import type { CollectionAfterChangeHook, CollectionAfterDeleteHook } from 'payload'

import type { I18nConfig } from '../i18n/index.js'

import { buildLocalizedPath, getLocaleCodes } from '../i18n/index.js'

type RevalidateFn = (path: string) => void

type BuildRevalidateHookArgs = {
  config: I18nConfig
  /** Home slug (string or per-locale map) — home revalidates the root. */
  homeSlug?: Record<string, string> | string
  /**
   * next/cache revalidatePath, INJECTED by the project. The plugin never imports
   * next/cache itself — that would crash when Payload runs as plain Node
   * (generate:importmap). The project passes it: `revalidatePath` from 'next/cache'.
   */
  revalidatePath: RevalidateFn
}

type DocWithSlug = { slug?: unknown }

/** Resolve a doc's path in one locale (root for home). Null if no slug there. */
function pathForLocale(
  doc: DocWithSlug,
  locale: string,
  config: I18nConfig,
  homeSlug?: Record<string, string> | string,
): null | string {
  const slugField = doc.slug
  const slug =
    typeof slugField === 'string'
      ? slugField
      : slugField && typeof slugField === 'object'
        ? ((slugField as Record<string, unknown>)[locale] as string | undefined)
        : undefined
  if (!slug) {return null}
  return buildLocalizedPath({ config, homeSlug, locale, slugs: { [locale]: slug } }) ?? null
}

/**
 * Builds afterChange + afterDelete hooks that revalidate a page's ISR cache when
 * an editor saves or deletes it — so changes appear immediately instead of
 * waiting for the revalidate window. Without this, ISR means editors wait; with
 * it, ISR is usable for a CMS.
 *
 * Handles every locale, the root (home), AND a changed slug (revalidates both the
 * old and new path so neither goes stale). revalidatePath is injected — the
 * plugin never imports next/cache (safe under generate:importmap / plain Node).
 *
 *   // in your Media/Pages collection config, from a project file that CAN import next/cache:
 *   import { revalidatePath } from 'next/cache'
 *   import { buildRevalidateHook } from '@intecion/ipal-kit'
 *   const { afterChange, afterDelete } = buildRevalidateHook({ revalidatePath, config: i18nConfig })
 *   // hooks: { afterChange: [afterChange], afterDelete: [afterDelete] }
 */
export function buildRevalidateHook({
  config,
  homeSlug,
  revalidatePath,
}: BuildRevalidateHookArgs): {
  afterChange: CollectionAfterChangeHook
  afterDelete: CollectionAfterDeleteHook
} {
  const locales = getLocaleCodes(config)

  const afterChange: CollectionAfterChangeHook = ({ doc, previousDoc }) => {
    const seen = new Set<string>()
    for (const locale of locales) {
      // New path.
      const newPath = pathForLocale(doc as DocWithSlug, locale, config, homeSlug)
      if (newPath && !seen.has(newPath)) {
        revalidatePath(newPath)
        seen.add(newPath)
      }
      // Old path, if the slug changed — so the old URL doesn't serve stale content.
      if (previousDoc) {
        const oldPath = pathForLocale(previousDoc as DocWithSlug, locale, config, homeSlug)
        if (oldPath && oldPath !== newPath && !seen.has(oldPath)) {
          revalidatePath(oldPath)
          seen.add(oldPath)
        }
      }
    }
    return doc
  }

  const afterDelete: CollectionAfterDeleteHook = ({ doc }) => {
    const seen = new Set<string>()
    for (const locale of locales) {
      const path = pathForLocale(doc as DocWithSlug, locale, config, homeSlug)
      if (path && !seen.has(path)) {
        revalidatePath(path)
        seen.add(path)
      }
    }
    return doc
  }

  return { afterChange, afterDelete }
}