// SQL for the per-Team activity feed (TEAMS.md §4.2). Statements only; every
// decision about what a caller may SEE lives in teamActivity.model.js.

const { query } = require('../../utils/db')

const ACTIVITY_COLUMNS = `
  id, team_id, source, kind, summary, visibility,
  actor_member_key, actor_user_id, payload, occurred_at, created_at`

/**
 * Insert one item, idempotently when it carries a dedupe key.
 *
 * INSERT IGNORE against uq_team_activity_dedupe is what makes replay safe: a
 * sidecar reconnect backfills a window of events it already delivered, and
 * without this every reconnect would double-post the feed. The same trick
 * `shard_events` uses, for the same reason.
 *
 * The unique key is (team_id, dedupe_key) and MariaDB treats NULL as distinct in
 * a unique index, so items WITHOUT a key never collide with each other — an
 * un-keyed push is always an insert, which is the documented contract (§4.1:
 * `dedupeKey` is optional and "makes replay idempotent", so omitting it opts out).
 *
 * IGNORE would also swallow a genuine error — a bad FK, an over-long summary. The
 * model validates and truncates before calling, so what reaches here can only fail
 * on the dedupe key, and `affectedRows` reports which happened.
 */
async function insert(item) {
  const res = await query(
    `INSERT IGNORE INTO team_activity
       (team_id, source, kind, summary, visibility, actor_member_key, actor_user_id, payload, occurred_at, dedupe_key)
     VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`,
    [
      item.teamId,
      item.source,
      item.kind,
      item.summary,
      item.visibility,
      item.actorMemberKey,
      item.actorUserId,
      item.payload === null ? null : JSON.stringify(item.payload),
      new Date(item.occurredAt),
      item.dedupeKey,
    ],
  )
  return Number(res.affectedRows) > 0
}

/**
 * One page of a Team's feed, already narrowed to the visibilities the caller may
 * see.
 *
 * `visibilities` is always supplied by the model and never by a request
 * parameter — a caller naming its own visibility filter is the whole bug this
 * table's ENUM exists to prevent. Ordered newest first by `occurred_at`, the
 * game's clock, not `created_at`: a backfill that arrives late still sorts where
 * it happened.
 */
async function page(teamId, visibilities, { limit, offset }) {
  const slots = visibilities.map(() => '?').join(', ')
  return query(
    `SELECT ${ACTIVITY_COLUMNS} FROM team_activity
      WHERE team_id = ? AND visibility IN (${slots})
      ORDER BY occurred_at DESC, id DESC
      LIMIT ? OFFSET ?`,
    [teamId, ...visibilities, limit, offset],
  )
}

/** Total matching rows, for the same filter — so a client can page honestly. */
async function count(teamId, visibilities) {
  const slots = visibilities.map(() => '?').join(', ')
  const rows = await query(
    `SELECT COUNT(*) AS n FROM team_activity WHERE team_id = ? AND visibility IN (${slots})`,
    [teamId, ...visibilities],
  )
  return Number(rows[0] ? rows[0].n : 0)
}

/** Everything older than the retention horizon, across every Team. */
async function deleteOlderThan(days) {
  const res = await query(
    'DELETE FROM team_activity WHERE occurred_at < (NOW() - INTERVAL ? DAY)',
    [days],
  )
  return Number(res.affectedRows) || 0
}

/**
 * Which Teams currently exceed the per-Team row cap, and by how much.
 *
 * Asked first so the trim only runs for Teams that need it. A feed fed by a game
 * loop is the obvious unbounded-growth failure (§4.2), and on a shard with one
 * busy guild and fifty quiet ones this keeps the nightly job proportional to the
 * problem rather than to the number of Teams.
 */
async function overCap(cap) {
  return query(
    `SELECT team_id, COUNT(*) AS n FROM team_activity
      GROUP BY team_id HAVING n > ?`,
    [cap],
  )
}

/**
 * Trim one Team back to the newest `cap` rows.
 *
 * Expressed as "delete everything at or below the id of the cap-th newest row"
 * rather than as a correlated subquery on the same table, which MariaDB refuses
 * inside a DELETE (error 1093). The derived table is what makes it legal — the
 * subquery is materialised before the delete runs.
 */
async function trimToCap(teamId, cap) {
  const rows = await query(
    `SELECT id FROM team_activity
      WHERE team_id = ? ORDER BY occurred_at DESC, id DESC LIMIT 1 OFFSET ?`,
    [teamId, cap],
  )
  if (!rows[0]) return 0
  const res = await query(
    'DELETE FROM team_activity WHERE team_id = ? AND id <= ?',
    [teamId, rows[0].id],
  )
  return Number(res.affectedRows) || 0
}

module.exports = {
  insert,
  page,
  count,
  deleteOlderThan,
  overCap,
  trimToCap,
}