// Request-scoped schema.org nodes a page or another layer adds to the page's
// one JSON-LD @graph (an ItemList on a listing, a FAQPage under a FAQ block).
// useCmsSeo merges them with the CMS's nodes by @id (mergeGraph), so a page
// never carries a second JSON-LD script. The list lives on the Nuxt app
// instance, not in useState: it is rebuilt by the components' setup on the
// server and again on the client, so it never travels in the payload.

import type { MaybeRefOrGetter, ShallowRef } from 'vue'
import type { SeoSchemaNode } from '../utils/types.ts'

interface SchemaEntry {
  id: number
  node: MaybeRefOrGetter<SeoSchemaNode | null | undefined>
}

type AppWithNodes = { _seoSchemaNodes?: ShallowRef<SchemaEntry[]>; _seoSchemaNodeSeq?: number }

function store(): { list: ShallowRef<SchemaEntry[]>; app: AppWithNodes } {
  const app = useNuxtApp() as unknown as AppWithNodes
  app._seoSchemaNodes ??= shallowRef<SchemaEntry[]>([])
  return { list: app._seoSchemaNodes, app }
}

/** The nodes registered for the current page, resolved (refs and getters read). */
export function useSchemaNodes(): () => SeoSchemaNode[] {
  const { list } = store()
  return () => list.value.map((e) => toValue(e.node)).filter((n): n is SeoSchemaNode => !!n && typeof n === 'object')
}

/**
 * Adds `node` (a plain object, a ref or a getter; null adds nothing) to the
 * page's @graph for as long as the calling component lives. A node with the
 * @id of a CMS node is merged into it, the CMS values first.
 */
export function useSchemaNode(node: MaybeRefOrGetter<SeoSchemaNode | null | undefined>): void {
  const { list, app } = store()
  const id = (app._seoSchemaNodeSeq = (app._seoSchemaNodeSeq ?? 0) + 1)
  list.value = [...list.value, { id, node }]
  if (import.meta.client) {
    onScopeDispose(() => {
      list.value = list.value.filter((e) => e.id !== id)
    })
  }
}