from pip.req import InstallRequirement, RequirementSet, parse_requirements
from pip.basecommand import Command
from pip.exceptions import InstallationError


class UninstallCommand(Command):
    """
    Uninstall packages.

    pip is able to uninstall most installed packages. Known exceptions are:

    - Pure distutils packages installed with ``python setup.py install``, which
      leave behind no metadata to determine what files were installed.
    - Script wrappers installed by ``python setup.py develop``.
    """
    name = 'uninstall'
    usage = """
      %prog [options] <package> ...
      %prog [options] -r <requirements file> ..."""
    summary = 'Uninstall packages.'

    def __init__(self, *args, **kw):
        super(UninstallCommand, self).__init__(*args, **kw)
        self.cmd_opts.add_option(
            '-r', '--requirement',
            dest='requirements',
            action='append',
            default=[],
            metavar='file',
            help='Uninstall all the packages listed in the given requirements '
                 'file.  This option can be used multiple times.',
        )
        self.cmd_opts.add_option(
            '-y', '--yes',
            dest='yes',
            action='store_true',
            help="Don't ask for confirmation of uninstall deletions.")

        self.parser.insert_option_group(0, self.cmd_opts)

    def run(self, options, args):
        session = self._build_session(options)

        requirement_set = RequirementSet(
            build_dir=None,
            src_dir=None,
            download_dir=None,
            session=session,
        )
        for name in args:
            requirement_set.add_requirement(
                InstallRequirement.from_line(name))
        for filename in options.requirements:
            for req in parse_requirements(
                    filename,
                    options=options,
                    session=session):
                requirement_set.add_requirement(req)
        if not requirement_set.has_requirements:
            raise InstallationError(
                'You must give at least one requirement to %(name)s (see "pip '
                'help %(name)s")' % dict(name=self.name)
            )
        requirement_set.uninstall(auto_confirm=options.yes)
