// src/layout/file-tree/useFileTree.ts
import { useState, useCallback, useEffect } from 'react'
import type { AutomergeUrl } from '../../storage/document-runtime-contract'
import type { Vault } from '../../plugin/vault'
import { TFolder, type TAbstractFile } from '../../plugin/files'
import { loadExpandedFolders, saveExpandedFolders } from './file-tree-persistence'

export function useFileTree(vault: Vault, storageKey?: string) {
  const [expanded, setExpanded] = useState<Set<AutomergeUrl>>(() => loadExpandedFolders(storageKey))
  const [, setVersion] = useState(0)

  const toggleExpanded = useCallback((url: AutomergeUrl) => {
    setExpanded(prev => {
      const next = new Set(prev)
      if (next.has(url)) { next.delete(url) } else { next.add(url) }
      saveExpandedFolders(next, storageKey)
      return next
    })
  }, [storageKey])

  const isExpanded = useCallback((url: AutomergeUrl) => expanded.has(url), [expanded])

  const getFolderChildren = useCallback((folderUrl: AutomergeUrl): TAbstractFile[] => {
    const file = vault.getAbstractFileByUrl(folderUrl)
    if (!file || !(file instanceof TFolder)) return []
    return file.children
  }, [vault])

  useEffect(() => {
    const bump = () => setVersion(v => v + 1)
    const createRef = vault.on('create', bump)
    const deleteRef = vault.on('delete', bump)
    const renameRef = vault.on('rename', bump)
    // 'modify' fires when a file's stat changes (e.g. mtime updated by
    // an Automerge change). Without this subscription, the date-sort
    // modes wouldn't re-sort when an existing file is edited.
    const modifyRef = vault.on('modify', bump)
    const statsRef = vault.on('reams-internal-stats-hydrated', bump)
    return () => {
      vault.offref(createRef)
      vault.offref(deleteRef)
      vault.offref(renameRef)
      vault.offref(modifyRef)
      vault.offref(statsRef)
    }
  }, [vault])

  return {
    rootChildren: vault.getRoot().children,
    toggleExpanded,
    isExpanded,
    getFolderChildren,
  }
}