text: 'use strict'
  
  const Minipass = require('minipass')
  const path = require('path')
  const tar = require('tar')
  
  module.exports = extractStream
  module.exports._computeMode = computeMode
  
  function computeMode (fileMode, optMode, umask) {
    return (fileMode | optMode) & ~(umask || 0)
  }
  
  function pkgJsonTransform (spec, opts) {
    return entry => {
      if (entry.path === 'package.json') {
        const transformed = new Minipass()
        let str = ''
        entry.once('end', () => {
          const replaced = str.replace(
            /}\s*$/,
            `\n,"_resolved": ${
              JSON.stringify(opts.resolved || '')
            }\n,"_integrity": ${
              JSON.stringify(opts.integrity || '')
            }\n,"_from": ${
              JSON.stringify(spec.toString())
            }\n}\n`
          )
          transformed.write(replaced, () => transformed.end())
        })
        entry.on('error', e => transformed.emit('error'))
        entry.on('data', d => { str += d })
        return transformed
      }
    }
  }
  
  function extractStream (spec, dest, opts) {
    opts = opts || {}
    const sawIgnores = new Set()
    return tar.x({
      cwd: dest,
      filter: (name, entry) => !entry.header.type.match(/^.*link$/i),
      strip: 1,
      onwarn: msg => opts.log && opts.log.warn('tar', msg),
      uid: opts.uid,
      gid: opts.gid,
      transform: opts.resolved && pkgJsonTransform(spec, opts),
      onentry (entry) {
        if (entry.type.toLowerCase() === 'file') {
          entry.mode = computeMode(entry.mode, opts.fmode, opts.umask)
        } else if (entry.type.toLowerCase() === 'directory') {
          entry.mode = computeMode(entry.mode, opts.dmode, opts.umask)
        } else {
          entry.mode = computeMode(entry.mode, 0, opts.umask)
        }
  
        // Note: This mirrors logic in the fs read operations that are
        // employed during tarball creation, in the fstream-npm module.
        // It is duplicated here to handle tarballs that are created
        // using other means, such as system tar or git archive.
        if (entry.type.toLowerCase() === 'file') {
          const base = path.basename(entry.path)
          if (base === '.npmignore') {
            sawIgnores.add(entry.path)
          } else if (base === '.gitignore') {
            const npmignore = entry.path.replace(/\.gitignore$/, '.npmignore')
            if (!sawIgnores.has(npmignore)) {
              // Rename, may be clobbered later.
              entry.path = npmignore
            }
          }
        }
      }
    })
  }
  