// ── Zone presets (PLAN_REDESIGNS §3.1, D195, D210) ──────────────────────────
//
// An admin's own named set of ZoneManager flags and settings, for one server,
// several, or the fleet. A zone step offers the presets as the options field's
// dropdown; picking one COPIES its line into the step (D210), so a preset edited
// later changes no published event. That is also why a preset needs no history
// and deleting one is harmless.

const db = require('./zones.db')
const options = require('./zoneOptions')

const NAME_MAX = 64

class ZonePresetError extends Error {
  constructor(message, status = 400) {
    super(message)
    this.status = status
  }
}

/**
 * The page's whole state: each server with what it said about its zone mods,
 * the flags the form draws (every server's, grouped), the settings, and the
 * presets.
 */
async function describe() {
  const [servers, presets] = await Promise.all([db.listZoneServers(), db.listPresets()])
  const union = new Map()
  for (const s of servers) {
    for (const f of (s.zoneManager && s.zoneManager.flags) || []) {
      if (!union.has(f.toLowerCase())) union.set(f.toLowerCase(), f)
    }
  }
  return {
    servers: servers.map((s) => ({
      ...s,
      zoneManager: s.zoneManager ? { version: s.zoneManager.version, flagCount: (s.zoneManager.flags || []).length, flags: s.zoneManager.flags } : null,
    })),
    groups: options.grouped([...union.values()]),
    settings: Object.entries(options.SETTINGS).map(([key, spec]) => ({ key, ...spec })),
    presets: presets.map((p) => ({ ...p, line: options.format(p) })),
  }
}

/** Does a preset cover this server? */
function covers(preset, serverId) {
  return preset.allServers || preset.servers.includes(serverId)
}

/**
 * Checks a preset against every server it covers. A flag must be on each covered
 * server that has said which flags it has; a server that has not said (never
 * reached, no ZoneManager yet) is skipped, and the plugin checks the flag when a
 * step runs there.
 */
async function validate(input, id = null) {
  const name = String((input && input.name) || '').trim()
  if (!name || name.length > NAME_MAX) throw new ZonePresetError(`a preset's name is 1 to ${NAME_MAX} characters`)

  const allServers = input.allServers === true
  const requested = Array.isArray(input.servers) ? [...new Set(input.servers.map(String))] : []
  if (!allServers && requested.length === 0) throw new ZonePresetError('a preset is for at least one server, or for every server')

  const servers = await db.listZoneServers()
  const byId = new Map(servers.map((s) => [s.id, s]))
  for (const s of requested) {
    if (!byId.has(s)) throw new ZonePresetError(`no server "${s}"`, 404)
  }

  const checked = options.check({ flags: input.flags || [], settings: input.settings || {} })
  if (!checked.ok) throw new ZonePresetError(checked.error)

  const covered = allServers ? servers : requested.map((s) => byId.get(s))
  let flags = checked.flags
  for (const s of covered) {
    const known = s.zoneManager && s.zoneManager.flags
    if (!known || known.length === 0) continue
    const onServer = options.check({ flags }, known)
    if (!onServer.ok) throw new ZonePresetError(`${onServer.error.replace("this server's", `${s.name || s.id}'s`)}`)
    flags = onServer.flags
  }

  // Two presets of one name on one server would be two rows in the step's
  // dropdown nobody could tell apart. Across servers it is allowed (D189).
  const mine = { allServers, servers: requested }
  const others = (await db.listPresets()).filter((p) => p.id !== id && p.name.toLowerCase() === name.toLowerCase())
  for (const other of others) {
    if (allServers && other.allServers) throw new ZonePresetError(`a preset called "${name}" is already on every server`, 409)
    const shared = servers.find((s) => covers(mine, s.id) && covers(other, s.id))
    if (shared) throw new ZonePresetError(`a preset called "${name}" is already on ${shared.name || shared.id}`, 409)
  }

  return { name, flags, settings: checked.settings, allServers, servers: allServers ? [] : requested }
}

async function create(input, userId = null) {
  const clean = await validate(input)
  const id = await db.savePreset(clean, userId)
  return db.getPreset(id)
}

async function update(id, input) {
  const existing = await db.getPreset(id)
  if (!existing) throw new ZonePresetError('no such preset', 404)
  const clean = await validate(input, existing.id)
  await db.savePreset({ ...clean, id: existing.id })
  return db.getPreset(existing.id)
}

async function remove(id) {
  const existing = await db.getPreset(id)
  if (!existing) throw new ZonePresetError('no such preset', 404)
  await db.deletePreset(existing.id)
  return true
}

/**
 * The zone step's dropdown (D210): one row per preset, whose VALUE is the line
 * of text the step keeps. Grouped by the servers each is for, so an admin
 * authoring a step for one server can see which presets were made for it.
 */
async function optionRows() {
  const [presets, servers] = await Promise.all([db.listPresets(), db.listZoneServers()])
  const nameOf = new Map(servers.map((s) => [s.id, s.name || s.id]))
  return presets.map((p) => ({
    value: options.format(p),
    label: p.name,
    group: p.allServers ? 'Every server' : p.servers.map((s) => nameOf.get(s) || s).join(', '),
  }))
}

/** What one server's last hello said about ZoneManager and ZoneDomes, or null. */
async function serverZoneMods(serverId) {
  return (await db.listZoneServers()).find((s) => s.id === serverId) || null
}

module.exports = { ZonePresetError, describe, create, update, remove, optionRows, serverZoneMods, covers }