from __future__ import absolute_import

import logging
import re

import pip
from pip.req import InstallRequirement
from pip.req.req_file import COMMENT_RE
from pip.utils import get_installed_distributions
from pip._vendor import pkg_resources
from pip._vendor.packaging.utils import canonicalize_name
from pip._vendor.pkg_resources import RequirementParseError


logger = logging.getLogger(__name__)


def freeze(
        requirement=None,
        find_links=None, local_only=None, user_only=None, skip_regex=None,
        default_vcs=None,
        isolated=False,
        wheel_cache=None,
        skip=()):
    find_links = find_links or []
    skip_match = None

    if skip_regex:
        skip_match = re.compile(skip_regex).search

    dependency_links = []

    for dist in pkg_resources.working_set:
        if dist.has_metadata('dependency_links.txt'):
            dependency_links.extend(
                dist.get_metadata_lines('dependency_links.txt')
            )
    for link in find_links:
        if '#egg=' in link:
            dependency_links.append(link)
    for link in find_links:
        yield '-f %s' % link
    installations = {}
    for dist in get_installed_distributions(local_only=local_only,
                                            skip=(),
                                            user_only=user_only):
        try:
            req = pip.FrozenRequirement.from_dist(
                dist,
                dependency_links
            )
        except RequirementParseError:
            logger.warning(
                "Could not parse requirement: %s",
                dist.project_name
            )
            continue
        installations[req.name] = req

    if requirement:
        # the options that don't get turned into an InstallRequirement
        # should only be emitted once, even if the same option is in multiple
        # requirements files, so we need to keep track of what has been emitted
        # so that we don't emit it again if it's seen again
        emitted_options = set()
        for req_file_path in requirement:
            with open(req_file_path) as req_file:
                for line in req_file:
                    if (not line.strip() or
                            line.strip().startswith('#') or
                            (skip_match and skip_match(line)) or
                            line.startswith((
                                '-r', '--requirement',
                                '-Z', '--always-unzip',
                                '-f', '--find-links',
                                '-i', '--index-url',
                                '--pre',
                                '--trusted-host',
                                '--process-dependency-links',
                                '--extra-index-url'))):
                        line = line.rstrip()
                        if line not in emitted_options:
                            emitted_options.add(line)
                            yield line
                        continue

                    if line.startswith('-e') or line.startswith('--editable'):
                        if line.startswith('-e'):
                            line = line[2:].strip()
                        else:
                            line = line[len('--editable'):].strip().lstrip('=')
                        line_req = InstallRequirement.from_editable(
                            line,
                            default_vcs=default_vcs,
                            isolated=isolated,
                            wheel_cache=wheel_cache,
                        )
                    else:
                        line_req = InstallRequirement.from_line(
                            COMMENT_RE.sub('', line).strip(),
                            isolated=isolated,
                            wheel_cache=wheel_cache,
                        )

                    if not line_req.name:
                        logger.info(
                            "Skipping line in requirement file [%s] because "
                            "it's not clear what it would install: %s",
                            req_file_path, line.strip(),
                        )
                        logger.info(
                            "  (add #egg=PackageName to the URL to avoid"
                            " this warning)"
                        )
                    elif line_req.name not in installations:
                        logger.warning(
                            "Requirement file [%s] contains %s, but that "
                            "package is not installed",
                            req_file_path, COMMENT_RE.sub('', line).strip(),
                        )
                    else:
                        yield str(installations[line_req.name]).rstrip()
                        del installations[line_req.name]

        yield(
            '## The following requirements were added by '
            'pip freeze:'
        )
    for installation in sorted(
            installations.values(), key=lambda x: x.name.lower()):
        if canonicalize_name(installation.name) not in skip:
            yield str(installation).rstrip()