"use client"

import { useEffect, useState } from "react"

import { trackingApi } from "@/lib/api/tracking"
import { TrackingSettings } from "@/types/tracking"

// One request per page load, shared by every component that asks; the Product Configuration
// page calls invalidateTrackingSettings() after a toggle so the next read is fresh.
let cached: Promise<TrackingSettings> | null = null

function load(): Promise<TrackingSettings> {
  // A failed read falls back to the server's own default (serial numbers on).
  cached ??= trackingApi.settings().catch(() => ({ serialNumbersEnabled: true }))
  return cached
}

export function invalidateTrackingSettings() {
  cached = null
}

/**
 * Product Configuration tracking switches (docs/ITEM_TRACKING_PLAN.md §8). `serialNumbersEnabled`
 * is null until loaded — callers treat that like "on", the server default.
 */
export function useTrackingSettings(): { serialNumbersEnabled: boolean | null } {
  const [settings, setSettings] = useState<TrackingSettings | null>(null)

  useEffect(() => {
    let cancelled = false
    load().then((s) => { if (!cancelled) setSettings(s) })
    return () => { cancelled = true }
  }, [])

  return { serialNumbersEnabled: settings?.serialNumbersEnabled ?? null }
}