"""PEP 376 implementation."""

import os
import csv
import sys
import zipimport
from StringIO import StringIO
try:
    from hashlib import md5
except ImportError:
    from distutils2._backport.hashlib import md5

from distutils2.errors import PackagingError
from distutils2.version import suggest_normalized_version, VersionPredicate
from distutils2.metadata import Metadata
from distutils2.util import parse_requires


__all__ = [
    'Distribution', 'EggInfoDistribution', 'distinfo_dirname',
    'get_distributions', 'get_distribution', 'get_file_users',
    'provides_distribution', 'obsoletes_distribution',
    'enable_cache', 'disable_cache', 'clear_cache',
    'get_file_path', 'get_file']


# TODO update docs

DIST_FILES = ('INSTALLER', 'METADATA', 'RECORD', 'REQUESTED', 'RESOURCES')

# Cache
_cache_name = {}  # maps names to Distribution instances
_cache_name_egg = {}  # maps names to EggInfoDistribution instances
_cache_path = {}  # maps paths to Distribution instances
_cache_path_egg = {}  # maps paths to EggInfoDistribution instances
_cache_generated = False  # indicates if .dist-info distributions are cached
_cache_generated_egg = False  # indicates if .dist-info and .egg are cached
_cache_enabled = True


def enable_cache():
    """
    Enables the internal cache.

    Note that this function will not clear the cache in any case, for that
    functionality see :func:`clear_cache`.
    """
    global _cache_enabled

    _cache_enabled = True


def disable_cache():
    """
    Disables the internal cache.

    Note that this function will not clear the cache in any case, for that
    functionality see :func:`clear_cache`.
    """
    global _cache_enabled

    _cache_enabled = False


def clear_cache():
    """ Clears the internal cache. """
    global _cache_generated, _cache_generated_egg

    _cache_name.clear()
    _cache_name_egg.clear()
    _cache_path.clear()
    _cache_path_egg.clear()
    _cache_generated = False
    _cache_generated_egg = False


def _yield_distributions(include_dist, include_egg, paths):
    """
    Yield .dist-info and .egg(-info) distributions, based on the arguments

    :parameter include_dist: yield .dist-info distributions
    :parameter include_egg: yield .egg(-info) distributions
    """
    for path in paths:
        realpath = os.path.realpath(path)
        if not os.path.isdir(realpath):
            continue
        for dir in os.listdir(realpath):
            dist_path = os.path.join(realpath, dir)
            if include_dist and dir.endswith('.dist-info'):
                yield Distribution(dist_path)
            elif include_egg and (dir.endswith('.egg-info') or
                                  dir.endswith('.egg')):
                yield EggInfoDistribution(dist_path)


def _generate_cache(use_egg_info, paths):
    global _cache_generated, _cache_generated_egg

    if _cache_generated_egg or (_cache_generated and not use_egg_info):
        return
    else:
        gen_dist = not _cache_generated
        gen_egg = use_egg_info

        for dist in _yield_distributions(gen_dist, gen_egg, paths):
            if isinstance(dist, Distribution):
                _cache_path[dist.path] = dist
                if dist.name not in _cache_name:
                    _cache_name[dist.name] = []
                _cache_name[dist.name].append(dist)
            else:
                _cache_path_egg[dist.path] = dist
                if dist.name not in _cache_name_egg:
                    _cache_name_egg[dist.name] = []
                _cache_name_egg[dist.name].append(dist)

        if gen_dist:
            _cache_generated = True
        if gen_egg:
            _cache_generated_egg = True


class Distribution(object):
    """Created with the *path* of the ``.dist-info`` directory provided to the
    constructor. It reads the metadata contained in ``METADATA`` when it is
    instantiated."""

    name = ''
    """The name of the distribution."""

    version = ''
    """The version of the distribution."""

    metadata = None
    """A :class:`distutils2.metadata.Metadata` instance loaded with
    the distribution's ``METADATA`` file."""

    requested = False
    """A boolean that indicates whether the ``REQUESTED`` metadata file is
    present (in other words, whether the package was installed by user
    request or it was installed as a dependency)."""

    def __init__(self, path):
        if _cache_enabled and path in _cache_path:
            self.metadata = _cache_path[path].metadata
        else:
            metadata_path = os.path.join(path, 'METADATA')
            self.metadata = Metadata(path=metadata_path)

        self.name = self.metadata['Name']
        self.version = self.metadata['Version']
        self.path = path

        if _cache_enabled and path not in _cache_path:
            _cache_path[path] = self

    def __repr__(self):
        return '<Distribution %r %s at %r>' % (
            self.name, self.version, self.path)

    def __str__(self):
        return "%s %s" % (self.name, self.version)

    def _get_records(self, local=False):
        results = []
        record = self.get_distinfo_file('RECORD')
        try:
            record_reader = csv.reader(record, delimiter=',',
                                       lineterminator='\n')
            for row in record_reader:
                missing = [None for i in range(len(row), 3)]
                path, checksum, size = row + missing
                if local:
                    path = path.replace('/', os.sep)
                    path = os.path.join(sys.prefix, path)
                results.append((path, checksum, size))
        finally:
            record.close()
        return results

    def get_resource_path(self, relative_path):
        resources_file = self.get_distinfo_file('RESOURCES')
        try:
            resources_reader = csv.reader(resources_file, delimiter=',',
                                          lineterminator='\n')
            for relative, destination in resources_reader:
                if relative == relative_path:
                    return destination
        finally:
            resources_file.close()
        raise KeyError(
            'no resource file with relative path %r is installed' %
            relative_path)

    def list_installed_files(self, local=False):
        """
        Iterates over the ``RECORD`` entries and returns a tuple
        ``(path, md5, size)`` for each line. If *local* is ``True``,
        the returned path is transformed into a local absolute path.
        Otherwise the raw value from RECORD is returned.

        A local absolute path is an absolute path in which occurrences of
        ``'/'`` have been replaced by the system separator given by ``os.sep``.

        :parameter local: flag to say if the path should be returned as a local
                          absolute path

        :type local: boolean
        :returns: iterator of (path, md5, size)
        """
        for result in self._get_records(local):
            yield result

    def uses(self, path):
        """
        Returns ``True`` if path is listed in ``RECORD``. *path* can be a local
        absolute path or a relative ``'/'``-separated path.

        :rtype: boolean
        """
        for p, checksum, size in self._get_records():
            local_absolute = os.path.join(sys.prefix, p)
            if path == p or path == local_absolute:
                return True
        return False

    def get_distinfo_file(self, path, binary=False):
        """
        Returns a file located under the ``.dist-info`` directory. Returns a
        ``file`` instance for the file pointed by *path*.

        :parameter path: a ``'/'``-separated path relative to the
                         ``.dist-info`` directory or an absolute path;
                         If *path* is an absolute path and doesn't start
                         with the ``.dist-info`` directory path,
                         a :class:`PackagingError` is raised
        :type path: string
        :parameter binary: If *binary* is ``True``, opens the file in read-only
                           binary mode (``rb``), otherwise opens it in
                           read-only mode (``r``).
        :rtype: file object
        """
        open_flags = 'r'
        if binary:
            open_flags += 'b'

        # Check if it is an absolute path  # XXX use relpath, add tests
        if path.find(os.sep) >= 0:
            # it's an absolute path?
            distinfo_dirname, path = path.split(os.sep)[-2:]
            if distinfo_dirname != self.path.split(os.sep)[-1]:
                raise PackagingError(
                    'dist-info file %r does not belong to the %r %s '
                    'distribution' % (path, self.name, self.version))

        # The file must be relative
        if path not in DIST_FILES:
            raise PackagingError('invalid path for a dist-info file: %r' %
                                 path)

        path = os.path.join(self.path, path)
        return open(path, open_flags)

    def list_distinfo_files(self, local=False):
        """
        Iterates over the ``RECORD`` entries and returns paths for each line if
        the path is pointing to a file located in the ``.dist-info`` directory
        or one of its subdirectories.

        :parameter local: If *local* is ``True``, each returned path is
                          transformed into a local absolute path. Otherwise the
                          raw value from ``RECORD`` is returned.
        :type local: boolean
        :returns: iterator of paths
        """
        for path, checksum, size in self._get_records(local):
            # XXX add separator or use real relpath algo
            if path.startswith(self.path):
                yield path

    def __eq__(self, other):
        return isinstance(other, Distribution) and self.path == other.path

    # See http://docs.python.org/reference/datamodel#object.__hash__
    __hash__ = object.__hash__


class EggInfoDistribution(object):
    """Created with the *path* of the ``.egg-info`` directory or file provided
    to the constructor. It reads the metadata contained in the file itself, or
    if the given path happens to be a directory, the metadata is read from the
    file ``PKG-INFO`` under that directory."""

    name = ''
    """The name of the distribution."""

    version = ''
    """The version of the distribution."""

    metadata = None
    """A :class:`distutils2.metadata.Metadata` instance loaded with
    the distribution's ``METADATA`` file."""

    def __init__(self, path):
        self.path = path
        if _cache_enabled and path in _cache_path_egg:
            self.metadata = _cache_path_egg[path].metadata
            self.name = self.metadata['Name']
            self.version = self.metadata['Version']
            return

        requires = None

        if path.endswith('.egg'):
            if os.path.isdir(path):
                meta_path = os.path.join(path, 'EGG-INFO', 'PKG-INFO')
                self.metadata = Metadata(path=meta_path)
                req_path = os.path.join(path, 'EGG-INFO', 'requires.txt')
                requires = parse_requires(req_path)
            else:
                # FIXME handle the case where zipfile is not available
                zipf = zipimport.zipimporter(path)
                fileobj = StringIO(
                    zipf.get_data('EGG-INFO/PKG-INFO').decode('utf8'))
                self.metadata = Metadata(fileobj=fileobj)
                try:
                    requires = zipf.get_data('EGG-INFO/requires.txt')
                except IOError:
                    requires = None
            self.name = self.metadata['Name']
            self.version = self.metadata['Version']

        elif path.endswith('.egg-info'):
            if os.path.isdir(path):
                path = os.path.join(path, 'PKG-INFO')
                req_path = os.path.join(path, 'requires.txt')
                requires = parse_requires(req_path)
            self.metadata = Metadata(path=path)
            self.name = self.metadata['Name']
            self.version = self.metadata['Version']

        else:
            raise ValueError('path must end with .egg-info or .egg, got %r' %
                             path)

        if requires:
            if self.metadata['Metadata-Version'] == '1.1':
                # we can't have 1.1 metadata *and* Setuptools requires
                for field in ('Obsoletes', 'Requires', 'Provides'):
                    if field in self.metadata:
                        del self.metadata[field]
            self.metadata['Requires-Dist'] += requires

        if _cache_enabled:
            _cache_path_egg[self.path] = self

    def __repr__(self):
        return '<EggInfoDistribution %r %s at %r>' % (
            self.name, self.version, self.path)

    def __str__(self):
        return "%s %s" % (self.name, self.version)

    def list_installed_files(self, local=False):

        def _md5(path):
            f = open(path, 'rb')
            try:
                content = f.read()
            finally:
                f.close()
            return md5(content).hexdigest()

        def _size(path):
            return os.stat(path).st_size

        path = self.path
        if local:
            path = path.replace('/', os.sep)

        # XXX What about scripts and data files ?
        if os.path.isfile(path):
            return [(path, _md5(path), _size(path))]
        else:
            files = []
            for root, dir, files_ in os.walk(path):
                for item in files_:
                    item = os.path.join(root, item)
                    files.append((item, _md5(item), _size(item)))
            return files

        return []

    def uses(self, path):
        return False

    def __eq__(self, other):
        return (isinstance(other, EggInfoDistribution) and
                self.path == other.path)

    # See http://docs.python.org/reference/datamodel#object.__hash__
    __hash__ = object.__hash__


def distinfo_dirname(name, version):
    """
    The *name* and *version* parameters are converted into their
    filename-escaped form, i.e. any ``'-'`` characters are replaced
    with ``'_'`` other than the one in ``'dist-info'`` and the one
    separating the name from the version number.

    :parameter name: is converted to a standard distribution name by replacing
                     any runs of non- alphanumeric characters with a single
                     ``'-'``.
    :type name: string
    :parameter version: is converted to a standard version string. Spaces
                        become dots, and all other non-alphanumeric characters
                        (except dots) become dashes, with runs of multiple
                        dashes condensed to a single dash.
    :type version: string
    :returns: directory name
    :rtype: string"""
    file_extension = '.dist-info'
    name = name.replace('-', '_')
    normalized_version = suggest_normalized_version(version)
    # Because this is a lookup procedure, something will be returned even if
    #   it is a version that cannot be normalized
    if normalized_version is None:
        # Unable to achieve normality?
        normalized_version = version
    return '-'.join([name, normalized_version]) + file_extension


def get_distributions(use_egg_info=True, paths=None):
    """
    Provides an iterator that looks for ``.dist-info`` directories in
    ``sys.path`` and returns :class:`Distribution` instances for each one of
    them. If the parameters *use_egg_info* is ``True``, then the ``.egg-info``
    files and directores are iterated as well.

    :rtype: iterator of :class:`Distribution` and :class:`EggInfoDistribution`
            instances
    """
    if paths is None:
        paths = sys.path

    if not _cache_enabled:
        for dist in _yield_distributions(True, use_egg_info, paths):
            yield dist
    else:
        _generate_cache(use_egg_info, paths)

        for dist in _cache_path.values():
            yield dist

        if use_egg_info:
            for dist in _cache_path_egg.values():
                yield dist


def get_distribution(name, use_egg_info=True, paths=None):
    """
    Scans all elements in ``sys.path`` and looks for all directories
    ending with ``.dist-info``. Returns a :class:`Distribution`
    corresponding to the ``.dist-info`` directory that contains the
    ``METADATA`` that matches *name* for the *name* metadata field.
    If no distribution exists with the given *name* and the parameter
    *use_egg_info* is set to ``True``, then all files and directories ending
    with ``.egg-info`` are scanned. A :class:`EggInfoDistribution` instance is
    returned if one is found that has metadata that matches *name* for the
    *name* metadata field.

    This function only returns the first result found, as no more than one
    value is expected. If the directory is not found, ``None`` is returned.

    :rtype: :class:`Distribution` or :class:`EggInfoDistribution` or None
    """
    if paths is None:
        paths = sys.path

    if not _cache_enabled:
        for dist in _yield_distributions(True, use_egg_info, paths):
            if dist.name == name:
                return dist
    else:
        _generate_cache(use_egg_info, paths)

        if name in _cache_name:
            return _cache_name[name][0]
        elif use_egg_info and name in _cache_name_egg:
            return _cache_name_egg[name][0]
        else:
            return None


def obsoletes_distribution(name, version=None, use_egg_info=True):
    """
    Iterates over all distributions to find which distributions obsolete
    *name*.

    If a *version* is provided, it will be used to filter the results.
    If the argument *use_egg_info* is set to ``True``, then ``.egg-info``
    distributions will be considered as well.

    :type name: string
    :type version: string
    :parameter name:
    """
    for dist in get_distributions(use_egg_info):
        obsoleted = (dist.metadata['Obsoletes-Dist'] +
                     dist.metadata['Obsoletes'])
        for obs in obsoleted:
            o_components = obs.split(' ', 1)
            if len(o_components) == 1 or version is None:
                if name == o_components[0]:
                    yield dist
                    break
            else:
                try:
                    predicate = VersionPredicate(obs)
                except ValueError:
                    raise PackagingError(
                        'distribution %r has ill-formed obsoletes field: '
                        '%r' % (dist.name, obs))
                if name == o_components[0] and predicate.match(version):
                    yield dist
                    break


def provides_distribution(name, version=None, use_egg_info=True):
    """
    Iterates over all distributions to find which distributions provide *name*.
    If a *version* is provided, it will be used to filter the results. Scans
    all elements in ``sys.path``  and looks for all directories ending with
    ``.dist-info``. Returns a :class:`Distribution`  corresponding to the
    ``.dist-info`` directory that contains a ``METADATA`` that matches *name*
    for the name metadata. If the argument *use_egg_info* is set to ``True``,
    then all files and directories ending with ``.egg-info`` are considered
    as well and returns an :class:`EggInfoDistribution` instance.

    This function only returns the first result found, since no more than
    one values are expected. If the directory is not found, returns ``None``.

    :parameter version: a version specifier that indicates the version
                        required, conforming to the format in ``PEP-345``

    :type name: string
    :type version: string
    """
    predicate = None
    if not version is None:
        try:
            predicate = VersionPredicate(name + ' (' + version + ')')
        except ValueError:
            raise PackagingError('invalid name or version: %r, %r' %
                                 (name, version))

    for dist in get_distributions(use_egg_info):
        provided = dist.metadata['Provides-Dist'] + dist.metadata['Provides']

        for p in provided:
            p_components = p.rsplit(' ', 1)
            if len(p_components) == 1 or predicate is None:
                if name == p_components[0]:
                    yield dist
                    break
            else:
                p_name, p_ver = p_components
                if len(p_ver) < 2 or p_ver[0] != '(' or p_ver[-1] != ')':
                    raise PackagingError(
                        'distribution %r has invalid Provides field: %r' %
                        (dist.name, p))
                p_ver = p_ver[1:-1]  # trim off the parenthesis
                if p_name == name and predicate.match(p_ver):
                    yield dist
                    break


def get_file_users(path):
    """
    Iterates over all distributions to find out which distributions use
    *path*.

    :parameter path: can be a local absolute path or a relative
                     ``'/'``-separated path.
    :type path: string
    :rtype: iterator of :class:`Distribution` instances
    """
    for dist in get_distributions():
        if dist.uses(path):
            yield dist


def get_file_path(distribution_name, relative_path):
    """Return the path to a resource file."""
    dist = get_distribution(distribution_name)
    if dist is not None:
        return dist.get_resource_path(relative_path)
    raise LookupError('no distribution named %r found' % distribution_name)


def get_file(distribution_name, relative_path, *args, **kwargs):
    """Open and return a resource file."""
    return open(get_file_path(distribution_name, relative_path),
                *args, **kwargs)