#!/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.
"""A limited-functionality wallet, which may replace a real wallet in tests"""

from copy import deepcopy
from decimal import Decimal
from enum import Enum
from test_framework.address import ADDRESS_BCRT1_P2SH_OP_TRUE
from test_framework.descriptors import descsum_create
from test_framework.key import ECKey
from random import choice
from typing import Optional
from test_framework.messages import (
    COIN,
    COutPoint,
    CTransaction,
    CTxIn,
    CTxOut,
    tx_from_hex,
)
from test_framework.script import (
    CScript,
    SignatureHash,
    OP_CHECKSIG,
    OP_TRUE,
    OP_NOP,
    SIGHASH_ALL,
)
from test_framework.util import (
    assert_equal,
    assert_greater_than_or_equal,
)

DEFAULT_FEE = Decimal("0.0001")

class MiniWalletMode(Enum):
    """Determines the transaction type the MiniWallet is creating and spending.

    For most purposes, the default mode ADDRESS_OP_TRUE should be sufficient;
    it simply uses a fixed P2SH address whose coins are spent with a
    witness stack of OP_TRUE, i.e. following an anyone-can-spend policy.
    However, if the transactions need to be modified by the user (e.g. prepending
    scriptSig for testing opcodes that are activated by a soft-fork), or the txs
    should contain an actual signature, the raw modes RAW_OP_TRUE and RAW_P2PK
    can be useful. Summary of modes:

                    |      output       |           |  tx is   | can modify |  needs
         mode       |    description    |  address  | standard | scriptSig  | signing
    ----------------+-------------------+-----------+----------+------------+----------
    ADDRESS_OP_TRUE | anyone-can-spend  |  bech32   |   yes    |    no      |   no
    RAW_OP_TRUE     | anyone-can-spend  |  - (raw)  |   no     |    yes     |   no
    RAW_P2PK        | pay-to-public-key |  - (raw)  |   yes    |    yes     |   yes
    """
    ADDRESS_OP_TRUE = 1
    RAW_OP_TRUE = 2
    RAW_P2PK = 3


class MiniWallet:
    def __init__(self, test_node, *, mode=MiniWalletMode.ADDRESS_OP_TRUE):
        self._test_node = test_node
        self._utxos = []
        self._priv_key = None
        self._address = None

        assert isinstance(mode, MiniWalletMode)
        if mode == MiniWalletMode.RAW_OP_TRUE:
            self._scriptPubKey = bytes(CScript([OP_TRUE]))
        elif mode == MiniWalletMode.RAW_P2PK:
            # use simple deterministic private key (k=1)
            self._priv_key = ECKey()
            self._priv_key.set((1).to_bytes(32, 'big'), True)
            pub_key = self._priv_key.get_pubkey()
            self._scriptPubKey = bytes(CScript([pub_key.get_bytes(), OP_CHECKSIG]))
        elif mode == MiniWalletMode.ADDRESS_OP_TRUE:
            self._address = ADDRESS_BCRT1_P2SH_OP_TRUE
            self._scriptPubKey = bytes.fromhex(self._test_node.validateaddress(self._address)['scriptPubKey'])

    def rescan_utxos(self):
        """Drop all utxos and rescan the utxo set"""
        self._utxos = []
        res = self._test_node.scantxoutset(action="start", scanobjects=[self.get_descriptor()])
        assert_equal(True, res['success'])
        for utxo in res['unspents']:
            self._utxos.append({'txid': utxo['txid'], 'vout': utxo['vout'], 'value': utxo['amount'], 'height': utxo['height']})

    def scan_blocks(self, *, start=1, num):
        """Scan the blocks for self._address outputs and add them to self._utxos"""
        for i in range(start, start + num):
            block = self._test_node.getblock(blockhash=self._test_node.getblockhash(i), verbosity=2)
            for tx in block['tx']:
                self.scan_tx(tx)

    def scan_tx(self, tx):
        """Scan the tx for self._scriptPubKey outputs and add them to self._utxos"""
        for out in tx['vout']:
            if out['scriptPubKey']['hex'] == self._scriptPubKey.hex():
                self._utxos.append({'txid': tx['txid'], 'vout': out['n'], 'value': out['value'], 'height': 0})

    def sign_tx(self, tx, fixed_length=True):
        """Sign tx that has been created by MiniWallet in P2PK mode"""
        assert self._priv_key is not None
        (sighash, err) = SignatureHash(CScript(self._scriptPubKey), tx, 0, SIGHASH_ALL)
        assert err is None
        # for exact fee calculation, create only signatures with fixed size by default (>49.89% probability):
        # 65 bytes: high-R val (33 bytes) + low-S val (32 bytes)
        # with the DER header/skeleton data of 6 bytes added, this leads to a target size of 71 bytes
        der_sig = b''
        while not len(der_sig) == 71:
            der_sig = self._priv_key.sign_ecdsa(sighash)
            if not fixed_length:
                break
        tx.vin[0].scriptSig = CScript([der_sig + bytes(bytearray([SIGHASH_ALL]))])

    def generate(self, num_blocks):
        """Generate blocks with coinbase outputs to the internal address, and append the outputs to the internal list"""
        blocks = self._test_node.generatetodescriptor(num_blocks, self.get_descriptor())
        for b in blocks:
            block_info = self._test_node.getblock(blockhash=b, verbosity=2)
            cb_tx = block_info['tx'][0]
            self._utxos.append({'txid': cb_tx['txid'], 'vout': 0, 'value': cb_tx['vout'][0]['value'], 'height': block_info['height']})
        return blocks

    def get_descriptor(self):
        return descsum_create(f'raw({self._scriptPubKey.hex()})')

    def get_address(self):
        return self._address

    def get_utxo(self, *, txid: Optional[str]='', mark_as_spent=True):
        """
        Returns a utxo and marks it as spent (pops it from the internal list)

        Args:
        txid: get the first utxo we find from a specific transaction

        Note: Can be used to get the change output immediately after a send_self_transfer
        """
        index = -1  # by default the last utxo
        if txid:
            utxo = next(filter(lambda utxo: txid == utxo['txid'], self._utxos))
            index = self._utxos.index(utxo)
        if mark_as_spent:
            return self._utxos.pop(index)
        else:
            return self._utxos[index]

    def send_self_transfer(self, **kwargs):
        """Create and send a tx with the specified fee_rate. Fee may be exact or at most one satoshi higher than needed."""
        tx = self.create_self_transfer(**kwargs)
        self.sendrawtransaction(from_node=kwargs['from_node'], tx_hex=tx['hex'])
        return tx

    def create_self_transfer(self, *, fee_rate=Decimal("0.003"), from_node, utxo_to_spend=None, mempool_valid=True, locktime=0, sequence=0):
        """Create and return a tx with the specified fee_rate. Fee may be exact or at most one satoshi higher than needed."""
        self._utxos = sorted(self._utxos, key=lambda k: (k['value'], -k['height']))
        utxo_to_spend = utxo_to_spend or self._utxos.pop()  # Pick the largest utxo (if none provided) and hope it covers the fee
        if self._priv_key is None:
            vsize = Decimal(85)  # anyone-can-spend
        else:
            vsize = Decimal(168)  # P2PK (73 bytes scriptSig + 35 bytes scriptPubKey + 60 bytes other)
        send_value = int(COIN * (utxo_to_spend['value'] - fee_rate * (vsize / 1000)))
        assert send_value > 0

        tx = CTransaction()
        tx.vin = [CTxIn(COutPoint(int(utxo_to_spend['txid'], 16), utxo_to_spend['vout']), nSequence=sequence)]
        tx.vout = [CTxOut(send_value, self._scriptPubKey)]
        tx.nLockTime = locktime
        if not self._address:
            # raw script
            if self._priv_key is not None:
                # P2PK, need to sign
                self.sign_tx(tx)
            else:
                # anyone-can-spend
                tx.vin[0].scriptSig = CScript([OP_NOP] * 24)  # pad to identical size
        else:
            tx.vin[0].scriptSig = CScript([CScript([OP_TRUE])])
        tx_hex = tx.serialize().hex()

        tx_info = from_node.testmempoolaccept([tx_hex])[0]
        assert_equal(mempool_valid, tx_info['allowed'])
        if mempool_valid:
            assert_equal(len(tx_hex) // 2, vsize) # 1 byte = 2 character
            assert_equal(tx_info['fees']['base'], utxo_to_spend['value'] - Decimal(send_value) / COIN)
        return {'txid': tx_info['txid'], 'hex': tx_hex, 'tx': tx}

    def sendrawtransaction(self, *, from_node, tx_hex):
        from_node.sendrawtransaction(tx_hex)
        self.scan_tx(from_node.decoderawtransaction(tx_hex))

def make_chain(node, address, privkeys, parent_txid, parent_value, n=0, parent_locking_script=None, fee=DEFAULT_FEE):
    """Build a transaction that spends parent_txid.vout[n] and produces one output with
    amount = parent_value with a fee deducted.
    Return tuple (CTransaction object, raw hex, nValue, scriptPubKey of the output created).
    """
    inputs = [{"txid": parent_txid, "vout": n}]
    my_value = parent_value - fee
    outputs = {address : my_value}
    rawtx = node.createrawtransaction(inputs, outputs)
    prevtxs = [{
        "txid": parent_txid,
        "vout": n,
        "scriptPubKey": parent_locking_script,
        "amount": parent_value,
    }] if parent_locking_script else None
    signedtx = node.signrawtransactionwithkey(hexstring=rawtx, privkeys=privkeys, prevtxs=prevtxs)
    assert signedtx["complete"]
    tx = tx_from_hex(signedtx["hex"])
    return (tx, signedtx["hex"], my_value, tx.vout[0].scriptPubKey.hex())

def create_child_with_parents(node, address, privkeys, parents_tx, values, locking_scripts, fee=DEFAULT_FEE):
    """Creates a transaction that spends the first output of each parent in parents_tx."""
    num_parents = len(parents_tx)
    total_value = sum(values)
    inputs = [{"txid": tx.rehash(), "vout": 0} for tx in parents_tx]
    outputs = {address : total_value - fee}
    rawtx_child = node.createrawtransaction(inputs, outputs)
    prevtxs = []
    for i in range(num_parents):
        prevtxs.append({"txid": parents_tx[i].rehash(), "vout": 0, "scriptPubKey": locking_scripts[i], "amount": values[i]})
    signedtx_child = node.signrawtransactionwithkey(hexstring=rawtx_child, privkeys=privkeys, prevtxs=prevtxs)
    assert signedtx_child["complete"]
    return signedtx_child["hex"]

def create_raw_chain(node, first_coin, address, privkeys, chain_length=25):
    """Helper function: create a "chain" of chain_length transactions. The nth transaction in the
    chain is a child of the n-1th transaction and parent of the n+1th transaction.
    """
    parent_locking_script = None
    txid = first_coin["txid"]
    chain_hex = []
    chain_txns = []
    value = first_coin["amount"]

    for _ in range(chain_length):
        (tx, txhex, value, parent_locking_script) = make_chain(node, address, privkeys, txid, value, 0, parent_locking_script)
        txid = tx.rehash()
        chain_hex.append(txhex)
        chain_txns.append(tx)

    return (chain_hex, chain_txns)

def bulk_transaction(tx, node, target_weight, privkeys, prevtxs=None):
    """Pad a transaction with extra outputs until it reaches a target weight (or higher).
    returns CTransaction object
    """
    tx_heavy = deepcopy(tx)
    assert_greater_than_or_equal(target_weight, tx_heavy.get_weight())
    while tx_heavy.get_weight() < target_weight:
        random_spk = "6a4d0200"  # OP_RETURN OP_PUSH2 512 bytes
        for _ in range(512*2):
            random_spk += choice("0123456789ABCDEF")
        tx_heavy.vout.append(CTxOut(0, bytes.fromhex(random_spk)))
    # Re-sign the transaction
    if privkeys:
        signed = node.signrawtransactionwithkey(tx_heavy.serialize().hex(), privkeys, prevtxs)
        return tx_from_hex(signed["hex"])
    # OP_TRUE
    tx_heavy.vin[0].scriptSig = CScript([CScript([OP_TRUE])])
    return tx_heavy