"""Exact trading values, vocabulary and validation (no binary floats)."""
import re
from decimal import Decimal, localcontext, ROUND_HALF_UP
from models import valid_date

TYPES = {'buy': 'Kauf', 'sell': 'Verkauf'}
SOURCES = {'manual': 'Manuell', 'savings_plan': 'Sparplan', 'roundup': 'Round-up', 'cashback': 'Cashback', 'rebalancing': 'Rebalancing', 'other': 'Sonstiges'}
STRATEGIES = {'core': 'Core', 'income': 'Income', 'conviction': 'Conviction', 'dip_buy': 'Dip Buy', 'speculation': 'Spekulation', 'rebalancing': 'Rebalancing', 'other': 'Sonstiges'}
CENT = Decimal('0.01')
ZERO = Decimal(0)


class TradingValidationError(ValueError):
    """Safe, user-facing domain error, never contains database internals."""


def decimal_value(value, label, places=12, positive=False):
    if not isinstance(value, (str, Decimal)):
        raise TradingValidationError(f'{label} als Dezimalstring eingeben.')
    text = str(value).strip().replace(',', '.')
    if not re.fullmatch(r'\d{1,12}(?:\.\d{1,' + str(places) + r'})?', text):
        raise TradingValidationError(f'{label}: maximal 12 Vorkomma- und {places} Nachkommastellen, ohne Tausendertrennzeichen.')
    number = Decimal(text)
    if positive and number <= 0:
        raise TradingValidationError(f'{label} muss größer als 0 sein.')
    return number


def currency_code(value):
    code = str(value).strip().upper()
    if not re.fullmatch('[A-Z]{3}', code):
        raise TradingValidationError('Währung als dreistelligen Code eingeben, z. B. EUR.')
    return code


def fixed(value, places=2):
    with localcontext() as ctx:
        ctx.prec = 60
        return format(Decimal(value).quantize(Decimal(1).scaleb(-places), rounding=ROUND_HALF_UP), f'.{places}f')


def exact(value):
    return format(Decimal(value), 'f')


def display_decimal(value, places=2):
    return fixed(value, places).replace('.', ',')


def validate_trade(data):
    try:
        day = valid_date(data.get('date', ''))
    except ValueError as error:
        raise TradingValidationError(str(error)) from None
    try:
        asset_id = int(data.get('asset_id', ''))
        if isinstance(data.get('asset_id'), bool) or not 1 <= asset_id <= 9223372036854775807:
            raise ValueError
    except (ValueError, TypeError):
        raise TradingValidationError('Bitte eine gültige Position auswählen.') from None
    kind, source = data.get('transaction_type', 'buy'), data.get('source', 'manual')
    strategy = data.get('strategy_tag') or None
    if kind not in TYPES or source not in SOURCES or (strategy is not None and strategy not in STRATEGIES):
        raise TradingValidationError('Ungültiger Typ, Source oder Strategie-Tag.')
    quantity = decimal_value(data.get('quantity', ''), 'Stückzahl', positive=True)
    price = decimal_value(data.get('price_per_unit', ''), 'Kurs')
    fees = decimal_value(data.get('fees', '0'), 'Gebühren', places=2)
    note = (data.get('note') or '').strip()
    if len(note) > 2000:
        raise TradingValidationError('Notiz darf maximal 2000 Zeichen enthalten.')
    return dict(date=day, asset_id=asset_id, transaction_type=kind, quantity=exact(quantity),
                price_per_unit=exact(price), currency=currency_code(data.get('currency', 'EUR')),
                fees=fixed(fees), source=source, strategy_tag=strategy, note=note or None)