# -*- 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 2007-2015 by the Sphinx team, see AUTHORS.
    :license: BSD, see LICENSE for details.
"""

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

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

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


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

request.install_opener(request.build_opener(*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 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 = uri.find('://') == -1
    join = localuri and path.join or posixpath.join
    try:
        if inv.find('://') != -1:
            f = request.urlopen(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:
                app.info('loading intersphinx inventory from %s...' % inv)
                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]
    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}
