# -*- mode: python; coding: utf-8 -*-
# Re2o est un logiciel d'administration développé initiallement au rezometz. Il
# se veut agnostique au réseau considéré, de manière à être installable en
# quelques clics.
#
# Copyright © 2020  Jean-Romain Garnier
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
"""logs.models
The models definitions for the logs app
"""
from reversion.models import Version
from django.utils.translation import ugettext_lazy as _
from django.contrib.auth.models import Group

from machines.models import IpList
from machines.models import Interface
from machines.models import Machine
from users.models import User


class MachineHistoryEvent:
    def __init__(self, user, machine, interface, start=None, end=None):
        """
        :param user: User, The user owning the maching at the time of the event
        :param machine: Version, the machine version related to the interface
        :param interface: Version, the interface targeted by this event
        :param start: datetime, the date at which this version was created
        :param end: datetime, the date at which this version was replace by a new one
        """
        self.user = user
        self.machine = machine
        self.interface = interface
        self.ipv4 = IpList.objects.get(id=interface.field_dict["ipv4_id"]).ipv4
        self.mac = self.interface.field_dict["mac_address"]
        self.start_date = start
        self.end_date = end
        self.comment = interface.revision.get_comment() or None

    def is_similar(self, elt2):
        """
        Checks whether two events are similar enough to be merged
        :return: bool
        """
        return (
            elt2 is not None
            and self.user.id == elt2.user.id
            and self.ipv4 == elt2.ipv4
            and self.machine.field_dict["id"] == elt2.machine.field_dict["id"]
            and self.interface.field_dict["id"] == elt2.interface.field_dict["id"]
        )

    def __repr__(self):
        return "{} ({} - ): from {} to {} ({})".format(
            self.machine,
            self.mac,
            self.ipv4,
            self.start_date,
            self.end_date,
            self.comment or "No comment"
        )


class MachineHistory:
    def __init__(self):
        self.events = []
        self.__last_evt = None

    def get(self, search, params):
        """
        :param search: ip or mac to lookup
        :param params: dict built by the search view
        :return: list or None, a list of MachineHistoryEvent
        """
        self.start = params.get("s", None)
        self.end = params.get("e", None)
        search_type = params.get("t", 0)

        self.events = []
        if search_type == "ip":
            return self.__get_by_ip(search)
        elif search_type == "mac":
            return self.__get_by_mac(search)

        return None

    def __add_revision(self, user, machine, interface):
        """
        Add a new revision to the chronological order
        :param user: User, The user owning the maching at the time of the event
        :param machine: Version, the machine version related to the interface
        :param interface: Version, the interface targeted by this event
        """
        evt = MachineHistoryEvent(user, machine, interface)
        evt.start_date = interface.revision.date_created

        # Try not to recreate events if it's unnecessary
        if evt.is_similar(self.__last_evt):
            return

        # Mark the end of validity of the last element
        if self.__last_evt and not self.__last_evt.end_date:
            self.__last_evt.end_date = evt.start_date

            # If the event ends before the given date, remove it
            if self.start and evt.start_date.date() < self.start:
                self.__last_evt = None
                self.events.pop()

        # Make sure the new event starts before the given end date
        if self.end and evt.start_date.date() > self.end:
            return

        # Save the new element
        self.events.append(evt)
        self.__last_evt = evt

    def __get_interfaces_for_ip(self, ip):
        """
        :param ip: str
        :return: An iterable object with the Version objects
                 of Interfaces with the given IP
        """
        # TODO: What if ip list was deleted?
        try:
            ip_id = IpList.objects.get(ipv4=ip).id
        except IpList.DoesNotExist:
            return []

        return filter(
            lambda x: x.field_dict["ipv4_id"] == ip_id,
            Version.objects.get_for_model(Interface).order_by("revision__date_created")
        )

    def __get_interfaces_for_mac(self, mac):
        """
        :param mac: str
        :return: An iterable object with the Version objects
                 of Interfaces with the given MAC address
        """
        return filter(
            lambda x: str(x.field_dict["mac_address"]) == mac,
            Version.objects.get_for_model(Interface).order_by("revision__date_created")
        )

    def __get_machines_for_interface(self, interface):
        """
        :param interface: Version, the interface for which to find the machines
        :return: An iterable object with the Version objects of Machine to
                 which the given interface was attributed
        """
        machine_id = interface.field_dict["machine_id"]
        return filter(
            lambda x: x.field_dict["id"] == machine_id,
            Version.objects.get_for_model(Machine).order_by("revision__date_created")
        )

    def __get_user_for_machine(self, machine):
        """
        :param machine: Version, the machine of which the owner must be found
        :return: The user to which the given machine belongs
        """
        # TODO: What if user was deleted?
        user_id = machine.field_dict["user_id"]
        return User.objects.get(id=user_id)

    def __get_by_ip(self, ip):
        """
        :param ip: str, The IP to lookup
        :returns: list, a list of MachineHistoryEvent
        """
        interfaces = self.__get_interfaces_for_ip(ip)

        for interface in interfaces:
            machines = self.__get_machines_for_interface(interface)

            for machine in machines:
                user = self.__get_user_for_machine(machine)
                self.__add_revision(user, machine, interface)

        return self.events

    def __get_by_mac(self, mac):
        """
        :param mac: str, The MAC address to lookup
        :returns: list, a list of MachineHistoryEvent
        """
        interfaces = self.__get_interfaces_for_mac(mac)

        for interface in interfaces:
            machines = self.__get_machines_for_interface(interface)

            for machine in machines:
                user = self.__get_user_for_machine(machine)
                self.__add_revision(user, machine, interface)

        return self.events


class UserHistoryEvent:
    def __init__(self, user, version, previous_version=None, edited_fields=None):
        """
        :param user: User, The user who's history is being built
        :param version: Version, the version of the user for this event
        :param previous_version: Version, the version of the user before this event
        :param edited_fields: list, The list of modified fields by this event
        """
        self.user = user
        self.version = version
        self.previous_version = previous_version
        self.edited_fields = edited_fields
        self.date = version.revision.date_created
        self.performed_by = version.revision.user
        self.comment = version.revision.get_comment() or None

    def __repr(self, name, value):
        """
        Returns the best representation of the given field
        :param name: the name of the field
        :param value: the value of the field
        :return: object
        """
        if name == "groups":
            if len(value) == 0:
                # Removed all the user's groups
                return _("None")

            # value is a list of ints
            groups = []
            for gid in value:
                # Try to get the group name, if it's not deleted
                try:
                    groups.append(Group.objects.get(id=gid).name)
                except Group.DoesNotExist:
                    # TODO: Find the group name in the versions?
                    groups.append(_("Deleted"))

            return ", ".join(groups)
        elif name == "state":
            if value is not None:
                return User.STATES[value][1]
            else:
                return _("Unknown")
        elif name == "email_state":
            if value is not None:
                return User.EMAIL_STATES[value][1]
            else:
                return _("Unknown")

        if value is None:
            return _("None")

        return value

    def edits(self, hide=["password", "pwd_ntlm"]):
        """
        Build a list of the changes performed during this event
        :param hide: list, the list of fields for which not to show details
        :return: str
        """
        edits = []

        for field in self.edited_fields:
            if field in hide:
                # Don't show sensitive information
                edits.append((field, None, None))
            else:
                edits.append((
                    field,
                    self.__repr(field, self.previous_version.field_dict[field]),
                    self.__repr(field, self.version.field_dict[field])
                ))

        return edits

    def __repr__(self):
        return "{} edited fields {} of {} ({})".format(
            self.performed_by,
            self.edited_fields or "nothing",
            self.user,
            self.comment or "No comment"
        )


class UserHistory:
    def __init__(self):
        self.events = []
        self.__last_version = None

    def get(self, user):
        """
        :param user: User, the user to lookup
        :return: list or None, a list of UserHistoryEvent, in reverse chronological order
        """
        self.events = []

        # Get all the versions for this user, with the oldest first
        user_versions = filter(
            lambda x: x.field_dict["id"] == user.id,
            Version.objects.get_for_model(User).order_by("revision__date_created")
        )

        for version in user_versions:
            self.__add_revision(user, version)

        return self.events[::-1]

    def __compute_diff(self, v1, v2, ignoring=["last_login", "pwd_ntlm", "email_change_date"]):
        """
        Find the edited field between two versions
        :param v1: Version
        :param v2: Version
        :param ignoring: List, a list of fields to ignore
        :return: List of field names
        """
        fields = []

        for key in v1.field_dict.keys():
            if key not in ignoring and v1.field_dict[key] != v2.field_dict[key]:
                fields.append(key)

        return fields

    def __add_revision(self, user, version):
        """
        Add a new revision to the chronological order
        :param user: User, The user displayed in this history
        :param version: Version, The version of the user for this event
        """
        diff = None
        if self.__last_version is not None:
            diff = self.__compute_diff(version, self.__last_version)

        # Ignore "empty" events like login
        if not diff:
            self.__last_version = version
            return

        evt = UserHistoryEvent(user, version, self.__last_version, diff)
        self.events.append(evt)
        self.__last_version = version