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

module.exports = function(packagePath) {
  const nodeModulesPath = path.join(packagePath, 'node_modules')
  const nodeModulesBackupPath = path.join(packagePath, 'node_modules.bak')

  if (fs.existsSync(nodeModulesBackupPath)) {
    throw new Error("Cannot back up " + nodeModulesPath + "; " + nodeModulesBackupPath + " already exists")
  }

  // some packages may have no node_modules after deduping, but we still want
  // to "back-up" and later restore that fact
  if (!fs.existsSync(nodeModulesPath)) {
    const msg = "Skipping backing up " + nodeModulesPath + " as it does not exist"
    console.log(msg.gray)

    const restore = function stubRestoreNodeModules() {
      if (fs.existsSync(nodeModulesPath)) {
        fs.removeSync(nodeModulesPath)
      }
    }

    return {restore, nodeModulesPath, nodeModulesBackupPath}
  }

  fs.copySync(nodeModulesPath, nodeModulesBackupPath)

  const restore = function restoreNodeModules() {
    if (!fs.existsSync(nodeModulesBackupPath)) {
      throw new Error("Cannot restore " + nodeModulesPath + "; " + nodeModulesBackupPath + " does not exist")
    }
    
    if (fs.existsSync(nodeModulesPath)) {
      fs.removeSync(nodeModulesPath)
    }
    fs.renameSync(nodeModulesBackupPath, nodeModulesPath)
  }

  return {restore, nodeModulesPath, nodeModulesBackupPath}
}