#!/usr/bin/env python3
# Copyright (c) 2015-2017 The Bitcoin Core developers
# Distributed under the MIT software license, see the accompanying
# file COPYING or http://www.opensource.org/licenses/mit-license.php.
"""Utilities for manipulating blocks and transactions."""

from .address import (
    key_to_p2sh_p2wpkh,
    key_to_p2wpkh,
    script_to_p2sh_p2wsh,
    script_to_p2wsh,
)
from .mininode import *
from .script import (
    CScript,
    OP_0,
    OP_1,
    OP_CHECKMULTISIG,
    OP_CHECKSIG,
    OP_RETURN,
    OP_TRUE,
    hash160,
)
from .util import assert_equal

# Create a block (with regtest difficulty)
def create_block(hashprev, coinbase, nTime=None):
    block = CBlock()
    if nTime is None:
        import time
        block.nTime = int(time.time()+600)
    else:
        block.nTime = nTime
    block.hashPrevBlock = hashprev
    block.nBits = 0x207fffff # Will break after a difficulty adjustment...
    block.vtx.append(coinbase)
    block.hashMerkleRoot = block.calc_merkle_root()

    # In kevacoin, nNonce is used to store the height of the block, which will
    # be used in cn_slow_hash computation.
    block.nNonce = coinbase.height
    assert block.nNonce > 0
    block.major_version = 10 # CN variant 4
    block.timestamp = block.nTime
    # Give merkle root a random value.
    block.merkle_root = uint256_from_str(bytes.fromhex("3cf6c3b6da3f4058853ee70369ee43d473aca91ae8fc8f44a645beb21c392d80"))
    block.calc_sha256()
    return block

# From BIP141
WITNESS_COMMITMENT_HEADER = b"\xaa\x21\xa9\xed"


def get_witness_script(witness_root, witness_nonce):
    witness_commitment = uint256_from_str(hash256(ser_uint256(witness_root)+ser_uint256(witness_nonce)))
    output_data = WITNESS_COMMITMENT_HEADER + ser_uint256(witness_commitment)
    return CScript([OP_RETURN, output_data])


# According to BIP141, blocks with witness rules active must commit to the
# hash of all in-block transactions including witness.
def add_witness_commitment(block, nonce=0):
    # First calculate the merkle root of the block's
    # transactions, with witnesses.
    witness_nonce = nonce
    witness_root = block.calc_witness_merkle_root()
    # witness_nonce should go to coinbase witness.
    block.vtx[0].wit.vtxinwit = [CTxInWitness()]
    block.vtx[0].wit.vtxinwit[0].scriptWitness.stack = [ser_uint256(witness_nonce)]

    # witness commitment is the last OP_RETURN output in coinbase
    block.vtx[0].vout.append(CTxOut(0, get_witness_script(witness_root, witness_nonce)))
    block.vtx[0].rehash()
    block.hashMerkleRoot = block.calc_merkle_root()
    block.rehash()


def serialize_script_num(value):
    r = bytearray(0)
    if value == 0:
        return r
    neg = value < 0
    absvalue = -value if neg else value
    while (absvalue):
        r.append(int(absvalue & 0xff))
        absvalue >>= 8
    if r[-1] & 0x80:
        r.append(0x80 if neg else 0)
    elif neg:
        r[-1] |= 0x80
    return r

# Create a coinbase transaction, assuming no miner fees.
# If pubkey is passed in, the coinbase output will be a P2PK output;
# otherwise an anyone-can-spend output.
def create_coinbase(height, pubkey = None):
    coinbase = CTransaction()
    coinbase.vin.append(CTxIn(COutPoint(0, 0xffffffff),
                ser_string(serialize_script_num(height)), 0xffffffff))
    coinbaseoutput = CTxOut()
    coinbaseoutput.nValue = 500 * COIN
    halvings = int(height/150) # regtest
    coinbaseoutput.nValue >>= halvings
    if (pubkey != None):
        coinbaseoutput.scriptPubKey = CScript([pubkey, OP_CHECKSIG])
    else:
        coinbaseoutput.scriptPubKey = CScript([OP_TRUE])
    coinbase.vout = [ coinbaseoutput ]
    coinbase.calc_sha256()

    # Kevacoin needs to know the height, because it is used as a parameter of
    # cn_slow_hash.
    coinbase.height = height

    return coinbase

# Create a transaction.
# If the scriptPubKey is not specified, make it anyone-can-spend.
def create_transaction(prevtx, n, sig, value, scriptPubKey=CScript()):
    tx = CTransaction()
    assert(n < len(prevtx.vout))
    tx.vin.append(CTxIn(COutPoint(prevtx.sha256, n), sig, 0xffffffff))
    tx.vout.append(CTxOut(value, scriptPubKey))
    tx.calc_sha256()
    return tx

def get_legacy_sigopcount_block(block, fAccurate=True):
    count = 0
    for tx in block.vtx:
        count += get_legacy_sigopcount_tx(tx, fAccurate)
    return count

def get_legacy_sigopcount_tx(tx, fAccurate=True):
    count = 0
    for i in tx.vout:
        count += i.scriptPubKey.GetSigOpCount(fAccurate)
    for j in tx.vin:
        # scriptSig might be of type bytes, so convert to CScript for the moment
        count += CScript(j.scriptSig).GetSigOpCount(fAccurate)
    return count

# Create a scriptPubKey corresponding to either a P2WPKH output for the
# given pubkey, or a P2WSH output of a 1-of-1 multisig for the given
# pubkey. Returns the hex encoding of the scriptPubKey.
def witness_script(use_p2wsh, pubkey):
    if (use_p2wsh == False):
        # P2WPKH instead
        pubkeyhash = hash160(hex_str_to_bytes(pubkey))
        pkscript = CScript([OP_0, pubkeyhash])
    else:
        # 1-of-1 multisig
        witness_program = CScript([OP_1, hex_str_to_bytes(pubkey), OP_1, OP_CHECKMULTISIG])
        scripthash = sha256(witness_program)
        pkscript = CScript([OP_0, scripthash])
    return bytes_to_hex_str(pkscript)

# Return a transaction (in hex) that spends the given utxo to a segwit output,
# optionally wrapping the segwit output using P2SH.
def create_witness_tx(node, use_p2wsh, utxo, pubkey, encode_p2sh, amount):
    if use_p2wsh:
        program = CScript([OP_1, hex_str_to_bytes(pubkey), OP_1, OP_CHECKMULTISIG])
        addr = script_to_p2sh_p2wsh(program) if encode_p2sh else script_to_p2wsh(program)
    else:
        addr = key_to_p2sh_p2wpkh(pubkey) if encode_p2sh else key_to_p2wpkh(pubkey)
    if not encode_p2sh:
        assert_equal(node.validateaddress(addr)['scriptPubKey'], witness_script(use_p2wsh, pubkey))
    return node.createrawtransaction([utxo], {addr: amount})

# Create a transaction spending a given utxo to a segwit output corresponding
# to the given pubkey: use_p2wsh determines whether to use P2WPKH or P2WSH;
# encode_p2sh determines whether to wrap in P2SH.
# sign=True will have the given node sign the transaction.
# insert_redeem_script will be added to the scriptSig, if given.
def send_to_witness(use_p2wsh, node, utxo, pubkey, encode_p2sh, amount, sign=True, insert_redeem_script=""):
    tx_to_witness = create_witness_tx(node, use_p2wsh, utxo, pubkey, encode_p2sh, amount)
    if (sign):
        signed = node.signrawtransaction(tx_to_witness)
        assert("errors" not in signed or len(["errors"]) == 0)
        return node.sendrawtransaction(signed["hex"])
    else:
        if (insert_redeem_script):
            tx = FromHex(CTransaction(), tx_to_witness)
            tx.vin[0].scriptSig += CScript([hex_str_to_bytes(insert_redeem_script)])
            tx_to_witness = ToHex(tx)

    return node.sendrawtransaction(tx_to_witness)