import { parseSync } from '@babel/core'
import traverse from '@babel/traverse'
import * as t from '@babel/types'
import * as path from 'path'
import { readFileSync } from 'fs'

// https://github.com/layne0625/auto-export-plugin/blob/master/index.js
// path must be absolute
// not throw anything to make sure it work correctly with promise.all
export const isFileContainExport = ({
  fileName,
  currentWorkingDirectory,
  babelConfigPath,
}: {
  currentWorkingDirectory: string
  fileName: string
  babelConfigPath?: string
}): Promise<string | null> => {
  return new Promise(resolve => {
    const filePath = path.resolve(currentWorkingDirectory, fileName)
    const fileContent = readFileSync(filePath).toString()
    try {
      /**Test Reminder */
      let ast = null
      if (!babelConfigPath) {
        ast = parseSync(fileContent, {
          sourceType: 'module',
          filename: fileName,
          configFile: babelConfigPath,
        })
      } else {
        ast = parseSync(fileContent, {
          sourceType: 'module',
          filename: fileName,
        })
      }

      // this thing run synchoronously
      // @ts-ignore
      traverse(ast, {
        ExportAllDeclaration() {
          resolve(fileName)
        },
        // 主要处理export const a = 1这种写法
        ExportNamedDeclaration(path) {
          // 考虑到一个文件中可能变量声明语法较多但不一定是export，所以对于`export const a = 1`这种写法，没有采用像其他3种方式一样单独对类型做处理，而是在ExportNamedDeclaration中进一步做判断并处理
          if (t.isVariableDeclaration(path.node.declaration)) {
            resolve(fileName)
          }
        },

        // 处理 export function getOne(){}写法
        FunctionDeclaration(path) {
          if (t.isExportNamedDeclaration(path.parent)) {
            resolve(fileName)
          }
        },

        // 处理const A = 1; export { A }这种写法
        ExportSpecifier() {
          resolve(fileName)
        },

        // 处理export default写法， 如果是export default会用文件名作为变量名
        ExportDefaultDeclaration() {
          resolve(fileName)
        },
      })
      resolve(null)
    } catch (error) {
      console.log(`Fail to parse file "${filePath}". Err: "${error}"`)

      resolve(null)
    }
  })
}