from datetime import datetime, timedelta, timezone
from typing import Mapping

from sqlalchemy.exc import IntegrityError
from sqlmodel import Session, select

from trading_journal import models


def _check_enum(enum_cls, value, field_name: str):
    if value is None:
        raise ValueError(f"{field_name} is required")
    # already an enum member
    if isinstance(value, enum_cls):
        return value
    # strict string match: must match exactly enum name or enum value (case-sensitive)
    if isinstance(value, str):
        for m in enum_cls:
            if m.name == value or str(m.value) == value:
                return m
    allowed = [m.name for m in enum_cls]
    raise ValueError(f"Invalid {field_name!s}: {value!r}. Allowed: {allowed}")


# Trades
def create_trade(session: Session, trade_data: Mapping) -> models.Trades:
    if hasattr(trade_data, "dict"):
        data = trade_data.dict(exclude_unset=True)
    else:
        data = dict(trade_data)
    allowed = {c.name for c in models.Trades.__table__.columns}
    payload = {k: v for k, v in data.items() if k in allowed}
    if "symbol" not in payload:
        raise ValueError("symbol is required")
    if "underlying_currency" not in payload:
        raise ValueError("underlying_currency is required")
    payload["underlying_currency"] = _check_enum(
        models.UnderlyingCurrency, payload["underlying_currency"], "underlying_currency"
    )
    if "trade_type" not in payload:
        raise ValueError("trade_type is required")
    payload["trade_type"] = _check_enum(
        models.TradeType, payload["trade_type"], "trade_type"
    )
    if "trade_strategy" not in payload:
        raise ValueError("trade_strategy is required")
    payload["trade_strategy"] = _check_enum(
        models.TradeStrategy, payload["trade_strategy"], "trade_strategy"
    )
    # trade_time_utc is the creation moment: always set to now (caller shouldn't provide)
    now = datetime.now(timezone.utc)
    payload.pop("trade_time_utc", None)
    payload["trade_time_utc"] = now
    if "trade_date" not in payload or payload.get("trade_date") is None:
        payload["trade_date"] = payload["trade_time_utc"].date()
    cycle_id = payload.get("cycle_id")
    user_id = payload.get("user_id")
    if "quantity" not in payload:
        raise ValueError("quantity is required")
    if "price_cents" not in payload:
        raise ValueError("price_cents is required")
    if "commission_cents" not in payload:
        payload["commission_cents"] = 0
    quantity: int = payload["quantity"]
    price_cents: int = payload["price_cents"]
    commission_cents: int = payload["commission_cents"]
    if "gross_cash_flow_cents" not in payload:
        payload["gross_cash_flow_cents"] = -quantity * price_cents
    if "net_cash_flow_cents" not in payload:
        payload["net_cash_flow_cents"] = (
            payload["gross_cash_flow_cents"] - commission_cents
        )

    # If no cycle_id provided, create Cycle instance but don't call create_cycle()
    created_cycle = None
    if cycle_id is None:
        c_payload = {
            "user_id": user_id,
            "symbol": payload["symbol"],
            "underlying_currency": payload["underlying_currency"],
            "friendly_name": "Auto-created Cycle by trade "
            + payload.get("friendly_name", ""),
            "status": models.CycleStatus.OPEN,
            "start_date": payload["trade_date"],
        }
        created_cycle = models.Cycles(**c_payload)
        session.add(created_cycle)
        # do NOT flush here; will flush together with trade below

    # If cycle_id provided, validate existence and ownership
    if cycle_id is not None:
        cycle = session.get(models.Cycles, cycle_id)
        if cycle is None:
            raise ValueError("cycle_id does not exist")
        else:
            if cycle.user_id != user_id:
                raise ValueError("cycle.user_id does not match trade.user_id")

    # Build trade instance; if we created a Cycle instance, link via relationship so a single flush will persist both and populate ids
    t_payload = dict(payload)
    # remove cycle_id if we're using created_cycle; relationship will set it on flush
    if created_cycle is not None:
        t_payload.pop("cycle_id", None)
    t = models.Trades(**t_payload)
    if created_cycle is not None:
        t.cycle = created_cycle

    session.add(t)
    try:
        session.flush()
    except IntegrityError as e:
        session.rollback()
        raise ValueError("create_trade integrity error") from e
    session.refresh(t)
    return t


def get_trade_by_id(session: Session, trade_id: int) -> models.Trades | None:
    return session.get(models.Trades, trade_id)


def get_trade_by_user_id_and_friendly_name(
    session: Session, user_id: int, friendly_name: str
) -> models.Trades | None:
    statement = select(models.Trades).where(
        models.Trades.user_id == user_id,
        models.Trades.friendly_name == friendly_name,
    )
    return session.exec(statement).first()


def get_trades_by_user_id(session: Session, user_id: int) -> list[models.Trades]:
    statement = select(models.Trades).where(
        models.Trades.user_id == user_id,
    )
    return session.exec(statement).all()


def update_trade_note(session: Session, trade_id: int, note: str) -> models.Trades:
    trade: models.Trades | None = session.get(models.Trades, trade_id)
    if trade is None:
        raise ValueError("trade_id does not exist")
    trade.notes = note
    session.add(trade)
    try:
        session.flush()
    except IntegrityError as e:
        session.rollback()
        raise ValueError("update_trade_note integrity error") from e
    session.refresh(trade)
    return trade


def invalidate_trade(session: Session, trade_id: int) -> models.Trades:
    trade: models.Trades | None = session.get(models.Trades, trade_id)
    if trade is None:
        raise ValueError("trade_id does not exist")
    if trade.is_invalidated:
        raise ValueError("trade is already invalidated")
    trade.is_invalidated = True
    trade.invalidated_at = datetime.now(timezone.utc)
    session.add(trade)
    try:
        session.flush()
    except IntegrityError as e:
        session.rollback()
        raise ValueError("invalidate_trade integrity error") from e
    session.refresh(trade)
    return trade


def replace_trade(
    session: Session, old_trade_id: int, new_trade_data: Mapping
) -> models.Trades:
    invalidate_trade(session, old_trade_id)
    if hasattr(new_trade_data, "dict"):
        data = new_trade_data.dict(exclude_unset=True)
    else:
        data = dict(new_trade_data)
    data["replaced_by_trade_id"] = old_trade_id
    new_trade = create_trade(session, data)
    return new_trade


# Cycles
def create_cycle(session: Session, cycle_data: Mapping) -> models.Cycles:
    if hasattr(cycle_data, "dict"):
        data = cycle_data.dict(exclude_unset=True)
    else:
        data = dict(cycle_data)
    allowed = {c.name for c in models.Cycles.__table__.columns}
    payload = {k: v for k, v in data.items() if k in allowed}
    if "user_id" not in payload:
        raise ValueError("user_id is required")
    if "symbol" not in payload:
        raise ValueError("symbol is required")
    if "underlying_currency" not in payload:
        raise ValueError("underlying_currency is required")
    payload["underlying_currency"] = _check_enum(
        models.UnderlyingCurrency, payload["underlying_currency"], "underlying_currency"
    )
    if "status" not in payload:
        raise ValueError("status is required")
    payload["status"] = _check_enum(models.CycleStatus, payload["status"], "status")
    if "start_date" not in payload:
        raise ValueError("start_date is required")

    c = models.Cycles(**payload)
    session.add(c)
    try:
        session.flush()
    except IntegrityError as e:
        session.rollback()
        raise ValueError("create_cycle integrity error") from e
    session.refresh(c)
    return c


IMMUTABLE_CYCLE_FIELDS = {"id", "user_id", "start_date", "created_at"}


def update_cycle(
    session: Session, cycle_id: int, update_data: Mapping
) -> models.Cycles:
    cycle: models.Cycles | None = session.get(models.Cycles, cycle_id)
    if cycle is None:
        raise ValueError("cycle_id does not exist")
    if hasattr(update_data, "dict"):
        data = update_data.dict(exclude_unset=True)
    else:
        data = dict(update_data)

    allowed = {c.name for c in models.Cycles.__table__.columns}
    for k, v in data.items():
        if k in IMMUTABLE_CYCLE_FIELDS:
            raise ValueError(f"field {k!r} is immutable")
        if k not in allowed:
            continue
        if k == "underlying_currency":
            v = _check_enum(models.UnderlyingCurrency, v, "underlying_currency")
        if k == "status":
            v = _check_enum(models.CycleStatus, v, "status")
        setattr(cycle, k, v)
    session.add(cycle)
    try:
        session.flush()
    except IntegrityError as e:
        session.rollback()
        raise ValueError("update_cycle integrity error") from e
    session.refresh(cycle)
    return cycle


# Users
IMMUTABLE_USER_FIELDS = {"id", "username", "created_at"}


def create_user(session: Session, user_data: Mapping) -> models.Users:
    if hasattr(user_data, "dict"):
        data = user_data.dict(exclude_unset=True)
    else:
        data = dict(user_data)
    allowed = {c.name for c in models.Users.__table__.columns}
    payload = {k: v for k, v in data.items() if k in allowed}
    if "username" not in payload:
        raise ValueError("username is required")
    if "password_hash" not in payload:
        raise ValueError("password_hash is required")

    u = models.Users(**payload)
    session.add(u)
    try:
        session.flush()
    except IntegrityError as e:
        session.rollback()
        raise ValueError("create_user integrity error") from e
    session.refresh(u)
    return u


def update_user(session: Session, user_id: int, update_data: Mapping) -> models.Users:
    user: models.Users | None = session.get(models.Users, user_id)
    if user is None:
        raise ValueError("user_id does not exist")
    if hasattr(update_data, "dict"):
        data = update_data.dict(exclude_unset=True)
    else:
        data = dict(update_data)
    allowed = {c.name for c in models.Users.__table__.columns}
    for k, v in data.items():
        if k in IMMUTABLE_USER_FIELDS:
            raise ValueError(f"field {k!r} is immutable")
        if k in allowed:
            setattr(user, k, v)
    session.add(user)
    try:
        session.flush()
    except IntegrityError as e:
        session.rollback()
        raise ValueError("update_user integrity error") from e
    session.refresh(user)
    return user


# Sessions
def create_login_session(
    session: Session,
    user_id: int,
    session_token_hash: str,
    session_length_seconds: int = 86400,
    last_used_ip: str | None = None,
    user_agent: str | None = None,
    device_name: str | None = None,
) -> models.Sessions:
    user: models.Users | None = session.get(models.Users, user_id)
    if user is None:
        raise ValueError("user_id does not exist")
    now = datetime.now(timezone.utc)
    expires_at = now + timedelta(seconds=session_length_seconds)
    s = models.Sessions(
        user_id=user.id,
        session_token_hash=session_token_hash,
        created_at=now,
        expires_at=expires_at,
        last_seen_at=now,
        last_used_ip=last_used_ip,
        user_agent=user_agent,
        device_name=device_name,
    )
    session.add(s)
    try:
        session.flush()
    except IntegrityError as e:
        session.rollback()
        raise ValueError("create_login_session integrity error") from e
    session.refresh(s)
    return s


def get_login_session_by_token_hash_and_user_id(
    session: Session, session_token_hash: str, user_id: int
) -> models.Sessions | None:
    statement = select(models.Sessions).where(
        models.Sessions.session_token_hash == session_token_hash,
        models.Sessions.user_id == user_id,
        models.Sessions.expires_at > datetime.now(timezone.utc),
    )

    return session.exec(statement).first()


IMMUTABLE_SESSION_FIELDS = {"id", "user_id", "session_token_hash", "created_at"}


def update_login_session(
    session: Session, session_token_hashed: str, update_session: Mapping
) -> models.Sessions | None:
    login_session: models.Sessions | None = session.exec(
        select(models.Sessions).where(
            models.Sessions.session_token_hash == session_token_hashed,
            models.Sessions.expires_at > datetime.now(timezone.utc),
        )
    ).first()
    if login_session is None:
        return None
    if hasattr(update_session, "dict"):
        data = update_session.dict(exclude_unset=True)
    else:
        data = dict(update_session)
    allowed = {c.name for c in models.Sessions.__table__.columns}
    for k, v in data.items():
        if k in allowed and k not in IMMUTABLE_SESSION_FIELDS:
            setattr(login_session, k, v)
    session.add(login_session)
    try:
        session.flush()
    except IntegrityError as e:
        session.rollback()
        raise ValueError("update_login_session integrity error") from e
    session.refresh(login_session)
    return login_session


def delete_login_session(session: Session, session_token_hash: str) -> None:
    login_session: models.Sessions | None = session.exec(
        select(models.Sessions).where(
            models.Sessions.session_token_hash == session_token_hash,
        )
    ).first()
    if login_session is None:
        return
    session.delete(login_session)
    try:
        session.flush()
    except IntegrityError as e:
        session.rollback()
        raise ValueError("delete_login_session integrity error") from e