# Copyright (C) 2009-2010 Raul Jimenez
# Released under GNU LGPL 2.1
# See LICENSE.txt for more information
"""
This module intends to implement the routing policy specified in NICE:

-
-
-
-

"""


import random
import core.ptime as time
import heapq

import logging

import core.identifier as identifier
import core.message as message
from core.querier import Query
import core.node as node
from core.node import Node, RoutingNode
from core.routing_table import RoutingTable

logger = logging.getLogger('dht')

NUM_BUCKETS = identifier.ID_SIZE_BITS
"""
We need 160 sbuckets to cover all the cases. See the following table:
Index | Distance      | Comment
0     | [2^0,2^1)     | All bits equal but the least significant bit
1     | [2^1,2^2)     | All bits equal till the second least significant bit
...
158   | [2^159,2^160) | The most significant bit is equal the second is not
159   | [2^159,2^160) | The most significant bit is different

IMPORTANT: Notice there is NO bucket for -1
-1    | 0             | The bit strings are equal
"""

DEFAULT_NUM_NODES = 8
NODES_PER_BUCKET = [] # 16, 32, 64, 128, 256]
NODES_PER_BUCKET[:0] = [DEFAULT_NUM_NODES] \
    * (NUM_BUCKETS - len(NODES_PER_BUCKET))

REFRESH_PERIOD = 15 * 60 # 15 minutes
QUARANTINE_PERIOD = 3 * 60 # 3 minutes

MAX_NUM_TIMEOUTS = 2
PING_DELAY_AFTER_TIMEOUT = 30 #seconds


MIN_RNODES_BOOTSTRAP = 10
NUM_NODES_PER_BOOTSTRAP_STEP = 1

BOOTSTRAP_MODE = 'bootstrap_mode'
FIND_CLOSEST_MODE = 'find_closest_mode'
NORMAL_MODE = 'normal_mode'
_MAINTENANCE_DELAY = {BOOTSTRAP_MODE: .2,
                     FIND_CLOSEST_MODE: 3,
                     NORMAL_MODE: 6}


class RoutingManager(object):
    
    def __init__(self, my_node, bootstrap_nodes):
        self.my_node = my_node
        #Copy the bootstrap list
        self.bootstrap_nodes = iter(bootstrap_nodes)
        
        self.table = RoutingTable(my_node, NODES_PER_BUCKET)
        self.ping_msg = message.OutgoingPingQuery(my_node.id)
        self.find_closest_msg = message.OutgoingFindNodeQuery(
            my_node.id,
            my_node.id)

        # maintenance variables
        self._next_stale_maintenance_index = 0
        self._maintenance_mode = BOOTSTRAP_MODE
        self._replacement_queue = _ReplacementQueue(self.table)
        self._query_received_queue = _QueryReceivedQueue(self.table)
        self._found_nodes_queue = _FoundNodesQueue(self.table)
        self._maintenance_tasks = [self._ping_a_staled_rnode,
                                   self._ping_a_query_received_node,
                                   self._ping_a_found_node,
                                   self._ping_a_replacement_node,
                                   ]
        
    def do_maintenance(self):
        queries_to_send = []
        maintenance_lookup_target = None
        if self._maintenance_mode == BOOTSTRAP_MODE:
            try:
                node_ = self.bootstrap_nodes.next()
                queries_to_send = [self._get_maintenance_query(node_)]
            except (StopIteration):
                maintenance_lookup_target = self.my_node.id
                self._maintenance_mode = NORMAL_MODE
        elif self._maintenance_mode == NORMAL_MODE:
            for _ in range(len(self._maintenance_tasks)):
                # We try maintenance tasks till one of them actually does work
                # or we have tried them all (whatever happens first) We loop
                # in range because I'm going to modify self._maintenance_tasks
                task = self._maintenance_tasks.pop(0)
                self._maintenance_tasks.append(task)
                node_ = task()
                if node_:
                    queries_to_send = [self._get_maintenance_query(node_)]
                    # This task did do some work. We are done here!
                    break
        
        return (_MAINTENANCE_DELAY[self._maintenance_mode],
                queries_to_send, maintenance_lookup_target)

    def _ping_a_staled_rnode(self):
        # Don't have self._next_stale_maintenance_index lower than
        # lowest_bucket
        
        starting_index = self._next_stale_maintenance_index
        result = None
        while not result:
            # Find a non-empty bucket
            sbucket = self.table.get_sbucket(
                self._next_stale_maintenance_index)
            m_bucket = sbucket.main
            self._next_stale_maintenance_index = (
                self._next_stale_maintenance_index + 1) % (NUM_BUCKETS - 1)
            if m_bucket:
                rnode = m_bucket.get_stalest_rnode()
                if time.time() > rnode.last_seen + QUARANTINE_PERIOD:
                    result = rnode
            if self._next_stale_maintenance_index == starting_index:
                # No node to be pinged in the whole table.
                break
        return result

    def _ping_a_found_node(self):
        num_pings = 1
        if self.table.num_rnodes < MIN_RNODES_BOOTSTRAP:
            # Extra ping when bootstrapping
            num_pings += 1
        for _ in range(num_pings):
            node_ = self._found_nodes_queue.pop(0)
            if node_:
                logger.debug('pinging node found: %r', node_)
                return node_
        return

    def _ping_a_query_received_node(self):
        return self._query_received_queue.pop(0)

    def _ping_a_replacement_node(self):
        return self._replacement_queue.pop(0)
                                  
    def _get_maintenance_query(self, node_):
        if not node_.id: 
            # Bootstrap nodes don't have id
            return Query(self.find_closest_msg, node_)

        if random.choice((False, True)):
            # 50% chance to send find_node with my id as target
            return Query(self.find_closest_msg, node_)

        # 50% chance to send a find_node to fill up a non-full bucket
        target_log_distance = self.table.find_next_bucket_with_room_index(
            node_=node_)
        if target_log_distance:
            target = self.my_node.id.generate_close_id(target_log_distance)
            return Query(
                message.OutgoingFindNodeQuery(self.my_node.id, target),
                node_)
        else:
            # Every bucket is full. We send a ping instead.
            return Query(self.ping_msg, node_)
        
    def on_query_received(self, node_):
        '''
        Return None when nothing to do
        Return a list of queries when queries need to be sent (the queries
        will be sent out by the caller)
        '''
        log_distance = self.my_node.log_distance(node_)
        try:
            sbucket = self.table.get_sbucket(log_distance)
        except(IndexError):
            return # Got a query from myself. Just ignore it.

        m_bucket = sbucket.main
        r_bucket = sbucket.replacement
        rnode = m_bucket.get_rnode(node_)
        if rnode:
            # node in routing table: inform rnode
            self._update_rnode_on_query_received(rnode)
            return
        
        # node is not in the routing table
        if m_bucket.there_is_room():
            # There is room in the bucket: queue it
            self._query_received_queue.add(node_, log_distance)
            return
        # No room in the main routing table
        # Add to replacement table (if the bucket is not full)
        worst_rnode = self._worst_rnode(r_bucket.rnodes)
        if worst_rnode \
                and worst_rnode.timeouts_in_a_row() > MAX_NUM_TIMEOUTS:
            r_bucket.remove(worst_rnode)
            rnode = node_.get_rnode(log_distance)
            r_bucket.add(rnode)
            self._update_rnode_on_query_received(rnode)
        return
            
    def on_response_received(self, node_, rtt, nodes):
        if nodes:
            logger.debug('nodes found: %r', nodes)
        self._found_nodes_queue.add(nodes)

        logger.debug('on response received %f', rtt)
        log_distance = self.my_node.log_distance(node_)
        try:
            sbucket = self.table.get_sbucket(log_distance)
        except(IndexError):
            return # Got a response from myself. Just ignore it.
        m_bucket = sbucket.main
        r_bucket = sbucket.replacement
        rnode = m_bucket.get_rnode(node_)
        if rnode:
            # node in routing table: update
            self._update_rnode_on_response_received(rnode, rtt)
            return
        # The node is not in main
        rnode = r_bucket.get_rnode(node_)
        if rnode:
            # node in replacement table
            # let's see whether there is room in the main
            self._update_rnode_on_response_received(rnode, rtt)
            #TODO: leave this for the maintenance task
            if m_bucket.there_is_room():
                m_bucket.add(rnode)
                self.table.update_lowest_index(log_distance)
                self.table.num_rnodes += 1
                self._update_rnode_on_response_received(rnode, rtt)
                r_bucket.remove(rnode)
            return
        # The node is nowhere
        # Add to main table (if the bucket is not full)
        #TODO: check whether in replacement_mode
        if m_bucket.there_is_room():
            rnode = node_.get_rnode(log_distance)
            m_bucket.add(rnode)
            self.table.update_lowest_index(log_distance)
            self.table.num_rnodes += 1
            self._update_rnode_on_response_received(rnode, rtt)
            return
        # The main bucket is full

        # Get the worst node in replacement bucket and see whether
        # it's bad enough to be replaced by node_
        worst_rnode = self._worst_rnode(r_bucket.rnodes)
        if worst_rnode \
                and worst_rnode.timeouts_in_a_row() > MAX_NUM_TIMEOUTS:
            # This node is better candidate than worst_rnode
            r_bucket.remove(worst_rnode)
            rnode = node_.get_rnode(log_distance)
            r_bucket.add(rnode)
            self._update_rnode_on_response_received(rnode, rtt)
        return
        
    def on_error_received(self, node_):
        pass
    
    def on_timeout(self, node_):
        if not node_.id:
            return # This is a bootstrap node (just addr, no id)
        log_distance = self.my_node.log_distance(node_)
        try:
            sbucket = self.table.get_sbucket(log_distance)
        except (IndexError):
            return # Got a timeout from myself, WTF? Just ignore.
        m_bucket = sbucket.main
        r_bucket = sbucket.replacement
        rnode = m_bucket.get_rnode(node_)
        if rnode:
            # node in routing table: kick it out
            self._update_rnode_on_timeout(rnode)
            m_bucket.remove(rnode)
            self.table.update_lowest_index(log_distance)
            self.table.num_rnodes -= 1

            for r_rnode in r_bucket.sorted_by_rtt():
                self._replacement_queue.add(r_rnode)
            if r_bucket.there_is_room():
                r_bucket.add(rnode)
            else:
                worst_rnode = self._worst_rnode(r_bucket.rnodes)
                if worst_rnode:
                    # Replace worst node in replacement table
                    r_bucket.remove(worst_rnode)
                    r_bucket.add(rnode)
        # Node is not in main table
        rnode = r_bucket.get_rnode(node_)
        if rnode:
            # Node in replacement table: just update rnode
            self._update_rnode_on_timeout(rnode)
            
    def get_closest_rnodes(self, log_distance, num_nodes, exclude_myself):
        if not num_nodes:
            num_nodes = NODES_PER_BUCKET[log_distance]
        return self.table.get_closest_rnodes(log_distance, num_nodes,
                                             exclude_myself)

    def get_main_rnodes(self):
        return self.table.get_main_rnodes()

    def print_stats(self):
        self.table.print_stats()

    def _update_rnode_on_query_received(self, rnode):
        """Register a query from node.

        You should call this method when receiving a query from this node.

        """
        current_time = time.time()
        rnode.last_action_ts = time.time()
        rnode.msgs_since_timeout += 1
        rnode.num_queries += 1
        rnode.add_event(current_time, node.QUERY)
        rnode.last_seen = current_time

    def _update_rnode_on_response_received(self, rnode, rtt):
        """Register a reply from rnode.

        You should call this method when receiving a response from this rnode.

        """
        rnode.rtt = rtt
        current_time = time.time()
        #rnode._reset_refresh_task()
        if rnode.in_quarantine:
            rnode.in_quarantine = \
                rnode.last_action_ts < current_time - QUARANTINE_PERIOD
                
        rnode.last_action_ts = current_time
        rnode.num_responses += 1
        rnode.add_event(time.time(), node.RESPONSE)
        rnode.last_seen = current_time

    def _update_rnode_on_timeout(self, rnode):
        """Register a timeout for this rnode.

        You should call this method when getting a timeout for this node.

        """
        rnode.last_action_ts = time.time()
        rnode.msgs_since_timeout = 0
        rnode.num_timeouts += 1
        rnode.add_event(time.time(), node.TIMEOUT)

    def _worst_rnode(self, rnodes):
        max_num_timeouts = -1
        worst_rnode_so_far = None
        for rnode in rnodes:
            num_timeouots = rnode.timeouts_in_a_row()
            if num_timeouots >= max_num_timeouts:
                max_num_timeouts = num_timeouots
                worst_rnode_so_far = rnode
        return worst_rnode_so_far

        
class _ReplacementQueue(object):

    def __init__(self, table):
        self.table = table
        self._queue = []

    def add(self, rnode):
        self._queue.append(rnode)

    def pop(self, _):
        while self._queue:
            rnode = self._queue.pop(0)
            log_distance = self.table.my_node.log_distance(rnode)
            sbucket = self.table.get_sbucket(log_distance)
            m_bucket = sbucket.main
            if m_bucket.there_is_room():
                # room in main: return it
                return rnode
        return

class _QueryReceivedQueue(object):

    def __init__(self, table):
        self.table = table
        self._queue = []
        self._queued_nodes_set = set()
        self._nodes_queued_per_bucket = [0 for _ in range(160)]

    def add(self, node_, log_distance):
        # The caller already checked that there is room in the bucket
#        print 'received queue', len(self._queue)
        if node_ in self._queued_nodes_set:
            # This node is already queued
            return
        num_nodes_queued = self._nodes_queued_per_bucket[log_distance]
        if num_nodes_queued >= 8:
            # many nodes queued for this bucket already
            return
        self._queued_nodes_set.add(node_)
        self._nodes_queued_per_bucket[log_distance] = (
            num_nodes_queued + 1)
        self._queue.append((time.time(), node_))

    def pop(self, _):
        while self._queue:
            ts, node_ = self._queue[0]
            time_in_queue = time.time() - ts
            if time_in_queue < QUARANTINE_PERIOD:
                return
            # Quarantine period passed
            log_distance = self.table.my_node.log_distance(node_)
            self._queued_nodes_set.remove(node_)
            self._nodes_queued_per_bucket[log_distance] = (
                self._nodes_queued_per_bucket[log_distance] - 1)
            del self._queue[0]
            sbucket = self.table.get_sbucket(log_distance)
            m_bucket = sbucket.main
            if m_bucket.there_is_room():
                # room in main: return it
                return node_
        return

class _FoundNodesQueue(object):

    def __init__(self, table):
        self.table = table
        self._queue = []
        self._queued_nodes_set = set()
        self._nodes_queued_per_bucket = [0 for _ in range(160)]

    def add(self, nodes):
#        print 'found queue', len(self._queue)
        for node_ in nodes:
            if node_ in self._queued_nodes_set:
                # This node has already been queued
                continue
            log_distance = self.table.my_node.log_distance(node_)
            num_nodes_queued = self._nodes_queued_per_bucket[log_distance]
            if num_nodes_queued >= 8:
                # many nodes queued for this bucket already
                continue
            try:
                sbucket = self.table.get_sbucket(log_distance)
            except(IndexError):
                continue # this node is myself (index == -1)
            m_bucket = sbucket.main
            rnode = m_bucket.get_rnode(node_)
            if not rnode and m_bucket.there_is_room():
                # Not in the main: add to the queue if there is room in main
                self._nodes_queued_per_bucket[log_distance] = (
                    num_nodes_queued + 1)
                self._queued_nodes_set.add(node_)
                self._queue.append(node_)

    def pop(self, _): 
        while self._queue:
            node_ = self._queue.pop(0)
            self._queued_nodes_set.remove(node_)
            log_distance = self.table.my_node.log_distance(node_)
            sbucket = self.table.get_sbucket(log_distance)
            m_bucket = sbucket.main
            rnode = m_bucket.get_rnode(node_)
            if not rnode and m_bucket.there_is_room():
                # Not in the main: return it if there is room in main
                return node_
        return

            
class RoutingManagerMock(object):

    def get_closest_rnodes(self, target_id):
        import test_const as tc
        if target_id == tc.INFO_HASH_ZERO:
            return (tc.NODES_LD_IH[155][4], 
                    tc.NODES_LD_IH[157][3],
                    tc.NODES_LD_IH[158][1],
                    tc.NODES_LD_IH[159][0],
                    tc.NODES_LD_IH[159][2],)
        else:
            return tc.NODES
