#
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# regarding copyright ownership.  The ASF licenses this file
# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
# with the License.  You may obtain a copy of the License at
#
#   http://www.apache.org/licenses/LICENSE-2.0
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# Unless required by applicable law or agreed to in writing,
# software distributed under the License is distributed on an
# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
# KIND, either express or implied.  See the License for the
# specific language governing permissions and limitations
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from ..dispatch import LOG_INFO, LOG_TRACE, LOG_DEBUG
from data import LinkState
from .address import Address

class NodeTracker(object):
    """
    This module is responsible for tracking the set of router nodes that are known to this
    router.  It tracks whether they are neighbor or remote and whether they are reachable.

    This module is also responsible for assigning a unique mask bit value to each router.
    The mask bit is used in the main router to represent sets of valid destinations for addresses.
    """
    def __init__(self, container, max_routers):
        self.container             = container
        self.my_id                 = container.id
        self.max_routers           = max_routers
        self.link_state            = LinkState(None, self.my_id, 0, {})
        self.link_state_changed    = False
        self.recompute_topology    = False
        self.last_topology_change  = 0
        self.flux_mode             = False
        self.nodes                 = {}  # id => RouterNode
        self.nodes_by_link_id      = {}  # link-id => node-id
        self.maskbits              = []
        self.next_maskbit          = 1   # Reserve bit '0' to represent this router
        for i in range(max_routers):
            self.maskbits.append(None)
        self.maskbits[0]      = True
        self.neighbor_max_age = self.container.config.helloMaxAge
        self.ls_max_age       = self.container.config.remoteLsMaxAge
        self.flux_interval    = self.container.config.raIntervalFlux * 2
        self.container.router_adapter.get_agent().add_implementation(self, "router.node")


    def refresh_entity(self, attributes):
        """Refresh management attributes"""
        attributes.update({
            "id": self.my_id,
            "instance": self.container.instance, # Boot number, integer
            "linkState": [ls for ls in self.link_state.peers], # List of neighbour nodes
            "nextHop":  "(self)",
            "validOrigins": [],
            "address": Address.topological(self.my_id, area=self.container.area)
        })


    def _do_expirations(self, now):
        """
        Run through the list of routers and check for expired conditions
        """
        for node_id, node in self.nodes.items():
            ##
            ## If the node is a neighbor, check the neighbor refresh time to see
            ## if we've waited too long for a refresh.  If so, disconnect the link
            ## and remove the node from the local link state.
            ##
            if node.is_neighbor():
                if now - node.neighbor_refresh_time > self.neighbor_max_age:
                    node.remove_link()
                    if self.link_state.del_peer(node_id):
                        self.link_state_changed = True

            ##
            ## Check the age of the node's link state.  If it's too old, clear it out.
            ##
            if now - node.link_state.last_seen > self.ls_max_age:
                if node.link_state.has_peers():
                    node.link_state.del_all_peers()
                    self.recompute_topology = True

            ##
            ## If the node has empty link state, check to see if it appears in any other
            ## node's link state.  If it does not, then delete the node.
            ##
            if not node.link_state.has_peers() and not node.is_neighbor():
                delete_node = True
                for _id, _n in self.nodes.items():
                    if _id != node_id:
                        if _n.link_state.is_peer(node_id):
                            delete_node = False
                            break
                if delete_node:
                    ##
                    ## The keep_alive_count is set to zero when a new node is first
                    ## discovered.  Since we can learn about a node before we receive
                    ## its link state, the keep_alive_count is used to prevent the
                    ## node from being deleted before we can learn more about it.
                    ##
                    node.keep_alive_count += 1
                    if node.keep_alive_count > 2:
                        node.delete()
                        self.nodes.pop(node_id)


    def tick(self, now):
        send_ra = False

        ##
        ## Expire neighbors and link state
        ##
        self._do_expirations(now)

        ##
        ## Enter flux mode if things are changing
        ##
        if self.link_state_changed or self.recompute_topology:
            self.last_topology_change = now
            if not self.flux_mode:
                self.flux_mode = True
                self.container.log(LOG_TRACE, "Entered Router Flux Mode")

        ##
        ## Handle local link state changes
        ##
        if self.link_state_changed:
            self.link_state_changed = False
            self.link_state.bump_sequence()
            self.recompute_topology = True
            send_ra = True
            self.container.log_ls(LOG_TRACE, "Local Link State: %r" % self.link_state)

        ##
        ## Recompute the topology
        ##
        if self.recompute_topology:
            self.recompute_topology = False
            collection = {self.my_id : self.link_state}
            for node_id, node in self.nodes.items():
                collection[node_id] = node.link_state
            next_hops, costs, valid_origins = self.container.path_engine.calculate_routes(collection)
            self.container.log_ls(LOG_TRACE, "Computed next hops: %r" % next_hops)
            self.container.log_ls(LOG_TRACE, "Computed costs: %r" % costs)
            self.container.log_ls(LOG_TRACE, "Computed valid origins: %r" % valid_origins)

            ##
            ## Update the next hops and valid origins for each node
            ##
            for node_id, next_hop_id in next_hops.items():
                node     = self.nodes[node_id]
                next_hop = self.nodes[next_hop_id]
                vo       = valid_origins[node_id]
                cost     = costs[node_id]
                node.set_next_hop(next_hop)
                node.set_valid_origins(vo)
                node.set_cost(cost)

        ##
        ## Send link-state requests and mobile-address requests to the nodes
        ## that have pending requests and are reachable
        ##
        for node_id, node in self.nodes.items():
            if node.link_state_requested():
                self.container.link_state_engine.send_lsr(node_id)
            if node.mobile_address_requested():
                self.container.mobile_address_engine.send_mar(node_id, node.mobile_address_sequence)

        ##
        ## If local changes have been made to the list of mobile addresses, send
        ## an unsolicited mobile-address-update to all routers.
        ##
        mobile_seq = self.container.mobile_address_engine.tick(now)
        self.container.link_state_engine.set_mobile_seq(mobile_seq)

        ##
        ## Send an immediate RA if our link state changed
        ##
        if send_ra:
            self.container.link_state_engine.send_ra(now)


    def neighbor_refresh(self, node_id, instance, link_id, cost, now):
        """
        Invoked when the hello protocol has received positive confirmation
        of continued bi-directional connectivity with a neighbor router.
        """

        ##
        ## If the node id is not known, create a new RouterNode to track it.
        ##
        if node_id not in self.nodes:
            self.nodes[node_id] = RouterNode(self, node_id, instance)
        node = self.nodes[node_id]

        ##
        ## Set the link_id to indicate this is a neighbor router.  If the link_id
        ## changed, update the index and add the neighbor to the local link state.
        ##
        if node.set_link_id(link_id):
            self.nodes_by_link_id[link_id] = node
            node.request_link_state()
            if self.link_state.add_peer(node_id, cost):
                self.link_state_changed = True

        ##
        ## Update the refresh time for later expiration checks
        ##
        node.neighbor_refresh_time = now

        ##
        ## If the instance was updated (i.e. the neighbor restarted suddenly),
        ## schedule a topology recompute and a link-state-request to that router.
        ##
        if node.update_instance(instance):
            self.recompute_topology = True
            node.request_link_state()


    def link_lost(self, link_id):
        """
        Invoked when an inter-router link is dropped.
        """
        self.container.log_ls(LOG_INFO, "Link to Neighbor Router Lost - link_tag=%d" % link_id)
        node_id = self.link_id_to_node_id(link_id)
        if node_id:
            self.nodes_by_link_id.pop(link_id)
            node = self.nodes[node_id]
            node.remove_link()
            if self.link_state.del_peer(node_id):
                self.link_state_changed = True


    def in_flux_mode(self, now):
        result = (now - self.last_topology_change) <= self.flux_interval
        if not result and self.flux_mode:
            self.flux_mode = False
            self.container.log(LOG_TRACE, "Exited Router Flux Mode")
        return result


    def ra_received(self, node_id, ls_seq, mobile_seq, instance, now):
        """
        Invoked when a router advertisement is received from another router.
        """
        ##
        ## If the node id is not known, create a new RouterNode to track it.
        ##
        if node_id not in self.nodes:
            self.nodes[node_id] = RouterNode(self, node_id, instance)
        node = self.nodes[node_id]

        ##
        ## If the instance was updated (i.e. the router restarted suddenly),
        ## schedule a topology recompute and a link-state-request to that router.
        ##
        if node.update_instance(instance):
            self.recompute_topology = True
            node.request_link_state()

        ##
        ## Update the last seen time to now to control expiration of the link state.
        ##
        node.link_state.last_seen = now

        ##
        ## Check the link state sequence.  Send a link state request if our records are
        ## not up to date.
        ##
        if node.link_state.ls_seq < ls_seq:
            self.container.link_state_engine.send_lsr(node_id)

        ##
        ## Check the mobile sequence.  Send a mobile-address-request if we are
        ## behind the advertized sequence.
        ##
        if node.mobile_address_sequence < mobile_seq:
            node.mobile_address_request()


    def router_learned(self, node_id):
        """
        Invoked when we learn about another router by any means
        """
        if node_id not in self.nodes and node_id != self.my_id:
            self.nodes[node_id] = RouterNode(self, node_id, None)


    def link_state_received(self, node_id, link_state, instance, now):
        """
        Invoked when a link state update is received from another router.
        """
        ##
        ## If the node id is not known, create a new RouterNode to track it.
        ##
        if node_id not in self.nodes:
            self.nodes[node_id] = RouterNode(self, node_id, instance)
        node = self.nodes[node_id]

        ##
        ## If the new link state is more up-to-date than the stored link state,
        ## update it and schedule a topology recompute.
        ##
        if link_state.ls_seq > node.link_state.ls_seq:
            node.link_state = link_state
            node.link_state.last_seen = now
            self.recompute_topology = True

            ##
            ## Look through the new link state for references to nodes that we don't
            ## know about.  Schedule link state requests for those nodes to be sent
            ## after we next recompute the topology.
            ##
            for peer in node.link_state.peers:
                if peer not in self.nodes:
                    self.router_learned(peer)


    def router_node(self, node_id):
        return self.nodes[node_id]


    def link_id_to_node_id(self, link_id):
        if link_id in self.nodes_by_link_id:
            return self.nodes_by_link_id[link_id].id
        return None


    def _allocate_maskbit(self):
        if self.next_maskbit == None:
            raise Exception("Exceeded Maximum Router Count")
        result = self.next_maskbit
        self.next_maskbit = None
        self.maskbits[result] = True
        for n in range(result + 1, self.max_routers):
            if self.maskbits[n] == None:
                self.next_maskbit = n
                break
        return result


    def _free_maskbit(self, i):
        self.maskbits[i] = None
        if self.next_maskbit == None or i < self.next_maskbit:
            self.next_maskbit = i


class RouterNode(object):
    """
    RouterNode is used to track remote routers in the router network.
    """

    def __init__(self, parent, node_id, instance):
        self.parent                  = parent
        self.adapter                 = parent.container.router_adapter
        self.log                     = parent.container.log
        self.id                      = node_id
        self.instance                = instance
        self.maskbit                 = self.parent._allocate_maskbit()
        self.neighbor_refresh_time   = 0.0
        self.peer_link_id            = None
        self.link_state              = LinkState(None, self.id, 0, {})
        self.next_hop_router         = None
        self.cost                    = None
        self.valid_origins           = None
        self.mobile_addresses        = []
        self.mobile_address_sequence = 0
        self.need_ls_request         = True
        self.need_mobile_request     = False
        self.keep_alive_count        = 0
        self.adapter.add_router("amqp:/_topo/0/%s/qdrouter" % self.id, self.maskbit)
        self.log(LOG_TRACE, "Node %s created: maskbit=%d" % (self.id, self.maskbit))
        self.adapter.get_agent().add_implementation(self, "router.node")

    def refresh_entity(self, attributes):
        """Refresh management attributes"""
        attributes.update({
            "id": self.id,
            "instance": self.instance, # Boot number, integer
            "linkState": [ls for ls in self.link_state.peers], # List of neighbour nodes
            "nextHop":  self.next_hop_router and self.next_hop_router.id,
            "validOrigins": self.valid_origins,
            "address": Address.topological(self.id, area=self.parent.container.area),
            "routerLink": self.peer_link_id,
            "cost": self.cost
        })

    def _logify(self, addr):
        cls   = addr[0]
        phase = None
        if cls == 'M':
            phase = addr[1]
            return "%s;class=%c;phase=%c" % (addr[2:], cls, phase)
        return "%s;class=%c" % (addr[1:], cls)


    def set_link_id(self, link_id):
        if self.peer_link_id == link_id:
            return False
        self.peer_link_id = link_id
        self.next_hop_router = None
        self.adapter.set_link(self.maskbit, link_id)
        self.adapter.remove_next_hop(self.maskbit)
        self.log(LOG_TRACE, "Node %s link set: link_id=%r" % (self.id, link_id))
        return True


    def remove_link(self):
        if self.peer_link_id != None:
            self.peer_link_id = None
            self.adapter.remove_link(self.maskbit)
            self.log(LOG_TRACE, "Node %s link removed" % self.id)


    def delete(self):
        self.adapter.get_agent().remove_implementation(self)
        self.unmap_all_addresses()
        self.adapter.del_router(self.maskbit)
        self.parent._free_maskbit(self.maskbit)
        self.log(LOG_TRACE, "Node %s deleted" % self.id)


    def set_next_hop(self, next_hop):
        if self.id == next_hop.id:
            return
        if self.next_hop_router and self.next_hop_router.id == next_hop.id:
            return
        self.next_hop_router = next_hop
        self.adapter.set_next_hop(self.maskbit, next_hop.maskbit)
        self.log(LOG_TRACE, "Node %s next hop set: %s" % (self.id, next_hop.id))


    def set_valid_origins(self, valid_origins):
        if self.valid_origins == valid_origins:
            return
        self.valid_origins = valid_origins
        vo_mb = [self.parent.nodes[N].maskbit for N in valid_origins]
        self.adapter.set_valid_origins(self.maskbit, vo_mb)
        self.log(LOG_TRACE, "Node %s valid origins: %r" % (self.id, valid_origins))


    def set_cost(self, cost):
        if self.cost == cost:
            return
        self.cost = cost
        self.adapter.set_cost(self.maskbit, cost)
        self.log(LOG_TRACE, "Node %s cost: %d" % (self.id, cost))


    def remove_next_hop(self):
        if self.next_hop_router:
            self.next_hop_router = None
            self.adapter.remove_next_hop(self.maskbit)
            self.log(LOG_TRACE, "Node %s next hop removed" % self.id)


    def is_neighbor(self):
        return self.peer_link_id != None


    def request_link_state(self):
        """
        Set the link-state-requested flag so we can send this node a link-state
        request at the most opportune time.
        """
        self.need_ls_request = True


    def link_state_requested(self):
        """
        Return True iff we need to request this node's link state AND the node is
        reachable.  There's no point in sending it a request if we don't know how to
        reach it.
        """
        if self.need_ls_request and (self.peer_link_id != None or self.next_hop_router != None):
            self.need_ls_request = False
            return True
        return False


    def mobile_address_request(self):
        self.need_mobile_request = True


    def mobile_address_requested(self):
        if self.need_mobile_request and (self.peer_link_id != None or self.next_hop_router != None):
            self.need_mobile_request = False
            return True
        return False


    def map_address(self, addr):
        self.mobile_addresses.append(addr)
        self.adapter.map_destination(addr, self.maskbit)
        self.log(LOG_DEBUG, "Remote destination %s mapped to router %s" % (self._logify(addr), self.id))


    def unmap_address(self, addr):
        self.mobile_addresses.remove(addr)
        self.adapter.unmap_destination(addr, self.maskbit)
        self.log(LOG_DEBUG, "Remote destination %s unmapped from router %s" % (self._logify(addr), self.id))


    def unmap_all_addresses(self):
        self.mobile_address_sequence = 0
        for addr in self.mobile_addresses:
            self.unmap_address(addr)


    def overwrite_addresses(self, addrs):
        added   = []
        deleted = []
        for a in addrs:
            if a not in self.mobile_addresses:
                added.append(a)
        for a in self.mobile_addresses:
            if a not in addrs:
                deleted.append(a)
        for a in added:
            self.map_address(a)
        for a in deleted:
            self.unmap_address(a)


    def update_instance(self, instance):
        if instance == None:
            return False
        if self.instance == None:
            self.instance = instance
            return False
        if self.instance == instance:
            return False

        self.instance = instance
        self.link_state.del_all_peers()
        self.unmap_all_addresses()
        self.log(LOG_INFO, "Detected Restart of Router Node %s" % self.id)
        return True