"""CSV export of transactions (review ARCH-18 / wishlist #4)."""

import csv
import io
from datetime import datetime
from typing import Optional

from sqlmodel import Session, col, select

from app.models.models import Transaction, TransactionSource, TransactionType

COLUMNS = [
    "id", "date", "merchant", "city", "amount", "currency",
    "transaction_type", "source", "bank", "category", "notes", "reference",
]


def build_transactions_csv(
    session: Session,
    *,
    source: Optional[TransactionSource] = None,
    transaction_type: Optional[TransactionType] = None,
    start_date: Optional[datetime] = None,
    end_date: Optional[datetime] = None,
) -> str:
    q = select(Transaction)
    if source:
        q = q.where(Transaction.source == source)
    if transaction_type:
        q = q.where(Transaction.transaction_type == transaction_type)
    if start_date:
        q = q.where(Transaction.date >= start_date)
    if end_date:
        q = q.where(Transaction.date < end_date)
    q = q.order_by(col(Transaction.date).desc(), col(Transaction.id).desc())

    buf = io.StringIO()
    writer = csv.writer(buf)
    writer.writerow(COLUMNS)
    for tx in session.exec(q).all():
        writer.writerow(
            [
                tx.id,
                tx.date.isoformat(),
                tx.merchant,
                tx.city or "",
                f"{tx.amount:.2f}",
                tx.currency.value,
                tx.transaction_type.value,
                tx.source.value,
                tx.bank.value,
                tx.category.name if tx.category else "",
                tx.notes or "",
                tx.reference or "",
            ]
        )
    return buf.getvalue()