// ── Event series — the arc ─────────────────────────────────────────────────
//
// EVENTS.md §D and §I. "Royal Spy Mission → Risky Partner → Message From the
// Void" is continuity that exists nowhere in the tooling this feature replaces
// (§ "What the real calendar shows, and what it is missing": *no series or
// recurrence field*). One small table buys it, and this is the policy half.
//
// **Why the writes are `admin, editor` and not `admin`.** A series is authoring,
// and it is the same act as writing the definition that goes in it — §N2's
// narrow gate is about *committing the deployment to a run* (publish, start),
// which naming an arc does not do. An editor who can write the events but not
// the arc they belong to would have to ask an admin to type a title.
//
// **A slug is derived once and then frozen**, exactly as a definition's is: the
// public arc page lives at `/events/series/:slug` (Phase 14), and a slug that
// moved would break every link to it. Renaming the series is free.

const db = require('./eventSeries.db')
const { slugify, uniqueSlug } = require('../teams/teamSlug')

const MAX_NAME = 160
const MAX_DESCRIPTION = 2000

const trimOrNull = (v, max) => {
  if (v === undefined || v === null) return null
  const s = String(v).trim()
  return s === '' ? null : s.slice(0, max)
}

const list = () => db.list()

const getById = (id) => db.getById(id)

async function validate(input, { existing = null } = {}) {
  const errors = []
  const body = input && typeof input === 'object' ? input : {}

  const name = trimOrNull(body.name, MAX_NAME)
  if (!name) errors.push('name is required')

  const description = trimOrNull(body.description, MAX_DESCRIPTION)

  const orderingRaw = body.ordering === undefined ? (existing?.ordering ?? 0) : body.ordering
  const ordering = Number(orderingRaw)
  if (!Number.isInteger(ordering) || ordering < 0 || ordering > 9999) {
    errors.push('ordering must be an integer 0..9999')
  }

  if (errors.length) return { ok: false, errors }
  return { ok: true, series: { name, description, ordering } }
}

async function create(input, userId) {
  const checked = await validate(input)
  if (!checked.ok) return { ok: false, status: 400, errors: checked.errors }

  // The taken set is read here rather than inside `uniqueSlug` because that
  // helper is pure — the same shape the team and definition paths use.
  const taken = (await db.list()).map((s) => s.slug)
  const slug = uniqueSlug(checked.series.name, taken, { fallback: 'series' })

  const id = await db.insert({ ...checked.series, slug, created_by: userId || null })
  return { ok: true, status: 201, series: await db.getById(id) }
}

async function update(id, input, userId) {
  const existing = await db.getById(id)
  if (!existing) return { ok: false, status: 404, errors: ['no such series'] }

  const checked = await validate(input, { existing })
  if (!checked.ok) return { ok: false, status: 400, errors: checked.errors }

  // The slug is the existing one, deliberately: renaming a series must not move
  // the address its arc page lives at.
  await db.update(id, { ...checked.series, slug: existing.slug })
  return { ok: true, status: 200, series: await db.getById(id) }
}

/**
 * Delete a series, detaching whatever belonged to it.
 *
 * The count comes back so the caller can say *"3 events were detached"* rather
 * than leaving an operator to notice on the calendar. `series_id` is
 * `ON DELETE SET NULL`, so nothing is destroyed and re-attaching is a dropdown.
 */
async function remove(id) {
  const existing = await db.getById(id)
  if (!existing) return { ok: false, status: 404, errors: ['no such series'] }
  await db.remove(id)
  return { ok: true, status: 200, detached: Number(existing.definition_count || 0) }
}

module.exports = { list, getById, validate, create, update, remove, slugify, MAX_NAME }