"use client"

/**
 * Campus-only greeting chrome — plain type vs the brand-tinted cover banner.
 *
 * Shell-global like `use-home-variant`: it is a preference about `/home/campus`,
 * not product-scoped state.
 */

import * as React from "react"

import {
  getStorageItem,
  setStorageItem,
  subscribeToStorageKey,
} from "@exxatdesignux/ui/lib/persisted-state"

export type CampusBannerMode = "greeting" | "full"

export const CAMPUS_BANNER_MODES: {
  id: CampusBannerMode
  label: string
  description: string
}[] = [
  {
    id: "greeting",
    label: "Greeting banner",
    description: "Greeting and school picker only",
  },
  {
    id: "full",
    label: "Full banner",
    description: "Brand cover with greeting anchored at the foot",
  },
]

const STORAGE_KEY = "campus-banner-mode"
const VERSION = 1
const DEFAULT_MODE: CampusBannerMode = "full"

export function isCampusBannerMode(value: unknown): value is CampusBannerMode {
  return value === "greeting" || value === "full"
}

const listeners = new Set<() => void>()
let snapshot: CampusBannerMode | null = null
let hydrated = false

function subscribe(onChange: () => void) {
  listeners.add(onChange)
  const unsubscribeStorage = subscribeToStorageKey(STORAGE_KEY, () => {
    hydrated = false
    onChange()
  })
  return () => {
    listeners.delete(onChange)
    unsubscribeStorage()
  }
}

function read(): CampusBannerMode {
  if (hydrated && snapshot) return snapshot
  hydrated = true

  const raw = getStorageItem(STORAGE_KEY)
  if (raw) {
    try {
      const parsed: unknown = JSON.parse(raw)
      if (
        typeof parsed === "object" &&
        parsed !== null &&
        (parsed as { v?: number }).v === VERSION &&
        isCampusBannerMode((parsed as { d?: unknown }).d)
      ) {
        snapshot = (parsed as { d: CampusBannerMode }).d
        return snapshot
      }
    } catch {
      // Unparseable payload — fall through to the default.
    }
  }

  snapshot = DEFAULT_MODE
  return snapshot
}

export function setCampusBannerMode(next: CampusBannerMode) {
  snapshot = next
  hydrated = true
  setStorageItem(STORAGE_KEY, JSON.stringify({ v: VERSION, d: next }))
  for (const listener of listeners) listener()
}

export function useCampusBannerMode(): CampusBannerMode {
  return React.useSyncExternalStore(subscribe, read, () => DEFAULT_MODE)
}