book.py

# CoinTaxman
# Copyright (C) 2021  Carsten Docktor <https://github.com/provinzio>

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as
# published by the Free Software Foundation, either version 3 of the
# License, or (at your option) any later version.

# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Affero General Public License for more details.

# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

import collections
import csv
import datetime
import decimal
import re
from collections import defaultdict
from pathlib import Path
from typing import Any, Optional

import config
import log_config
import misc
import transaction as tr
from core import kraken_asset_map
from database import set_price_db
from price_data import PriceData

log = log_config.getLogger(__name__)


class Book:
    # Need to track state of duplicate deposit/withdrawal entries
    # All deposits/withdrawals are held back until they occur a second time
    # Initialize non-existing fields with None once they're called
    kraken_held_ops: defaultdict[str, defaultdict[str, Any]] = defaultdict(
        lambda: defaultdict(lambda: None)
    )

    def __init__(self, price_data: PriceData) -> None:
        self.price_data = price_data

        self.operations: list[tr.Operation] = []

    def __bool__(self) -> bool:
        return bool(self.operations)

    def create_operation(
        self,
        operation: str,
        utc_time: datetime.datetime,
        platform: str,
        change: decimal.Decimal,
        coin: str,
        row: int,
        file_path: Path,
        remark: Optional[str] = None,
    ) -> tr.Operation:

        try:
            Op = getattr(tr, operation)
        except AttributeError:
            log.error(
                f"Could not recognize {operation=} from {platform=} in "
                f"{file_path=} {row=}. "
                "The operation type might have been removed or renamed. "
                "Please open an issue or PR."
            )
            raise RuntimeError

        kwargs = {}
        if remark:
            kwargs["remarks"] = [remark]

        op = Op(utc_time, platform, change, coin, [row], file_path, **kwargs)
        assert isinstance(op, tr.Operation)
        return op

    def _append_operation(
        self,
        op: tr.Operation,
    ) -> None:
        # Discard operations after the `TAX_YEAR`.
        # Ignore operations which make no change.
        if op.utc_time.year <= config.TAX_YEAR and op.change != 0:
            self.operations.append(op)

    def append_operation(
        self,
        operation: str,
        utc_time: datetime.datetime,
        platform: str,
        change: decimal.Decimal,
        coin: str,
        row: int,
        file_path: Path,
        remark: Optional[str] = None,
    ) -> None:
        # Discard operations after the `TAX_YEAR`.
        # Ignore operations which make no change.
        if utc_time.year <= config.TAX_YEAR and change != 0:
            op = self.create_operation(
                operation,
                utc_time,
                platform,
                change,
                coin,
                row,
                file_path,
                remark=remark,
            )

            self._append_operation(op)

    def _read_binance(self, file_path: Path, version: int = 1) -> None:
        platform = "binance"
        operation_mapping = {
            "Distribution": "Airdrop",
            "Cash Voucher distribution": "Airdrop",
            "Cashback Voucher": "Airdrop",
            "Rewards Distribution": "Airdrop",
            "Simple Earn Flexible Airdrop": "Airdrop",
            "Airdrop Assets": "Airdrop",
            "Crypto Box": "Airdrop",
            "Launchpool Airdrop": "Airdrop",
            "Megadrop Rewards": "Airdrop",
            #
            "Savings Interest": "CoinLendInterest",
            "Savings purchase": "CoinLend",
            "Savings Principal redemption": "CoinLendEnd",
            "Savings distribution": "CoinLendInterest",
            "Simple Earn Flexible Subscription": "CoinLend",
            "Simple Earn Flexible Redemption": "CoinLendEnd",
            "Simple Earn Flexible Interest": "CoinLendInterest",
            "Simple Earn Locked Subscription": "CoinLend",
            "Simple Earn Locked Redemption": "CoinLendEnd",
            "Simple Earn Locked Rewards": "CoinLendInterest",
            "Savings Distribution": "CoinLendInterest",
            #
            "BNB Vault Rewards": "CoinLendInterest",
            "Launchpool Earnings Withdrawal": "CoinLendInterest",
            #
            "Commission History": "Commission",
            "Commission Fee Shared With You": "Commission",
            "Referrer rebates": "Commission",
            "Referral Kickback": "Commission",
            "Commission Rebate": "Commission",
            # DeFi yield farming
            "Liquid Swap add": "CoinLend",
            "Liquid Swap remove": "CoinLendEnd",
            "Liquid Swap rewards": "CoinLendInterest",
            "Launchpool Interest": "CoinLendInterest",
            #
            "Super BNB Mining": "StakingInterest",
            "POS savings interest": "StakingInterest",
            "POS savings purchase": "Staking",
            "POS savings redemption": "StakingEnd",
            "ETH 2.0 Staking Rewards": "StakingInterest",
            "Staking Purchase": "Staking",
            "Staking Rewards": "StakingInterest",
            "Staking Redemption": "StakingEnd",
            #
            "Fiat Deposit": "Deposit",
            "Withdraw": "Withdrawal",
            #
            "Transaction Buy": "Buy",
            "Transaction Spend": "Sell",
            "Transaction Revenue": "Buy",
            "Transaction Sold": "Sell",
            "Transaction Fee": "Fee",
            "Asset Recovery": "Sell",
        }

        with open(file_path, encoding="utf8") as f:
            reader = csv.reader(f)

            # Skip header.
            next(reader)

            for rowlist in reader:
                if version == 1:
                    _utc_time, account, operation, coin, _change, remark = rowlist
                elif version == 2:
                    (
                        _,
                        _utc_time,
                        account,
                        operation,
                        coin,
                        _change,
                        remark,
                    ) = rowlist
                else:
                    log.error("File version not Supported " + str(file_path))
                    raise NotImplementedError

                row = reader.line_num

                # Parse data.
                utc_time = datetime.datetime.strptime(_utc_time, "%Y-%m-%d %H:%M:%S")
                utc_time = utc_time.replace(tzinfo=datetime.timezone.utc)
                change = misc.force_decimal(_change)
                operation = operation_mapping.get(operation, operation)
                if operation in (
                    "The Easiest Way to Trade",
                    "Small assets exchange BNB",
                    "Small Assets Exchange BNB",
                    "Transaction Related",
                    "Large OTC trading",
                    "Sell",
                    "Buy",
                    "Binance Convert",
                ):
                    operation = "Sell" if change < 0 else "Buy"

                if operation == "Liquid Swap add/sell":
                    operation = "CoinLendEnd" if change < 0 else "CoinLend"

                if operation == "Commission" and account != "Spot":
                    # All comissions will be handled the same way.
                    # As of now, only Spot Binance Operations are supported,
                    # so we have to change the account type to Spot.
                    account = "Spot"

                if (
                    account in ("Spot", "P2P")
                    and operation
                    in (
                        "transfer_in",
                        "transfer_out",
                    )
                    or (
                        account in ("Spot", "Funding")
                        and operation == "Transfer Between Main and Funding Wallet"
                    )
                ):
                    # Ignore transfers
                    continue

                change = abs(change)

                # Validate data.
                supported_account_types = ("Spot", "Savings", "Earn", "Funding")
                assert account in supported_account_types, (
                    f"Other types than {supported_account_types} are currently "
                    f"not supported.  Given account type is `{account}`. "
                    "Please create an Issue or PR."
                )
                assert operation
                assert coin
                assert change

                if remark:
                    # Ignore default remarks
                    if remark in (
                        "Withdraw fee is included",
                        "Binance Earn",
                        "Binance Pay",
                        "Binance Launchpool",
                    ) or remark.endswith(" to BNB"):
                        remark = None

                    # Do not warn for specific remarks
                    elif remark.startswith("Korrekturbuchung."):
                        pass

                    # Warn on other binance remarks, becuase all remarks should be some
                    # unnecessary default text which we'd like to ignore
                    else:
                        log.warning(
                            "I may have missed a remark in %s:%i: `%s`.",
                            file_path,
                            row,
                            remark,
                        )

                self.append_operation(
                    operation, utc_time, platform, change, coin, row, file_path, remark
                )

    def _read_binance_v2(self, file_path: Path) -> None:
        self._read_binance(file_path=file_path, version=2)

    def _read_coinbase(self, file_path: Path) -> None:
        platform = "coinbase"
        operation_mapping = {
            "Receive": "Deposit",
            "Send": "Withdrawal",
            "Coinbase Earn": "Buy",
            "Learning Reward": "Buy",
            "Rewards Income": "Staking",
        }

        with open(file_path, encoding="utf8") as f:
            reader = csv.reader(f)

            # Skip header.
            try:
                assert next(reader)  # header line
                assert next(reader) == []
                assert next(reader) == []
                assert next(reader) == []
                assert next(reader) == ["Transactions"]
                assert next(reader)  # user row
                assert next(reader) == []

                fields = next(reader)
                num_columns = len(fields)
                # Coinbase export format from late 2021 and ongoing
                if num_columns == 10:
                    assert fields == [
                        "Timestamp",
                        "Transaction Type",
                        "Asset",
                        "Quantity Transacted",
                        "Spot Price Currency",
                        "Spot Price at Transaction",
                        "Subtotal",
                        "Total (inclusive of fees)",
                        "Fees",
                        "Notes",
                    ] or fields == [
                        "Timestamp",
                        "Transaction Type",
                        "Asset",
                        "Quantity Transacted",
                        "Spot Price Currency",
                        "Spot Price at Transaction",
                        "Subtotal",
                        "Total (inclusive of fees and/or spread)",
                        "Fees and/or Spread",
                        "Notes",
                    ]
                # Coinbase export format from mid 2021 and before
                elif num_columns == 9:
                    assert fields == [
                        "Timestamp",
                        "Transaction Type",
                        "Asset",
                        "Quantity Transacted",
                        "EUR Spot Price at Transaction",
                        "EUR Subtotal",
                        "EUR Total (inclusive of fees)",
                        "EUR Fees",
                        "Notes",
                    ]
                else:
                    raise RuntimeError(
                        "Unknown Coinbase format: "
                        "Number of rows do not match known versions: "
                        f"{file_path}."
                    )
            except AssertionError as e:
                msg = (
                    "Unable to read coinbase file: Malformed header. "
                    f"Skipping {file_path}."
                )
                e.args += (msg,)
                log.exception(e)
                return

            for columns in reader:

                # Coinbase export format from late 2021 and ongoing
                if num_columns == 10:
                    (
                        _utc_time,
                        operation,
                        coin,
                        _change,
                        _currency_spot,
                        _eur_spot,
                        _eur_subtotal,
                        _eur_total,
                        _eur_fee,
                        remark,
                    ) = columns

                # Coinbase export format from mid 2021 and before
                elif num_columns == 9:
                    (
                        _utc_time,
                        operation,
                        coin,
                        _change,
                        _eur_spot,  # Rounded price from CSV, unused
                        _eur_subtotal,  # Cost without fees
                        _eur_total,
                        _eur_fee,
                        remark,
                    ) = columns
                    _currency_spot = "EUR"

                row = reader.line_num

                # Parse data.
                utc_time = datetime.datetime.strptime(_utc_time, "%Y-%m-%dT%H:%M:%SZ")
                utc_time = utc_time.replace(tzinfo=datetime.timezone.utc)
                operation = operation_mapping.get(operation, operation)
                change = misc.force_decimal(_change)
                # `eur_subtotal` and `eur_fee` are None for withdrawals.
                eur_subtotal = misc.xdecimal(_eur_subtotal)
                if eur_subtotal is None:
                    # Cost without fees from CSV is missing. This can happen for
                    # old transactions (<2018), event though something was bought.
                    # Calculate the `eur_subtotal` from `eur_spot`.
                    if eur_spot := misc.xdecimal(_eur_spot):
                        eur_subtotal = eur_spot * change
                eur_fee = misc.xdecimal(_eur_fee)

                # Validate data.
                assert operation
                assert coin
                assert change
                assert _currency_spot == "EUR"

                # Calculated price
                if eur_subtotal:
                    assert isinstance(eur_subtotal, decimal.Decimal)
                    price_calc = eur_subtotal / change
                    # Save price in our local database for later.
                    set_price_db(platform, coin, "EUR", utc_time, price_calc)

                if operation == "Convert":
                    # Parse change + coin from remark, which is
                    # in format "Converted 0,123 ETH to 0,456 BTC".
                    match = re.match(
                        r"^Converted [0-9,\.]+ [A-Z]+ to "
                        r"(?P<change>[0-9,\.]+) (?P<coin>[A-Z]+)$",
                        remark,
                    )
                    assert match

                    _convert_change = match.group("change").replace(",", ".")
                    convert_change = misc.force_decimal(_convert_change)
                    convert_coin = match.group("coin")

                    eur_total = misc.force_decimal(_eur_total)
                    convert_eur_spot = eur_total / convert_change

                    self.append_operation(
                        "Sell", utc_time, platform, change, coin, row, file_path
                    )
                    self.append_operation(
                        "Buy",
                        utc_time,
                        platform,
                        convert_change,
                        convert_coin,
                        row,
                        file_path,
                    )

                    # Save convert price in local database, too.
                    set_price_db(
                        platform, convert_coin, "EUR", utc_time, convert_eur_spot
                    )
                else:
                    # Add operation normally to the list.
                    self.append_operation(
                        operation, utc_time, platform, change, coin, row, file_path
                    )

                    # If it's a sell, add the corresponding buy to complement
                    # the trading pair.
                    if operation == "Sell":
                        assert isinstance(eur_subtotal, decimal.Decimal)
                        self.append_operation(
                            "Buy",
                            utc_time,
                            platform,
                            eur_subtotal,
                            "EUR",
                            row,
                            file_path,
                        )
                    # If it's a buy, add the corresponding sell to complement
                    # the trading pair.
                    elif operation == "Buy":
                        assert isinstance(eur_subtotal, decimal.Decimal)
                        self.append_operation(
                            "Sell",
                            utc_time,
                            platform,
                            eur_subtotal,
                            "EUR",
                            row,
                            file_path,
                        )

                # Add paid fees to the list.
                if eur_fee:
                    assert isinstance(eur_fee, decimal.Decimal)
                    self.append_operation(
                        "Fee", utc_time, platform, eur_fee, "EUR", row, file_path
                    )

    def _read_coinbase_v2(self, file_path: Path) -> None:
        self._read_coinbase(file_path=file_path)

    def _read_coinbase_v3(self, file_path: Path) -> None:
        self._read_coinbase(file_path=file_path)

    def _read_coinbase_pro(self, file_path: Path) -> None:
        platform = "coinbase_pro"
        operation_mapping = {
            "BUY": "Buy",
            "SELL": "Sell",
        }

        with open(file_path, encoding="utf8") as f:
            reader = csv.reader(f)

            # Skip header.
            next(reader)

            for (
                portfolio,
                trade_id,
                product,
                operation,
                _utc_time,
                _size,
                size_unit,
                _price,
                _fee,
                total,
                price_fee_total_unit,
            ) in reader:
                row = reader.line_num

                # Parse data.
                utc_time = datetime.datetime.strptime(
                    _utc_time, "%Y-%m-%dT%H:%M:%S.%fZ"
                )
                utc_time = utc_time.replace(tzinfo=datetime.timezone.utc)
                operation = operation_mapping.get(operation, operation)
                size = misc.force_decimal(_size)
                price = misc.force_decimal(_price)
                fee = misc.xdecimal(_fee)
                total_price = size * price

                # Unused variables.
                del portfolio
                del trade_id
                del product
                del total

                # Validate data.
                assert operation
                assert size
                assert size_unit
                assert price_fee_total_unit

                self.append_operation(
                    operation, utc_time, platform, size, size_unit, row, file_path
                )

                if operation == "Sell":
                    self.append_operation(
                        "Buy",
                        utc_time,
                        platform,
                        total_price,
                        price_fee_total_unit,
                        row,
                        file_path,
                    )
                elif operation == "Buy":
                    self.append_operation(
                        "Sell",
                        utc_time,
                        platform,
                        total_price,
                        price_fee_total_unit,
                        row,
                        file_path,
                    )
                if fee:
                    self.append_operation(
                        "Fee",
                        utc_time,
                        platform,
                        fee,
                        price_fee_total_unit,
                        row,
                        file_path,
                    )

    def _read_kraken_trades(self, file_path: Path) -> None:
        log.error(
            f"{file_path.name}: "
            "Looks like this is a Kraken 'Trades' history, "
            "but we need the 'Ledgers' history. "
            "(See: Wiki - Exchange Kraken)"
        )

    def _read_kraken_ledgers(self, file_path: Path) -> None:
        fee_sign_of_file: Optional[bool] = None

        platform = "kraken"
        operation_mapping = {
            "spend": "Sell",  # Sell ordered via 'Buy Crypto' or 'Dust Sweeping'
            "receive": "Buy",  # Buy ordered via 'Buy Crypto' or 'Dust Sweeping'
            "reward": "StakingInterest",
            "staking": "StakingInterest",
            "deposit": "Deposit",
            "withdrawal": "Withdrawal",
            "rollover": "MarginFee",
        }

        with open(file_path, encoding="utf8") as f:
            reader = csv.reader(f)

            # Skip header.
            next(reader)

            for columns in reader:

                num_columns = len(columns)
                # Kraken ledgers export format from 2025 and ongoing
                if num_columns == 11:
                    (
                        txid,
                        refid,
                        _utc_time,
                        _type,
                        subtype,
                        aclass,
                        _asset,
                        _wallet,
                        _amount,
                        _fee,
                        balance,
                    ) = columns

                # Kraken ledgers export format from October 2020 until 2025
                elif num_columns == 10:
                    (
                        txid,
                        refid,
                        _utc_time,
                        _type,
                        subtype,
                        aclass,
                        _asset,
                        _amount,
                        _fee,
                        balance,
                    ) = columns

                # Kraken ledgers export format from September 2020 and before
                elif num_columns == 9:
                    (
                        txid,
                        refid,
                        _utc_time,
                        _type,
                        aclass,
                        _asset,
                        _amount,
                        _fee,
                        balance,
                    ) = columns
                else:
                    log.error(
                        f"{file_path}: Unknown Kraken ledgers format: "
                        "Number of rows do not match known versions."
                    )
                    raise RuntimeError

                row = reader.line_num

                # Parse data.
                utc_time = datetime.datetime.strptime(_utc_time, "%Y-%m-%d %H:%M:%S")
                utc_time = utc_time.replace(tzinfo=datetime.timezone.utc)
                change = misc.force_decimal(_amount)
                # remove the appended .S for staked assets
                _asset = _asset.removesuffix(".S")
                coin = kraken_asset_map.get(_asset, _asset)
                fee = misc.force_decimal(_fee)
                # An older implementation expected always positive fees
                # It seems that newer ledger files can have negative fee
                # values instead.
                if fee != 0:
                    # As soon as the first fee!=0 appears, check whether the
                    # fees are positive or negative. All fees in the file
                    # should have the same sign.
                    if fee_sign_of_file is None:
                        fee_sign_of_file = fee < 0
                    # Adjust the fee sign so that fees are always positive.
                    if fee_sign_of_file is True:
                        fee *= -1
                    if fee < 0:
                        log.error(
                            f"{file_path} row {row}: Unexpected fee sign. "
                            "All fees should have the same sign. "
                            "Please create an Issue or PR."
                        )
                        raise RuntimeError

                operation = operation_mapping.get(_type)
                if operation is None:
                    if _type == "trade":
                        operation = "Sell" if change < 0 else "Buy"
                    elif _type == "margin":
                        # Margin positions for Kraken always fall under income from
                        # capital, as the user can decide until the end if it is closed
                        # or settled. "rollover" entries contain margin fees between
                        # start and end. The start of a margin position is denoted with
                        # a "margin" entry with zero change. For closed positions, the
                        # end is marked with a "margin" entry containing the net
                        # gain/loss of the position.
                        # If the change is zero, consider only the fees.
                        if change == 0:
                            operation = "MarginFee"
                        elif change > 0:
                            operation = "MarginGain"
                        else:
                            operation = "MarginLoss"
                    elif _type == "settled":
                        # "settled" entries mark the end of settled positions.
                        operation = "MarginGain" if change > 0 else "MarginLoss"
                    elif _type == "transfer":
                        if num_columns == 9:
                            # for backwards compatibility assume Airdrop for staking
                            log.warning(
                                f"{file_path} row {row}: Staking is not supported for"
                                "old Kraken ledger formats. "
                                "Please create an Issue or PR."
                            )
                            operation = "Airdrop"
                        elif subtype == "stakingfromspot":
                            operation = "Staking"
                        elif subtype == "stakingtospot":
                            operation = "StakingEnd"
                        elif subtype in ["spottostaking", "spotfromstaking"]:
                            # duplicate entries for staking actions
                            continue
                        elif subtype in ["spottofutures", "spotfromfutures"]:
                            # transfer between spot and futures
                            continue
                        else:
                            log.error(
                                f"{file_path} row {row}: Order subtype '{subtype}' is "
                                "currently not supported. Please create an Issue or PR."
                            )
                            raise RuntimeError
                    elif _type == "earn":
                        if subtype == "reward":
                            operation = "StakingInterest"
                        elif subtype == "migration":
                            # Migration of "x.S" legacy staking balance to new staking
                            # infrastructure in "earn / bonded" wallet
                            continue
                        elif subtype == "allocation":
                            if change > 0:
                                operation = "Staking"
                            else:
                                # duplicate entries for staking actions
                                continue
                        elif subtype == "deallocation":
                            if change > 0:
                                operation = "StakingEnd"
                            else:
                                # duplicate entries for staking actions
                                continue
                        else:
                            log.error(
                                f"{file_path} row {row}: Order subtype '{subtype}' is "
                                "currently not supported. Please create an Issue or PR."
                            )
                            raise RuntimeError
                    else:
                        log.error(
                            f"{file_path} row {row}: Other order type '{_type}' is "
                            "currently not supported. Please create an Issue or PR."
                        )
                        raise RuntimeError
                change = abs(change)

                # Validate data.
                assert operation
                assert coin

                # Margin trading: Add operations and fees to list.
                if operation in ["MarginFee", "MarginGain", "MarginLoss"]:
                    if operation == "MarginFee":
                        assert (
                            change == 0
                        ), "Margin fee operation should only contain fee."
                    if change:
                        # Add margin gain/losses to operation list.
                        self.append_operation(
                            operation, utc_time, platform, change, coin, row, file_path
                        )
                    if fee:
                        self.append_operation(
                            "MarginFee", utc_time, platform, fee, coin, row, file_path
                        )

                # Skip duplicate entries for deposits / withdrawals and additional
                # deposit / withdrawal lines for staking / unstaking / staking reward
                # actions.
                # The second deposit and the first withdrawal need to be considered,
                # since these are the points in time where the user actually has the
                # assets at their disposal. The first deposit and second withdrawal are
                # in the public trade history and are skipped.
                # For staking / unstaking / staking reward actions, deposits /
                # withdrawals only occur once and will be ignored.
                # The "appended" flag stores if an operation for a given refid has
                # already been appended to the operations list:
                # == None: Initial value (first occurrence)
                # == False: No operation has been appended (second occurrence)
                # == True: Operation has already been appended, this should not happen
                elif operation in ["Deposit", "Withdrawal"]:
                    assert change
                    # First, create the operations
                    op = self.create_operation(
                        operation, utc_time, platform, change, coin, row, file_path
                    )
                    op_fee = None
                    if fee != 0:
                        op_fee = self.create_operation(
                            "Fee", utc_time, platform, fee, coin, row, file_path
                        )
                    # If this is the first occurrence, set the "appended" flag to false
                    # and don't append the operation to the list. Instead, store the
                    # data for verifying or appending it later.
                    if self.kraken_held_ops[refid]["appended"] is None:
                        self.kraken_held_ops[refid]["appended"] = False
                        self.kraken_held_ops[refid]["operation"] = op
                        self.kraken_held_ops[refid]["operation_fee"] = op_fee
                    # If this is the second occurrence, append a new operation, set the
                    # "appended" flag to True and assert that the data of this operation
                    # agrees with the data of the first occurrence.
                    elif self.kraken_held_ops[refid]["appended"] is False:
                        self.kraken_held_ops[refid]["appended"] = True
                        try:
                            # Make sure, that the found operations with the
                            # same refid  have the same operation type, amount
                            # of change and same coin.
                            assert isinstance(
                                op, type(self.kraken_held_ops[refid]["operation"])
                            ), (
                                "operation "
                                f"({op.type_name} != "
                                f'{self.kraken_held_ops[refid]["operation"].type_name})'
                            )
                            assert (
                                op.change
                                == self.kraken_held_ops[refid]["operation"].change
                            ), (
                                "change "
                                f"({op.change} != "
                                f'{self.kraken_held_ops[refid]["operation"].change})'
                            )
                            assert (
                                op.coin == self.kraken_held_ops[refid]["operation"].coin
                            ), (
                                "coin "
                                f"({op.coin} != "
                                f'{self.kraken_held_ops[refid]["operation"].coin})'
                            )
                        except AssertionError as e:
                            # Row is internally saved as list[int].
                            first_row = self.kraken_held_ops[refid]["operation"].line[0]
                            log.error(
                                "Two internal kraken operations matched by the "
                                f"same {refid=} don't have the same {e}.\n"
                                "CoinTaxman expects, that these two operations "
                                "have the same type of operation, amount of "
                                "change and the same coin.\n"
                                f"See {file_path} in row {first_row} and "
                                f"{row}.\n"
                                "Please create an Issue or PR."
                            )
                            raise RuntimeError
                        # For deposits, this is all we need to do before appending the
                        # operation. For withdrawals, we need to append the first
                        # withdrawal as soon as the second withdrawal occurs. Therefore,
                        # overwrite the operation with the stored first withdrawal.
                        if operation == "Withdrawal":
                            op = self.kraken_held_ops[refid]["operation"]
                            op_fee = self.kraken_held_ops[refid]["operation_fee"]
                        # Finally, append the operations and delete the stored
                        # operations to reduce memory consumption
                        self._append_operation(op)
                        if op_fee:
                            self._append_operation(op_fee)
                        del self.kraken_held_ops[refid]["operation"]
                        del self.kraken_held_ops[refid]["operation_fee"]
                    # If an operation with the same refid has been already appended,
                    # this is the third occurrence. Throw an error if this happens.
                    elif self.kraken_held_ops[refid]["appended"] is True:
                        log.error(
                            f"{file_path} row {row}: More than two entries with refid "
                            f"{refid} should not exist ({operation}). "
                            "Please create an Issue or PR."
                        )
                        raise RuntimeError
                    # This should never happen
                    else:
                        log.error(
                            f"{file_path} row {row}: Unknown value for appended "
                            f"operation flag {self.kraken_held_ops[refid]['appended']}."
                            "Please create an Issue or PR."
                        )
                        raise TypeError

                # for all other operation types
                else:
                    assert change
                    self.append_operation(
                        operation, utc_time, platform, change, coin, row, file_path
                    )
                    if fee != 0:
                        self.append_operation(
                            "Fee", utc_time, platform, fee, coin, row, file_path
                        )
                    if operation == "StakingInterest":
                        # For Kraken, the rewarded coins are added to the staked
                        # portfolio. TODO (for MULTI_DEPOT only): Directly add the
                        # rewarded coins to the staking depot (not like here with the
                        # detour of adding it to spot and then staking the same amount)
                        self.append_operation(
                            "Staking", utc_time, platform, change, coin, row, file_path
                        )

    def _read_kraken_ledgers_old(self, file_path: Path) -> None:
        self._read_kraken_ledgers(file_path)

    def _read_kraken_ledgers_v2(self, file_path: Path) -> None:
        self._read_kraken_ledgers(file_path)

    def _read_bitpanda_pro_trades(self, file_path: Path) -> None:
        """Reads a trade statement from Bitpanda Pro.

        Args:
            file_path (Path): Path to Bitpanda trade history.
        """

        platform = "bitpanda_pro"
        with open(file_path, encoding="utf8") as f:
            reader = csv.reader(f)

            # skip header
            next(reader)
            line = next(reader)

            transaction_file_warn = (
                f"{file_path} looks like a Bitpanda transaction file."
                " Skipping. Please download the trade history instead."
            )

            # for transactions, it's currently written "id" (small)
            if line[0].startswith("Account id :"):
                log.warning(transaction_file_warn)
                return

            assert line[0].startswith("Account ID:")
            line = next(reader)
            # empty line - still keep this check in case Bitpanda changes the
            # transaction file to match the trade header (casing)
            if not line:
                log.warning(transaction_file_warn)
                return

            elif line[0] != "Bitpanda Pro trade history":
                log.warning(
                    f"{file_path} doesn't look like a Bitpanda trade file. Skipping."
                )
                return

            line = next(reader)
            assert line in [
                [
                    "Order ID",
                    "Trade ID",
                    "Type",
                    "Market",
                    "Amount",
                    "Amount Currency",
                    "Price",
                    "Price Currency",
                    "Fee",
                    "Fee Currency",
                    "Time (UTC)",
                ],
                [
                    "Order ID",
                    "Trade ID",
                    "Type",
                    "Market",
                    "Amount",
                    "Amount Currency",
                    "Price",
                    "Price Currency",
                    "Fee",
                    "Fee Currency",
                    "Time (UTC)",
                    "BEST_EUR Rate",
                ],
            ]

            for current_line in reader:
                if len(current_line) == 11:
                    (
                        _order_id,
                        _trace_id,
                        operation,
                        trade_pair,
                        amount,
                        amount_currency,
                        _price,
                        price_currency,
                        fee,
                        fee_currency,
                        _utc_time,
                    ) = current_line
                    best_price = None
                elif len(current_line) == 12:
                    (
                        _order_id,
                        _trace_id,
                        operation,
                        trade_pair,
                        amount,
                        amount_currency,
                        _price,
                        price_currency,
                        fee,
                        fee_currency,
                        _utc_time,
                        best_price,
                    ) = current_line
                else:
                    raise NotImplementedError

                row = reader.line_num

                # trade pair is of form e.g. BTC_EUR
                assert [amount_currency, price_currency] == trade_pair.split("_")

                # At the time of writing (2021-05-02),
                # there were only these two operations
                assert operation in ["BUY", "SELL"], "Unsupported operation"

                change = misc.force_decimal(amount)
                assert change > 0, "Unexpected value for 'Amount' column"

                # see _get_price_bitpanda_pro in price_data.py
                assert price_currency == "EUR", (
                    "Only Euro is supported as 'price' currency, "
                    "since price fetching is not fully implemented yet."
                )

                # sanity checks
                assert (
                    fee_currency == "BEST"
                    or (operation == "SELL" and fee_currency == price_currency)
                    or (operation == "BUY" and fee_currency == amount_currency)
                ), "Invalid fee currency"

                utc_time = misc.parse_iso_timestamp(_utc_time)

                coin = amount_currency

                self.append_operation(
                    operation.title(), utc_time, platform, change, coin, row, file_path
                )

                # Save price in our local database for later.
                price = misc.force_decimal(_price)
                set_price_db(platform, coin, price_currency, utc_time, price)
                if best_price:
                    set_price_db(
                        platform,
                        "BEST",
                        "EUR",
                        utc_time,
                        misc.force_decimal(best_price),
                    )

                self.append_operation(
                    "Fee",
                    utc_time,
                    platform,
                    misc.force_decimal(fee),
                    fee_currency,
                    row,
                    file_path,
                )

    def _read_bitpanda(self, file_path: Path) -> None:
        """Reads a trade statement from Bitpanda.

        Args:
            file_path (Path): Path to Bitpanda trade history.
        """

        platform = "bitpanda"

        operation_mapping = {
            "deposit": "Deposit",
            "withdrawal": "Withdrawal",
            "buy": "Buy",
            "sell": "Sell",
        }

        with open(file_path, encoding="utf8") as f:
            reader = csv.reader(f)
            line = next(reader)

            # skip header, there are multiple lines
            while line != [
                "Transaction ID",
                "Timestamp",
                "Transaction Type",
                "In/Out",
                "Amount Fiat",
                "Fiat",
                "Amount Asset",
                "Asset",
                "Asset market price",
                "Asset market price currency",
                "Asset class",
                "Product ID",
                "Fee",
                "Fee asset",
                "Spread",
                "Spread Currency",
            ]:
                try:
                    line = next(reader)
                except StopIteration:
                    log.error(f"Expected header not found in file {file_path}")
                    raise RuntimeError

            for (
                _tx_id,
                csv_utc_time,
                operation,
                _inout,
                amount_fiat,
                fiat,
                amount_asset,
                asset,
                _asset_price,
                asset_price_currency,
                asset_class,
                _product_id,
                fee,
                fee_currency,
                _spread,
                _spread_currency,
            ) in reader:
                row = reader.line_num

                # make RFC3339 timestamp ISO 8601 parseable
                if csv_utc_time[-1] == "Z":
                    csv_utc_time = csv_utc_time[:-1] + "+00:00"

                # timezone information is already taken care of with this
                utc_time = datetime.datetime.fromisoformat(csv_utc_time)

                # transfer ops seem to be akin to airdrops. In my case I got a
                # CocaCola transfer, which I don't want to track. Would need to
                # be implemented if need be.
                if operation == "transfer":
                    log.warning(
                        f"'Transfer' operations are not "
                        f"implemented, skipping row {row} of file {file_path}"
                    )
                    continue

                # fail for unknown ops
                try:
                    operation = operation_mapping[operation]
                except KeyError:
                    log.error(
                        f"Unsupported operation '{operation}' "
                        f"in row {row} of file {file_path}"
                    )
                    raise RuntimeError

                if operation in ["Deposit", "Withdrawal"]:
                    if asset_class == "Fiat":
                        change = misc.force_decimal(amount_fiat)
                        if fiat != asset:
                            log.error(
                                f"Asset {asset} should be {fiat} in "
                                f"row {row} of file {file_path}"
                            )
                            raise RuntimeError
                    elif asset_class == "Cryptocurrency":
                        change = misc.force_decimal(amount_asset)
                    else:
                        log.error(
                            f"Unknown asset class {asset_class}: Should be 'Fiat' or "
                            f"'Cryptocurrency' in row {row} of file {file_path}"
                        )
                        raise RuntimeError
                elif operation in ["Buy", "Sell"]:
                    if asset_price_currency != config.FIAT:
                        log.error(
                            f"Only {config.FIAT} is supported as "
                            "'Asset market price currency', since price fetching for "
                            "fiat currencies is not fully implemented yet."
                        )
                        raise RuntimeError
                    change = misc.force_decimal(amount_asset)
                    change_fiat = misc.force_decimal(amount_fiat)
                    # Save price in our local database for later.
                    # Rounded price in CSV
                    # price = misc.force_decimal(asset_price)
                    # Calculated price
                    price_calc = change_fiat / change
                    set_price_db(platform, asset, config.FIAT, utc_time, price_calc)

                if change < 0:
                    log.error(
                        f"Unexpected value for the amount '{change}' of this "
                        f"{operation} in row {row} of file {file_path}"
                    )
                    raise RuntimeError

                self.append_operation(
                    operation, utc_time, platform, change, asset, row, file_path
                )

                # add buy / sell operation for fiat currency
                if operation == "Buy":
                    self.append_operation(
                        "Sell",
                        utc_time,
                        platform,
                        change_fiat,
                        config.FIAT,
                        row,
                        file_path,
                    )
                elif operation == "Sell":
                    self.append_operation(
                        "Buy",
                        utc_time,
                        platform,
                        change_fiat,
                        config.FIAT,
                        row,
                        file_path,
                    )

                if fee != "-":
                    self.append_operation(
                        "Fee",
                        utc_time,
                        platform,
                        misc.force_decimal(fee),
                        fee_currency,
                        row,
                        file_path,
                    )

    def _read_custom_eur(self, file_path: Path) -> None:
        fiat = "EUR"

        with open(file_path, encoding="utf8") as f:
            reader = csv.reader(f)

            # Skip header.
            next(reader)

            for line in reader:
                row = reader.line_num

                # Skip empty lines.
                if not line:
                    continue

                (
                    operation_type,
                    _buy_quantity,
                    buy_asset,
                    _buy_value_in_fiat,
                    _sell_quantity,
                    sell_asset,
                    _sell_value_in_fiat,
                    _fee_quantity,
                    fee_asset,
                    _fee_value_in_fiat,
                    platform,
                    _timestamp,
                    remark,
                ) = line

                # Parse data.
                try:
                    utc_time = datetime.datetime.strptime(
                        _timestamp, "%m/%d/%Y %H:%M:%S"
                    )
                except ValueError:
                    utc_time = datetime.datetime.strptime(
                        _timestamp, "%m/%d/%Y %H:%M:%S.%f"
                    )
                utc_time = utc_time.replace(tzinfo=datetime.timezone.utc)
                buy_quantity = misc.xdecimal(_buy_quantity)
                buy_value_in_fiat = misc.xdecimal(_buy_value_in_fiat)
                sell_quantity = misc.xdecimal(_sell_quantity)
                sell_value_in_fiat = misc.xdecimal(_sell_value_in_fiat)
                fee_quantity = misc.xdecimal(_fee_quantity)
                fee_value_in_fiat = misc.xdecimal(_fee_value_in_fiat)

                # ... and define which operation to add.
                add_operations: list[
                    tuple[str, decimal.Decimal, str, Optional[decimal.Decimal]]
                ] = []
                if operation_type != "Withdrawal":
                    assert buy_quantity
                    assert buy_asset

                    op = "Buy" if operation_type == "Trade" else operation_type
                    add_operations.append(
                        (op, buy_quantity, buy_asset, buy_value_in_fiat)
                    )

                if operation_type not in ("Deposit", "Airdrop"):
                    assert sell_quantity
                    assert sell_asset

                    op = "Sell" if operation_type == "Trade" else operation_type
                    add_operations.append(
                        (op, sell_quantity, sell_asset, sell_value_in_fiat)
                    )

                if fee_asset:
                    assert fee_quantity
                    assert fee_value_in_fiat

                    add_operations.append(
                        ("Fee", fee_quantity, fee_asset, fee_value_in_fiat)
                    )

                for operation, change, coin, change_in_fiat in add_operations:
                    # Add operation to book.
                    self.append_operation(
                        operation,
                        utc_time,
                        platform,
                        change,
                        coin,
                        row,
                        file_path,
                        remark=remark,
                    )
                    # Add price from csv.
                    if change_in_fiat and coin != fiat:
                        price = change_in_fiat / change
                        log.debug(
                            f"Adding {fiat}/{coin} price from custom CSV: "
                            f"{price} for {platform} at {utc_time}"
                        )
                        set_price_db(
                            platform,
                            coin,
                            fiat,
                            utc_time,
                            price,
                            overwrite=True,
                        )

    def detect_exchange(self, file_path: Path) -> Optional[str]:
        if file_path.suffix == ".csv":

            expected_header_row = {
                "binance": 1,
                "binance_v2": 1,
                "coinbase": 1,
                "coinbase_v2": 1,
                "coinbase_v3": 1,
                "coinbase_pro": 1,
                "kraken_ledgers_old": 1,
                "kraken_ledgers": 1,
                "kraken_ledgers_v2": 1,
                "kraken_trades": 1,
                "bitpanda_pro_trades": 4,
                "bitpanda": 7,
                "custom_eur": 1,
            }

            expected_headers = {
                "binance": [
                    "UTC_Time",
                    "Account",
                    "Operation",
                    "Coin",
                    "Change",
                    "Remark",
                ],
                "binance_v2": [
                    "User_ID",
                    "UTC_Time",
                    "Account",
                    "Operation",
                    "Coin",
                    "Change",
                    "Remark",
                ],
                "coinbase": [
                    "You can use this transaction report to inform your "
                    "likely tax obligations. For US customers, Sells, "
                    "Converts, and Rewards Income, and Coinbase Earn "
                    "transactions are taxable events. For final tax "
                    "obligations, please consult your tax advisor."
                ],
                "coinbase_v2": [
                    "You can use this transaction report to inform your "
                    "likely tax obligations. For US customers, Sells, "
                    "Converts, Rewards Income, Coinbase Earn "
                    "transactions, and Donations are taxable events. "
                    "For final tax obligations, please consult your tax advisor."
                ],
                "coinbase_v3": [
                    "You can use this transaction report to inform your "
                    "likely tax obligations. For US customers, Sells, "
                    "Converts, Rewards Income, Learning Rewards, "
                    "and Donations are taxable events. "
                    "For final tax obligations, please consult your tax advisor."
                ],
                "coinbase_pro": [
                    "portfolio",
                    "trade id",
                    "product",
                    "side",
                    "created at",
                    "size",
                    "size unit",
                    "price",
                    "fee",
                    "total",
                    "price/fee/total unit",
                ],
                "kraken_ledgers_old": [
                    "txid",
                    "refid",
                    "time",
                    "type",
                    "aclass",
                    "asset",
                    "amount",
                    "fee",
                    "balance",
                ],
                "kraken_ledgers": [
                    "txid",
                    "refid",
                    "time",
                    "type",
                    "subtype",
                    "aclass",
                    "asset",
                    "amount",
                    "fee",
                    "balance",
                ],
                "kraken_ledgers_v2": [
                    "txid",
                    "refid",
                    "time",
                    "type",
                    "subtype",
                    "aclass",
                    "asset",
                    "wallet",
                    "amount",
                    "fee",
                    "balance",
                ],
                "kraken_trades": [
                    "txid",
                    "ordertxid",
                    "pair",
                    "time",
                    "type",
                    "ordertype",
                    "price",
                    "cost",
                    "fee",
                    "vol",
                    "margin",
                    "misc",
                    "ledgers",
                ],
                "bitpanda_pro_trades": [
                    "Order ID",
                    "Trade ID",
                    "Type",
                    "Market",
                    "Amount",
                    "Amount Currency",
                    "Price",
                    "Price Currency",
                    "Fee",
                    "Fee Currency",
                    "Time (UTC)",
                ],
                "bitpanda": [
                    "Transaction ID",
                    "Timestamp",
                    "Transaction Type",
                    "In/Out",
                    "Amount Fiat",
                    "Fiat",
                    "Amount Asset",
                    "Asset",
                    "Asset market price",
                    "Asset market price currency",
                    "Asset class",
                    "Product ID",
                    "Fee",
                    "Fee asset",
                    "Spread",
                    "Spread Currency",
                ],
                "custom_eur": [
                    "Type",
                    "Buy Quantity",
                    "Buy Asset",
                    "Buy Value in EUR",
                    "Sell Quantity",
                    "Sell Asset",
                    "Sell Value in EUR",
                    "Fee Quantity",
                    "Fee Asset",
                    "Fee Value in EUR",
                    "Wallet",
                    "Timestamp UTC",
                    "Note",
                ],
            }
            with open(file_path, encoding="utf8") as f:
                reader = csv.reader(f)
                # check all potential headers at their expected header row
                for exchange, expected in expected_headers.items():
                    header_row_num = expected_header_row[exchange]
                    # iterate since header row may appear earlier
                    for _ in range(header_row_num):
                        header = next(reader, None)
                        if header == expected:
                            return exchange
                    # rewind the file after each header check
                    f.seek(0)

        return None

    def resolve_deposits(self) -> None:
        """Match withdrawals to deposits.

        A match is found when:
            A. The coin is the same  and
            B. The deposit amount is between 0.99 and 1 times the withdrawal amount.
        """
        transfer_operations = (
            op for op in self.operations if isinstance(op, (tr.Deposit, tr.Withdrawal))
        )
        # Sort deposit and withdrawal operations by time so that deposits
        # come after withdrawal.
        sorted_transfer_operations = sorted(
            transfer_operations,
            key=lambda op: (isinstance(op, tr.Deposit), op.utc_time),
        )

        def is_match(withdrawal: tr.Withdrawal, deposit: tr.Deposit) -> bool:
            return (
                withdrawal.coin == deposit.coin
                and withdrawal.change * decimal.Decimal(0.99)
                <= deposit.change
                <= withdrawal.change
            )

        withdrawal_queue: list[tr.Withdrawal] = []
        unmatched_deposits: list[tr.Deposit] = []

        for op in sorted_transfer_operations:
            if op.coin == config.FIAT:
                # Do not match home fiat deposit/withdrawals.
                continue

            if isinstance(op, tr.Withdrawal):
                # Add new withdrawal to queue.
                withdrawal_queue.append(op)

            elif isinstance(op, tr.Deposit):
                try:
                    # Find a matching withdrawal for this deposit.
                    # If multiple are found, take the first (regarding utc_time).
                    match = next(w for w in withdrawal_queue if is_match(w, op))
                except StopIteration:
                    unmatched_deposits.append(op)
                else:
                    # Match the found withdrawal and remove it from queue.
                    op.link = match
                    match.has_link = True
                    withdrawal_queue.remove(match)
                    log.debug(
                        "Linking withdrawal with deposit: "
                        f"{match.change} {match.coin} "
                        f"({match.platform}, {match.utc_time}) "
                        f"-> {op.change} {op.coin} "
                        f"({op.platform}, {op.utc_time})"
                    )

        if unmatched_deposits:
            log.warning(
                "Unable to match all deposits with withdrawals. "
                "Have you added all account statements? "
                "Following deposits couldn't be matched:\n"
                + (
                    "\n".join(
                        f" - {op.change} {op.coin} to {op.platform} at {op.utc_time}"
                        for op in unmatched_deposits
                    )
                )
            )
            for op in unmatched_deposits:
                op.remarks.append("Herkunft der Einzahlung unbekannt")
        if withdrawal_queue:
            log.warning(
                "Unable to match all withdrawals with deposits. "
                "Have you added all account statements? "
                "Following withdrawals couldn't be matched:\n"
                + (
                    "\n".join(
                        f" - {op.change} {op.coin} from {op.platform} at {op.utc_time}"
                        for op in withdrawal_queue
                    )
                )
            )
            for op in withdrawal_queue:
                op.remarks.append("Ziel der Auszahlung unbekannt")

        log.info("Finished withdrawal/deposit matching")

    def get_price_from_csv(self) -> None:
        """Calculate coin prices from buy/sell operations in CSV files.

        When exactly one buy and sell happend at the exact same time,
        these two operations might belong together and we can calculate
        the paid price for this transaction.
        """
        # Group operations by platform.
        for platform, platform_operations in misc.group_by(
            self.operations, "platform"
        ).items():
            # Group operations by time.
            # Look at all operations which happend at the same time.
            for timestamp, time_operations in misc.group_by(
                platform_operations, "utc_time"
            ).items():
                buytr = selltr = None
                buycount = sellcount = 0

                # Extract the buy and sell operation.
                for operation in time_operations:
                    if isinstance(operation, tr.Buy):
                        buytr = operation
                        buycount += 1
                    elif isinstance(operation, tr.Sell):
                        selltr = operation
                        sellcount += 1

                # Skip the operations of this timestamp when there aren't
                # exactly one buy and one sell operation.
                # We can only match the buy and sell operations, when there
                # are exactly one buy and one sell operation.
                if not (buycount == 1 and sellcount == 1):
                    continue

                assert isinstance(timestamp, datetime.datetime)
                assert isinstance(buytr, tr.Buy)
                assert isinstance(selltr, tr.Sell)

                # Price definition example for buying BTC with EUR:
                # Symbol: BTCEUR
                # coin: BTC (buytr.coin)
                # reference coin: EUR (selltr.coin)
                # price = traded EUR / traded BTC
                price = decimal.Decimal(selltr.change / buytr.change)

                log.debug(
                    f"Adding {buytr.coin}/{selltr.coin} price from CSV: "
                    f"{price} for {platform} at {timestamp}"
                )

                set_price_db(
                    platform,
                    buytr.coin,
                    selltr.coin,
                    timestamp,
                    price,
                    overwrite=True,
                )

    def merge_identical_operations(self) -> None:
        grouped_ops = misc.group_by(self.operations, tr.Operation.identical_columns)
        self.operations = [tr.Operation.merge(*ops) for ops in grouped_ops.values()]

    def match_fees(self) -> None:
        # Split operations in fees and other operations.
        operations = []
        all_fees: list[tr.Fee] = []

        for op in self.operations:
            if isinstance(op, tr.Fee):
                all_fees.append(op)
            else:
                operations.append(op)

        # Only keep none fee operations in book.
        self.operations = operations

        # Match fees to book operations.
        for platform, _fees in misc.group_by(all_fees, "platform").items():
            for utc_time, fees in misc.group_by(_fees, "utc_time").items():

                # Find matching operations by platform and time.
                matching_operations = {
                    idx: op
                    for idx, op in enumerate(self.operations)
                    if op.platform == platform and op.utc_time == utc_time
                }

                # Group matching operations in dict with
                # { operation typename: list of indices }
                t_op = collections.defaultdict(list)
                for idx, op in matching_operations.items():
                    t_op[op.type_name].append(idx)

                # Check if this is a buy/sell-pair.
                # Fees might occure by other operation types,
                # but this is currently not implemented.
                is_buy_sell_pair = all(
                    (
                        len(matching_operations) == 2,
                        len(t_op[tr.Buy.type_name_c()]) == 1,
                        len(t_op[tr.Sell.type_name_c()]) == 1,
                    )
                )
                if is_buy_sell_pair:
                    # Fees have to be added to all buys and sells.
                    # 1. Fees on sells are the transaction cost,
                    #    which might be fully tax relevant for this sell
                    #    and which gets removed from the account balance
                    # 2. Fees on buys increase the buy-in price of the coins
                    #    which is relevant when selling these (not buying)
                    (sell_idx,) = t_op[tr.Sell.type_name_c()]
                    (buy_idx,) = t_op[tr.Buy.type_name_c()]
                    assert self.operations[sell_idx].fees is None
                    assert self.operations[buy_idx].fees is None
                    self.operations[sell_idx].fees = fees
                    self.operations[buy_idx].fees = fees
                else:
                    log.warning(
                        "Fee matching is not implemented for this case. "
                        "Your fees will be discarded and are not evaluated in "
                        "the tax evaluation. "
                        "Please create an Issue or PR. "
                        f"Found {len(matching_operations)} matching operations:\n"
                        f"{matching_operations=}\n{fees=}\n"
                    )

    def resolve_trades(self) -> None:
        # Match trades which belong together (traded at same time).
        for _, _operations in misc.group_by(self.operations, "platform").items():
            for _, matching_operations in misc.group_by(
                _operations, "utc_time"
            ).items():
                # Count matching operations by type with dict
                # { operation typename: list of operations }
                t_op = collections.defaultdict(list)
                for op in matching_operations:
                    t_op[op.type_name].append(op)

                # Check if this is a buy/sell-pair.
                # Fees might occure by other operation types,
                # but this is currently not implemented.
                is_buy_sell_pair = all(
                    (
                        len(matching_operations) == 2,
                        len(t_op[tr.Buy.type_name_c()]) == 1,
                        len(t_op[tr.Sell.type_name_c()]) == 1,
                    )
                )
                if is_buy_sell_pair:
                    # Add link that this is a trade pair.
                    (buy_op,) = t_op[tr.Buy.type_name_c()]
                    assert isinstance(buy_op, tr.Buy)
                    (sell_op,) = t_op[tr.Sell.type_name_c()]
                    assert isinstance(sell_op, tr.Sell)
                    assert buy_op.link is None
                    assert buy_op.buying_cost is None
                    buy_op.link = sell_op
                    assert sell_op.link is None
                    assert sell_op.selling_value is None
                    sell_op.link = buy_op
                    continue

                # Binance allows to convert small assets in one go to BNB.
                # Our `merge_identical_column` function merges all BNB which
                # gets bought at that time together.
                # BUG Trade connection can not be established with our current
                #     method.
                # Calculate the buying cost of this type of operation by all
                # small asset sells.
                is_binance_bnb_small_asset_transfer = all(
                    (
                        all(op.platform == "binance" for op in matching_operations),
                        len(t_op[tr.Buy.type_name_c()]) == 1,
                        len(t_op[tr.Sell.type_name_c()]) >= 1,
                        len(t_op.keys()) == 2,
                    )
                )

                if is_binance_bnb_small_asset_transfer:
                    (buy_op,) = t_op[tr.Buy.type_name_c()]
                    assert isinstance(buy_op, tr.Buy)
                    sell_ops = t_op[tr.Sell.type_name_c()]
                    assert all(isinstance(op, tr.Sell) for op in sell_ops)
                    assert buy_op.link is None
                    assert buy_op.buying_cost is None
                    buying_costs = [self.price_data.get_cost(op) for op in sell_ops]
                    buy_op.buying_cost = misc.dsum(buying_costs)
                    assert len(sell_ops) == len(buying_costs)
                    for sell_op, buying_cost in zip(sell_ops, buying_costs):
                        assert isinstance(sell_op, tr.Sell)
                        assert sell_op.link is None
                        assert sell_op.selling_value is None
                        percent = buying_cost / buy_op.buying_cost
                        sell_op.selling_value = self.price_data.get_partial_cost(
                            buy_op, percent
                        )
                    continue

    def read_file(self, file_path: Path) -> None:
        """Import transactions form an account statement.

        Detect the exchange of the file. The file will be ignored with a
        warning, if the detecting or reading functionality is not implemented.

        Args:
            file_path (Path): Path to account statement.
        """
        assert file_path.is_file()

        if exchange := self.detect_exchange(file_path):

            try:
                read_file = getattr(self, f"_read_{exchange}")
            except AttributeError:
                log.warning(
                    f"Unable to read files from the exchange `{exchange}`. "
                    f"Skipping `{file_path}`."
                )
                return

            log.info("Reading file from exchange %s at %s", exchange, file_path)
            read_file(file_path)
        elif file_path.suffix not in (
            ".zip",
            ".rar",
        ):
            log.warning(
                f"Unable to detect the exchange of file `{file_path}`. "
                "Skipping file."
            )

    def get_account_statement_paths(self, statements_dir: Path) -> list[Path]:
        """Return file paths of all account statements in `statements_dir`.

        Args:
            statements_dir (str): Folder in which account statements
                                  will be searched.

        Returns:
            list[Path]: List of account statement file paths.
        """
        file_paths: list[Path] = []

        if statements_dir.is_dir():
            for file_path in statements_dir.iterdir():
                # Ignore .gitkeep and temporary excel files.
                filename = file_path.stem
                if filename == ".gitkeep" or filename.startswith("~$"):
                    continue

                file_paths.append(file_path)
        return file_paths

    def read_files(self) -> bool:
        """Read all account statements from the folder specified in the config.

        Returns:
            bool: Return True if everything went as expected.
        """
        paths = self.get_account_statement_paths(config.ACCOUNT_STATMENTS_PATH)

        if not paths:
            log.warning(
                "No account statement files located in %s.",
                config.ACCOUNT_STATMENTS_PATH,
            )
            return False

        for file_path in paths:
            self.read_file(file_path)

        if not bool(self):
            log.warning("Unable to import any data.")
            return False

        return True