// ── event_versions — SQL only ──────────────────────────────────────────────
//
// EVENTS.md §D. Immutable: there is an insert and there are reads, and there is
// deliberately no update and no delete. A run pins a version, and that pin is
// what makes the run reproducible and an audit answerable after the definition
// has been edited underneath it.

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

const hydrate = (row) => row && { ...row, spec: parseJson(row.spec, null) }

const listForDefinition = async (definitionId) =>
  (
    await query(
      `SELECT v.id, v.definition_id, v.version, v.published_at, v.published_by, u.username AS published_by_username
         FROM event_versions v
         LEFT JOIN users u ON u.id = v.published_by
        WHERE v.definition_id = ?
        ORDER BY v.version DESC`,
      [definitionId],
    )
  ).map((row) => row)

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

/**
 * The next version number for a definition.
 *
 * Read separately and then INSERTed, which is a read-then-write — and it is safe
 * only because `UNIQUE (definition_id, version)` is behind it. Two publishes
 * racing for version 4 is one 1062 the caller reports, not two rows called 4.
 * The unique index is the mechanism; this query is the ergonomics.
 */
const nextVersion = async (definitionId) => {
  const [row] = await query(
    'SELECT COALESCE(MAX(version), 0) + 1 AS next FROM event_versions WHERE definition_id = ?',
    [definitionId],
  )
  return Number(row?.next || 1)
}

const insert = async (definitionId, version, spec, userId) => {
  const result = await query(
    'INSERT INTO event_versions (definition_id, version, spec, published_by) VALUES (?, ?, ?, ?)',
    [definitionId, version, JSON.stringify(spec), userId],
  )
  return result.insertId
}

/**
 * Record that a dry run passed against this version (Phase 6).
 *
 * A version is immutable in every respect that describes the EVENT — its spec,
 * its number, who published it. These two columns describe something that
 * happened to it afterwards, which is why they can be written at all: a pass is
 * a fact about a review, not a change to the plan reviewed.
 *
 * Deliberately not idempotent-checked: verifying twice stamps the second one, and
 * the later reviewer is the more useful answer to "who last looked at this
 * before it ran unattended".
 */
const markVerified = async (id, userId, at = new Date()) => {
  const result = await query(
    'UPDATE event_versions SET verified_at = ?, verified_by = ? WHERE id = ?',
    [at, userId, id],
  )
  return (result.affectedRows || 0) > 0
}

module.exports = { listForDefinition, getById, nextVersion, insert, markVerified }