from embit import script
from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from app.audit.log import write_audit_log
from app.db.models import PendingTransaction, User, UtxoEvent, Withdrawal
from app.electrum.client import ElectrumClient
from app.rounds.config import get_round_config
from app.wallet.balance import recompute_balance
from app.wallet.hd import derive_user_key
from app.wallet.psbt_builder import InsufficientFundsError, Utxo, build_signed_transaction


class WithdrawalError(Exception):
    pass


async def request_withdrawal(
    session: AsyncSession, client: ElectrumClient, user: User, external_address: str, amount_sats: int
) -> Withdrawal:
    config = await get_round_config(session)
    if amount_sats < config.min_amount_sats:
        raise WithdrawalError(f"amount below the minimum of {config.min_amount_sats} sats")

    unspent = (
        await session.scalars(
            select(UtxoEvent).where(UtxoEvent.user_id == user.id, UtxoEvent.spent_txid.is_(None))
        )
    ).all()
    if sum(u.amount_sats for u in unspent) < amount_sats:
        raise WithdrawalError("insufficient balance")

    user_key = derive_user_key(user.derivation_index)
    from_script = script.p2wpkh(user_key.to_public())
    utxos = [Utxo(u.txid, u.vout, u.amount_sats) for u in unspent]

    try:
        built = build_signed_transaction(
            signing_key=user_key,
            from_script=from_script,
            utxos=utxos,
            to_address=external_address,
            amount_sats=amount_sats,
            change_address=user.address,
            fee_rate_sat_vb=config.fee_rate_sat_vb,
        )
    except InsufficientFundsError as exc:
        raise WithdrawalError(str(exc)) from exc

    await client.broadcast(built.raw_hex)

    spent_by_key = {(u.txid, u.vout): u for u in unspent}
    for spent in built.spent_utxos:
        spent_by_key[(spent.txid, spent.vout)].spent_txid = built.txid
    await recompute_balance(session, user.id)

    withdrawal = Withdrawal(
        user_id=user.id,
        external_address=external_address,
        amount_requested_sats=amount_sats,
        amount_sent_sats=built.recipient_sats,
        txid=built.txid,
        status="broadcast",
    )
    session.add(withdrawal)
    await session.flush()
    session.add(
        PendingTransaction(
            kind="withdrawal",
            withdrawal_id=withdrawal.id,
            user_id=user.id,
            current_txid=built.txid,
            fee_rate_sat_vb=config.fee_rate_sat_vb,
            raw_tx_hex=built.raw_hex,
            status="pending",
        )
    )
    await write_audit_log(
        session,
        "withdrawal_sent",
        {"txid": built.txid, "amount_sent_sats": built.recipient_sats, "external_address": external_address},
        user_id=user.id,
    )

    await session.commit()
    await session.refresh(withdrawal)
    return withdrawal