# -*- coding: utf-8 -*-
"""
    sphinx.ext.intersphinx
    ~~~~~~~~~~~~~~~~~~~~~~

    Insert links to objects documented in remote Sphinx documentation.

    This works as follows:

    * Each Sphinx HTML build creates a file named "objects.inv" that contains a
      mapping from object names to URIs relative to the HTML set's root.

    * Projects using the Intersphinx extension can specify links to such mapping
      files in the `intersphinx_mapping` config value.  The mapping will then be
      used to resolve otherwise missing references to objects into links to the
      other documentation.

    * By default, the mapping file is assumed to be at the same location as the
      rest of the documentation; however, the location of the mapping file can
      also be specified individually, e.g. if the docs should be buildable
      without Internet access.

    :copyright: Copyright 2007-2016 by the Sphinx team, see AUTHORS.
    :license: BSD, see LICENSE for details.
"""

from __future__ import print_function

import time
import zlib
import codecs
import posixpath
from os import path
import re

from six import iteritems
from six.moves.urllib import parse, request
from docutils import nodes
from docutils.utils import relative_path

import sphinx
from sphinx.locale import _
from sphinx.builders.html import INVENTORY_FILENAME


default_handlers = [request.ProxyHandler(), request.HTTPRedirectHandler(),
                    request.HTTPHandler()]
try:
    default_handlers.append(request.HTTPSHandler)
except AttributeError:
    pass

default_opener = request.build_opener(*default_handlers)

UTF8StreamReader = codecs.lookup('utf-8')[2]


def read_inventory_v1(f, uri, join):
    f = UTF8StreamReader(f)
    invdata = {}
    line = next(f)
    projname = line.rstrip()[11:]
    line = next(f)
    version = line.rstrip()[11:]
    for line in f:
        name, type, location = line.rstrip().split(None, 2)
        location = join(uri, location)
        # version 1 did not add anchors to the location
        if type == 'mod':
            type = 'py:module'
            location += '#module-' + name
        else:
            type = 'py:' + type
            location += '#' + name
        invdata.setdefault(type, {})[name] = (projname, version, location, '-')
    return invdata


def read_inventory_v2(f, uri, join, bufsize=16*1024):
    invdata = {}
    line = f.readline()
    projname = line.rstrip()[11:].decode('utf-8')
    line = f.readline()
    version = line.rstrip()[11:].decode('utf-8')
    line = f.readline().decode('utf-8')
    if 'zlib' not in line:
        raise ValueError

    def read_chunks():
        decompressor = zlib.decompressobj()
        for chunk in iter(lambda: f.read(bufsize), b''):
            yield decompressor.decompress(chunk)
        yield decompressor.flush()

    def split_lines(iter):
        buf = b''
        for chunk in iter:
            buf += chunk
            lineend = buf.find(b'\n')
            while lineend != -1:
                yield buf[:lineend].decode('utf-8')
                buf = buf[lineend+1:]
                lineend = buf.find(b'\n')
        assert not buf

    for line in split_lines(read_chunks()):
        # be careful to handle names with embedded spaces correctly
        m = re.match(r'(?x)(.+?)\s+(\S*:\S*)\s+(\S+)\s+(\S+)\s+(.*)',
                     line.rstrip())
        if not m:
            continue
        name, type, prio, location, dispname = m.groups()
        if type == 'py:module' and type in invdata and \
                name in invdata[type]:  # due to a bug in 1.1 and below,
                                        # two inventory entries are created
                                        # for Python modules, and the first
                                        # one is correct
            continue
        if location.endswith(u'$'):
            location = location[:-1] + name
        location = join(uri, location)
        invdata.setdefault(type, {})[name] = (projname, version,
                                              location, dispname)
    return invdata


def _strip_basic_auth(url):
    """Returns *url* with basic auth credentials removed. Also returns the
    basic auth username and password if they're present in *url*.

    E.g.: https://user:pass@example.com => https://example.com

    *url* need not include basic auth credentials.

    :param url: url which may or may not contain basic auth credentials
    :type url: ``str``

    :return: 3-``tuple`` of:

      * (``str``) -- *url* with any basic auth creds removed
      * (``str`` or ``NoneType``) -- basic auth username or ``None`` if basic
        auth username not given
      * (``str`` or ``NoneType``) -- basic auth password or ``None`` if basic
        auth password not given

    :rtype: ``tuple``
    """
    url_parts = parse.urlsplit(url)
    username = url_parts.username
    password = url_parts.password
    frags = list(url_parts)
    # swap out "user[:pass]@hostname" for "hostname"
    frags[1] = url_parts.hostname
    url = parse.urlunsplit(frags)
    return (url, username, password)


def _read_from_url(url):
    """Reads data from *url* with an HTTP *GET*.

    This function supports fetching from resources which use basic HTTP auth as
    laid out by RFC1738 § 3.1. See § 5 for grammar definitions for URLs.

    .. seealso:

       https://www.ietf.org/rfc/rfc1738.txt

    :param url: URL of an HTTP resource
    :type url: ``str``

    :return: data read from resource described by *url*
    :rtype: ``file``-like object
    """
    url, username, password = _strip_basic_auth(url)
    if username is not None and password is not None:
        # case: url contains basic auth creds
        password_mgr = request.HTTPPasswordMgrWithDefaultRealm()
        password_mgr.add_password(None, url, username, password)
        handler = request.HTTPBasicAuthHandler(password_mgr)
        opener = request.build_opener(default_handlers + [handler])
    else:
        opener = default_opener

    return opener.open(url)


def _get_safe_url(url):
    """Gets version of *url* with basic auth passwords obscured. This function
    returns results suitable for printing and logging.

    E.g.: https://user:12345@example.com => https://user:********@example.com

    .. note::

       The number of astrisks is invariant in the length of the basic auth
       password, so minimal information is leaked.

    :param url: a url
    :type url: ``str``

    :return: *url* with password obscured
    :rtype: ``str``
    """
    safe_url = url
    url, username, _ = _strip_basic_auth(url)
    if username is not None:
        # case: url contained basic auth creds; obscure password
        url_parts = parse.urlsplit(url)
        safe_netloc = '{0}@{1}'.format(username, url_parts.hostname)
        # replace original netloc w/ obscured version
        frags = list(url_parts)
        frags[1] = safe_netloc
        safe_url = parse.urlunsplit(frags)

    return safe_url


def fetch_inventory(app, uri, inv):
    """Fetch, parse and return an intersphinx inventory file."""
    # both *uri* (base URI of the links to generate) and *inv* (actual
    # location of the inventory file) can be local or remote URIs
    localuri = '://' not in uri
    if not localuri:
        # case: inv URI points to remote resource; strip any existing auth
        uri, _, _ = _strip_basic_auth(uri)
    join = localuri and path.join or posixpath.join
    try:
        if '://' in inv:
            f = _read_from_url(inv)
        else:
            f = open(path.join(app.srcdir, inv), 'rb')
    except Exception as err:
        app.warn('intersphinx inventory %r not fetchable due to '
                 '%s: %s' % (inv, err.__class__, err))
        return
    try:
        line = f.readline().rstrip().decode('utf-8')
        try:
            if line == '# Sphinx inventory version 1':
                invdata = read_inventory_v1(f, uri, join)
            elif line == '# Sphinx inventory version 2':
                invdata = read_inventory_v2(f, uri, join)
            else:
                raise ValueError
            f.close()
        except ValueError:
            f.close()
            raise ValueError('unknown or unsupported inventory version')
    except Exception as err:
        app.warn('intersphinx inventory %r not readable due to '
                 '%s: %s' % (inv, err.__class__.__name__, err))
    else:
        return invdata


def load_mappings(app):
    """Load all intersphinx mappings into the environment."""
    now = int(time.time())
    cache_time = now - app.config.intersphinx_cache_limit * 86400
    env = app.builder.env
    if not hasattr(env, 'intersphinx_cache'):
        env.intersphinx_cache = {}
        env.intersphinx_inventory = {}
        env.intersphinx_named_inventory = {}
    cache = env.intersphinx_cache
    update = False
    for key, value in iteritems(app.config.intersphinx_mapping):
        if isinstance(value, tuple):
            # new format
            name, (uri, inv) = key, value
            if not name.isalnum():
                app.warn('intersphinx identifier %r is not alphanumeric' % name)
        else:
            # old format, no name
            name, uri, inv = None, key, value
        # we can safely assume that the uri<->inv mapping is not changed
        # during partial rebuilds since a changed intersphinx_mapping
        # setting will cause a full environment reread
        if not isinstance(inv, tuple):
            invs = (inv, )
        else:
            invs = inv

        for inv in invs:
            if not inv:
                inv = posixpath.join(uri, INVENTORY_FILENAME)
            # decide whether the inventory must be read: always read local
            # files; remote ones only if the cache time is expired
            if '://' not in inv or uri not in cache \
                    or cache[uri][1] < cache_time:
                safe_inv_url = _get_safe_url(inv)
                app.info(
                    'loading intersphinx inventory from %s...' % safe_inv_url)
                invdata = fetch_inventory(app, uri, inv)
                if invdata:
                    cache[uri] = (name, now, invdata)
                    update = True
                    break

    if update:
        env.intersphinx_inventory = {}
        env.intersphinx_named_inventory = {}
        # Duplicate values in different inventories will shadow each
        # other; which one will override which can vary between builds
        # since they are specified using an unordered dict.  To make
        # it more consistent, we sort the named inventories and then
        # add the unnamed inventories last.  This means that the
        # unnamed inventories will shadow the named ones but the named
        # ones can still be accessed when the name is specified.
        cached_vals = list(cache.values())
        named_vals = sorted(v for v in cached_vals if v[0])
        unnamed_vals = [v for v in cached_vals if not v[0]]
        for name, _x, invdata in named_vals + unnamed_vals:
            if name:
                env.intersphinx_named_inventory[name] = invdata
            for type, objects in iteritems(invdata):
                env.intersphinx_inventory.setdefault(
                    type, {}).update(objects)


def missing_reference(app, env, node, contnode):
    """Attempt to resolve a missing reference via intersphinx references."""
    target = node['reftarget']
    if node['reftype'] == 'any':
        # we search anything!
        objtypes = ['%s:%s' % (domain.name, objtype)
                    for domain in env.domains.values()
                    for objtype in domain.object_types]
        domain = None
    elif node['reftype'] == 'doc':
        domain = 'std'  # special case
        objtypes = ['std:doc']
    else:
        domain = node.get('refdomain')
        if not domain:
            # only objects in domains are in the inventory
            return
        objtypes = env.domains[domain].objtypes_for_role(node['reftype'])
        if not objtypes:
            return
        objtypes = ['%s:%s' % (domain, objtype) for objtype in objtypes]
    to_try = [(env.intersphinx_inventory, target)]
    in_set = None
    if ':' in target:
        # first part may be the foreign doc set name
        setname, newtarget = target.split(':', 1)
        if setname in env.intersphinx_named_inventory:
            in_set = setname
            to_try.append((env.intersphinx_named_inventory[setname], newtarget))
    for inventory, target in to_try:
        for objtype in objtypes:
            if objtype not in inventory or target not in inventory[objtype]:
                continue
            proj, version, uri, dispname = inventory[objtype][target]
            if '://' not in uri and node.get('refdoc'):
                # get correct path in case of subdirectories
                uri = path.join(relative_path(node['refdoc'], env.srcdir), uri)
            newnode = nodes.reference('', '', internal=False, refuri=uri,
                                      reftitle=_('(in %s v%s)') % (proj, version))
            if node.get('refexplicit'):
                # use whatever title was given
                newnode.append(contnode)
            elif dispname == '-' or \
                    (domain == 'std' and node['reftype'] == 'keyword'):
                # use whatever title was given, but strip prefix
                title = contnode.astext()
                if in_set and title.startswith(in_set+':'):
                    newnode.append(contnode.__class__(title[len(in_set)+1:],
                                                      title[len(in_set)+1:]))
                else:
                    newnode.append(contnode)
            else:
                # else use the given display name (used for :ref:)
                newnode.append(contnode.__class__(dispname, dispname))
            return newnode
    # at least get rid of the ':' in the target if no explicit title given
    if in_set is not None and not node.get('refexplicit', True):
        if len(contnode) and isinstance(contnode[0], nodes.Text):
            contnode[0] = nodes.Text(newtarget, contnode[0].rawsource)


def setup(app):
    app.add_config_value('intersphinx_mapping', {}, True)
    app.add_config_value('intersphinx_cache_limit', 5, False)
    app.connect('missing-reference', missing_reference)
    app.connect('builder-inited', load_mappings)
    return {'version': sphinx.__display_version__, 'parallel_read_safe': True}


if __name__ == '__main__':
    # debug functionality to print out an inventory
    import sys

    class MockApp(object):
        srcdir = ''

        def warn(self, msg):
            print(msg, file=sys.stderr)

    filename = sys.argv[1]
    invdata = fetch_inventory(MockApp(), '', filename)
    for key in sorted(invdata or {}):
        print(key)
        for entry, einfo in sorted(invdata[key].items()):
            print('\t%-40s %s%s' % (entry,
                                    einfo[3] != '-' and '%-40s: ' % einfo[3] or '',
                                    einfo[2]))
