text: # Copyright 2013-2019 Lawrence Livermore National Security, LLC and other
  # Spack Project Developers. See the top-level COPYRIGHT file for details.
  #
  # SPDX-License-Identifier: (Apache-2.0 OR MIT)
  
  import codecs
  import os
  import re
  import tarfile
  import shutil
  import tempfile
  import hashlib
  from contextlib import closing
  import ruamel.yaml as yaml
  
  import json
  
  from six.moves.urllib.error import URLError
  
  import llnl.util.tty as tty
  from llnl.util.filesystem import mkdirp, install_tree
  
  import spack.cmd
  import spack.fetch_strategy as fs
  import spack.util.gpg as gpg_util
  import spack.relocate as relocate
  import spack.util.spack_yaml as syaml
  import spack.mirror
  import spack.util.url as url_util
  import spack.util.web as web_util
  
  from spack.spec import Spec
  from spack.stage import Stage
  from spack.util.gpg import Gpg
  from spack.util.executable import ProcessError
  
  _build_cache_relative_path = 'build_cache'
  
  BUILD_CACHE_INDEX_TEMPLATE = '''
  <html>
  <head>
    <title>{title}</title>
  </head>
  <body>
  <ul>
  {path_list}
  </ul>
  </body>
  </html>
  '''
  
  BUILD_CACHE_INDEX_ENTRY_TEMPLATE = '  <li><a href="{path}">{path}</a></li>'
  
  
  class NoOverwriteException(Exception):
      """
      Raised when a file exists and must be overwritten.
      """
  
      def __init__(self, file_path):
          err_msg = "\n%s\nexists\n" % file_path
          err_msg += "Use -f option to overwrite."
          super(NoOverwriteException, self).__init__(err_msg)
  
  
  class NoGpgException(spack.error.SpackError):
      """
      Raised when gpg2 is not in PATH
      """
      pass
  
  
  class NoKeyException(spack.error.SpackError):
      """
      Raised when gpg has no default key added.
      """
      pass
  
  
  class PickKeyException(spack.error.SpackError):
      """
      Raised when multiple keys can be used to sign.
      """
  
      def __init__(self, keys):
          err_msg = "Multi keys available for signing\n%s\n" % keys
          err_msg += "Use spack buildcache create -k <key hash> to pick a key."
          super(PickKeyException, self).__init__(err_msg)
  
  
  class NoVerifyException(spack.error.SpackError):
      """
      Raised if file fails signature verification.
      """
      pass
  
  
  class NoChecksumException(spack.error.SpackError):
      """
      Raised if file fails checksum verification.
      """
      pass
  
  
  class NewLayoutException(spack.error.SpackError):
      """
      Raised if directory layout is different from buildcache.
      """
      pass
  
  
  def has_gnupg2():
      try:
          gpg_util.Gpg.gpg()('--version', output=os.devnull)
          return True
      except ProcessError:
          return False
  
  
  def build_cache_relative_path():
      return _build_cache_relative_path
  
  
  def build_cache_prefix(prefix):
      return os.path.join(prefix, build_cache_relative_path())
  
  
  def buildinfo_file_name(prefix):
      """
      Filename of the binary package meta-data file
      """
      name = os.path.join(prefix, ".spack/binary_distribution")
      return name
  
  
  def read_buildinfo_file(prefix):
      """
      Read buildinfo file
      """
      filename = buildinfo_file_name(prefix)
      with open(filename, 'r') as inputfile:
          content = inputfile.read()
          buildinfo = yaml.load(content)
      return buildinfo
  
  
  def write_buildinfo_file(prefix, workdir, rel=False):
      """
      Create a cache file containing information
      required for the relocation
      """
      text_to_relocate = []
      binary_to_relocate = []
      link_to_relocate = []
      blacklist = (".spack", "man")
      # Do this at during tarball creation to save time when tarball unpacked.
      # Used by make_package_relative to determine binaries to change.
      for root, dirs, files in os.walk(prefix, topdown=True):
          dirs[:] = [d for d in dirs if d not in blacklist]
          for filename in files:
              path_name = os.path.join(root, filename)
              m_type, m_subtype = relocate.mime_type(path_name)
              if os.path.islink(path_name):
                  link = os.readlink(path_name)
                  if os.path.isabs(link):
                      # Relocate absolute links into the spack tree
                      if link.startswith(spack.store.layout.root):
                          rel_path_name = os.path.relpath(path_name, prefix)
                          link_to_relocate.append(rel_path_name)
                      else:
                          msg = 'Absolute link %s to %s ' % (path_name, link)
                          msg += 'outside of stage %s ' % prefix
                          msg += 'cannot be relocated.'
                          tty.warn(msg)
  
              if relocate.needs_binary_relocation(m_type, m_subtype):
                  if not filename.endswith('.o'):
                      rel_path_name = os.path.relpath(path_name, prefix)
                      binary_to_relocate.append(rel_path_name)
              if relocate.needs_text_relocation(m_type, m_subtype):
                  rel_path_name = os.path.relpath(path_name, prefix)
                  text_to_relocate.append(rel_path_name)
  
      # Create buildinfo data and write it to disk
      buildinfo = {}
      buildinfo['relative_rpaths'] = rel
      buildinfo['buildpath'] = spack.store.layout.root
      buildinfo['spackprefix'] = spack.paths.prefix
      buildinfo['relative_prefix'] = os.path.relpath(
          prefix, spack.store.layout.root)
      buildinfo['relocate_textfiles'] = text_to_relocate
      buildinfo['relocate_binaries'] = binary_to_relocate
      buildinfo['relocate_links'] = link_to_relocate
      filename = buildinfo_file_name(workdir)
      with open(filename, 'w') as outfile:
          outfile.write(syaml.dump(buildinfo, default_flow_style=True))
  
  
  def tarball_directory_name(spec):
      """
      Return name of the tarball directory according to the convention
      <os>-<architecture>/<compiler>/<package>-<version>/
      """
      return "%s/%s/%s-%s" % (spec.architecture,
                              str(spec.compiler).replace("@", "-"),
                              spec.name, spec.version)
  
  
  def tarball_name(spec, ext):
      """
      Return the name of the tarfile according to the convention
      <os>-<architecture>-<package>-<dag_hash><ext>
      """
      return "%s-%s-%s-%s-%s%s" % (spec.architecture,
                                   str(spec.compiler).replace("@", "-"),
                                   spec.name,
                                   spec.version,
                                   spec.dag_hash(),
                                   ext)
  
  
  def tarball_path_name(spec, ext):
      """
      Return the full path+name for a given spec according to the convention
      <tarball_directory_name>/<tarball_name>
      """
      return os.path.join(tarball_directory_name(spec),
                          tarball_name(spec, ext))
  
  
  def checksum_tarball(file):
      # calculate sha256 hash of tar file
      block_size = 65536
      hasher = hashlib.sha256()
      with open(file, 'rb') as tfile:
          buf = tfile.read(block_size)
          while len(buf) > 0:
              hasher.update(buf)
              buf = tfile.read(block_size)
      return hasher.hexdigest()
  
  
  def sign_tarball(key, force, specfile_path):
      # Sign the packages if keys available
      if not has_gnupg2():
          raise NoGpgException(
              "gpg2 is not available in $PATH .\n"
              "Use spack install gnupg and spack load gnupg.")
      else:
          if key is None:
              keys = Gpg.signing_keys()
              if len(keys) == 1:
                  key = keys[0]
              if len(keys) > 1:
                  raise PickKeyException(str(keys))
              if len(keys) == 0:
                  msg = "No default key available for signing.\n"
                  msg += "Use spack gpg init and spack gpg create"
                  msg += " to create a default key."
                  raise NoKeyException(msg)
      if os.path.exists('%s.asc' % specfile_path):
          if force:
              os.remove('%s.asc' % specfile_path)
          else:
              raise NoOverwriteException('%s.asc' % specfile_path)
      Gpg.sign(key, specfile_path, '%s.asc' % specfile_path)
  
  
  def generate_package_index(cache_prefix):
      """Create the build cache index page.
  
      Creates (or replaces) the "index.html" page at the location given in
      cache_prefix.  This page contains a link for each binary package (*.yaml)
      and signing key (*.key) under cache_prefix.
      """
      tmpdir = tempfile.mkdtemp()
      try:
          index_html_path = os.path.join(tmpdir, 'index.html')
          file_list = (
              entry
              for entry in web_util.list_url(cache_prefix)
              if (entry.endswith('.yaml')
                  or entry.endswith('.key')))
  
          with open(index_html_path, 'w') as f:
              f.write(BUILD_CACHE_INDEX_TEMPLATE.format(
                  title='Spack Package Index',
                  path_list='\n'.join(
                      BUILD_CACHE_INDEX_ENTRY_TEMPLATE.format(path=path)
                      for path in file_list)))
  
          web_util.push_to_url(
              index_html_path,
              url_util.join(cache_prefix, 'index.html'),
              keep_original=False,
              extra_args={'ContentType': 'text/html'})
      finally:
          shutil.rmtree(tmpdir)
  
  
  def build_tarball(spec, outdir, force=False, rel=False, unsigned=False,
                    allow_root=False, key=None, regenerate_index=False):
      """
      Build a tarball from given spec and put it into the directory structure
      used at the mirror (following <tarball_directory_name>).
      """
      if not spec.concrete:
          raise ValueError('spec must be concrete to build tarball')
  
      # set up some paths
      tmpdir = tempfile.mkdtemp()
      cache_prefix = build_cache_prefix(tmpdir)
  
      tarfile_name = tarball_name(spec, '.tar.gz')
      tarfile_dir = os.path.join(cache_prefix, tarball_directory_name(spec))
      tarfile_path = os.path.join(tarfile_dir, tarfile_name)
      spackfile_path = os.path.join(
          cache_prefix, tarball_path_name(spec, '.spack'))
  
      remote_spackfile_path = url_util.join(
          outdir, os.path.relpath(spackfile_path, tmpdir))
  
      mkdirp(tarfile_dir)
      if web_util.url_exists(remote_spackfile_path):
          if force:
              web_util.remove_url(remote_spackfile_path)
          else:
              raise NoOverwriteException(url_util.format(remote_spackfile_path))
  
      # need to copy the spec file so the build cache can be downloaded
      # without concretizing with the current spack packages
      # and preferences
      spec_file = os.path.join(spec.prefix, ".spack", "spec.yaml")
      specfile_name = tarball_name(spec, '.spec.yaml')
      specfile_path = os.path.realpath(
          os.path.join(cache_prefix, specfile_name))
  
      remote_specfile_path = url_util.join(
          outdir, os.path.relpath(specfile_path, os.path.realpath(tmpdir)))
  
      if web_util.url_exists(remote_specfile_path):
          if force:
              web_util.remove_url(remote_specfile_path)
          else:
              raise NoOverwriteException(url_util.format(remote_specfile_path))
  
      # make a copy of the install directory to work with
      workdir = os.path.join(tempfile.mkdtemp(), os.path.basename(spec.prefix))
      install_tree(spec.prefix, workdir, symlinks=True)
  
      # create info for later relocation and create tar
      write_buildinfo_file(spec.prefix, workdir, rel=rel)
  
      # optionally make the paths in the binaries relative to each other
      # in the spack install tree before creating tarball
      if rel:
          try:
              make_package_relative(workdir, spec, allow_root)
          except Exception as e:
              shutil.rmtree(workdir)
              shutil.rmtree(tarfile_dir)
              shutil.rmtree(tmpdir)
              tty.die(e)
      else:
          try:
              make_package_placeholder(workdir, spec, allow_root)
          except Exception as e:
              shutil.rmtree(workdir)
              shutil.rmtree(tarfile_dir)
              shutil.rmtree(tmpdir)
              tty.die(e)
  
      # create compressed tarball of the install prefix
      with closing(tarfile.open(tarfile_path, 'w:gz')) as tar:
          tar.add(name='%s' % workdir,
                  arcname='%s' % os.path.basename(spec.prefix))
      # remove copy of install directory
      shutil.rmtree(workdir)
  
      # get the sha256 checksum of the tarball
      checksum = checksum_tarball(tarfile_path)
  
      # add sha256 checksum to spec.yaml
      with open(spec_file, 'r') as inputfile:
          content = inputfile.read()
          spec_dict = yaml.load(content)
      bchecksum = {}
      bchecksum['hash_algorithm'] = 'sha256'
      bchecksum['hash'] = checksum
      spec_dict['binary_cache_checksum'] = bchecksum
      # Add original install prefix relative to layout root to spec.yaml.
      # This will be used to determine is the directory layout has changed.
      buildinfo = {}
      buildinfo['relative_prefix'] = os.path.relpath(
          spec.prefix, spack.store.layout.root)
      spec_dict['buildinfo'] = buildinfo
      spec_dict['full_hash'] = spec.full_hash()
  
      tty.debug('The full_hash ({0}) of {1} will be written into {2}'.format(
          spec_dict['full_hash'],
          spec.name,
          url_util.format(remote_specfile_path)))
      tty.debug(spec.tree())
  
      with open(specfile_path, 'w') as outfile:
          outfile.write(syaml.dump(spec_dict))
  
      # sign the tarball and spec file with gpg
      if not unsigned:
          sign_tarball(key, force, specfile_path)
      # put tarball, spec and signature files in .spack archive
      with closing(tarfile.open(spackfile_path, 'w')) as tar:
          tar.add(name='%s' % tarfile_path, arcname='%s' % tarfile_name)
          tar.add(name='%s' % specfile_path, arcname='%s' % specfile_name)
          if not unsigned:
              tar.add(name='%s.asc' % specfile_path,
                      arcname='%s.asc' % specfile_name)
  
      # cleanup file moved to archive
      os.remove(tarfile_path)
      if not unsigned:
          os.remove('%s.asc' % specfile_path)
  
      web_util.push_to_url(
          spackfile_path, remote_spackfile_path, keep_original=False)
      web_util.push_to_url(
          specfile_path, remote_specfile_path, keep_original=False)
  
      try:
          # create an index.html for the build_cache directory so specs can be
          # found
          if regenerate_index:
              generate_package_index(url_util.join(
                  outdir, os.path.relpath(cache_prefix, tmpdir)))
      finally:
          shutil.rmtree(tmpdir)
  
      return None
  
  
  def download_tarball(spec):
      """
      Download binary tarball for given package into stage area
      Return True if successful
      """
      if not spack.mirror.MirrorCollection():
          tty.die("Please add a spack mirror to allow " +
                  "download of pre-compiled packages.")
  
      tarball = tarball_path_name(spec, '.spack')
  
      for mirror in spack.mirror.MirrorCollection().values():
          url = url_util.join(
              mirror.fetch_url, _build_cache_relative_path, tarball)
  
          # stage the tarball into standard place
          stage = Stage(url, name="build_cache", keep=True)
          try:
              stage.fetch()
              return stage.save_filename
          except fs.FetchError:
              continue
  
      return None
  
  
  def make_package_relative(workdir, spec, allow_root):
      """
      Change paths in binaries to relative paths. Change absolute symlinks
      to relative symlinks.
      """
      prefix = spec.prefix
      buildinfo = read_buildinfo_file(workdir)
      old_path = buildinfo['buildpath']
      orig_path_names = list()
      cur_path_names = list()
      for filename in buildinfo['relocate_binaries']:
          orig_path_names.append(os.path.join(prefix, filename))
          cur_path_names.append(os.path.join(workdir, filename))
      if spec.architecture.platform == 'darwin':
          relocate.make_macho_binaries_relative(cur_path_names, orig_path_names,
                                                old_path, allow_root)
      else:
          relocate.make_elf_binaries_relative(cur_path_names, orig_path_names,
                                              old_path, allow_root)
      orig_path_names = list()
      cur_path_names = list()
      for filename in buildinfo.get('relocate_links', []):
          orig_path_names.append(os.path.join(prefix, filename))
          cur_path_names.append(os.path.join(workdir, filename))
      relocate.make_link_relative(cur_path_names, orig_path_names)
  
  
  def make_package_placeholder(workdir, spec, allow_root):
      """
      Check if package binaries are relocatable.
      Change links to placeholder links.
      """
      prefix = spec.prefix
      buildinfo = read_buildinfo_file(workdir)
      cur_path_names = list()
      for filename in buildinfo['relocate_binaries']:
          cur_path_names.append(os.path.join(workdir, filename))
      relocate.check_files_relocatable(cur_path_names, allow_root)
  
      cur_path_names = list()
      for filename in buildinfo.get('relocate_links', []):
          cur_path_names.append(os.path.join(workdir, filename))
      relocate.make_link_placeholder(cur_path_names, workdir, prefix)
  
  
  def relocate_package(workdir, spec, allow_root):
      """
      Relocate the given package
      """
      buildinfo = read_buildinfo_file(workdir)
      new_path = str(spack.store.layout.root)
      new_prefix = str(spack.paths.prefix)
      old_path = str(buildinfo['buildpath'])
      old_prefix = str(buildinfo.get('spackprefix',
                                     '/not/in/buildinfo/dictionary'))
      rel = buildinfo.get('relative_rpaths', False)
      if rel:
          return
  
      tty.msg("Relocating package from",
              "%s to %s." % (old_path, new_path))
      path_names = set()
      for filename in buildinfo['relocate_textfiles']:
          path_name = os.path.join(workdir, filename)
          # Don't add backup files generated by filter_file during install step.
          if not path_name.endswith('~'):
              path_names.add(path_name)
      relocate.relocate_text(path_names, oldpath=old_path,
                             newpath=new_path, oldprefix=old_prefix,
                             newprefix=new_prefix)
      # If the binary files in the package were not edited to use
      # relative RPATHs, then the RPATHs need to be relocated
      if rel:
          if old_path != new_path:
              files_to_relocate = list(filter(
                  lambda pathname: not relocate.file_is_relocatable(
                      pathname, paths_to_relocate=[old_path, old_prefix]),
                  map(lambda filename: os.path.join(workdir, filename),
                      buildinfo['relocate_binaries'])))
  
              if len(old_path) < len(new_path) and files_to_relocate:
                  tty.debug('Cannot do a binary string replacement with padding '
                            'for package because %s is longer than %s.' %
                            (new_path, old_path))
              else:
                  for path_name in files_to_relocate:
                      relocate.replace_prefix_bin(path_name, old_path, new_path)
      else:
          path_names = set()
          for filename in buildinfo['relocate_binaries']:
              path_name = os.path.join(workdir, filename)
              path_names.add(path_name)
          if spec.architecture.platform == 'darwin':
              relocate.relocate_macho_binaries(path_names, old_path,
                                               new_path, allow_root)
          else:
              relocate.relocate_elf_binaries(path_names, old_path,
                                             new_path, allow_root)
          path_names = set()
          for filename in buildinfo.get('relocate_links', []):
              path_name = os.path.join(workdir, filename)
              path_names.add(path_name)
          relocate.relocate_links(path_names, old_path, new_path)
  
  
  def extract_tarball(spec, filename, allow_root=False, unsigned=False,
                      force=False):
      """
      extract binary tarball for given package into install area
      """
      if os.path.exists(spec.prefix):
          if force:
              shutil.rmtree(spec.prefix)
          else:
              raise NoOverwriteException(str(spec.prefix))
  
      tmpdir = tempfile.mkdtemp()
      stagepath = os.path.dirname(filename)
      spackfile_name = tarball_name(spec, '.spack')
      spackfile_path = os.path.join(stagepath, spackfile_name)
      tarfile_name = tarball_name(spec, '.tar.gz')
      tarfile_path = os.path.join(tmpdir, tarfile_name)
      specfile_name = tarball_name(spec, '.spec.yaml')
      specfile_path = os.path.join(tmpdir, specfile_name)
  
      with closing(tarfile.open(spackfile_path, 'r')) as tar:
          tar.extractall(tmpdir)
      if not unsigned:
          if os.path.exists('%s.asc' % specfile_path):
              try:
                  Gpg.verify('%s.asc' % specfile_path, specfile_path)
              except Exception as e:
                  shutil.rmtree(tmpdir)
                  tty.die(e)
          else:
              shutil.rmtree(tmpdir)
              raise NoVerifyException(
                  "Package spec file failed signature verification.\n"
                  "Use spack buildcache keys to download "
                  "and install a key for verification from the mirror.")
      # get the sha256 checksum of the tarball
      checksum = checksum_tarball(tarfile_path)
  
      # get the sha256 checksum recorded at creation
      spec_dict = {}
      with open(specfile_path, 'r') as inputfile:
          content = inputfile.read()
          spec_dict = syaml.load(content)
      bchecksum = spec_dict['binary_cache_checksum']
  
      # if the checksums don't match don't install
      if bchecksum['hash'] != checksum:
          shutil.rmtree(tmpdir)
          raise NoChecksumException(
              "Package tarball failed checksum verification.\n"
              "It cannot be installed.")
  
      new_relative_prefix = str(os.path.relpath(spec.prefix,
                                                spack.store.layout.root))
      # if the original relative prefix is in the spec file use it
      buildinfo = spec_dict.get('buildinfo', {})
      old_relative_prefix = buildinfo.get('relative_prefix', new_relative_prefix)
      # if the original relative prefix and new relative prefix differ the
      # directory layout has changed and the  buildcache cannot be installed
      if old_relative_prefix != new_relative_prefix:
          shutil.rmtree(tmpdir)
          msg = "Package tarball was created from an install "
          msg += "prefix with a different directory layout.\n"
          msg += "It cannot be relocated."
          raise NewLayoutException(msg)
  
      # extract the tarball in a temp directory
      with closing(tarfile.open(tarfile_path, 'r')) as tar:
          tar.extractall(path=tmpdir)
      # the base of the install prefix is used when creating the tarball
      # so the pathname should be the same now that the directory layout
      # is confirmed
      workdir = os.path.join(tmpdir, os.path.basename(spec.prefix))
      install_tree(workdir, spec.prefix, symlinks=True)
  
      # cleanup
      os.remove(tarfile_path)
      os.remove(specfile_path)
  
      try:
          relocate_package(spec.prefix, spec, allow_root)
      except Exception as e:
          shutil.rmtree(spec.prefix)
          tty.die(e)
      else:
          manifest_file = os.path.join(spec.prefix,
                                       spack.store.layout.metadata_dir,
                                       spack.store.layout.manifest_file_name)
          if not os.path.exists(manifest_file):
              spec_id = spec.format('{name}/{hash:7}')
              tty.warn('No manifest file in tarball for spec %s' % spec_id)
      finally:
          shutil.rmtree(tmpdir)
  
  
  #: Internal cache for get_specs
  _cached_specs = None
  
  
  def get_specs(force=False):
      """
      Get spec.yaml's for build caches available on mirror
      """
      global _cached_specs
  
      if _cached_specs:
          tty.debug("Using previously-retrieved specs")
          return _cached_specs
  
      if not spack.mirror.MirrorCollection():
          tty.warn("No Spack mirrors are currently configured")
          return {}
  
      urls = set()
      for mirror in spack.mirror.MirrorCollection().values():
          fetch_url_build_cache = url_util.join(
              mirror.fetch_url, _build_cache_relative_path)
  
          mirror_dir = url_util.local_file_path(fetch_url_build_cache)
          if mirror_dir:
              tty.msg("Finding buildcaches in %s" % mirror_dir)
              if os.path.exists(mirror_dir):
                  files = os.listdir(mirror_dir)
                  for file in files:
                      if re.search('spec.yaml', file):
                          link = url_util.join(fetch_url_build_cache, file)
                          urls.add(link)
          else:
              tty.msg("Finding buildcaches at %s" %
                      url_util.format(fetch_url_build_cache))
              p, links = web_util.spider(
                  url_util.join(fetch_url_build_cache, 'index.html'))
              for link in links:
                  if re.search("spec.yaml", link):
                      urls.add(link)
  
      _cached_specs = []
      for link in urls:
          with Stage(link, name="build_cache", keep=True) as stage:
              if force and os.path.exists(stage.save_filename):
                  os.remove(stage.save_filename)
              if not os.path.exists(stage.save_filename):
                  try:
                      stage.fetch()
                  except fs.FetchError:
                      continue
              with open(stage.save_filename, 'r') as f:
                  # read the spec from the build cache file. All specs
                  # in build caches are concrete (as they are built) so
                  # we need to mark this spec concrete on read-in.
                  spec = Spec.from_yaml(f)
                  spec._mark_concrete()
                  _cached_specs.append(spec)
  
      return _cached_specs
  
  
  def get_keys(install=False, trust=False, force=False):
      """
      Get pgp public keys available on mirror
      """
      if not spack.mirror.MirrorCollection():
          tty.die("Please add a spack mirror to allow " +
                  "download of build caches.")
  
      keys = set()
  
      for mirror in spack.mirror.MirrorCollection().values():
          fetch_url_build_cache = url_util.join(
              mirror.fetch_url, _build_cache_relative_path)
  
          mirror_dir = url_util.local_file_path(fetch_url_build_cache)
          if mirror_dir:
              tty.msg("Finding public keys in %s" % mirror_dir)
              files = os.listdir(mirror_dir)
              for file in files:
                  if re.search(r'\.key', file):
                      link = url_util.join(fetch_url_build_cache, file)
                      keys.add(link)
          else:
              tty.msg("Finding public keys at %s" %
                      url_util.format(fetch_url_build_cache))
              p, links = web_util.spider(fetch_url_build_cache, depth=1)
  
              for link in links:
                  if re.search(r'\.key', link):
                      keys.add(link)
  
          for link in keys:
              with Stage(link, name="build_cache", keep=True) as stage:
                  if os.path.exists(stage.save_filename) and force:
                      os.remove(stage.save_filename)
                  if not os.path.exists(stage.save_filename):
                      try:
                          stage.fetch()
                      except fs.FetchError:
                          continue
              tty.msg('Found key %s' % link)
              if install:
                  if trust:
                      Gpg.trust(stage.save_filename)
                      tty.msg('Added this key to trusted keys.')
                  else:
                      tty.msg('Will not add this key to trusted keys.'
                              'Use -t to install all downloaded keys')
  
  
  def needs_rebuild(spec, mirror_url, rebuild_on_errors=False):
      if not spec.concrete:
          raise ValueError('spec must be concrete to check against mirror')
  
      pkg_name = spec.name
      pkg_version = spec.version
  
      pkg_hash = spec.dag_hash()
      pkg_full_hash = spec.full_hash()
  
      tty.debug('Checking {0}-{1}, dag_hash = {2}, full_hash = {3}'.format(
          pkg_name, pkg_version, pkg_hash, pkg_full_hash))
      tty.debug(spec.tree())
  
      # Try to retrieve the .spec.yaml directly, based on the known
      # format of the name, in order to determine if the package
      # needs to be rebuilt.
      cache_prefix = build_cache_prefix(mirror_url)
      spec_yaml_file_name = tarball_name(spec, '.spec.yaml')
      file_path = os.path.join(cache_prefix, spec_yaml_file_name)
  
      result_of_error = 'Package ({0}) will {1}be rebuilt'.format(
          spec.short_spec, '' if rebuild_on_errors else 'not ')
  
      try:
          _, _, yaml_file = web_util.read_from_url(file_path)
          yaml_contents = codecs.getreader('utf-8')(yaml_file).read()
      except URLError as url_err:
          err_msg = [
              'Unable to determine whether {0} needs rebuilding,',
              ' caught URLError attempting to read from {1}.',
          ]
          tty.error(''.join(err_msg).format(spec.short_spec, file_path))
          tty.debug(url_err)
          tty.warn(result_of_error)
          return rebuild_on_errors
  
      if not yaml_contents:
          tty.error('Reading {0} returned nothing'.format(file_path))
          tty.warn(result_of_error)
          return rebuild_on_errors
  
      spec_yaml = syaml.load(yaml_contents)
  
      # If either the full_hash didn't exist in the .spec.yaml file, or it
      # did, but didn't match the one we computed locally, then we should
      # just rebuild.  This can be simplified once the dag_hash and the
      # full_hash become the same thing.
      if ('full_hash' not in spec_yaml or
              spec_yaml['full_hash'] != pkg_full_hash):
          if 'full_hash' in spec_yaml:
              reason = 'hash mismatch, remote = {0}, local = {1}'.format(
                  spec_yaml['full_hash'], pkg_full_hash)
          else:
              reason = 'full_hash was missing from remote spec.yaml'
          tty.msg('Rebuilding {0}, reason: {1}'.format(
              spec.short_spec, reason))
          tty.msg(spec.tree())
          return True
  
      return False
  
  
  def check_specs_against_mirrors(mirrors, specs, output_file=None,
                                  rebuild_on_errors=False):
      """Check all the given specs against buildcaches on the given mirrors and
      determine if any of the specs need to be rebuilt.  Reasons for needing to
      rebuild include binary cache for spec isn't present on a mirror, or it is
      present but the full_hash has changed since last time spec was built.
  
      Arguments:
          mirrors (dict): Mirrors to check against
          specs (iterable): Specs to check against mirrors
          output_file (string): Path to output file to be written.  If provided,
              mirrors with missing or out-of-date specs will be formatted as a
              JSON object and written to this file.
          rebuild_on_errors (boolean): Treat any errors encountered while
              checking specs as a signal to rebuild package.
  
      Returns: 1 if any spec was out-of-date on any mirror, 0 otherwise.
  
      """
      rebuilds = {}
      for mirror in spack.mirror.MirrorCollection(mirrors).values():
          tty.msg('Checking for built specs at %s' % mirror.fetch_url)
  
          rebuild_list = []
  
          for spec in specs:
              if needs_rebuild(spec, mirror.fetch_url, rebuild_on_errors):
                  rebuild_list.append({
                      'short_spec': spec.short_spec,
                      'hash': spec.dag_hash()
                  })
  
          if rebuild_list:
              rebuilds[mirror.fetch_url] = {
                  'mirrorName': mirror.name,
                  'mirrorUrl': mirror.fetch_url,
                  'rebuildSpecs': rebuild_list
              }
  
      if output_file:
          with open(output_file, 'w') as outf:
              outf.write(json.dumps(rebuilds))
  
      return 1 if rebuilds else 0
  
  
  def _download_buildcache_entry(mirror_root, descriptions):
      for description in descriptions:
          description_url = os.path.join(mirror_root, description['url'])
          path = description['path']
          fail_if_missing = description['required']
  
          mkdirp(path)
  
          stage = Stage(
              description_url, name="build_cache", path=path, keep=True)
  
          try:
              stage.fetch()
          except fs.FetchError as e:
              tty.debug(e)
              if fail_if_missing:
                  tty.error('Failed to download required url {0}'.format(
                      description_url))
                  return False
  
      return True
  
  
  def download_buildcache_entry(file_descriptions):
      if not spack.mirror.MirrorCollection():
          tty.die("Please add a spack mirror to allow " +
                  "download of buildcache entries.")
  
      for mirror in spack.mirror.MirrorCollection().values():
          mirror_root = os.path.join(
              mirror.fetch_url,
              _build_cache_relative_path)
  
          if _download_buildcache_entry(mirror_root, file_descriptions):
              return True
          else:
              continue
  
      return False
  