def download_file(url, dest=None, chunk_size=1024, replace="ask",
                  label="Downloading {dest_basename} ({size:.2f}MB)",
                  expected_extension=None):
    """Download a file from a given URL and display progress.

    :param dest: If the destination exists and is a directory, the filename
        will be guessed from the Content-Disposition header. If the destination
        is an existing file, the user will either be prompted to overwrite, or
        the file will be replaced (depending on the value of **replace**). If
        the destination does not exist, it will be used as the filename.
    :param int chunk_size: bytes read in at a time.
    :param replace: If `False`, an existing destination file will not be
        overwritten.
    :param label: a string which is formatted and displayed as the progress bar
        label. Variables provided include *dest_basename*, *dest*, and *size*.
    :param expected_extension: if set, the filename will be sanitized to ensure
        it has the given extension. The extension should not start with a dot
        (`.`).
    """
    dest = Path(dest or url.split("/")[-1])
    response = get(url, stream=True)
    if (dest.exists()
            and dest.is_dir()
            and "Content-Disposition" in response.headers):
        content_disposition = rfc6266.parse_requests_response(response)
        if expected_extension is not None:
            filename = content_disposition.filename_sanitized(
                expected_extension)
        filename = secure_filename(filename)
        dest = dest / filename
    if dest.exists() and not dest.is_dir():
        if (replace is False
                or replace == "ask"
                and not click.confirm("Replace {}?".format(dest))):
            return str(dest)
    size = int(response.headers.get("content-length", 0))
    label = label.format(dest=dest, dest_basename=dest.name,
                         size=size/1024.0/1024)
    with click.open_file(str(dest), "wb") as f:
        content_iter = response.iter_content(chunk_size=chunk_size)
        with click.progressbar(content_iter, length=size/1024,
                               label=label) as bar:
            for chunk in bar:
                if chunk:
                    f.write(chunk)
                    f.flush()
    return str(dest)
def configure(self, spec, prefix):
        """Make adjustments to the OpenFOAM configuration files in their various
        locations: etc/bashrc, etc/config.sh/FEATURE and customizations that
        don't properly fit get placed in the etc/prefs.sh file (similiarly for
        csh).
        """
        # Filtering bashrc, cshrc
        edits = {}
        edits.update(self.foam_arch.foam_dict())
        rewrite_environ_files(  # Adjust etc/bashrc and etc/cshrc
            edits,
            posix=join_path('etc', 'bashrc'),
            cshell=join_path('etc', 'cshrc'))

        # MPI content, with absolute paths
        user_mpi = mplib_content(spec)

        # Content for etc/prefs.{csh,sh}
        self.etc_prefs = {
            r'MPI_ROOT': spec['mpi'].prefix,  # Absolute
            r'MPI_ARCH_FLAGS': '"%s"' % user_mpi['FLAGS'],
            r'MPI_ARCH_INC':   '"%s"' % user_mpi['PINC'],
            r'MPI_ARCH_LIBS':  '"%s"' % user_mpi['PLIBS'],
        }

        # Content for etc/config.{csh,sh}/ files
        self.etc_config = {
            'CGAL': {},
            'scotch': {},
            'metis': {},
            'paraview': [],
            'gperftools': [],  # Currently unused
        }

        if True:
            self.etc_config['scotch'] = {
                'SCOTCH_ARCH_PATH': spec['scotch'].prefix,
                # For src/parallel/decompose/Allwmake
                'SCOTCH_VERSION': 'scotch-{0}'.format(spec['scotch'].version),
            }

        if '+metis' in spec:
            self.etc_config['metis'] = {
                'METIS_ARCH_PATH': spec['metis'].prefix,
            }

        # Write prefs files according to the configuration.
        # Only need prefs.sh for building, but install both for end-users
        if self.etc_prefs:
            write_environ(
                self.etc_prefs,
                posix=join_path('etc', 'prefs.sh'),
                cshell=join_path('etc', 'prefs.csh'))

        # Adjust components to use SPACK variants
        for component, subdict in self.etc_config.items():
            # Versions up to 3.0 used an etc/config/component.sh naming
            # convention instead of etc/config.sh/component
            if spec.satisfies('@:3.0'):
                write_environ(
                    subdict,
                    posix=join_path('etc', 'config',  component) + '.sh',
                    cshell=join_path('etc', 'config', component) + '.csh')
            else:
                write_environ(
                    subdict,
                    posix=join_path('etc', 'config.sh',  component),
                    cshell=join_path('etc', 'config.csh', component))