"""
NETCONF for APK Distributions server:
    Module Management System

Copyright © 2020 Adélie Software in the Public Benefit, Inc.

Released under the terms of the NCSA license.  See the LICENSE file included
with this source distribution for more information.

SPDX-License-Identifier: NCSA
"""

import hashlib

from logging import getLogger
from lxml import etree
from netconf import error, nsmap_add, util
from taillight import Signal

from ncserver.base.util import _


MODULE_SET_CHANGE_SIGNAL = Signal(('base/ModuleManager', 'module_set_changed'))
"""Signal fired when the module set changes.  This implies the
yang-library-change notification should be fired, when this is supported."""


QName = etree.QName  # pylint: disable=I1101


def _import_compatible(existing, improps):
    """Determine if an imported module is compatible with the existing
    module that has the same name/revision.

    :param existing:
    The dictionary of properties for the existing module.

    :param improps:
    The dictionary of properties for the candidate module.

    :returns bool:
    True if compatible, False otherwise.
    """
    return (improps.keys() == existing.keys() and
            all([existing[key] == improps[key] for key in existing.keys()]))


def _gen_modnode(parent, module):
    """Generate a yanglib:module node.

    The generated node is in the NMDA format.  With some massaging, it
    could be used for the deprecated non-NMDA format.

    :param parent:
    The parent XML node.

    :param module:
    The module.

    :returns:
    The generated module node.
    """
    modnode = util.subelm(parent, 'yanglib:module')
    modnode.append(util.leaf_elm('yanglib:name', module.M_NAME))
    modnode.append(util.leaf_elm('yanglib:revision', module.M_REVISION))
    modnode.append(util.leaf_elm('yanglib:namespace', module.M_NS))
    if getattr(module, 'M_FEATURES', None) is not None:
        for feature in module.M_FEATURES:
            modnode.append(util.leaf_elm('yanglib:feature', feature))
    return modnode


def _gen_modnode_import(parent, nodename, imname, improps):
    """Generate a node for an import-only module.

    :param parent:
    The parent XML node.

    :param nodename:
    The name of the XML node to create.  For NMDA library contents, use
    'yanglib:import-only-module'; otherwise, use 'yanglib:module'.

    :param imname:
    The name of the imported module in M_IMPORTS syntax.

    :param improps:
    The M_IMPORTS property dictionary for this imported module.

    :returns:
    The generated module node.
    """
    imn_name, imn_rev = imname.split('@')
    modnode = util.subelm(parent, nodename)
    modnode.append(util.leaf_elm('yanglib:name', imn_name))
    modnode.append(util.leaf_elm('yanglib:revision', imn_rev))
    modnode.append(util.leaf_elm('yanglib:namespace', improps['ns']))
    return modnode


class ModuleManager:
    """Manages the modules for the NETCONF for APK Distributions server.

    :ivar modules:
        Dictionary of loaded modules.

    :ivar library:
        Dictionary of loaded YANG models.
    """

    M_ABI_VERSION = 1
    M_PREFIX = "yanglib"
    M_NS = "urn:ietf:params:xml:ns:yang:ietf-yang-library"
    M_NAME = "ietf-yang-library"
    M_REVISION = "2019-01-04"
    M_IMPORTS = {'ietf-yang-types@2013-07-15':
                 {'ns': "urn:ietf:params:xml:ns:yang:ietf-yang-types",
                  'prefix': "yang"},
                 'ietf-inet-types@2013-07-15':
                 {'ns': "urn:ietf:params:xml:ns:yang:ietf-inet-types",
                  'prefix': "inet"},
                 'ietf-datastores@2018-02-14':
                 {'ns': "urn:ietf:params:xml:ns:yang:ietf-datastores",
                  'prefix': "ds"}}

    def __init__(self):
        self.modules = {'ncserver.base.modman': self}
        self.imports = dict(self.M_IMPORTS)
        self.library = {'ncserver.base.modman':
                        '{}@{}'.format(self.M_NAME, self.M_REVISION)}
        nsmap_add(self.M_PREFIX, self.M_NS)
        self.logger = getLogger('base/ModuleManager')

    def _module_for_ns(self, namespace):
        """Find a module that implements the specified namespace.

        :param str namespace:
            The namespace of the module to locate.

        :returns:
            The module that implements the namespace, or None.
        """
        for mod in self.modules.values():
            if mod.M_NS == namespace:
                return mod

        return None

    def load_module(self, name):
        """Load a module.

        :param str name:
            The name of the module to load.

        :returns:
            Either the name of the module (if loaded), or None (on error).
        """
        if name in self.modules:
            self.logger.warning(_("Module '%s' is already loaded; skipping"),
                                name)
            return name

        self.logger.debug(_("Discovering module '%s'..."), name)

        mod = None
        try:
            mod = __import__(name, globals(), locals(), [name], 0)
        except ImportError:
            self.logger.error(_("Module '%s' was not found."), name)
            return None

        if any([getattr(mod, attr, None) is None
                for attr in ['M_ABI_VERSION', 'M_NS', 'M_PREFIX', 'M_NAME']]):
            self.logger.error(_("'%s' is not a valid module."), name)
            return None

        if mod.M_ABI_VERSION != 1:
            self.logger.error(_("Module '%s' requires ABI version %d."), name,
                              mod.M_ABI_VERSION)
            return None

        if self._module_for_ns(mod.M_NS) is not None:
            self.logger.error(
                    _("Module '%s' implements duplicate namespace %s."), name,
                    mod.M_NS
            )

        if getattr(mod, 'M_IMPORTS', None) is not None:
            for imname, improps in mod.M_IMPORTS.items():
                if imname in self.imports:
                    if not _import_compatible(self.imports[imname], improps):
                        self.logger.error(_("Module '%s' has incompatible "
                                            "imported module '%s'"), name,
                                          imname)
                        return None
                else:
                    self.imports[imname] = improps

        self.logger.info(_("Loading module '%s' with ABI %d for namespace %s"),
                         name, mod.M_ABI_VERSION, mod.M_NS)

        self.modules[name] = mod
        self.library[name] = '{}@{}'.format(mod.M_NAME, mod.M_REVISION)
        nsmap_add(mod.M_PREFIX, mod.M_NS)
        MODULE_SET_CHANGE_SIGNAL.call(name, mod)
        return name

    def capabilities(self) -> list:
        """Determine the NETCONF capabilities for this server."""
        capabs = []

        def _cap_for_module(module):
            base = '{ns}?module={mod}&revision={rev}'.format(
                    ns=module.M_NS, mod=module.M_NAME, rev=module.M_REVISION
            )
            if getattr(module, 'M_FEATURES', None) is not None:
                return '{base}&features={feat}'.format(
                        base=base, feat=','.join(module.M_FEATURES)
                )
            return base

        def _cap_for_import(imname, improp):
            name, rev = imname.split('@')
            return '{ns}?module={mod}&revision={rev}'.format(
                    ns=improp['ns'], mod=name, rev=rev
            )

        for imdata in self.imports.items():
            capabs.append(_cap_for_import(*imdata))
        for module in self.modules.values():
            capabs.append(_cap_for_module(module))
        capabs.append('{ns}?revision={rev}&module-set-id={id}'.format(
                ns='urn:ietf:params:netconf:capability:yang-library:1.0',
                rev='2019-01-04', id=self._module_set_id()
        ))

        return capabs

    def running(self, node):
        """Return running configuration information."""
        # ietf-yang-library is state-only.

    def _module_set_id(self):
        """Retrieve the module set ID for this server."""
        module_set_id = hashlib.sha256(','.join(self.modules.keys()).encode())
        return module_set_id.hexdigest()

    def _gen_yang_library(self, node):
        """Generate yanglib:yang-library node.

        :param node:
        The XML node to append to.
        """
        lib = util.subelm(node, 'yanglib:yang-library', nsmap={
            'ds': "urn:ietf:params:xml:ns:yang:ietf-datastores"
        })
        modset = util.subelm(lib, 'yanglib:module-set')
        modset.append(util.leaf_elm('yanglib:name', 'netconfapk'))
        for module in self.modules.values():
            _gen_modnode(modset, module)
        for imname, improps in self.imports.items():
            _gen_modnode_import(modset, 'yanglib:import-only-module', imname,
                                improps)
        schema = util.subelm(lib, 'yanglib:schema')
        schema.append(util.leaf_elm('yanglib:name', 'apkschema'))
        schema.append(util.leaf_elm('yanglib:module-set', 'netconfapk'))

        for store in ['ds:running', 'ds:operational']:
            dsnode = util.subelm(lib, 'yanglib:datastore')
            dsnode.append(util.leaf_elm('yanglib:name', store))
            dsnode.append(util.leaf_elm('yanglib:schema', 'apkschema'))

        lib.append(util.leaf_elm('yanglib:content-id', self._module_set_id()))
        return lib

    def operational(self, node):
        """Return configuration and device state information."""
        # NDMA-enabled yang-library node.
        self._gen_yang_library(node)

        # Deprecated modules-state node.
        modstate = util.subelm(node, 'yanglib:modules-state')
        modstate.append(util.leaf_elm('yanglib:module-set-id',
                        self._module_set_id()))
        for module in self.modules.values():
            modnode = _gen_modnode(modstate, module)
            modnode.append(util.leaf_elm('yanglib:conformance-type',
                                         'implement'))
        for imname, improps in self.imports.items():
            modnode = _gen_modnode_import(modstate, 'yanglib:module', imname,
                                          improps)
            modnode.append(util.leaf_elm('yanglib:conformance-type', 'import'))

    def collect_running(self, node):
        """Collect all available information for the <running> datastore."""
        for mod in self.modules.values():
            mod.running(node)

    def collect_operational(self, node):
        """Collect all available information for the <operational> datastore"""
        for mod in self.modules.values():
            mod.operational(node)

    def collect_edit(self, rpc, node, def_op):
        """Send off edit operations to the requested module(s)."""
        for child in node:
            namespace = QName(child.tag).namespace
            module = self._module_for_ns(namespace)
            if module is None:
                raise error.UnknownNamespaceAppError(
                        rpc, child, error.RPCERR_TYPE_APPLICATION
                )
            if getattr(module, 'edit', None) is None:
                raise error.OperationNotSupportedAppError(rpc)
            self.logger.debug('Dispatching edit-config to %s', module.M_NAME)
            module.edit(rpc, child, def_op)