"""
Handling of Core Metadata for Python packages (including reading and writing).

See: https://packaging.python.org/en/latest/specifications/core-metadata/
"""

import os
import stat
import textwrap
from email import message_from_file
from email.message import Message
from tempfile import NamedTemporaryFile
from typing import Optional, List

from distutils.util import rfc822_escape

from . import _normalization, _reqs
from .extern.packaging.markers import Marker
from .extern.packaging.requirements import Requirement
from .extern.packaging.version import Version
from .warnings import SetuptoolsDeprecationWarning


def get_metadata_version(self):
    mv = getattr(self, 'metadata_version', None)
    if mv is None:
        mv = Version('2.1')
        self.metadata_version = mv
    return mv


def rfc822_unescape(content: str) -> str:
    """Reverse RFC-822 escaping by removing leading whitespaces from content."""
    lines = content.splitlines()
    if len(lines) == 1:
        return lines[0].lstrip()
    return '\n'.join((lines[0].lstrip(), textwrap.dedent('\n'.join(lines[1:]))))


def _read_field_from_msg(msg: Message, field: str) -> Optional[str]:
    """Read Message header field."""
    value = msg[field]
    if value == 'UNKNOWN':
        return None
    return value


def _read_field_unescaped_from_msg(msg: Message, field: str) -> Optional[str]:
    """Read Message header field and apply rfc822_unescape."""
    value = _read_field_from_msg(msg, field)
    if value is None:
        return value
    return rfc822_unescape(value)


def _read_list_from_msg(msg: Message, field: str) -> Optional[List[str]]:
    """Read Message header field and return all results as list."""
    values = msg.get_all(field, None)
    if values == []:
        return None
    return values


def _read_payload_from_msg(msg: Message) -> Optional[str]:
    value = msg.get_payload().strip()
    if value == 'UNKNOWN' or not value:
        return None
    return value


def read_pkg_file(self, file):
    """Reads the metadata values from a file object."""
    msg = message_from_file(file)

    self.metadata_version = Version(msg['metadata-version'])
    self.name = _read_field_from_msg(msg, 'name')
    self.version = _read_field_from_msg(msg, 'version')
    self.description = _read_field_from_msg(msg, 'summary')
    # we are filling author only.
    self.author = _read_field_from_msg(msg, 'author')
    self.maintainer = None
    self.author_email = _read_field_from_msg(msg, 'author-email')
    self.maintainer_email = None
    self.url = _read_field_from_msg(msg, 'home-page')
    self.download_url = _read_field_from_msg(msg, 'download-url')
    self.license = _read_field_unescaped_from_msg(msg, 'license')

    self.long_description = _read_field_unescaped_from_msg(msg, 'description')
    if self.long_description is None and self.metadata_version >= Version('2.1'):
        self.long_description = _read_payload_from_msg(msg)
    self.description = _read_field_from_msg(msg, 'summary')

    if 'keywords' in msg:
        self.keywords = _read_field_from_msg(msg, 'keywords').split(',')

    self.platforms = _read_list_from_msg(msg, 'platform')
    self.classifiers = _read_list_from_msg(msg, 'classifier')

    # PEP 314 - these fields only exist in 1.1
    if self.metadata_version == Version('1.1'):
        self.requires = _read_list_from_msg(msg, 'requires')
        self.provides = _read_list_from_msg(msg, 'provides')
        self.obsoletes = _read_list_from_msg(msg, 'obsoletes')
    else:
        self.requires = None
        self.provides = None
        self.obsoletes = None

    self.license_files = _read_list_from_msg(msg, 'license-file')


def single_line(val):
    """
    Quick and dirty validation for Summary pypa/setuptools#1390.
    """
    if '\n' in val:
        # TODO: Replace with `raise ValueError("newlines not allowed")`
        # after reviewing #2893.
        msg = "newlines are not allowed in `summary` and will break in the future"
        SetuptoolsDeprecationWarning.emit("Invalid config.", msg)
        # due_date is undefined. Controversial change, there was a lot of push back.
        val = val.strip().split('\n')[0]
    return val


def write_pkg_info(self, base_dir):
    """Write the PKG-INFO file into the release tree."""
    temp = ""
    final = os.path.join(base_dir, 'PKG-INFO')
    try:
        # Use a temporary file while writing to avoid race conditions
        # (e.g. `importlib.metadata` reading `.egg-info/PKG-INFO`):
        with NamedTemporaryFile("w", encoding="utf-8", dir=base_dir, delete=False) as f:
            temp = f.name
            self.write_pkg_file(f)
        permissions = stat.S_IMODE(os.lstat(temp).st_mode)
        os.chmod(temp, permissions | stat.S_IRGRP | stat.S_IROTH)
        os.replace(temp, final)  # atomic operation.
    finally:
        if temp and os.path.exists(temp):
            os.remove(temp)


# Based on Python 3.5 version
def write_pkg_file(self, file):  # noqa: C901  # is too complex (14)  # FIXME
    """Write the PKG-INFO format data to a file object."""
    version = self.get_metadata_version()

    def write_field(key, value):
        file.write("%s: %s\n" % (key, value))

    write_field('Metadata-Version', str(version))
    write_field('Name', self.get_name())
    write_field('Version', self.get_version())

    summary = self.get_description()
    if summary:
        write_field('Summary', single_line(summary))

    optional_fields = (
        ('Home-page', 'url'),
        ('Download-URL', 'download_url'),
        ('Author', 'author'),
        ('Author-email', 'author_email'),
        ('Maintainer', 'maintainer'),
        ('Maintainer-email', 'maintainer_email'),
    )

    for field, attr in optional_fields:
        attr_val = getattr(self, attr, None)
        if attr_val is not None:
            write_field(field, attr_val)

    license = self.get_license()
    if license:
        write_field('License', rfc822_escape(license))

    for project_url in self.project_urls.items():
        write_field('Project-URL', '%s, %s' % project_url)

    keywords = ','.join(self.get_keywords())
    if keywords:
        write_field('Keywords', keywords)

    platforms = self.get_platforms() or []
    for platform in platforms:
        write_field('Platform', platform)

    self._write_list(file, 'Classifier', self.get_classifiers())

    # PEP 314
    self._write_list(file, 'Requires', self.get_requires())
    self._write_list(file, 'Provides', self.get_provides())
    self._write_list(file, 'Obsoletes', self.get_obsoletes())

    # Setuptools specific for PEP 345
    if hasattr(self, 'python_requires'):
        write_field('Requires-Python', self.python_requires)

    # PEP 566
    if self.long_description_content_type:
        write_field('Description-Content-Type', self.long_description_content_type)

    self._write_list(file, 'License-File', self.license_files or [])
    _write_requirements(self, file)

    long_description = self.get_long_description()
    if long_description:
        file.write("\n%s" % long_description)
        if not long_description.endswith("\n"):
            file.write("\n")


def _write_requirements(self, file):
    for req in _reqs.parse(self.install_requires):
        file.write(f"Requires-Dist: {req}\n")

    processed_extras = {}
    for augmented_extra, reqs in self.extras_require.items():
        # Historically, setuptools allows "augmented extras": `<extra>:<condition>`
        unsafe_extra, _, condition = augmented_extra.partition(":")
        unsafe_extra = unsafe_extra.strip()
        extra = _normalization.safe_extra(unsafe_extra)

        if extra:
            _write_provides_extra(file, processed_extras, extra, unsafe_extra)
        for req in _reqs.parse_strings(reqs):
            r = _include_extra(req, extra, condition.strip())
            file.write(f"Requires-Dist: {r}\n")

    return processed_extras


def _include_extra(req: str, extra: str, condition: str) -> Requirement:
    r = Requirement(req)  # create a fresh object that can be modified
    parts = (
        f"({r.marker})" if r.marker else None,
        f"({condition})" if condition else None,
        f"extra == {extra!r}" if extra else None,
    )
    r.marker = Marker(" and ".join(x for x in parts if x))
    return r


def _write_provides_extra(file, processed_extras, safe, unsafe):
    previous = processed_extras.get(safe)
    if previous == unsafe:
        SetuptoolsDeprecationWarning.emit(
            'Ambiguity during "extra" normalization for dependencies.',
            f"""
            {previous!r} and {unsafe!r} normalize to the same value:\n
                {safe!r}\n
            In future versions, setuptools might halt the build process.
            """,
            see_url="https://peps.python.org/pep-0685/",
        )
    else:
        processed_extras[safe] = unsafe
        file.write(f"Provides-Extra: {safe}\n")
