#!/usr/bin/env python3
# Copyright (c) 2020 The Bitcoin Core developers
# Distributed under the MIT software license, see the accompanying
# file COPYING or http://www.opensource.org/licenses/mit-license.php.

import argparse
import base64
import json
import logging
import math
import os
import re
import struct
import sys
import time
import subprocess

from io import BytesIO

PATH_BASE_CONTRIB_SIGNET = os.path.abspath(os.path.dirname(os.path.realpath(__file__)))
PATH_BASE_TEST_FUNCTIONAL = os.path.abspath(os.path.join(PATH_BASE_CONTRIB_SIGNET, "..", "..", "test", "functional"))
sys.path.insert(0, PATH_BASE_TEST_FUNCTIONAL)

from test_framework.blocktools import get_witness_script, script_BIP34_coinbase_height # noqa: E402
from test_framework.messages import CBlock, CBlockHeader, COutPoint, CTransaction, CTxIn, CTxInWitness, CTxOut, from_hex, deser_string, ser_compact_size, ser_string, ser_uint256, tx_from_hex # noqa: E402
from test_framework.script import CScriptOp # noqa: E402

logging.basicConfig(
    format='%(asctime)s %(levelname)s %(message)s',
    level=logging.INFO,
    datefmt='%Y-%m-%d %H:%M:%S')

SIGNET_HEADER = b"\xec\xc7\xda\xa2"
PSBT_SIGNET_BLOCK = b"\xfc\x06signetb"    # proprietary PSBT global field holding the block being signed
RE_MULTIMINER = re.compile("^(\d+)(-(\d+))?/(\d+)$")

# #### some helpers that could go into test_framework

# like from_hex, but without the hex part
def from_binary(cls, stream):
    """deserialize a binary stream (or bytes object) into an object"""
    # handle bytes object by turning it into a stream
    was_bytes = isinstance(stream, bytes)
    if was_bytes:
        stream = BytesIO(stream)
    obj = cls()
    obj.deserialize(stream)
    if was_bytes:
        assert len(stream.read()) == 0
    return obj

class PSBTMap:
    """Class for serializing and deserializing PSBT maps"""

    def __init__(self, map=None):
        self.map = map if map is not None else {}

    def deserialize(self, f):
        m = {}
        while True:
            k = deser_string(f)
            if len(k) == 0:
                break
            v = deser_string(f)
            if len(k) == 1:
                k = k[0]
            assert k not in m
            m[k] = v
        self.map = m

    def serialize(self):
        m = b""
        for k,v in self.map.items():
            if isinstance(k, int) and 0 <= k and k <= 255:
                k = bytes([k])
            m += ser_compact_size(len(k)) + k
            m += ser_compact_size(len(v)) + v
        m += b"\x00"
        return m

class PSBT:
    """Class for serializing and deserializing PSBTs"""

    def __init__(self):
        self.g = PSBTMap()
        self.i = []
        self.o = []
        self.tx = None

    def deserialize(self, f):
        assert f.read(5) == b"psbt\xff"
        self.g = from_binary(PSBTMap, f)
        assert 0 in self.g.map
        self.tx = from_binary(CTransaction, self.g.map[0])
        self.i = [from_binary(PSBTMap, f) for _ in self.tx.vin]
        self.o = [from_binary(PSBTMap, f) for _ in self.tx.vout]
        return self

    def serialize(self):
        assert isinstance(self.g, PSBTMap)
        assert isinstance(self.i, list) and all(isinstance(x, PSBTMap) for x in self.i)
        assert isinstance(self.o, list) and all(isinstance(x, PSBTMap) for x in self.o)
        assert 0 in self.g.map
        tx = from_binary(CTransaction, self.g.map[0])
        assert len(tx.vin) == len(self.i)
        assert len(tx.vout) == len(self.o)

        psbt = [x.serialize() for x in [self.g] + self.i + self.o]
        return b"psbt\xff" + b"".join(psbt)

    def to_base64(self):
        return base64.b64encode(self.serialize()).decode("utf8")

    @classmethod
    def from_base64(cls, b64psbt):
        return from_binary(cls, base64.b64decode(b64psbt))

# #####

def create_coinbase(height, value, spk):
    cb = CTransaction()
    cb.vin = [CTxIn(COutPoint(0, 0xffffffff), script_BIP34_coinbase_height(height), 0xffffffff)]
    cb.vout = [CTxOut(value, spk)]
    return cb

def signet_txs(block, challenge):
    # assumes signet solution has not been added yet so does not need
    # to be removed

    txs = block.vtx[:]
    txs[0] = CTransaction(txs[0])
    txs[0].vout[-1].scriptPubKey += CScriptOp.encode_op_pushdata(SIGNET_HEADER)
    hashes = []
    for tx in txs:
        tx.rehash()
        hashes.append(ser_uint256(tx.sha256))
    mroot = block.get_merkle_root(hashes)

    sd = b""
    sd += struct.pack("<i", block.nVersion)
    sd += ser_uint256(block.hashPrevBlock)
    sd += ser_uint256(mroot)
    sd += struct.pack("<I", block.nTime)

    to_spend = CTransaction()
    to_spend.nVersion = 0
    to_spend.nLockTime = 0
    to_spend.vin = [CTxIn(COutPoint(0, 0xFFFFFFFF), b"\x00" + CScriptOp.encode_op_pushdata(sd), 0)]
    to_spend.vout = [CTxOut(0, challenge)]
    to_spend.rehash()

    spend = CTransaction()
    spend.nVersion = 0
    spend.nLockTime = 0
    spend.vin = [CTxIn(COutPoint(to_spend.sha256, 0), b"", 0)]
    spend.vout = [CTxOut(0, b"\x6a")]

    return spend, to_spend

def do_createpsbt(block, signme, spendme):
    psbt = PSBT()
    psbt.g = PSBTMap( {0: signme.serialize(),
                       PSBT_SIGNET_BLOCK: block.serialize()
                     } )
    psbt.i = [ PSBTMap( {0: spendme.serialize(),
                         3: bytes([1,0,0,0])})
             ]
    psbt.o = [ PSBTMap() ]
    return psbt.to_base64()

def do_decode_psbt(b64psbt):
    psbt = PSBT.from_base64(b64psbt)

    assert len(psbt.tx.vin) == 1
    assert len(psbt.tx.vout) == 1
    assert PSBT_SIGNET_BLOCK in psbt.g.map

    scriptSig = psbt.i[0].map.get(7, b"")
    scriptWitness = psbt.i[0].map.get(8, b"\x00")

    return from_binary(CBlock, psbt.g.map[PSBT_SIGNET_BLOCK]), ser_string(scriptSig) + scriptWitness

def finish_block(block, signet_solution, grind_cmd):
    block.vtx[0].vout[-1].scriptPubKey += CScriptOp.encode_op_pushdata(SIGNET_HEADER + signet_solution)
    block.vtx[0].rehash()
    block.hashMerkleRoot = block.calc_merkle_root()
    if grind_cmd is None:
        block.solve()
    else:
        headhex = CBlockHeader.serialize(block).hex()
        cmd = grind_cmd.split(" ") + [headhex]
        newheadhex = subprocess.run(cmd, stdout=subprocess.PIPE, input=b"", check=True).stdout.strip()
        newhead = from_hex(CBlockHeader(), newheadhex.decode('utf8'))
        block.nNonce = newhead.nNonce
        block.rehash()
    return block

def generate_psbt(tmpl, reward_spk, *, blocktime=None):
    signet_spk = tmpl["signet_challenge"]
    signet_spk_bin = bytes.fromhex(signet_spk)

    cbtx = create_coinbase(height=tmpl["height"], value=tmpl["coinbasevalue"], spk=reward_spk)
    cbtx.vin[0].nSequence = 2**32-2
    cbtx.rehash()

    block = CBlock()
    block.nVersion = tmpl["version"]
    block.hashPrevBlock = int(tmpl["previousblockhash"], 16)
    block.nTime = tmpl["curtime"] if blocktime is None else blocktime
    if block.nTime < tmpl["mintime"]:
        block.nTime = tmpl["mintime"]
    block.nBits = int(tmpl["bits"], 16)
    block.nNonce = 0
    block.vtx = [cbtx] + [tx_from_hex(t["data"]) for t in tmpl["transactions"]]

    witnonce = 0
    witroot = block.calc_witness_merkle_root()
    cbwit = CTxInWitness()
    cbwit.scriptWitness.stack = [ser_uint256(witnonce)]
    block.vtx[0].wit.vtxinwit = [cbwit]
    block.vtx[0].vout.append(CTxOut(0, bytes(get_witness_script(witroot, witnonce))))

    signme, spendme = signet_txs(block, signet_spk_bin)

    return do_createpsbt(block, signme, spendme)

def get_reward_address(args, height):
    if args.address is not None:
        return args.address

    if '*' not in args.descriptor:
        addr = json.loads(args.bcli("deriveaddresses", args.descriptor))[0]
        args.address = addr
        return addr

    remove = [k for k in args.derived_addresses.keys() if k+20 <= height]
    for k in remove:
        del args.derived_addresses[k]

    addr = args.derived_addresses.get(height, None)
    if addr is None:
        addrs = json.loads(args.bcli("deriveaddresses", args.descriptor, "[%d,%d]" % (height, height+20)))
        addr = addrs[0]
        for k, a in enumerate(addrs):
            args.derived_addresses[height+k] = a

    return addr

def get_reward_addr_spk(args, height):
    assert args.address is not None or args.descriptor is not None

    if hasattr(args, "reward_spk"):
        return args.address, args.reward_spk

    reward_addr = get_reward_address(args, height)
    reward_spk = bytes.fromhex(json.loads(args.bcli("getaddressinfo", reward_addr))["scriptPubKey"])
    if args.address is not None:
        # will always be the same, so cache
        args.reward_spk = reward_spk

    return reward_addr, reward_spk

def do_genpsbt(args):
    tmpl = json.load(sys.stdin)
    _, reward_spk = get_reward_addr_spk(args, tmpl["height"])
    psbt = generate_psbt(tmpl, reward_spk)
    print(psbt)

def do_solvepsbt(args):
    block, signet_solution = do_decode_psbt(sys.stdin.read())
    block = finish_block(block, signet_solution, args.grind_cmd)
    print(block.serialize().hex())

def nbits_to_target(nbits):
    shift = (nbits >> 24) & 0xff
    return (nbits & 0x00ffffff) * 2**(8*(shift - 3))

def target_to_nbits(target):
    tstr = "{0:x}".format(target)
    if len(tstr) < 6:
        tstr = ("000000"+tstr)[-6:]
    if len(tstr) % 2 != 0:
        tstr = "0" + tstr
    if int(tstr[0],16) >= 0x8:
        # avoid "negative"
        tstr = "00" + tstr
    fix = int(tstr[:6], 16)
    sz = len(tstr)//2
    if tstr[6:] != "0"*(sz*2-6):
        fix += 1

    return int("%02x%06x" % (sz,fix), 16)

def seconds_to_hms(s):
    if s == 0:
        return "0s"
    neg = (s < 0)
    if neg:
        s = -s
    out = ""
    if s % 60 > 0:
        out = "%ds" % (s % 60)
    s //= 60
    if s % 60 > 0:
        out = "%dm%s" % (s % 60, out)
    s //= 60
    if s > 0:
        out = "%dh%s" % (s, out)
    if neg:
        out = "-" + out
    return out

def next_block_delta(last_nbits, last_hash, ultimate_target, do_poisson):
    # strategy:
    #  1) work out how far off our desired target we are
    #  2) cap it to a factor of 4 since that's the best we can do in a single retarget period
    #  3) use that to work out the desired average interval in this retarget period
    #  4) if doing poisson, use the last hash to pick a uniformly random number in [0,1), and work out a random multiplier to vary the average by
    #  5) cap the resulting interval between 1 second and 1 hour to avoid extremes

    INTERVAL = 600.0*2016/2015 # 10 minutes, adjusted for the off-by-one bug

    current_target = nbits_to_target(last_nbits)
    retarget_factor = ultimate_target / current_target
    retarget_factor = max(0.25, min(retarget_factor, 4.0))

    avg_interval = INTERVAL * retarget_factor

    if do_poisson:
        det_rand = int(last_hash[-8:], 16) * 2**-32
        this_interval_variance = -math.log1p(-det_rand)
    else:
        this_interval_variance = 1

    this_interval = avg_interval * this_interval_variance
    this_interval = max(1, min(this_interval, 3600))

    return this_interval

def next_block_is_mine(last_hash, my_blocks):
    det_rand = int(last_hash[-16:-8], 16)
    return my_blocks[0] <= (det_rand % my_blocks[2]) < my_blocks[1]

def do_generate(args):
    if args.max_blocks is not None:
        if args.ongoing:
            logging.error("Cannot specify both --ongoing and --max-blocks")
            return 1
        if args.max_blocks < 1:
            logging.error("N must be a positive integer")
            return 1
        max_blocks = args.max_blocks
    elif args.ongoing:
        max_blocks = None
    else:
        max_blocks = 1

    if args.set_block_time is not None and max_blocks != 1:
        logging.error("Cannot specify --ongoing or --max-blocks > 1 when using --set-block-time")
        return 1
    if args.set_block_time is not None and args.set_block_time < 0:
        args.set_block_time = time.time()
        logging.info("Treating negative block time as current time (%d)" % (args.set_block_time))

    if args.min_nbits:
        if args.nbits is not None:
            logging.error("Cannot specify --nbits and --min-nbits")
            return 1
        args.nbits = "1e0377ae"
        logging.info("Using nbits=%s" % (args.nbits))

    if args.set_block_time is None:
        if args.nbits is None or len(args.nbits) != 8:
            logging.error("Must specify --nbits (use calibrate command to determine value)")
            return 1

    if args.multiminer is None:
       my_blocks = (0,1,1)
    else:
        if not args.ongoing:
            logging.error("Cannot specify --multiminer without --ongoing")
            return 1
        m = RE_MULTIMINER.match(args.multiminer)
        if m is None:
            logging.error("--multiminer argument must be k/m or j-k/m")
            return 1
        start,_,stop,total = m.groups()
        if stop is None:
            stop = start
        start, stop, total = map(int, (start, stop, total))
        if stop < start or start <= 0 or total < stop or total == 0:
            logging.error("Inconsistent values for --multiminer")
            return 1
        my_blocks = (start-1, stop, total)

    ultimate_target = nbits_to_target(int(args.nbits,16))

    mined_blocks = 0
    bestheader = {"hash": None}
    lastheader = None
    while max_blocks is None or mined_blocks < max_blocks:

        # current status?
        bci = json.loads(args.bcli("getblockchaininfo"))

        if bestheader["hash"] != bci["bestblockhash"]:
            bestheader = json.loads(args.bcli("getblockheader", bci["bestblockhash"]))

        if lastheader is None:
            lastheader = bestheader["hash"]
        elif bestheader["hash"] != lastheader:
            next_delta = next_block_delta(int(bestheader["bits"], 16), bestheader["hash"], ultimate_target, args.poisson)
            next_delta += bestheader["time"] - time.time()
            next_is_mine = next_block_is_mine(bestheader["hash"], my_blocks)
            logging.info("Received new block at height %d; next in %s (%s)", bestheader["height"], seconds_to_hms(next_delta), ("mine" if next_is_mine else "backup"))
            lastheader = bestheader["hash"]

        # when is the next block due to be mined?
        now = time.time()
        if args.set_block_time is not None:
            logging.debug("Setting start time to %d", args.set_block_time)
            mine_time = args.set_block_time
            action_time = now
            is_mine = True
        elif bestheader["height"] == 0:
            time_delta = next_block_delta(int(bestheader["bits"], 16), bci["bestblockhash"], ultimate_target, args.poisson)
            time_delta *= 100 # 100 blocks
            logging.info("Backdating time for first block to %d minutes ago" % (time_delta/60))
            mine_time = now - time_delta
            action_time = now
            is_mine = True
        else:
            time_delta = next_block_delta(int(bestheader["bits"], 16), bci["bestblockhash"], ultimate_target, args.poisson)
            mine_time = bestheader["time"] + time_delta

            is_mine = next_block_is_mine(bci["bestblockhash"], my_blocks)

            action_time = mine_time
            if not is_mine:
                action_time += args.backup_delay

            if args.standby_delay > 0:
                action_time += args.standby_delay
            elif mined_blocks == 0:
                # for non-standby, always mine immediately on startup,
                # even if the next block shouldn't be ours
                action_time = now

        # don't want fractional times so round down
        mine_time = int(mine_time)
        action_time = int(action_time)

        # can't mine a block 2h in the future; 1h55m for some safety
        action_time = max(action_time, mine_time - 6900)

        # ready to go? otherwise sleep and check for new block
        if now < action_time:
            sleep_for = min(action_time - now, 60)
            if mine_time < now:
                # someone else might have mined the block,
                # so check frequently, so we don't end up late
                # mining the next block if it's ours
                sleep_for = min(20, sleep_for)
            minestr = "mine" if is_mine else "backup"
            logging.debug("Sleeping for %s, next block due in %s (%s)" % (seconds_to_hms(sleep_for), seconds_to_hms(mine_time - now), minestr))
            time.sleep(sleep_for)
            continue

        # gbt
        tmpl = json.loads(args.bcli("getblocktemplate", '{"rules":["signet","segwit"]}'))
        if tmpl["previousblockhash"] != bci["bestblockhash"]:
            logging.warning("GBT based off unexpected block (%s not %s), retrying", tmpl["previousblockhash"], bci["bestblockhash"])
            time.sleep(1)
            continue

        logging.debug("GBT template: %s", tmpl)

        if tmpl["mintime"] > mine_time:
            logging.info("Updating block time from %d to %d", mine_time, tmpl["mintime"])
            mine_time = tmpl["mintime"]
            if mine_time > now:
                logging.error("GBT mintime is in the future: %d is %d seconds later than %d", mine_time, (mine_time-now), now)
                return 1

        # address for reward
        reward_addr, reward_spk = get_reward_addr_spk(args, tmpl["height"])

        # mine block
        logging.debug("Mining block delta=%s start=%s mine=%s", seconds_to_hms(mine_time-bestheader["time"]), mine_time, is_mine)
        mined_blocks += 1
        psbt = generate_psbt(tmpl, reward_spk, blocktime=mine_time)
        input_stream = os.linesep.join([psbt, "true", "ALL"]).encode('utf8')
        psbt_signed = json.loads(args.bcli("-stdin", "walletprocesspsbt", input=input_stream))
        if not psbt_signed.get("complete",False):
            logging.debug("Generated PSBT: %s" % (psbt,))
            sys.stderr.write("PSBT signing failed\n")
            return 1
        block, signet_solution = do_decode_psbt(psbt_signed["psbt"])
        block = finish_block(block, signet_solution, args.grind_cmd)

        # submit block
        r = args.bcli("-stdin", "submitblock", input=block.serialize().hex().encode('utf8'))

        # report
        bstr = "block" if is_mine else "backup block"

        next_delta = next_block_delta(block.nBits, block.hash, ultimate_target, args.poisson)
        next_delta += block.nTime - time.time()
        next_is_mine = next_block_is_mine(block.hash, my_blocks)

        logging.debug("Block hash %s payout to %s", block.hash, reward_addr)
        logging.info("Mined %s at height %d; next in %s (%s)", bstr, tmpl["height"], seconds_to_hms(next_delta), ("mine" if next_is_mine else "backup"))
        if r != "":
            logging.warning("submitblock returned %s for height %d hash %s", r, tmpl["height"], block.hash)
        lastheader = block.hash

def do_calibrate(args):
    if args.nbits is not None and args.seconds is not None:
        sys.stderr.write("Can only specify one of --nbits or --seconds\n")
        return 1
    if args.nbits is not None and len(args.nbits) != 8:
        sys.stderr.write("Must specify 8 hex digits for --nbits\n")
        return 1

    TRIALS = 600 # gets variance down pretty low
    TRIAL_BITS = 0x1e3ea75f # takes about 5m to do 600 trials

    header = CBlockHeader()
    header.nBits = TRIAL_BITS
    targ = nbits_to_target(header.nBits)

    start = time.time()
    count = 0
    for i in range(TRIALS):
        header.nTime = i
        header.nNonce = 0
        headhex = header.serialize().hex()
        cmd = args.grind_cmd.split(" ") + [headhex]
        newheadhex = subprocess.run(cmd, stdout=subprocess.PIPE, input=b"", check=True).stdout.strip()

    avg = (time.time() - start) * 1.0 / TRIALS

    if args.nbits is not None:
        want_targ = nbits_to_target(int(args.nbits,16))
        want_time = avg*targ/want_targ
    else:
        want_time = args.seconds if args.seconds is not None else 25
        want_targ = int(targ*(avg/want_time))

    print("nbits=%08x for %ds average mining time" % (target_to_nbits(want_targ), want_time))
    return 0

def bitcoin_cli(basecmd, args, **kwargs):
    cmd = basecmd + ["-signet"] + args
    logging.debug("Calling bitcoin-cli: %r", cmd)
    out = subprocess.run(cmd, stdout=subprocess.PIPE, **kwargs, check=True).stdout
    if isinstance(out, bytes):
        out = out.decode('utf8')
    return out.strip()

def main():
    parser = argparse.ArgumentParser()
    parser.add_argument("--cli", default="bitcoin-cli", type=str, help="bitcoin-cli command")
    parser.add_argument("--debug", action="store_true", help="Print debugging info")
    parser.add_argument("--quiet", action="store_true", help="Only print warnings/errors")

    cmds = parser.add_subparsers(help="sub-commands")
    genpsbt = cmds.add_parser("genpsbt", help="Generate a block PSBT for signing")
    genpsbt.set_defaults(fn=do_genpsbt)

    solvepsbt = cmds.add_parser("solvepsbt", help="Solve a signed block PSBT")
    solvepsbt.set_defaults(fn=do_solvepsbt)

    generate = cmds.add_parser("generate", help="Mine blocks")
    generate.set_defaults(fn=do_generate)
    generate.add_argument("--ongoing", action="store_true", help="Keep mining blocks")
    generate.add_argument("--max-blocks", default=None, type=int, help="Max blocks to mine (default=1)")
    generate.add_argument("--set-block-time", default=None, type=int, help="Set block time (unix timestamp)")
    generate.add_argument("--nbits", default=None, type=str, help="Target nBits (specify difficulty)")
    generate.add_argument("--min-nbits", action="store_true", help="Target minimum nBits (use min difficulty)")
    generate.add_argument("--poisson", action="store_true", help="Simulate randomised block times")
    generate.add_argument("--multiminer", default=None, type=str, help="Specify which set of blocks to mine (eg: 1-40/100 for the first 40%%, 2/3 for the second 3rd)")
    generate.add_argument("--backup-delay", default=300, type=int, help="Seconds to delay before mining blocks reserved for other miners (default=300)")
    generate.add_argument("--standby-delay", default=0, type=int, help="Seconds to delay before mining blocks (default=0)")

    calibrate = cmds.add_parser("calibrate", help="Calibrate difficulty")
    calibrate.set_defaults(fn=do_calibrate)
    calibrate.add_argument("--nbits", type=str, default=None)
    calibrate.add_argument("--seconds", type=int, default=None)

    for sp in [genpsbt, generate]:
        sp.add_argument("--address", default=None, type=str, help="Address for block reward payment")
        sp.add_argument("--descriptor", default=None, type=str, help="Descriptor for block reward payment")

    for sp in [solvepsbt, generate, calibrate]:
        sp.add_argument("--grind-cmd", default=None, type=str, required=(sp==calibrate), help="Command to grind a block header for proof-of-work")

    args = parser.parse_args(sys.argv[1:])

    args.bcli = lambda *a, input=b"", **kwargs: bitcoin_cli(args.cli.split(" "), list(a), input=input, **kwargs)

    if hasattr(args, "address") and hasattr(args, "descriptor"):
        if args.address is None and args.descriptor is None:
            sys.stderr.write("Must specify --address or --descriptor\n")
            return 1
        elif args.address is not None and args.descriptor is not None:
            sys.stderr.write("Only specify one of --address or --descriptor\n")
            return 1
        args.derived_addresses = {}

    if args.debug:
        logging.getLogger().setLevel(logging.DEBUG)
    elif args.quiet:
        logging.getLogger().setLevel(logging.WARNING)
    else:
        logging.getLogger().setLevel(logging.INFO)

    if hasattr(args, "fn"):
        return args.fn(args)
    else:
        logging.error("Must specify command")
        return 1

if __name__ == "__main__":
    main()