import { promises as fs } from 'node:fs'
import { dirname, isAbsolute, relative, resolve, sep, join } from 'node:path'
import { randomUUID } from 'node:crypto'
import type { RevertChange } from '@shared/revert'
import { getRevertChanges } from '@shared/revert'
import type { ChatMessage } from '@shared/types'

async function replaceFile(path: string, content: string | null): Promise<void> {
  if (content === null) { await fs.unlink(path); return }
  const temporary = join(dirname(path), `.ycode-restore-${randomUUID()}.tmp`)
  try { await fs.writeFile(temporary, content, 'utf8'); await fs.rename(temporary, path) }
  finally { await fs.unlink(temporary).catch(() => undefined) }
}
/** Validate every current file before applying any change; roll back if a write fails. */
export async function restoreWorkspaceFiles(workspace: string, changes: RevertChange[]): Promise<() => Promise<void>> {
  const root = await fs.realpath(workspace)
  const validated: RevertChange[] = []
  for (const change of changes) {
    const path = await fs.realpath(resolve(change.path))
    const rel = relative(root, path)
    if (!rel || rel === '..' || rel.startsWith(`..${sep}`) || isAbsolute(rel)) throw new Error('恢复文件不在当前工作区内')
    if (await fs.readFile(path, 'utf8') !== change.after) throw new Error(`文件已被外部修改，未执行恢复：${rel}`)
    validated.push({ ...change, path })
  }
  const applied: RevertChange[] = []
  const undo = async (): Promise<void> => {
    for (const change of [...applied].reverse()) await replaceFile(change.path, change.after)
  }
  try {
    for (const change of validated) {
      if (await fs.readFile(change.path, 'utf8') !== change.after) throw new Error('文件在恢复前已变化')
      await replaceFile(change.path, change.before)
      applied.push(change)
    }
  } catch (error) { await undo(); throw error }
  return undo
}

/**
 * 编辑提交前的产物回退（原版 userMessage.edit.hint：产物回退至此消息前版本）。
 * 返回撤销函数；该消息之后没有可回退的写入时返回 undefined。
 * 记录不完整时由 getRevertChanges 抛错，调用方应中止提交而不是静默保留文件修改。
 */
export async function rollbackEditedArtifacts(workspace: string, messages: ChatMessage[], userMessageId: string): Promise<(() => Promise<void>) | undefined> {
  const changes = getRevertChanges(messages, userMessageId)
  if (!changes.length) return undefined
  return restoreWorkspaceFiles(workspace, changes)
}