'use strict'

const fs = require('fs')
const path = require('path')

/**
 * Webpack 4 ��ʶ�� package.json �� exports ��·����@aws-sdk v3 ����ʹ�� exports��
 * �轫 @aws-sdk/<pkg>/<subpath> ӳ�䵽ʵ�� dist �ļ������� browser ��������
 */
function pickExportTarget(exportConfig) {
  if (!exportConfig || typeof exportConfig !== 'object') {
    return null
  }
  const browser = exportConfig.browser
  if (browser) {
    if (typeof browser === 'string') {
      return browser
    }
    return browser.import || browser.require || browser.module
  }
  return exportConfig.module || exportConfig.import || exportConfig.require || exportConfig.node
}

function buildAwsSdkAliases(projectRoot) {
  const aliases = {}
  const awsSdkDir = path.join(projectRoot, 'node_modules', '@aws-sdk')
  if (!fs.existsSync(awsSdkDir)) {
    return aliases
  }

  for (const pkgName of fs.readdirSync(awsSdkDir)) {
    const pkgRoot = path.join(awsSdkDir, pkgName)
    const pkgJsonPath = path.join(pkgRoot, 'package.json')
    if (!fs.existsSync(pkgJsonPath)) {
      continue
    }

    let pkgJson
    try {
      pkgJson = require(pkgJsonPath)
    } catch (e) {
      continue
    }

    const exportsField = pkgJson.exports
    if (!exportsField || typeof exportsField !== 'object') {
      continue
    }

    for (const [subpath, exportConfig] of Object.entries(exportsField)) {
      if (subpath === '.' || subpath === './package.json') {
        continue
      }
      if (!subpath.startsWith('./')) {
        continue
      }

      const target = pickExportTarget(exportConfig)
      if (!target || typeof target !== 'string') {
        continue
      }

      const aliasKey = `@aws-sdk/${pkgName}/${subpath.slice(2)}`
      aliases[aliasKey] = path.resolve(pkgRoot, target)
    }
  }

  return aliases
}

module.exports = { buildAwsSdkAliases }