# -*- coding: utf-8 -*-
#
# Electrum - lightweight Bitcoin client
# Copyright (C) 2018 The Electrum developers
#
# Permission is hereby granted, free of charge, to any person
# obtaining a copy of this software and associated documentation files
# (the "Software"), to deal in the Software without restriction,
# including without limitation the rights to use, copy, modify, merge,
# publish, distribute, sublicense, and/or sell copies of the Software,
# and to permit persons to whom the Software is furnished to do so,
# subject to the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.

from datetime import datetime
import time
import random
import queue
import os
import json
import threading
import concurrent
from collections import defaultdict
from typing import Sequence, List, Tuple, Optional, Dict, NamedTuple, TYPE_CHECKING, Set
import binascii
import base64

from . import constants
from .util import bh2u, profiler, get_headers_dir, is_ip_address, list_enabled_bits, print_msg, chunks
from .logging import Logger
from .storage import JsonDB
from .lnverifier import LNChannelVerifier, verify_sig_for_channel_update
from .crypto import sha256d
from . import ecc
from .lnutil import (LN_GLOBAL_FEATURES_KNOWN_SET, LNPeerAddr, NUM_MAX_EDGES_IN_PAYMENT_PATH,
                     NotFoundChanAnnouncementForUpdate)
from .lnmsg import encode_msg
from .channel_db import ChannelDB

if TYPE_CHECKING:
    from .lnchannel import Channel
    from .network import Network

class NoChannelPolicy(Exception):
    def __init__(self, short_channel_id: bytes):
        super().__init__(f'cannot find channel policy for short_channel_id: {bh2u(short_channel_id)}')


class RouteEdge(NamedTuple("RouteEdge", [('node_id', bytes),
                                         ('short_channel_id', bytes),
                                         ('fee_base_msat', int),
                                         ('fee_proportional_millionths', int),
                                         ('cltv_expiry_delta', int)])):
    """if you travel through short_channel_id, you will reach node_id"""

    def fee_for_edge(self, amount_msat: int) -> int:
        return self.fee_base_msat \
               + (amount_msat * self.fee_proportional_millionths // 1_000_000)

    @classmethod
    def from_channel_policy(cls, channel_policy: 'Policy',
                            short_channel_id: bytes, end_node: bytes) -> 'RouteEdge':
        assert type(short_channel_id) is bytes
        assert type(end_node) is bytes
        return RouteEdge(end_node,
                         short_channel_id,
                         channel_policy.fee_base_msat,
                         channel_policy.fee_proportional_millionths,
                         channel_policy.cltv_expiry_delta)

    def is_sane_to_use(self, amount_msat: int) -> bool:
        # TODO revise ad-hoc heuristics
        # cltv cannot be more than 2 weeks
        if self.cltv_expiry_delta > 14 * 144: return False
        total_fee = self.fee_for_edge(amount_msat)
        # fees below 50 sat are fine
        if total_fee > 50_000:
            # fee cannot be higher than amt
            if total_fee > amount_msat: return False
            # fee cannot be higher than 5000 sat
            if total_fee > 5_000_000: return False
            # unless amt is tiny, fee cannot be more than 10%
            if amount_msat > 1_000_000 and total_fee > amount_msat/10: return False
        return True


def is_route_sane_to_use(route: List[RouteEdge], invoice_amount_msat: int, min_final_cltv_expiry: int) -> bool:
    """Run some sanity checks on the whole route, before attempting to use it.
    called when we are paying; so e.g. lower cltv is better
    """
    if len(route) > NUM_MAX_EDGES_IN_PAYMENT_PATH:
        return False
    amt = invoice_amount_msat
    cltv = min_final_cltv_expiry
    for route_edge in reversed(route[1:]):
        if not route_edge.is_sane_to_use(amt): return False
        amt += route_edge.fee_for_edge(amt)
        cltv += route_edge.cltv_expiry_delta
    total_fee = amt - invoice_amount_msat
    # TODO revise ad-hoc heuristics
    # cltv cannot be more than 2 months
    if cltv > 60 * 144: return False
    # fees below 50 sat are fine
    if total_fee > 50_000:
        # fee cannot be higher than amt
        if total_fee > invoice_amount_msat: return False
        # fee cannot be higher than 5000 sat
        if total_fee > 5_000_000: return False
        # unless amt is tiny, fee cannot be more than 10%
        if invoice_amount_msat > 1_000_000 and total_fee > invoice_amount_msat/10: return False
    return True


class LNPathFinder(Logger):

    def __init__(self, channel_db: ChannelDB):
        Logger.__init__(self)
        self.channel_db = channel_db
        self.blacklist = set()

    def add_to_blacklist(self, short_channel_id):
        self.logger.info(f'blacklisting channel {bh2u(short_channel_id)}')
        self.blacklist.add(short_channel_id)

    def _edge_cost(self, short_channel_id: bytes, start_node: bytes, end_node: bytes,
                   payment_amt_msat: int, ignore_costs=False) -> Tuple[float, int]:
        """Heuristic cost of going through a channel.
        Returns (heuristic_cost, fee_for_edge_msat).
        """
        channel_info = self.channel_db.get_channel_info(short_channel_id)  # type: ChannelInfo
        if channel_info is None:
            return float('inf'), 0
        channel_policy = self.channel_db.get_policy_for_node(short_channel_id, start_node)
        if channel_policy is None:
            return float('inf'), 0
        # channels that did not publish both policies often return temporary channel failure
        if self.channel_db.get_policy_for_node(short_channel_id, end_node) is None:
            return float('inf'), 0
        if channel_policy.is_disabled():
            return float('inf'), 0
        route_edge = RouteEdge.from_channel_policy(channel_policy, short_channel_id, end_node)
        if payment_amt_msat < channel_policy.htlc_minimum_msat:
            return float('inf'), 0  # payment amount too little
        if channel_info.capacity_sat is not None and \
                payment_amt_msat // 1000 > channel_info.capacity_sat:
            return float('inf'), 0  # payment amount too large
        if channel_policy.htlc_maximum_msat is not None and \
                payment_amt_msat > channel_policy.htlc_maximum_msat:
            return float('inf'), 0  # payment amount too large
        if not route_edge.is_sane_to_use(payment_amt_msat):
            return float('inf'), 0  # thanks but no thanks
        fee_msat = route_edge.fee_for_edge(payment_amt_msat) if not ignore_costs else 0
        # TODO revise
        # paying 10 more satoshis ~ waiting one more block
        fee_cost = fee_msat / 1000 / 10
        cltv_cost = route_edge.cltv_expiry_delta if not ignore_costs else 0
        return cltv_cost + fee_cost + 1, fee_msat

    @profiler
    def find_path_for_payment(self, nodeA: bytes, nodeB: bytes,
                              invoice_amount_msat: int,
                              my_channels: List['Channel']=None) -> Sequence[Tuple[bytes, bytes]]:
        """Return a path from nodeA to nodeB.

        Returns a list of (node_id, short_channel_id) representing a path.
        To get from node ret[n][0] to ret[n+1][0], use channel ret[n+1][1];
        i.e. an element reads as, "to get to node_id, travel through short_channel_id"
        """
        assert type(nodeA) is bytes
        assert type(nodeB) is bytes
        assert type(invoice_amount_msat) is int
        if my_channels is None: my_channels = []
        my_channels = {chan.short_channel_id: chan for chan in my_channels}

        # FIXME paths cannot be longer than 21 edges (onion packet)...

        # run Dijkstra
        # The search is run in the REVERSE direction, from nodeB to nodeA,
        # to properly calculate compound routing fees.
        distance_from_start = defaultdict(lambda: float('inf'))
        distance_from_start[nodeB] = 0
        prev_node = {}
        nodes_to_explore = queue.PriorityQueue()
        nodes_to_explore.put((0, invoice_amount_msat, nodeB))  # order of fields (in tuple) matters!

        def inspect_edge():
            if edge_channel_id in my_channels:
                if edge_startnode == nodeA:  # payment outgoing, on our channel
                    if not my_channels[edge_channel_id].can_pay(amount_msat):
                        return
                else:  # payment incoming, on our channel. (funny business, cycle weirdness)
                    assert edge_endnode == nodeA, (bh2u(edge_startnode), bh2u(edge_endnode))
                    pass  # TODO?
            edge_cost, fee_for_edge_msat = self._edge_cost(
                edge_channel_id,
                start_node=edge_startnode,
                end_node=edge_endnode,
                payment_amt_msat=amount_msat,
                ignore_costs=(edge_startnode == nodeA))
            alt_dist_to_neighbour = distance_from_start[edge_endnode] + edge_cost
            if alt_dist_to_neighbour < distance_from_start[edge_startnode]:
                distance_from_start[edge_startnode] = alt_dist_to_neighbour
                prev_node[edge_startnode] = edge_endnode, edge_channel_id
                amount_to_forward_msat = amount_msat + fee_for_edge_msat
                nodes_to_explore.put((alt_dist_to_neighbour, amount_to_forward_msat, edge_startnode))

        # main loop of search
        while nodes_to_explore.qsize() > 0:
            dist_to_edge_endnode, amount_msat, edge_endnode = nodes_to_explore.get()
            if edge_endnode == nodeA:
                break
            if dist_to_edge_endnode != distance_from_start[edge_endnode]:
                # queue.PriorityQueue does not implement decrease_priority,
                # so instead of decreasing priorities, we add items again into the queue.
                # so there are duplicates in the queue, that we discard now:
                continue
            for edge_channel_id in self.channel_db.get_channels_for_node(edge_endnode):
                assert type(edge_channel_id) is bytes
                if edge_channel_id in self.blacklist:
                    continue
                channel_info = self.channel_db.get_channel_info(edge_channel_id)
                edge_startnode = channel_info.node2_id if channel_info.node1_id == edge_endnode else channel_info.node1_id
                inspect_edge()
        else:
            return None  # no path found

        # backtrack from search_end (nodeA) to search_start (nodeB)
        edge_startnode = nodeA
        path = []
        while edge_startnode != nodeB:
            edge_endnode, edge_taken = prev_node[edge_startnode]
            path += [(edge_endnode, edge_taken)]
            edge_startnode = edge_endnode
        return path

    def create_route_from_path(self, path, from_node_id: bytes) -> List[RouteEdge]:
        assert type(from_node_id) is bytes
        if path is None:
            raise Exception('cannot create route from None path')
        route = []
        prev_node_id = from_node_id
        for node_id, short_channel_id in path:
            channel_policy = self.channel_db.get_routing_policy_for_channel(prev_node_id, short_channel_id)
            if channel_policy is None:
                raise NoChannelPolicy(short_channel_id)
            route.append(RouteEdge.from_channel_policy(channel_policy, short_channel_id, node_id))
            prev_node_id = node_id
        return route