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

const listByUser = (userId) =>
  query(
    'SELECT stream_id, channel, mode FROM notification_channel_prefs WHERE user_id = ? ORDER BY stream_id, channel',
    [userId],
  )

// One (user, stream, channel) row. Upsert rather than insert-or-update in app
// code: the primary key is exactly the triple, so MariaDB decides, and two
// concurrent PUTs from a phone and a browser cannot race into a duplicate-key
// error.
const upsert = (userId, streamId, channel, mode) =>
  query(
    `INSERT INTO notification_channel_prefs (user_id, stream_id, channel, mode)
     VALUES (?, ?, ?, ?)
     ON DUPLICATE KEY UPDATE mode = VALUES(mode)`,
    [userId, streamId, channel, mode],
  )

// Every push row this user holds that is NOT in `keep`, set to 'off'. The legacy
// whole-set PUT's other half: it says "these streams and no others", and the
// rows it is silent about have to stop meaning 'instant'.
//
// It sets rather than deletes, so a user's explicit "no" survives a later change
// to push's `defaultMode` (§3.1 / channels.js). Deleting would fold "I turned
// this off" back into "I never said", and those are the same thing only for as
// long as the default happens to be 'off'.
async function offPushExcept(userId, keep) {
  if (!keep.length) {
    return query(
      "UPDATE notification_channel_prefs SET mode = 'off' WHERE user_id = ? AND channel = 'push' AND mode <> 'off'",
      [userId],
    )
  }
  const marks = keep.map(() => '?').join(', ')
  return query(
    `UPDATE notification_channel_prefs SET mode = 'off'
      WHERE user_id = ? AND channel = 'push' AND mode <> 'off' AND stream_id NOT IN (${marks})`,
    [userId, ...keep],
  )
}

/**
 * Turn one channel off for every named stream — the deployment-wide unsubscribe
 * (ENGAGEMENT.md Phase 6).
 *
 * It WRITES a row per stream rather than updating the rows that happen to exist,
 * and the difference is the same one `offPushExcept` argues: absence means the
 * channel's `defaultMode`, so updating only what is there would leave a user
 * unsubscribed today and re-subscribed the day a channel ships a non-off default.
 * An unsubscribe has to be a statement, not the absence of one.
 */
async function offForChannel(userId, channel, streamIds) {
  const ids = [...new Set(streamIds)].filter((s) => typeof s === 'string' && s)
  if (!ids.length) return null
  const values = ids.map(() => '(?, ?, ?, ?)').join(', ')
  const params = ids.flatMap((streamId) => [userId, streamId, channel, 'off'])
  return query(
    `INSERT INTO notification_channel_prefs (user_id, stream_id, channel, mode)
     VALUES ${values}
     ON DUPLICATE KEY UPDATE mode = VALUES(mode)`,
    params,
  )
}

module.exports = { listByUser, upsert, offPushExcept, offForChannel }