import type { Event, TreeDataProvider, WorkspaceFolder } from 'vscode'
import type { ExcludeSetting } from './fileEntries'
import * as path from 'node:path'
import { EventEmitter, FileType, ThemeIcon, TreeItem, TreeItemCollapsibleState, Uri, workspace } from 'vscode'
import { createExcludeMatcher, sortEntries } from './fileEntries'

export interface FileNode {
  uri: Uri
  folder: WorkspaceFolder
  isDirectory: boolean
  isRoot: boolean
}

/** 批量改文件（git checkout、构建输出）时合并成一次刷新。 */
const REFRESH_DELAY_MS = 300

/**
 * 侧栏的工作区文件树：每个工作区文件夹一个根节点，只看和打开。
 * 节点用 resourceUri，图标、git 改动颜色都由 VS Code 按文件图标主题和 SCM 装饰自动加上。
 */
export class FileTreeProvider implements TreeDataProvider<FileNode> {
  private readonly changed = new EventEmitter<void>()
  readonly onDidChangeTreeData: Event<void> = this.changed.event
  private readonly disposables: { dispose: () => unknown }[]
  private timer: NodeJS.Timeout | undefined

  /** @param openCommand 点文件时执行的命令，参数是文件 Uri */
  constructor(private readonly openCommand: string) {
    // 只关心增删：文件内容变化不影响树的结构
    const watcher = workspace.createFileSystemWatcher('**/*', false, true, false)
    this.disposables = [
      this.changed,
      watcher,
      watcher.onDidCreate(() => this.scheduleRefresh()),
      watcher.onDidDelete(() => this.scheduleRefresh()),
      workspace.onDidChangeWorkspaceFolders(() => this.refresh()),
      workspace.onDidChangeConfiguration((e) => {
        if (e.affectsConfiguration('files.exclude'))
          this.refresh()
      }),
    ]
  }

  refresh(): void {
    clearTimeout(this.timer)
    this.timer = undefined
    this.changed.fire()
  }

  getTreeItem(node: FileNode): TreeItem {
    if (!node.isDirectory) {
      const item = new TreeItem(node.uri, TreeItemCollapsibleState.None)
      item.iconPath = ThemeIcon.File
      item.command = { command: this.openCommand, title: '打开', arguments: [node.uri] }
      return item
    }
    const item = new TreeItem(node.uri, node.isRoot ? TreeItemCollapsibleState.Expanded : TreeItemCollapsibleState.Collapsed)
    item.iconPath = ThemeIcon.Folder
    if (node.isRoot)
      item.label = node.folder.name
    return item
  }

  async getChildren(node?: FileNode): Promise<FileNode[]> {
    if (!node)
      return (workspace.workspaceFolders ?? []).map(folder => ({ uri: folder.uri, folder, isDirectory: true, isRoot: true }))

    let entries: [string, FileType][]
    try {
      entries = await workspace.fs.readDirectory(node.uri)
    }
    catch {
      return [] // 目录刚被删掉或没有权限
    }
    const excluded = createExcludeMatcher(workspace.getConfiguration('files', node.folder).get<ExcludeSetting>('exclude'))
    const names = new Set(entries.map(([name]) => name))
    const dir = path.posix.relative(node.folder.uri.path, node.uri.path)
    return sortEntries(entries.map(([name, type]) => ({ name, isDirectory: (type & FileType.Directory) !== 0 })))
      .filter(entry => !excluded(dir ? `${dir}/${entry.name}` : entry.name, names))
      .map(entry => ({ uri: Uri.joinPath(node.uri, entry.name), folder: node.folder, isDirectory: entry.isDirectory, isRoot: false }))
  }

  dispose(): void {
    clearTimeout(this.timer)
    for (const disposable of this.disposables)
      disposable.dispose()
  }

  private scheduleRefresh(): void {
    clearTimeout(this.timer)
    this.timer = setTimeout(() => this.refresh(), REFRESH_DELAY_MS)
  }
}