import moment from "moment-timezone";
import { getRepository, In } from "typeorm";
import { DAYS, DBDateFormat, MINUTES, SECONDS, sleep } from "../../utils";
import { connection } from "../db";
import { SavedMessage } from "../entities/SavedMessage";

/**
 * How long message edits, deletions, etc. will include the original message content.
 * This is very heavy storage-wise, so keeping it as low as possible is ideal.
 */
const RETENTION_PERIOD = 1 * DAYS;
const BOT_MESSAGE_RETENTION_PERIOD = 30 * MINUTES;
const DELETED_MESSAGE_RETENTION_PERIOD = 5 * MINUTES;
const CLEAN_PER_LOOP = 100;

export async function cleanupMessages(): Promise<number> {
  let cleaned = 0;

  const messagesRepository = getRepository(SavedMessage);

  const deletedAtThreshold = moment.utc().subtract(DELETED_MESSAGE_RETENTION_PERIOD, "ms").format(DBDateFormat);
  const postedAtThreshold = moment.utc().subtract(RETENTION_PERIOD, "ms").format(DBDateFormat);
  const botPostedAtThreshold = moment.utc().subtract(BOT_MESSAGE_RETENTION_PERIOD, "ms").format(DBDateFormat);

  // SELECT + DELETE messages in batches
  // This is to avoid deadlocks that happened frequently when deleting with the same criteria as the select below
  // when a message was being inserted at the same time
  let ids: string[];
  do {
    const deletedMessageRows = await connection.query(
      `
      SELECT id
      FROM messages
      WHERE (
        deleted_at IS NOT NULL
        AND deleted_at <= ?
      )
      LIMIT ${CLEAN_PER_LOOP}
    `,
      [deletedAtThreshold],
    );

    const oldPostedRows = await connection.query(
      `
      SELECT id
      FROM messages
      WHERE (
        posted_at <= ?
        AND is_permanent = 0
      )
      LIMIT ${CLEAN_PER_LOOP}
    `,
      [postedAtThreshold],
    );

    const oldBotPostedRows = await connection.query(
      `
      SELECT id
      FROM messages
      WHERE (
        is_bot = 1
        AND posted_at <= ?
        AND is_permanent = 0
      )
      LIMIT ${CLEAN_PER_LOOP}
    `,
      [botPostedAtThreshold],
    );

    ids = Array.from(
      new Set([
        ...deletedMessageRows.map((r) => r.id),
        ...oldPostedRows.map((r) => r.id),
        ...oldBotPostedRows.map((r) => r.id),
      ]),
    );

    if (ids.length > 0) {
      await messagesRepository.delete({
        id: In(ids),
      });
      await sleep(1 * SECONDS);
    }

    cleaned += ids.length;
  } while (ids.length > 0);

  return cleaned;
}