
    if (mentionsEveryone(m.body)) flag.run(m.id);
  }

  const taken = (name: string) =>
    !!db.prepare(
      `SELECT 1 FROM users WHERE lower(username) = lower(?)
       UNION ALL SELECT 1 FROM user_aliases WHERE lower(username) = lower(?);`,
    ).get(name, name);
  const user = db.prepare(
    `SELECT id, username FROM users WHERE lower(username) = ?;`,
  ).get(EVERYONE) as { id: string; username: string } | undefined;
  if (user) {
    let n = 2;
    while (taken(`${EVERYONE}_${n}`)) n++;
    const renamed = `${EVERYONE}_${n}`;
    db.prepare(`UPDATE users SET username = ? WHERE id = ?;`).run(
      renamed,
      user.id,
    );
    console.log(
      `[migrate] user "${user.username}" is now "${renamed}": @${EVERYONE} is reserved`,
    );
  }
  const alias = db.prepare(
    `DELETE FROM user_aliases WHERE lower(username) = ? RETURNING user_id;`,
  ).get(EVERYONE) as { user_id: string } | undefined;
  if (alias) {
    console.log(
      `[migrate] the former name "${EVERYONE}" of user ${alias.user_id} is dropped: @${EVERYONE} is reserved`,
    );
  }
}