electrum/electrum/lnwatcher.py

import threading
from typing import NamedTuple, Iterable
import os
from collections import defaultdict

from .util import PrintError, bh2u, bfh, NoDynamicFeeEstimates, aiosafe
from .lnutil import EncumberedTransaction, Outpoint
from . import wallet
from .storage import WalletStorage
from .address_synchronizer import AddressSynchronizer


TX_MINED_STATUS_DEEP, TX_MINED_STATUS_SHALLOW, TX_MINED_STATUS_MEMPOOL, TX_MINED_STATUS_FREE = range(0, 4)


class LNWatcher(PrintError):
    # TODO if verifier gets an incorrect merkle proof, that tx will never verify!!
    # similarly, what if server ignores request for merkle proof?
    # maybe we should disconnect from server in these cases

    def __init__(self, network):
        self.network = network

        path = os.path.join(network.config.path, "watcher_db")
        storage = WalletStorage(path)
        self.addr_sync = AddressSynchronizer(storage)
        self.addr_sync.diagnostic_name = lambda: 'LnWatcherAS'
        self.addr_sync.start_network(network)
        self.lock = threading.RLock()
        self.watched_addresses = set()
        self.channel_info = storage.get('channel_info', {})  # access with 'lock'
        # TODO structure will need to change when we handle HTLCs......
        # [funding_outpoint_str][ctx_txid] -> set of EncumberedTransaction
        # access with 'lock'
        self.sweepstore = defaultdict(lambda: defaultdict(set))
        for funding_outpoint, ctxs in storage.get('sweepstore', {}).items():
            for ctx_txid, set_of_txns in ctxs.items():
                for e_tx in set_of_txns:
                    e_tx2 = EncumberedTransaction.from_json(e_tx)
                    self.sweepstore[funding_outpoint][ctx_txid].add(e_tx2)

        self.network.register_callback(self.on_network_update,
                                       ['network_updated', 'blockchain_updated', 'verified', 'wallet_updated'])

    def write_to_disk(self):
        # FIXME: json => every update takes linear instead of constant disk write
        with self.lock:
            storage = self.addr_sync.storage
            storage.put('channel_info', self.channel_info)
            # self.sweepstore
            sweepstore = {}
            for funding_outpoint, ctxs in self.sweepstore.items():
                sweepstore[funding_outpoint] = {}
                for ctx_txid, set_of_txns in ctxs.items():
                    sweepstore[funding_outpoint][ctx_txid] = [e_tx.to_json() for e_tx in set_of_txns]
            storage.put('sweepstore', sweepstore)
        storage.write()

    def watch_channel(self, address, outpoint):
        self.watch_address(address)
        with self.lock:
            if address not in self.channel_info:
                self.channel_info[address] = outpoint
            self.write_to_disk()

    @aiosafe
    async def on_network_update(self, event, *args):
        if event in ('verified', 'wallet_updated'):
            wallet = args[0]
            if wallet != self.addr_sync:
                return
        if not self.addr_sync.synchronizer:
            self.print_error("synchronizer not set yet")
            return
        if not self.addr_sync.synchronizer.is_up_to_date():
            return
        with self.lock:
            channel_info_items = list(self.channel_info.items())
        for address, outpoint in channel_info_items:
            await self.check_onchain_situation(outpoint)

    def watch_address(self, addr):
        with self.lock:
            self.watched_addresses.add(addr)
            self.addr_sync.add_address(addr)

    async def check_onchain_situation(self, funding_outpoint):
        txid, index = funding_outpoint.split(':')
        ctx_candidate_txid = self.addr_sync.spent_outpoints[txid].get(int(index))
        is_spent = ctx_candidate_txid is not None
        self.network.trigger_callback('channel_txo', funding_outpoint, is_spent)
        if not is_spent:
            return
        ctx_candidate = self.addr_sync.transactions.get(ctx_candidate_txid)
        if ctx_candidate is None:
            return
        #self.print_error("funding outpoint {} is spent by {}"
        #                 .format(funding_outpoint, ctx_candidate_txid))
        conf = self.addr_sync.get_tx_height(ctx_candidate_txid).conf
        # only care about confirmed and verified ctxs. TODO is this necessary?
        if conf == 0:
            return
        keep_watching_this = await self.inspect_ctx_candidate(funding_outpoint, ctx_candidate)
        if not keep_watching_this:
            self.stop_and_delete(funding_outpoint)

    def stop_and_delete(self, funding_outpoint):
        # TODO delete channel from watcher_db
        pass

    async def inspect_ctx_candidate(self, funding_outpoint, ctx):
        """Returns True iff found any not-deeply-spent outputs that we could
        potentially sweep at some point."""
        # make sure we are subscribed to all outputs of ctx
        not_yet_watching = False
        for o in ctx.outputs():
            if o.address not in self.watched_addresses:
                self.watch_address(o.address)
                not_yet_watching = True
        if not_yet_watching:
            return True
        # get all possible responses we have
        ctx_txid = ctx.txid()
        with self.lock:
            encumbered_sweep_txns = self.sweepstore[funding_outpoint][ctx_txid]
        if len(encumbered_sweep_txns) == 0:
            # no useful response for this channel close..
            if self.get_tx_mined_status(ctx_txid) == TX_MINED_STATUS_DEEP:
                self.print_error("channel close detected for {}. but can't sweep anything :(".format(funding_outpoint))
                return False
        # check if any response applies
        keep_watching_this = False
        local_height = self.network.get_local_height()
        for e_tx in encumbered_sweep_txns:
            conflicts = self.addr_sync.get_conflicting_transactions(e_tx.tx.txid(), e_tx.tx, include_self=True)
            conflict_mined_status = self.get_deepest_tx_mined_status_for_txids(conflicts)
            if conflict_mined_status != TX_MINED_STATUS_DEEP:
                keep_watching_this = True
            if conflict_mined_status == TX_MINED_STATUS_FREE:
                tx_height = self.addr_sync.get_tx_height(ctx_txid).height
                num_conf = local_height - tx_height + 1
                if num_conf >= e_tx.csv_delay:
                    try:
                        await self.network.broadcast_transaction(e_tx.tx)
                    except Exception as e:
                        self.print_error('broadcast: {}, {}'.format('failure', repr(e)))
                    else:
                        self.print_error('broadcast: {}'.format('success'))
                else:
                    self.print_error('waiting for CSV ({} < {}) for funding outpoint {} and ctx {}'
                                     .format(num_conf, e_tx.csv_delay, funding_outpoint, ctx.txid()))
        return keep_watching_this

    def add_sweep_tx(self, funding_outpoint: str, ctx_txid: str, encumbered_sweeptx: EncumberedTransaction):
        if encumbered_sweeptx is None:
            return
        with self.lock:
            self.sweepstore[funding_outpoint][ctx_txid].add(encumbered_sweeptx)
        self.write_to_disk()

    def get_tx_mined_status(self, txid: str):
        if not txid:
            return TX_MINED_STATUS_FREE
        tx_mined_status = self.addr_sync.get_tx_height(txid)
        height, conf = tx_mined_status.height, tx_mined_status.conf
        if conf > 100:
            return TX_MINED_STATUS_DEEP
        elif conf > 0:
            return TX_MINED_STATUS_SHALLOW
        elif height in (wallet.TX_HEIGHT_UNCONFIRMED, wallet.TX_HEIGHT_UNCONF_PARENT):
            return TX_MINED_STATUS_MEMPOOL
        elif height == wallet.TX_HEIGHT_LOCAL:
            return TX_MINED_STATUS_FREE
        elif height > 0 and conf == 0:
            # unverified but claimed to be mined
            return TX_MINED_STATUS_MEMPOOL
        else:
            raise NotImplementedError()

    def get_deepest_tx_mined_status_for_txids(self, set_of_txids: Iterable[str]):
        if not set_of_txids:
            return TX_MINED_STATUS_FREE
        # note: using "min" as lower status values are deeper
        return min(map(self.get_tx_mined_status, set_of_txids))