"""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.
"""

import concurrent.futures
import functools
import posixpath
import re
import sys
import time
from os import path
from types import ModuleType
from typing import IO, Any, Dict, List, Optional, Tuple, cast
from urllib.parse import urlsplit, urlunsplit

from docutils import nodes
from docutils.nodes import Element, Node, TextElement, system_message
from docutils.utils import Reporter, relative_path

import sphinx
from sphinx.addnodes import pending_xref
from sphinx.application import Sphinx
from sphinx.builders.html import INVENTORY_FILENAME
from sphinx.config import Config
from sphinx.domains import Domain
from sphinx.environment import BuildEnvironment
from sphinx.errors import ExtensionError
from sphinx.locale import _, __
from sphinx.transforms.post_transforms import ReferencesResolver
from sphinx.util import logging, requests
from sphinx.util.docutils import CustomReSTDispatcher, SphinxRole
from sphinx.util.inventory import InventoryFile
from sphinx.util.typing import Inventory, InventoryItem, RoleFunction

logger = logging.getLogger(__name__)


class InventoryAdapter:
    """Inventory adapter for environment"""

    def __init__(self, env: BuildEnvironment) -> None:
        self.env = env

        if not hasattr(env, 'intersphinx_cache'):
            self.env.intersphinx_cache = {}  # type: ignore
            self.env.intersphinx_inventory = {}  # type: ignore
            self.env.intersphinx_named_inventory = {}  # type: ignore

    @property
    def cache(self) -> Dict[str, Tuple[str, int, Inventory]]:
        return self.env.intersphinx_cache  # type: ignore

    @property
    def main_inventory(self) -> Inventory:
        return self.env.intersphinx_inventory  # type: ignore

    @property
    def named_inventory(self) -> Dict[str, Inventory]:
        return self.env.intersphinx_named_inventory  # type: ignore

    def clear(self) -> None:
        self.env.intersphinx_inventory.clear()  # type: ignore
        self.env.intersphinx_named_inventory.clear()  # type: ignore


def _strip_basic_auth(url: str) -> str:
    """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: *url* with any basic auth creds removed
    :rtype: ``str``
    """
    frags = list(urlsplit(url))
    # swap out "user[:pass]@hostname" for "hostname"
    if '@' in frags[1]:
        frags[1] = frags[1].split('@')[1]
    return urlunsplit(frags)


def _read_from_url(url: str, config: Optional[Config] = None) -> IO:
    """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
    """
    r = requests.get(url, stream=True, config=config, timeout=config.intersphinx_timeout)
    r.raise_for_status()
    r.raw.url = r.url
    # decode content-body based on the header.
    # ref: https://github.com/kennethreitz/requests/issues/2155
    r.raw.read = functools.partial(r.raw.read, decode_content=True)
    return r.raw


def _get_safe_url(url: str) -> str:
    """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

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

    :return: *url* with password removed
    :rtype: ``str``
    """
    parts = urlsplit(url)
    if parts.username is None:
        return url
    else:
        frags = list(parts)
        if parts.port:
            frags[1] = '{}@{}:{}'.format(parts.username, parts.hostname, parts.port)
        else:
            frags[1] = '{}@{}'.format(parts.username, parts.hostname)

        return urlunsplit(frags)


def fetch_inventory(app: Sphinx, uri: str, inv: Any) -> Any:
    """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)
    try:
        if '://' in inv:
            f = _read_from_url(inv, config=app.config)
        else:
            f = open(path.join(app.srcdir, inv), 'rb')
    except Exception as err:
        err.args = ('intersphinx inventory %r not fetchable due to %s: %s',
                    inv, err.__class__, str(err))
        raise
    try:
        if hasattr(f, 'url'):
            newinv = f.url  # type: ignore
            if inv != newinv:
                logger.info(__('intersphinx inventory has moved: %s -> %s'), inv, newinv)

                if uri in (inv, path.dirname(inv), path.dirname(inv) + '/'):
                    uri = path.dirname(newinv)
        with f:
            try:
                join = path.join if localuri else posixpath.join
                invdata = InventoryFile.load(f, uri, join)
            except ValueError as exc:
                raise ValueError('unknown or unsupported inventory version: %r' % exc) from exc
    except Exception as err:
        err.args = ('intersphinx inventory %r not readable due to %s: %s',
                    inv, err.__class__.__name__, str(err))
        raise
    else:
        return invdata


def fetch_inventory_group(
    name: str, uri: str, invs: Any, cache: Any, app: Any, now: float
) -> bool:
    cache_time = now - app.config.intersphinx_cache_limit * 86400
    failures = []
    try:
        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)
                logger.info(__('loading intersphinx inventory from %s...'), safe_inv_url)
                try:
                    invdata = fetch_inventory(app, uri, inv)
                except Exception as err:
                    failures.append(err.args)
                    continue
                if invdata:
                    cache[uri] = (name, now, invdata)
                    return True
        return False
    finally:
        if failures == []:
            pass
        elif len(failures) < len(invs):
            logger.info(__("encountered some issues with some of the inventories,"
                           " but they had working alternatives:"))
            for fail in failures:
                logger.info(*fail)
        else:
            issues = '\n'.join([f[0] % f[1:] for f in failures])
            logger.warning(__("failed to reach any of the inventories "
                              "with the following issues:") + "\n" + issues)


def load_mappings(app: Sphinx) -> None:
    """Load all intersphinx mappings into the environment."""
    now = int(time.time())
    inventories = InventoryAdapter(app.builder.env)

    with concurrent.futures.ThreadPoolExecutor() as pool:
        futures = []
        for name, (uri, invs) in app.config.intersphinx_mapping.values():
            futures.append(pool.submit(
                fetch_inventory_group, name, uri, invs, inventories.cache, app, now
            ))
        updated = [f.result() for f in concurrent.futures.as_completed(futures)]

    if any(updated):
        inventories.clear()

        # 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(inventories.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:
                inventories.named_inventory[name] = invdata
            for type, objects in invdata.items():
                inventories.main_inventory.setdefault(type, {}).update(objects)


def _create_element_from_result(domain: Domain, inv_name: Optional[str],
                                data: InventoryItem,
                                node: pending_xref, contnode: TextElement) -> Element:
    proj, version, uri, dispname = data
    if '://' not in uri and node.get('refdoc'):
        # get correct path in case of subdirectories
        uri = path.join(relative_path(node['refdoc'], '.'), uri)
    if version:
        reftitle = _('(in %s v%s)') % (proj, version)
    else:
        reftitle = _('(in %s)') % (proj,)
    newnode = nodes.reference('', '', internal=False, refuri=uri, reftitle=reftitle)
    if node.get('refexplicit'):
        # use whatever title was given
        newnode.append(contnode)
    elif dispname == '-' or \
            (domain.name == 'std' and node['reftype'] == 'keyword'):
        # use whatever title was given, but strip prefix
        title = contnode.astext()
        if inv_name is not None and title.startswith(inv_name + ':'):
            newnode.append(contnode.__class__(title[len(inv_name) + 1:],
                                              title[len(inv_name) + 1:]))
        else:
            newnode.append(contnode)
    else:
        # else use the given display name (used for :ref:)
        newnode.append(contnode.__class__(dispname, dispname))
    return newnode


def _resolve_reference_in_domain_by_target(
        inv_name: Optional[str], inventory: Inventory,
        domain: Domain, objtypes: List[str],
        target: str,
        node: pending_xref, contnode: TextElement) -> Optional[Element]:
    for objtype in objtypes:
        if objtype not in inventory:
            # Continue if there's nothing of this kind in the inventory
            continue

        if target in inventory[objtype]:
            # Case sensitive match, use it
            data = inventory[objtype][target]
        elif objtype == 'std:term':
            # Check for potential case insensitive matches for terms only
            target_lower = target.lower()
            insensitive_matches = list(filter(lambda k: k.lower() == target_lower,
                                              inventory[objtype].keys()))
            if insensitive_matches:
                data = inventory[objtype][insensitive_matches[0]]
            else:
                # No case insensitive match either, continue to the next candidate
                continue
        else:
            # Could reach here if we're not a term but have a case insensitive match.
            # This is a fix for terms specifically, but potentially should apply to
            # other types.
            continue
        return _create_element_from_result(domain, inv_name, data, node, contnode)
    return None


def _resolve_reference_in_domain(env: BuildEnvironment,
                                 inv_name: Optional[str], inventory: Inventory,
                                 honor_disabled_refs: bool,
                                 domain: Domain, objtypes: List[str],
                                 node: pending_xref, contnode: TextElement
                                 ) -> Optional[Element]:
    # we adjust the object types for backwards compatibility
    if domain.name == 'std' and 'cmdoption' in objtypes:
        # until Sphinx-1.6, cmdoptions are stored as std:option
        objtypes.append('option')
    if domain.name == 'py' and 'attribute' in objtypes:
        # Since Sphinx-2.1, properties are stored as py:method
        objtypes.append('method')

    # the inventory contains domain:type as objtype
    objtypes = ["{}:{}".format(domain.name, t) for t in objtypes]

    # now that the objtypes list is complete we can remove the disabled ones
    if honor_disabled_refs:
        disabled = env.config.intersphinx_disabled_reftypes
        objtypes = [o for o in objtypes if o not in disabled]

    # without qualification
    res = _resolve_reference_in_domain_by_target(inv_name, inventory, domain, objtypes,
                                                 node['reftarget'], node, contnode)
    if res is not None:
        return res

    # try with qualification of the current scope instead
    full_qualified_name = domain.get_full_qualified_name(node)
    if full_qualified_name is None:
        return None
    return _resolve_reference_in_domain_by_target(inv_name, inventory, domain, objtypes,
                                                  full_qualified_name, node, contnode)


def _resolve_reference(env: BuildEnvironment, inv_name: Optional[str], inventory: Inventory,
                       honor_disabled_refs: bool,
                       node: pending_xref, contnode: TextElement) -> Optional[Element]:
    # disabling should only be done if no inventory is given
    honor_disabled_refs = honor_disabled_refs and inv_name is None

    if honor_disabled_refs and '*' in env.config.intersphinx_disabled_reftypes:
        return None

    typ = node['reftype']
    if typ == 'any':
        for domain_name, domain in env.domains.items():
            if honor_disabled_refs \
                    and (domain_name + ":*") in env.config.intersphinx_disabled_reftypes:
                continue
            objtypes = list(domain.object_types)
            res = _resolve_reference_in_domain(env, inv_name, inventory,
                                               honor_disabled_refs,
                                               domain, objtypes,
                                               node, contnode)
            if res is not None:
                return res
        return None
    else:
        domain_name = node.get('refdomain')
        if not domain_name:
            # only objects in domains are in the inventory
            return None
        if honor_disabled_refs \
                and (domain_name + ":*") in env.config.intersphinx_disabled_reftypes:
            return None
        domain = env.get_domain(domain_name)
        objtypes = domain.objtypes_for_role(typ)
        if not objtypes:
            return None
        return _resolve_reference_in_domain(env, inv_name, inventory,
                                            honor_disabled_refs,
                                            domain, objtypes,
                                            node, contnode)


def inventory_exists(env: BuildEnvironment, inv_name: str) -> bool:
    return inv_name in InventoryAdapter(env).named_inventory


def resolve_reference_in_inventory(env: BuildEnvironment,
                                   inv_name: str,
                                   node: pending_xref, contnode: TextElement
                                   ) -> Optional[Element]:
    """Attempt to resolve a missing reference via intersphinx references.

    Resolution is tried in the given inventory with the target as is.

    Requires ``inventory_exists(env, inv_name)``.
    """
    assert inventory_exists(env, inv_name)
    return _resolve_reference(env, inv_name, InventoryAdapter(env).named_inventory[inv_name],
                              False, node, contnode)


def resolve_reference_any_inventory(env: BuildEnvironment,
                                    honor_disabled_refs: bool,
                                    node: pending_xref, contnode: TextElement
                                    ) -> Optional[Element]:
    """Attempt to resolve a missing reference via intersphinx references.

    Resolution is tried with the target as is in any inventory.
    """
    return _resolve_reference(env, None, InventoryAdapter(env).main_inventory,
                              honor_disabled_refs,
                              node, contnode)


def resolve_reference_detect_inventory(env: BuildEnvironment,
                                       node: pending_xref, contnode: TextElement
                                       ) -> Optional[Element]:
    """Attempt to resolve a missing reference via intersphinx references.

    Resolution is tried first with the target as is in any inventory.
    If this does not succeed, then the target is split by the first ``:``,
    to form ``inv_name:newtarget``. If ``inv_name`` is a named inventory, then resolution
    is tried in that inventory with the new target.
    """

    # ordinary direct lookup, use data as is
    res = resolve_reference_any_inventory(env, True, node, contnode)
    if res is not None:
        return res

    # try splitting the target into 'inv_name:target'
    target = node['reftarget']
    if ':' not in target:
        return None
    inv_name, newtarget = target.split(':', 1)
    if not inventory_exists(env, inv_name):
        return None
    node['reftarget'] = newtarget
    res_inv = resolve_reference_in_inventory(env, inv_name, node, contnode)
    node['reftarget'] = target
    return res_inv


def missing_reference(app: Sphinx, env: BuildEnvironment, node: pending_xref,
                      contnode: TextElement) -> Optional[Element]:
    """Attempt to resolve a missing reference via intersphinx references."""

    return resolve_reference_detect_inventory(env, node, contnode)


class IntersphinxDispatcher(CustomReSTDispatcher):
    """Custom dispatcher for external role.

    This enables :external:***:/:external+***: roles on parsing reST document.
    """

    def role(self, role_name: str, language_module: ModuleType, lineno: int, reporter: Reporter
             ) -> Tuple[RoleFunction, List[system_message]]:
        if len(role_name) > 9 and role_name.startswith(('external:', 'external+')):
            return IntersphinxRole(role_name), []
        else:
            return super().role(role_name, language_module, lineno, reporter)


class IntersphinxRole(SphinxRole):
    # group 1: just for the optionality of the inventory name
    # group 2: the inventory name (optional)
    # group 3: the domain:role or role part
    _re_inv_ref = re.compile(r"(\+([^:]+))?:(.*)")

    def __init__(self, orig_name: str) -> None:
        self.orig_name = orig_name

    def run(self) -> Tuple[List[Node], List[system_message]]:
        assert self.name == self.orig_name.lower()
        inventory, name_suffix = self.get_inventory_and_name_suffix(self.orig_name)
        if inventory and not inventory_exists(self.env, inventory):
            logger.warning(__('inventory for external cross-reference not found: %s'),
                           inventory, location=(self.env.docname, self.lineno))
            return [], []

        role_name = self.get_role_name(name_suffix)
        if role_name is None:
            logger.warning(__('role for external cross-reference not found: %s'), name_suffix,
                           location=(self.env.docname, self.lineno))
            return [], []

        result, messages = self.invoke_role(role_name)
        for node in result:
            if isinstance(node, pending_xref):
                node['intersphinx'] = True
                node['inventory'] = inventory

        return result, messages

    def get_inventory_and_name_suffix(self, name: str) -> Tuple[Optional[str], str]:
        assert name.startswith('external'), name
        assert name[8] in ':+', name
        # either we have an explicit inventory name, i.e,
        # :external+inv:role:        or
        # :external+inv:domain:role:
        # or we look in all inventories, i.e.,
        # :external:role:            or
        # :external:domain:role:
        inv, suffix = IntersphinxRole._re_inv_ref.fullmatch(name, 8).group(2, 3)
        return inv, suffix

    def get_role_name(self, name: str) -> Optional[Tuple[str, str]]:
        names = name.split(':')
        if len(names) == 1:
            # role
            default_domain = self.env.temp_data.get('default_domain')
            domain = default_domain.name if default_domain else None
            role = names[0]
        elif len(names) == 2:
            # domain:role:
            domain = names[0]
            role = names[1]
        else:
            return None

        if domain and self.is_existent_role(domain, role):
            return (domain, role)
        elif self.is_existent_role('std', role):
            return ('std', role)
        else:
            return None

    def is_existent_role(self, domain_name: str, role_name: str) -> bool:
        try:
            domain = self.env.get_domain(domain_name)
            if role_name in domain.roles:
                return True
            else:
                return False
        except ExtensionError:
            return False

    def invoke_role(self, role: Tuple[str, str]) -> Tuple[List[Node], List[system_message]]:
        domain = self.env.get_domain(role[0])
        if domain:
            role_func = domain.role(role[1])

            return role_func(':'.join(role), self.rawtext, self.text, self.lineno,
                             self.inliner, self.options, self.content)
        else:
            return [], []


class IntersphinxRoleResolver(ReferencesResolver):
    """pending_xref node resolver for intersphinx role.

    This resolves pending_xref nodes generated by :intersphinx:***: role.
    """

    default_priority = ReferencesResolver.default_priority - 1

    def run(self, **kwargs: Any) -> None:
        for node in self.document.findall(pending_xref):
            if 'intersphinx' not in node:
                continue
            contnode = cast(nodes.TextElement, node[0].deepcopy())
            inv_name = node['inventory']
            if inv_name is not None:
                assert inventory_exists(self.env, inv_name)
                newnode = resolve_reference_in_inventory(self.env, inv_name, node, contnode)
            else:
                newnode = resolve_reference_any_inventory(self.env, False, node, contnode)
            if newnode is None:
                typ = node['reftype']
                msg = (__('external %s:%s reference target not found: %s') %
                       (node['refdomain'], typ, node['reftarget']))
                logger.warning(msg, location=node, type='ref', subtype=typ)
                node.replace_self(contnode)
            else:
                node.replace_self(newnode)


def install_dispatcher(app: Sphinx, docname: str, source: List[str]) -> None:
    """Enable IntersphinxDispatcher.

    .. note:: The installed dispatcher will be uninstalled on disabling sphinx_domain
              automatically.
    """
    dispatcher = IntersphinxDispatcher()
    dispatcher.enable()


def normalize_intersphinx_mapping(app: Sphinx, config: Config) -> None:
    for key, value in config.intersphinx_mapping.copy().items():
        try:
            if isinstance(value, (list, tuple)):
                # new format
                name, (uri, inv) = key, value
                if not isinstance(name, str):
                    logger.warning(__('intersphinx identifier %r is not string. Ignored'),
                                   name)
                    config.intersphinx_mapping.pop(key)
                    continue
            else:
                # old format, no name
                name, uri, inv = None, key, value

            if not isinstance(inv, tuple):
                config.intersphinx_mapping[key] = (name, (uri, (inv,)))
            else:
                config.intersphinx_mapping[key] = (name, (uri, inv))
        except Exception as exc:
            logger.warning(__('Failed to read intersphinx_mapping[%s], ignored: %r'), key, exc)
            config.intersphinx_mapping.pop(key)


def setup(app: Sphinx) -> Dict[str, Any]:
    app.add_config_value('intersphinx_mapping', {}, True)
    app.add_config_value('intersphinx_cache_limit', 5, False)
    app.add_config_value('intersphinx_timeout', None, False)
    app.add_config_value('intersphinx_disabled_reftypes', ['std:doc'], True)
    app.connect('config-inited', normalize_intersphinx_mapping, priority=800)
    app.connect('builder-inited', load_mappings)
    app.connect('source-read', install_dispatcher)
    app.connect('missing-reference', missing_reference)
    app.add_post_transform(IntersphinxRoleResolver)
    return {
        'version': sphinx.__display_version__,
        'env_version': 1,
        'parallel_read_safe': True
    }


def inspect_main(argv: List[str]) -> None:
    """Debug functionality to print out an inventory"""
    if len(argv) < 1:
        print("Print out an inventory file.\n"
              "Error: must specify local path or URL to an inventory file.",
              file=sys.stderr)
        sys.exit(1)

    class MockConfig:
        intersphinx_timeout: Optional[int] = None
        tls_verify = False
        user_agent = None

    class MockApp:
        srcdir = ''
        config = MockConfig()

        def warn(self, msg: str) -> None:
            print(msg, file=sys.stderr)

    try:
        filename = argv[0]
        invdata = fetch_inventory(MockApp(), '', filename)  # type: ignore
        for key in sorted(invdata or {}):
            print(key)
            for entry, einfo in sorted(invdata[key].items()):
                print('\t%-40s %s%s' % (entry,
                                        '%-40s: ' % einfo[3] if einfo[3] != '-' else '',
                                        einfo[2]))
    except ValueError as exc:
        print(exc.args[0] % exc.args[1:])
    except Exception as exc:
        print('Unknown error: %r' % exc)


if __name__ == '__main__':
    import logging as _logging
    _logging.basicConfig()

    inspect_main(argv=sys.argv[1:])
