from __future__ import annotations

import csv
from datetime import date
from decimal import Decimal
from pathlib import Path
from typing import Any


def read_transaction_csv(
    path: Path,
    *,
    household_id: str,
    source_type: str,
    source_account_id: str | None,
    owner_user_id: str | None,
) -> list[dict[str, Any]]:
    rows: list[dict[str, Any]] = []
    with path.open(newline="", encoding="utf-8-sig") as handle:
        reader = csv.DictReader(handle)
        for row in reader:
            event_date = _pick(
                row, "event_date", "date", "booking_date", "Buchungstag", "Valutadatum"
            )
            amount = _pick(row, "amount", "Betrag", "value")
            if not event_date or not amount:
                continue
            merchant = _pick(
                row,
                "merchant",
                "counterparty",
                "Auftraggeber/Empfänger",
                "Name Zahlungsbeteiligter",
            )
            description = _pick(row, "description", "purpose", "Verwendungszweck", "Buchungstext")
            currency = _pick(row, "currency", "Waehrung", "Währung") or "EUR"
            provider_transaction_id = _pick(
                row, "provider_transaction_id", "transaction_id", "Umsatz ID"
            )
            normalized = {
                "household_id": household_id,
                "source_type": source_type,
                "source_account_id": source_account_id,
                "owner_user_id": owner_user_id,
                "source_reference": provider_transaction_id,
                "provider_transaction_id": provider_transaction_id,
                "raw_payload_json": row,
                "amount": str(_parse_amount(amount)),
                "currency": currency,
                "event_date": _parse_date(event_date).isoformat(),
                "merchant": merchant,
                "description": description,
                "event_type": "expense" if _parse_amount(amount) < 0 else "income",
                "status": "confirmed",
            }
            normalized["amount"] = str(abs(_parse_amount(amount)))
            rows.append(normalized)
    return rows


def _pick(row: dict[str, str], *keys: str) -> str | None:
    lowered = {key.lower(): value for key, value in row.items()}
    for key in keys:
        value = row.get(key) or lowered.get(key.lower())
        if value:
            return value.strip()
    return None


def _parse_amount(value: str) -> Decimal:
    normalized = value.strip().replace(".", "").replace(",", ".")
    return Decimal(normalized)


def _parse_date(value: str) -> date:
    stripped = value.strip()
    for fmt in ("%Y-%m-%d", "%d.%m.%Y", "%d/%m/%Y"):
        try:
            return (
                date.fromisoformat(stripped)
                if fmt == "%Y-%m-%d"
                else __import__("datetime").datetime.strptime(stripped, fmt).date()
            )
        except ValueError:
            continue
    raise ValueError(f"Unsupported date format: {value}")