// ── event_series — SQL only ────────────────────────────────────────────────
//
// EVENTS.md §D. The arc a definition may belong to. Phase 1 needed only the
// reads — `event_definitions.series_id` is a foreign key and the definition save
// path has to check it resolves — and Phase 4 adds the writes, because the
// calendar is what makes an arc visible and a form cannot offer a value nobody
// can create.
//
// `ordering` here places a SERIES among the others on the calendar. A
// definition's place WITHIN its arc is `event_definitions.series_order`, which
// is the column an editor drags; the two are deliberately different columns on
// different tables and the schema comment says so.

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

// `definition_count` is a correlated subquery rather than a join with a GROUP BY:
// the list is a handful of rows, and the delete path needs the same number to
// tell an operator what they are about to detach.
const SELECT_LIST = `
  SELECT s.*,
         (SELECT COUNT(*) FROM event_definitions d WHERE d.series_id = s.id) AS definition_count
    FROM event_series s
`

const list = async () => query(`${SELECT_LIST} ORDER BY s.ordering, s.name, s.id`)

const getById = async (id) => {
  const [row] = await query(`${SELECT_LIST} WHERE s.id = ?`, [id])
  return row || null
}

const getBySlug = async (slug) => {
  const [row] = await query(`${SELECT_LIST} WHERE s.slug = ?`, [slug])
  return row || null
}

const exists = async (id) => {
  const [row] = await query('SELECT id FROM event_series WHERE id = ?', [id])
  return Boolean(row)
}

/** Does any OTHER series hold this slug? The uniqueness pre-check. */
const slugTaken = async (slug, exceptId = null) => {
  const rows = exceptId
    ? await query('SELECT id FROM event_series WHERE slug = ? AND id <> ?', [slug, exceptId])
    : await query('SELECT id FROM event_series WHERE slug = ?', [slug])
  return rows.length > 0
}

const insert = async (s) => {
  const result = await query(
    `INSERT INTO event_series (name, slug, description, ordering, created_by)
     VALUES (?, ?, ?, ?, ?)`,
    [s.name, s.slug, s.description, s.ordering, s.created_by],
  )
  return Number(result.insertId)
}

const update = (id, s) =>
  query(
    `UPDATE event_series SET name = ?, slug = ?, description = ?, ordering = ? WHERE id = ?`,
    [s.name, s.slug, s.description, s.ordering, id],
  )

/**
 * A hard delete, and the one place in this feature that is one.
 *
 * A series is a label rather than authored content: nothing pins one, no run
 * references one, and `event_definitions.series_id` is `ON DELETE SET NULL`, so
 * removing a series detaches its definitions and destroys nothing. That is why
 * it is not archived the way a definition is — an archived label would be a
 * state every calendar query has to remember for no benefit. The model answers
 * with how many definitions were detached, so the operator learns what happened
 * rather than discovering it on the calendar.
 */
const remove = (id) => query('DELETE FROM event_series WHERE id = ?', [id])

module.exports = { list, getById, getBySlug, exists, slugTaken, insert, update, remove }