#!/usr/bin/env python3
"""Test plugin for adding inputs/outputs to a dual-funded transaction
"""

from pyln.client import Plugin, Millisatoshi
from pyln.proto import bech32_decode
from typing import Iterable, List, Optional
from wallycore import psbt_add_output_at, psbt_from_base64, psbt_to_base64, tx_output_init


plugin = Plugin()


def convertbits(data: Iterable[int], frombits: int, tobits: int, pad: bool = True) -> Optional[List[int]]:
    """General power-of-2 base conversion."""
    acc = 0
    bits = 0
    ret = []
    maxv = (1 << tobits) - 1
    max_acc = (1 << (frombits + tobits - 1)) - 1
    for value in data:
        if value < 0 or (value >> frombits):
            return None
        acc = ((acc << frombits) | value) & max_acc
        bits += frombits
        while bits >= tobits:
            bits -= tobits
            ret.append((acc >> bits) & maxv)
    if pad:
        if bits:
            ret.append((acc << (tobits - bits)) & maxv)
    elif bits >= frombits or ((acc << (tobits - bits)) & maxv):
        return None
    return ret


def get_script(bech_addr):
    hrp, data = bech32_decode(bech_addr)
    # FIXME: verify hrp matches expected network
    wprog = convertbits(data[1:], 5, 8, False)
    wit_ver = data[0]
    if wit_ver > 16:
        raise ValueError("Invalid witness version {}".format(wit_ver[0]))
    return bytes([wit_ver + 0x50 if wit_ver > 0 else wit_ver, len(wprog)] + wprog)


def find_feerate(best, their_min, their_max, our_min, our_max):
    if best >= our_min and best <= our_max:
        return best

    if their_max < our_min or their_min > our_max:
        return False

    if best < our_min:
        return our_min

    # best > our_max:
    return our_max


@plugin.hook('openchannel2')
def on_openchannel(openchannel2, plugin, **kwargs):
    # We mirror what the peer does, wrt to funding amount ...
    amount = openchannel2['their_funding']
    locktime = openchannel2['locktime']

    # ...unless they send us totally unacceptable feerates.
    feerate = find_feerate(openchannel2['funding_feerate_best'],
                           openchannel2['funding_feerate_min'],
                           openchannel2['funding_feerate_max'],
                           openchannel2['feerate_our_min'],
                           openchannel2['feerate_our_max'])

    # Their feerate range is out of bounds, we're not going to
    # participate.
    if not feerate:
        return {'result': 'continue'}

    funding = plugin.rpc.fundpsbt(amount,
                                  '{}perkw'.format(feerate),
                                  0, reserve=True,
                                  locktime=locktime)
    psbt_obj = psbt_from_base64(funding['psbt'])

    excess = Millisatoshi(funding['excess_msat'])
    change_cost = Millisatoshi(124 * feerate // 1000 * 1000)
    dust_limit = Millisatoshi(253 * 1000)
    if excess > (dust_limit + change_cost):
        addr = plugin.rpc.newaddr()['bech32']
        change = excess - change_cost
        output = tx_output_init(int(change.to_satoshi()), get_script(addr))
        psbt_add_output_at(psbt_obj, 0, 0, output)

    return {'result': 'continue', 'psbt': psbt_to_base64(psbt_obj, 0),
            'accepter_funding_msat': amount,
            'funding_feerate': feerate}


@plugin.hook('openchannel2_changed')
def on_tx_changed(openchannel2_changed, plugin, **kwargs):
    # In this example, we have nothing to add, so we
    # pass back the same psbt that was forwarded in here
    return {'result': 'continue', 'psbt': openchannel2_changed['psbt']}


@plugin.hook('openchannel2_sign')
def on_tx_sign(openchannel2_sign, plugin, **kwargs):
    psbt = openchannel2_sign['psbt']

    # We only sign the ones with our parity of a serial_id
    # FIXME: find the inputs with an odd-serial, these are ours
    # the key for a serial_id ::
    # our_inputs = [1]

    signed_psbt = plugin.rpc.signpsbt(psbt)['signed_psbt']
    return {'result': 'continue', 'psbt': signed_psbt}


plugin.run()