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

// JSON columns come back from the driver already parsed on some MariaDB/driver
// combinations and as a string on others (it depends on whether the column is a
// real JSON type or the LONGTEXT + CHECK alias MariaDB implements it as). Every
// read below goes through this, so no caller has to know which it got.
function parseJson(value, fallback) {
  if (value === null || value === undefined) return fallback
  if (typeof value !== 'string') return value
  try {
    return JSON.parse(value)
  } catch {
    return fallback
  }
}

const hydrate = (row) =>
  row && {
    ...row,
    enabled: Boolean(row.enabled),
    channels: parseJson(row.channels, []),
    template_keys: parseJson(row.template_keys, {}),
    conditions: parseJson(row.conditions, null),
    cancel_on: parseJson(row.cancel_on, []),
  }

const list = async () =>
  (await query('SELECT * FROM engagement_rules ORDER BY trigger_id, name, id')).map(hydrate)

const getById = async (id) => {
  const [row] = await query('SELECT * FROM engagement_rules WHERE id = ?', [id])
  return hydrate(row)
}

/**
 * Every ENABLED rule for one trigger. The engine's hot path: one indexed read
 * per emit, and `idx_engr_trigger (trigger_id, enabled)` is exactly this query.
 */
const enabledForTrigger = async (triggerId) =>
  (await query('SELECT * FROM engagement_rules WHERE trigger_id = ? AND enabled = 1', [triggerId])).map(hydrate)

/**
 * Every enabled rule that names `triggerId` in its `cancel_on`.
 *
 * A JSON_CONTAINS rather than a scan: `cancel_on` is a small array on a small
 * table, but this runs on EVERY emit — including the overwhelming majority that
 * cancel nothing — so it must not be a full table read of the rule set.
 */
const enabledCancelledBy = async (triggerId) =>
  (
    await query(
      "SELECT * FROM engagement_rules WHERE enabled = 1 AND cancel_on IS NOT NULL AND JSON_CONTAINS(cancel_on, JSON_QUOTE(?))",
      [triggerId],
    )
  ).map(hydrate)

const insert = async (rule) => {
  const result = await query(
    `INSERT INTO engagement_rules
       (trigger_id, name, enabled, audience, audience_segment_id, max_sends_per_hour,
        channels, template_keys, conditions, cooldown_seconds, delay_seconds, cancel_on, updated_by)
     VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`,
    [
      rule.trigger_id,
      rule.name,
      rule.enabled ? 1 : 0,
      rule.audience,
      rule.audience_segment_id,
      rule.max_sends_per_hour,
      JSON.stringify(rule.channels),
      JSON.stringify(rule.template_keys),
      rule.conditions === null ? null : JSON.stringify(rule.conditions),
      rule.cooldown_seconds,
      rule.delay_seconds,
      JSON.stringify(rule.cancel_on || []),
      rule.updated_by,
    ],
  )
  return result.insertId
}

const update = (id, rule) =>
  query(
    `UPDATE engagement_rules
        SET name = ?, enabled = ?, audience = ?, audience_segment_id = ?, max_sends_per_hour = ?,
            channels = ?, template_keys = ?, conditions = ?, cooldown_seconds = ?,
            delay_seconds = ?, cancel_on = ?, updated_by = ?
      WHERE id = ?`,
    [
      rule.name,
      rule.enabled ? 1 : 0,
      rule.audience,
      rule.audience_segment_id,
      rule.max_sends_per_hour,
      JSON.stringify(rule.channels),
      JSON.stringify(rule.template_keys),
      rule.conditions === null ? null : JSON.stringify(rule.conditions),
      rule.cooldown_seconds,
      rule.delay_seconds,
      JSON.stringify(rule.cancel_on || []),
      rule.updated_by,
      id,
    ],
  )

const remove = (id) => query('DELETE FROM engagement_rules WHERE id = ?', [id])

/** Does any rule still point at this segment? The check before a segment delete. */
const countUsingSegment = async (segmentId) => {
  const [row] = await query(
    'SELECT COUNT(*) AS n FROM engagement_rules WHERE audience_segment_id = ?',
    [segmentId],
  )
  return Number(row?.n || 0)
}

module.exports = {
  list,
  getById,
  enabledForTrigger,
  enabledCancelledBy,
  insert,
  update,
  remove,
  countUsingSegment,
  parseJson,
}