import { mkdirSync, readFileSync, writeFileSync } from 'node:fs'

export interface RolePanel {
  channelID: string
  /** unicode emoji, or `name:id` for custom emoji */
  emoji: string
  guildID: string
  /** users known to have the reaction, kept in step with role grants */
  reactors: Set<string>
  roleID: string
}

type StoredPanel = Omit<RolePanel, 'reactors'> & { reactors?: string[] }

const DATA_DIR = new URL('../data/', import.meta.url)
const FILE = new URL('role-panels.json', DATA_DIR)

function load(): Map<string, RolePanel> {
  let raw: string
  try {
    raw = readFileSync(FILE, 'utf8')
  } catch (error) {
    if ((error as NodeJS.ErrnoException).code === 'ENOENT') return new Map()
    throw error
  }
  return new Map(
    Object.entries(JSON.parse(raw) as Record<string, StoredPanel>).map(([messageID, panel]) => [
      messageID,
      // files written before reactors were tracked
      { ...panel, reactors: new Set(panel.reactors ?? []) }
    ])
  )
}

function save(): void {
  mkdirSync(DATA_DIR, { recursive: true })
  const json = JSON.stringify(
    Object.fromEntries(panels),
    (_, value: unknown) => (value instanceof Set ? [...value] : value),
    2
  )
  writeFileSync(FILE, json)
}

/** Panel registry, keyed by panel message ID. */
export const panels = load()

export function setPanel(messageID: string, panel: RolePanel): void {
  panels.set(messageID, panel)
  save()
}

export function deletePanel(messageID: string): boolean {
  if (!panels.delete(messageID)) return false
  save()
  return true
}

export function setReactor(panel: RolePanel, userID: string, reacted: boolean): void {
  if (reacted) panel.reactors.add(userID)
  else panel.reactors.delete(userID)
  save()
}