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

async function getAll() {
  return query('SELECT `key`, value, updated_at FROM settings ORDER BY `key`')
}

async function get(key) {
  const rows = await query('SELECT value FROM settings WHERE `key` = ? LIMIT 1', [key])
  return rows[0] ? rows[0].value : null
}

async function set(key, value, updatedBy = null) {
  await query(
    'INSERT INTO settings (`key`, value, updated_by) VALUES (?, ?, ?) ' +
      'ON DUPLICATE KEY UPDATE value = VALUES(value), updated_by = VALUES(updated_by)',
    [key, value, updatedBy],
  )
}

// One row WITH its provenance. `updated_by`/`updated_at` are already stored for
// every key; this is the only reader that needs them, because TEAMS.md §5.5.5
// makes the uploads acknowledgement a RECORDED consent rather than a displayed
// one, and "which admin accepted it, and when" is the question that has to be
// answerable afterwards.
async function getRow(key) {
  const rows = await query(
    'SELECT s.`key`, s.value, s.updated_by, s.updated_at, u.username AS updated_by_username '
      + 'FROM settings s LEFT JOIN users u ON u.id = s.updated_by WHERE s.`key` = ? LIMIT 1',
    [key],
  )
  return rows[0] || null
}

// Insert a default only if the key does not already exist.
async function seedDefault(key, value) {
  await query('INSERT IGNORE INTO settings (`key`, value) VALUES (?, ?)', [key, value])
}

/**
 * Take a one-shot guard, atomically. `true` means THIS caller wrote the row.
 *
 * The same `INSERT IGNORE` as `seedDefault`, and the difference is the whole
 * point: this one reports whether it won. A guard read with `get()` and written
 * later with `set()` is not a guard at all under concurrency — two processes
 * both read "absent" and both proceed — and this is used where proceeding twice
 * means seeding a rule group twice, i.e. two mails per event.
 *
 * The atomicity is the PRIMARY KEY's: exactly one INSERT can create a given
 * `key`, so exactly one caller sees `affectedRows === 1`. No transaction and no
 * lock, the same bargain `engagementWorker`'s claim makes.
 */
async function claim(key, value) {
  const res = await query('INSERT IGNORE INTO settings (`key`, value) VALUES (?, ?)', [key, value])
  return Number(res && res.affectedRows) === 1
}

// Delete a settings row. "Reset to defaults" for the theming/nav keys is the
// *absence* of a row, not a stored copy of the defaults — see
// docs/website/THEMING_AND_NAV.md §2. Deleting a key that was never set is a
// no-op, so reset is idempotent.
async function remove(key) {
  await query('DELETE FROM settings WHERE `key` = ?', [key])
}

module.exports = { getAll, get, getRow, set, seedDefault, claim, remove }