/**
 * The light in-app popup stack: its lifetime, its ordering, and its bound.
 *
 * The lifetime is the user's, read from the store at the moment a card is armed:
 * the settings page offers a few delays plus "never", and re-arming after a hover
 * picks the current choice up. `0` means the card waits for the user instead of a
 * timer.
 *
 * @module @dsh-plugin/session-notify/client/core/toasts
 */

import { TOAST_DURATION_MS, TOAST_LIMIT } from '../constants.js'

/**
 * Build the popup stack over one store.
 * @param deps - the plugin store, and the copy table a candidate is rendered with.
 * @returns the stack's operations, including the three the popup element calls back into.
 */
export function createToastStack({ store, copy }) {
  const timers = new Map()
  /** Cards the pointer is resting on: they carry no timer until it leaves. */
  const held = new Set()
  let seq = 0

  /** The configured lifetime, falling back to the default for a value this version cannot use. */
  const lifetime = () => {
    const configured = store.getSnapshot().dismissAfterMs
    return typeof configured === 'number' && configured >= 0 ? configured : TOAST_DURATION_MS
  }

  /** Drop one popup and cancel its lifetime timer. */
  const closeToast = (id) => {
    held.delete(id)
    const timer = timers.get(id)
    if (timer !== undefined) {
      clearTimeout(timer)
      timers.delete(id)
    }
    const snapshot = store.getSnapshot()
    if (!snapshot.toasts.some((toast) => toast.id === id)) return
    store.set({ ...snapshot, toasts: snapshot.toasts.filter((toast) => toast.id !== id) })
  }

  /**
   * Arm one popup's lifetime; hovering calls `hold` first, then this again.
   * A lifetime of `0` arms nothing: the card stays until it is dismissed.
   */
  const armToast = (id) => {
    held.delete(id)
    const timer = timers.get(id)
    if (timer !== undefined) clearTimeout(timer)
    timers.delete(id)
    const duration = lifetime()
    if (duration === 0) return
    timers.set(id, setTimeout(() => closeToast(id), duration))
  }

  /** Pause one popup's lifetime while the pointer rests on it. */
  const holdToast = (id) => {
    held.add(id)
    const timer = timers.get(id)
    if (timer === undefined) return
    clearTimeout(timer)
    timers.delete(id)
  }

  /**
   * Apply the current lifetime to the cards already on screen.
   *
   * Changing the setting restarts the countdown for what is visible — otherwise
   * a card raised under the old lifetime would still close on the old schedule.
   * A held card is left alone: the pointer is on it, so nothing may close it.
   */
  const rearmAll = () => {
    for (const toast of store.getSnapshot().toasts) {
      if (!held.has(toast.id)) armToast(toast.id)
    }
  }

  /**
   * Show one light in-app popup: the trigger as the title, the conversation
   * and its detail as the description, so the heading says what happened and
   * the line under it says where.
   */
  const showToast = (candidate) => {
    const notice = copy.copyFor(candidate)
    seq += 1
    const toast = {
      id: `dsn-${String(seq)}`,
      kind: notice.kind,
      title: notice.title,
      body: notice.body,
      sessionId: candidate.sessionId,
    }
    const snapshot = store.getSnapshot()
    const next = [toast, ...snapshot.toasts]
    for (const dropped of next.slice(TOAST_LIMIT)) {
      const timer = timers.get(dropped.id)
      if (timer !== undefined) {
        clearTimeout(timer)
        timers.delete(dropped.id)
      }
      held.delete(dropped.id)
    }
    store.set({ ...snapshot, toasts: next.slice(0, TOAST_LIMIT) })
    armToast(toast.id)
  }

  /** Cancel every lifetime timer: the plugin is being disposed, so nothing may fire later. */
  const dispose = () => {
    for (const timer of timers.values()) clearTimeout(timer)
    timers.clear()
    held.clear()
  }

  return { showToast, closeToast, armToast, holdToast, rearmAll, dispose }
}