"""Business logic of the finance module (datamodel-finance.md §2 and §9).

Every function filters by `user_id` and raises the French `AppError` subclasses
of the core; routers stay thin (CONVENTIONS C2.6).
"""

import uuid
from datetime import date
from decimal import Decimal
from typing import Any

from sqlalchemy import Select, delete, func, or_, select, update
from sqlalchemy.exc import IntegrityError
from sqlalchemy.orm import Session

from app.core.errors import (
    ConflictError,
    DomainValidationError,
    ForbiddenError,
    NotFoundError,
)
from app.modules.finance import stats as stats_service
from app.modules.finance.categorize import validate_actions, validate_matchers
from app.modules.finance.enums import (
    AccountKind,
    CategoryKind,
    CategorySource,
    SourceKind,
)
from app.modules.finance.models import (
    FinAccount,
    FinBudget,
    FinCategory,
    FinImportRun,
    FinRule,
    FinSourceProfile,
    FinTransaction,
)
from app.modules.finance.normalize import add_months, month_str
from app.modules.finance.pipeline import transaction_dedup_hash
from app.modules.finance.presets import (
    BUILTIN_PROFILES,
    TRANSFER_CATEGORY_NAME,
    default_category_tree,
)
from app.modules.imports.models import ImportRun

MAX_DEPTH_MESSAGE = "L'arbre des catégories est limité à deux niveaux."
SORTABLE_TRANSACTION_FIELDS = {
    "booked_date": FinTransaction.booked_date,
    "amount": FinTransaction.amount,
    "label_clean": FinTransaction.label_clean,
}


# ---------------------------------------------------------------------------
# Lazy seeding (built-in profiles + default category tree)
# ---------------------------------------------------------------------------


def _commit_seed(db: Session) -> None:
    """Commit seed rows, tolerating a concurrent request that seeded first."""
    try:
        db.commit()
    except IntegrityError:
        db.rollback()


def ensure_builtin_profiles(db: Session) -> None:
    existing = set(
        db.scalars(
            select(FinSourceProfile.name).where(FinSourceProfile.user_id.is_(None))
        ).all()
    )
    created = False
    for preset in BUILTIN_PROFILES:
        if preset["name"] in existing:
            continue
        db.add(
            FinSourceProfile(
                id=uuid.uuid4(),
                user_id=None,
                name=preset["name"],
                kind=preset["kind"],
                config=preset["config"],
                is_builtin=True,
            )
        )
        created = True
    if created:
        _commit_seed(db)


def ensure_user_categories(db: Session, user_id: int) -> None:
    exists = db.scalar(
        select(func.count())
        .select_from(FinCategory)
        .where(FinCategory.user_id == user_id)
    )
    if exists:
        return
    for root in default_category_tree():
        parent = FinCategory(
            id=uuid.uuid4(),
            user_id=user_id,
            parent_id=None,
            name=root["name"],
            icon=root["icon"],
            color=root["color"],
            kind=root["kind"],
            is_system=root["is_system"],
            sort_order=root["sort_order"],
        )
        db.add(parent)
        for child in root["children"]:
            db.add(
                FinCategory(
                    id=uuid.uuid4(),
                    user_id=user_id,
                    parent_id=parent.id,
                    name=child["name"],
                    icon=None,
                    color=None,
                    kind=root["kind"],
                    is_system=False,
                    sort_order=child["sort_order"],
                )
            )
    _commit_seed(db)


def ensure_seed(db: Session, user_id: int) -> None:
    ensure_builtin_profiles(db)
    ensure_user_categories(db, user_id)


# ---------------------------------------------------------------------------
# Accounts (§9.1)
# ---------------------------------------------------------------------------


def get_account(db: Session, user_id: int, account_id: uuid.UUID) -> FinAccount:
    account = db.get(FinAccount, account_id)
    if account is None or account.user_id != user_id:
        raise NotFoundError("Compte introuvable.")
    return account


def _account_dict(
    account: FinAccount,
    balances: dict[uuid.UUID, Decimal],
    counts: dict[uuid.UUID, int],
    last_dates: dict[uuid.UUID, Any],
) -> dict[str, Any]:
    data = {
        column.name: getattr(account, column.name)
        for column in FinAccount.__table__.columns
    }
    data["balance"] = stats_service.money(
        stats_service.money(account.initial_balance)
        + balances.get(account.id, Decimal("0.00"))
    )
    data["transaction_count"] = counts.get(account.id, 0)
    last = last_dates.get(account.id)
    data["last_transaction_date"] = (
        date.fromisoformat(last) if isinstance(last, str) else last
    )
    return data


def _last_transaction_dates(db: Session, user_id: int) -> dict[uuid.UUID, Any]:
    return dict(
        db.execute(
            select(FinTransaction.account_id, func.max(FinTransaction.booked_date))
            .where(FinTransaction.user_id == user_id)
            .group_by(FinTransaction.account_id)
        ).all()
    )


def list_accounts(
    db: Session, user_id: int, include_archived: bool = False
) -> list[dict[str, Any]]:
    stmt = select(FinAccount).where(FinAccount.user_id == user_id)
    if not include_archived:
        stmt = stmt.where(FinAccount.is_archived.is_(False))
    accounts = list(db.scalars(stmt.order_by(FinAccount.name.asc())).all())
    balances = stats_service.account_balances(db, user_id)
    counts = stats_service.account_transaction_counts(db, user_id)
    last_dates = _last_transaction_dates(db, user_id)
    return [
        _account_dict(account, balances, counts, last_dates) for account in accounts
    ]


def account_detail(db: Session, user_id: int, account_id: uuid.UUID) -> dict[str, Any]:
    account = get_account(db, user_id, account_id)
    return _account_dict(
        account,
        stats_service.account_balances(db, user_id),
        stats_service.account_transaction_counts(db, user_id),
        _last_transaction_dates(db, user_id),
    )


def create_account(db: Session, user_id: int, payload: Any) -> FinAccount:
    taken = db.scalar(
        select(func.count())
        .select_from(FinAccount)
        .where(FinAccount.user_id == user_id, FinAccount.name == payload.name)
    )
    if taken:
        raise ConflictError("Un compte porte déjà ce nom.")
    account = FinAccount(
        id=uuid.uuid4(),
        user_id=user_id,
        name=payload.name,
        kind=payload.kind,
        currency=payload.currency.upper(),
        institution=payload.institution,
        iban_masked=payload.iban_masked,
        initial_balance=payload.initial_balance,
    )
    db.add(account)
    db.commit()
    return account


def update_account(
    db: Session, user_id: int, account_id: uuid.UUID, payload: Any
) -> FinAccount:
    account = get_account(db, user_id, account_id)
    data = payload.model_dump(exclude_unset=True)
    if "name" in data and data["name"] != account.name:
        taken = db.scalar(
            select(func.count())
            .select_from(FinAccount)
            .where(
                FinAccount.user_id == user_id,
                FinAccount.name == data["name"],
                FinAccount.id != account_id,
            )
        )
        if taken:
            raise ConflictError("Un compte porte déjà ce nom.")
    if data.get("currency"):
        data["currency"] = data["currency"].upper()
    for key, value in data.items():
        setattr(account, key, value)
    db.commit()
    return account


def delete_account(db: Session, user_id: int, account_id: uuid.UUID) -> None:
    account = get_account(db, user_id, account_id)
    count = db.scalar(
        select(func.count())
        .select_from(FinTransaction)
        .where(FinTransaction.account_id == account.id)
    )
    if count:
        raise ConflictError(
            "Ce compte contient des transactions. Archivez le compte à la place."
        )
    db.delete(account)
    db.commit()


# ---------------------------------------------------------------------------
# Categories (§9.3)
# ---------------------------------------------------------------------------


def get_category(db: Session, user_id: int, category_id: uuid.UUID) -> FinCategory:
    category = db.get(FinCategory, category_id)
    if category is None or category.user_id != user_id:
        raise NotFoundError("Catégorie introuvable.")
    return category


def category_tree(db: Session, user_id: int) -> list[dict[str, Any]]:
    categories = list(
        db.scalars(
            select(FinCategory)
            .where(FinCategory.user_id == user_id)
            .order_by(FinCategory.sort_order.asc(), FinCategory.name.asc())
        ).all()
    )
    counts = dict(
        db.execute(
            select(FinTransaction.category_id, func.count())
            .where(FinTransaction.user_id == user_id)
            .group_by(FinTransaction.category_id)
        ).all()
    )

    def to_dict(category: FinCategory) -> dict[str, Any]:
        return {
            "id": category.id,
            "parent_id": category.parent_id,
            "name": category.name,
            "icon": category.icon,
            "color": category.color,
            "kind": category.kind,
            "is_system": category.is_system,
            "sort_order": category.sort_order,
            "transaction_count": counts.get(category.id, 0),
            "children": [],
        }

    nodes = {c.id: to_dict(c) for c in categories}
    roots: list[dict[str, Any]] = []
    for category in categories:
        node = nodes[category.id]
        if category.parent_id and category.parent_id in nodes:
            parent = nodes[category.parent_id]
            parent["children"].append(node)
            parent["transaction_count"] += node["transaction_count"]
        else:
            roots.append(node)
    return roots


def create_category(db: Session, user_id: int, payload: Any) -> FinCategory:
    kind = payload.kind
    parent: FinCategory | None = None
    if payload.parent_id is not None:
        parent = get_category(db, user_id, payload.parent_id)
        if parent.parent_id is not None:
            raise DomainValidationError(MAX_DEPTH_MESSAGE)
        kind = parent.kind
    if kind == CategoryKind.TRANSFER:
        raise DomainValidationError(
            "La catégorie « Virements internes » est unique et gérée par l'application."
        )
    sibling_clause = (
        FinCategory.parent_id.is_(None)
        if payload.parent_id is None
        else FinCategory.parent_id == payload.parent_id
    )
    taken = db.scalar(
        select(func.count())
        .select_from(FinCategory)
        .where(
            FinCategory.user_id == user_id,
            FinCategory.name == payload.name,
            sibling_clause,
        )
    )
    if taken:
        raise ConflictError("Une catégorie porte déjà ce nom à ce niveau.")
    category = FinCategory(
        id=uuid.uuid4(),
        user_id=user_id,
        parent_id=payload.parent_id,
        name=payload.name,
        icon=payload.icon,
        color=payload.color,
        kind=kind,
        is_system=False,
        sort_order=payload.sort_order,
    )
    db.add(category)
    db.commit()
    return category


def update_category(
    db: Session, user_id: int, category_id: uuid.UUID, payload: Any
) -> FinCategory:
    category = get_category(db, user_id, category_id)
    data = payload.model_dump(exclude_unset=True)
    if category.is_system and "name" in data:
        raise DomainValidationError(
            "Cette catégorie système ne peut pas être renommée."
        )
    if "parent_id" in data:
        new_parent_id = data["parent_id"]
        if new_parent_id is not None:
            has_children = db.scalar(
                select(func.count())
                .select_from(FinCategory)
                .where(FinCategory.parent_id == category.id)
            )
            if has_children:
                raise DomainValidationError(MAX_DEPTH_MESSAGE)
            parent = get_category(db, user_id, new_parent_id)
            if parent.parent_id is not None or parent.id == category.id:
                raise DomainValidationError(MAX_DEPTH_MESSAGE)
            category.kind = parent.kind
    for key, value in data.items():
        setattr(category, key, value)
    db.commit()
    return category


def delete_category(db: Session, user_id: int, category_id: uuid.UUID) -> None:
    category = get_category(db, user_id, category_id)
    if category.is_system:
        raise DomainValidationError(
            "Cette catégorie système ne peut pas être supprimée."
        )
    child_ids = list(
        db.scalars(
            select(FinCategory.id).where(FinCategory.parent_id == category.id)
        ).all()
    )
    all_ids = [category.id, *child_ids]
    db.execute(
        update(FinTransaction)
        .where(
            FinTransaction.user_id == user_id,
            FinTransaction.category_id.in_(all_ids),
        )
        .values(category_id=None, category_source=None)
    )
    db.execute(
        delete(FinBudget).where(
            FinBudget.user_id == user_id, FinBudget.category_id.in_(all_ids)
        )
    )
    # Rules pointing at a deleted category lose their action (disabled if empty).
    for rule in db.scalars(select(FinRule).where(FinRule.user_id == user_id)).all():
        actions = dict(rule.actions or {})
        target = actions.get("set_category_id")
        if target and uuid.UUID(str(target)) in set(all_ids):
            actions.pop("set_category_id", None)
            rule.actions = actions
            if not any(
                actions.get(key)
                for key in ("set_label_clean", "set_counterparty", "mark_transfer")
            ):
                rule.enabled = False
    db.delete(category)
    db.commit()


# ---------------------------------------------------------------------------
# Source profiles (§9.6)
# ---------------------------------------------------------------------------


def get_source_profile(
    db: Session, user_id: int, profile_id: uuid.UUID
) -> FinSourceProfile:
    profile = db.get(FinSourceProfile, profile_id)
    if profile is None or (profile.user_id is not None and profile.user_id != user_id):
        raise NotFoundError("Profil de source introuvable.")
    return profile


def list_source_profiles(db: Session, user_id: int) -> list[FinSourceProfile]:
    stmt = (
        select(FinSourceProfile)
        .where(
            or_(
                FinSourceProfile.user_id.is_(None),
                FinSourceProfile.user_id == user_id,
            )
        )
        .order_by(FinSourceProfile.is_builtin.desc(), FinSourceProfile.name.asc())
    )
    return list(db.scalars(stmt).all())


def find_profile_by_name(db: Session, name: str) -> FinSourceProfile | None:
    return db.scalars(
        select(FinSourceProfile).where(
            FinSourceProfile.user_id.is_(None), FinSourceProfile.name == name
        )
    ).first()


def _check_profile_name(db: Session, user_id: int, name: str) -> None:
    taken = db.scalar(
        select(func.count())
        .select_from(FinSourceProfile)
        .where(FinSourceProfile.user_id == user_id, FinSourceProfile.name == name)
    )
    if taken:
        raise ConflictError("Un profil de source porte déjà ce nom.")


def create_source_profile(db: Session, user_id: int, payload: Any) -> FinSourceProfile:
    _check_profile_name(db, user_id, payload.name)
    profile = FinSourceProfile(
        id=uuid.uuid4(),
        user_id=user_id,
        name=payload.name,
        kind=payload.kind,
        config=payload.config,
        is_builtin=False,
    )
    db.add(profile)
    db.commit()
    return profile


def clone_source_profile(
    db: Session, user_id: int, profile_id: uuid.UUID
) -> FinSourceProfile:
    source = get_source_profile(db, user_id, profile_id)
    name = f"{source.name} (copie)"
    suffix = 2
    while db.scalar(
        select(func.count())
        .select_from(FinSourceProfile)
        .where(FinSourceProfile.user_id == user_id, FinSourceProfile.name == name)
    ):
        name = f"{source.name} (copie {suffix})"
        suffix += 1
    clone = FinSourceProfile(
        id=uuid.uuid4(),
        user_id=user_id,
        name=name,
        kind=source.kind,
        config=dict(source.config or {}),
        is_builtin=False,
    )
    db.add(clone)
    db.commit()
    return clone


def update_source_profile(
    db: Session, user_id: int, profile_id: uuid.UUID, payload: Any
) -> FinSourceProfile:
    profile = get_source_profile(db, user_id, profile_id)
    if profile.is_builtin:
        raise ForbiddenError(
            "Les profils intégrés sont en lecture seule : dupliquez-le pour "
            "le modifier."
        )
    data = payload.model_dump(exclude_unset=True)
    if "name" in data and data["name"] != profile.name:
        _check_profile_name(db, user_id, data["name"])
    for key, value in data.items():
        setattr(profile, key, value)
    db.commit()
    return profile


def delete_source_profile(db: Session, user_id: int, profile_id: uuid.UUID) -> None:
    profile = get_source_profile(db, user_id, profile_id)
    if profile.is_builtin:
        raise ForbiddenError("Les profils intégrés ne peuvent pas être supprimés.")
    db.delete(profile)
    db.commit()


# ---------------------------------------------------------------------------
# Transactions (§9.2)
# ---------------------------------------------------------------------------


def transactions_query(
    db: Session,
    user_id: int,
    *,
    date_from: date | None = None,
    date_to: date | None = None,
    account_ids: list[uuid.UUID] | None = None,
    category_ids: list[str] | None = None,
    q: str | None = None,
    direction: str | None = None,
    amount_min: Decimal | None = None,
    amount_max: Decimal | None = None,
    is_transfer: bool | None = None,
    import_run_id: int | None = None,
    sort: str | None = None,
) -> Select:
    stmt = select(FinTransaction).where(FinTransaction.user_id == user_id)
    if date_from is not None:
        stmt = stmt.where(FinTransaction.booked_date >= date_from)
    if date_to is not None:
        stmt = stmt.where(FinTransaction.booked_date <= date_to)
    if account_ids:
        stmt = stmt.where(FinTransaction.account_id.in_(account_ids))
    if category_ids:
        wants_none = any(str(c).lower() == "none" for c in category_ids)
        try:
            explicit = [
                uuid.UUID(str(c)) for c in category_ids if str(c).lower() != "none"
            ]
        except ValueError as exc:
            raise DomainValidationError(
                "Filtre de catégorie invalide : identifiant ou « none » attendu."
            ) from exc
        expanded = set(explicit)
        if explicit:
            expanded |= set(
                db.scalars(
                    select(FinCategory.id).where(
                        FinCategory.user_id == user_id,
                        FinCategory.parent_id.in_(explicit),
                    )
                ).all()
            )
        clauses = []
        if expanded:
            clauses.append(FinTransaction.category_id.in_(list(expanded)))
        if wants_none:
            clauses.append(FinTransaction.category_id.is_(None))
        if clauses:
            stmt = stmt.where(or_(*clauses))
    if q:
        pattern = f"%{q}%"
        stmt = stmt.where(
            or_(
                FinTransaction.label_clean.ilike(pattern),
                FinTransaction.label_raw.ilike(pattern),
                FinTransaction.counterparty.ilike(pattern),
                FinTransaction.notes.ilike(pattern),
            )
        )
    if direction == "debit":
        stmt = stmt.where(FinTransaction.amount < 0)
    elif direction == "credit":
        stmt = stmt.where(FinTransaction.amount > 0)
    if amount_min is not None:
        stmt = stmt.where(func.abs(FinTransaction.amount) >= amount_min)
    if amount_max is not None:
        stmt = stmt.where(func.abs(FinTransaction.amount) <= amount_max)
    if is_transfer is True:
        stmt = stmt.where(FinTransaction.transfer_group_id.is_not(None))
    elif is_transfer is False:
        stmt = stmt.where(FinTransaction.transfer_group_id.is_(None))
    if import_run_id is not None:
        stmt = stmt.where(FinTransaction.import_run_id == import_run_id)

    sort = sort or "-booked_date"
    descending = sort.startswith("-")
    column = SORTABLE_TRANSACTION_FIELDS.get(sort.lstrip("-"))
    if column is None:
        raise DomainValidationError(
            "Champ de tri non autorisé.", details={"sort": sort}
        )
    order = column.desc() if descending else column.asc()
    return stmt.order_by(order, FinTransaction.id.desc())


def serialize_transactions(
    db: Session, user_id: int, transactions: list[FinTransaction]
) -> list[dict[str, Any]]:
    if not transactions:
        return []
    accounts = {
        a.id: a
        for a in db.scalars(
            select(FinAccount).where(FinAccount.user_id == user_id)
        ).all()
    }
    categories = {
        c.id: c
        for c in db.scalars(
            select(FinCategory).where(FinCategory.user_id == user_id)
        ).all()
    }
    out: list[dict[str, Any]] = []
    for tx in transactions:
        account = accounts.get(tx.account_id)
        category = categories.get(tx.category_id) if tx.category_id else None
        color = None
        if category is not None:
            color = category.color
            if color is None and category.parent_id:
                parent = categories.get(category.parent_id)
                color = parent.color if parent else None
        out.append(
            {
                "id": tx.id,
                "account_id": tx.account_id,
                "account_name": account.name if account else None,
                "booked_date": tx.booked_date,
                "value_date": tx.value_date,
                "amount": tx.amount,
                "currency": tx.currency,
                "label_raw": tx.label_raw,
                "label_clean": tx.label_clean,
                "counterparty": tx.counterparty,
                "category_id": tx.category_id,
                "category_name": category.name if category else None,
                "category_color": color,
                "category_source": tx.category_source,
                "notes": tx.notes,
                "transfer_group_id": tx.transfer_group_id,
                "external_id": tx.external_id,
                "import_run_id": tx.import_run_id,
            }
        )
    return out


def get_transaction(
    db: Session, user_id: int, transaction_id: uuid.UUID
) -> FinTransaction:
    tx = db.get(FinTransaction, transaction_id)
    if tx is None or tx.user_id != user_id:
        raise NotFoundError("Transaction introuvable.")
    return tx


def create_transaction(db: Session, user_id: int, payload: Any) -> FinTransaction:
    account = get_account(db, user_id, payload.account_id)
    amount = Decimal(payload.amount).quantize(Decimal("0.01"))
    label = payload.label_clean.strip()
    dedup_hash = transaction_dedup_hash(
        db, account.id, payload.booked_date, amount, label
    )
    category_source = CategorySource.USER if payload.category_id else None
    if payload.category_id:
        get_category(db, user_id, payload.category_id)
    tx = FinTransaction(
        id=uuid.uuid4(),
        user_id=user_id,
        account_id=account.id,
        booked_date=payload.booked_date,
        value_date=payload.value_date,
        amount=amount,
        currency=(payload.currency or account.currency or "EUR").upper(),
        label_raw=label,
        label_clean=label,
        counterparty=payload.counterparty,
        category_id=payload.category_id,
        category_source=category_source,
        notes=payload.notes,
    )
    tx.dedup_hash = dedup_hash
    db.add(tx)
    db.commit()
    return tx


def update_transaction(
    db: Session, user_id: int, transaction_id: uuid.UUID, payload: Any
) -> FinTransaction:
    tx = get_transaction(db, user_id, transaction_id)
    data = payload.model_dump(exclude_unset=True)
    if ("amount" in data or "booked_date" in data) and tx.import_run_id is not None:
        raise DomainValidationError(
            "La date et le montant d'une transaction importée ne sont pas modifiables."
        )
    if "category_id" in data:
        if data["category_id"] is None:
            tx.category_id = None
            tx.category_source = None
        else:
            get_category(db, user_id, data["category_id"])
            tx.category_id = data["category_id"]
            tx.category_source = CategorySource.USER
        data.pop("category_id")
    for key, value in data.items():
        setattr(tx, key, value)
    db.commit()
    return tx


def delete_transaction(db: Session, user_id: int, transaction_id: uuid.UUID) -> None:
    tx = get_transaction(db, user_id, transaction_id)
    if tx.import_run_id is not None:
        raise DomainValidationError(
            "Cette transaction provient d'un import : supprimez l'import "
            "complet ou ignorez la ligne."
        )
    db.delete(tx)
    db.commit()


def bulk_categorize(
    db: Session,
    user_id: int,
    transaction_ids: list[uuid.UUID],
    category_id: uuid.UUID | None,
) -> int:
    if category_id is not None:
        get_category(db, user_id, category_id)
    result = db.execute(
        update(FinTransaction)
        .where(
            FinTransaction.user_id == user_id,
            FinTransaction.id.in_(transaction_ids),
        )
        .values(
            category_id=category_id,
            category_source=CategorySource.USER if category_id else None,
        )
    )
    db.commit()
    return int(result.rowcount or 0)


# ---------------------------------------------------------------------------
# Rules (§9.4)
# ---------------------------------------------------------------------------


def get_rule(db: Session, user_id: int, rule_id: uuid.UUID) -> FinRule:
    rule = db.get(FinRule, rule_id)
    if rule is None or rule.user_id != user_id:
        raise NotFoundError("Règle introuvable.")
    return rule


def list_rules(db: Session, user_id: int) -> list[FinRule]:
    stmt = (
        select(FinRule)
        .where(FinRule.user_id == user_id)
        .order_by(FinRule.priority.asc(), FinRule.created_at.asc(), FinRule.id.asc())
    )
    return list(db.scalars(stmt).all())


def _validate_rule_payload(
    db: Session, user_id: int, matchers: dict[str, Any], actions: dict[str, Any]
) -> None:
    validate_matchers(matchers)
    validate_actions(actions)
    category_id = actions.get("set_category_id")
    if category_id:
        get_category(db, user_id, uuid.UUID(str(category_id)))
    account_id = matchers.get("account_id")
    if account_id:
        get_account(db, user_id, uuid.UUID(str(account_id)))


def create_rule(db: Session, user_id: int, payload: Any) -> FinRule:
    _validate_rule_payload(db, user_id, payload.matchers, payload.actions)
    rule = FinRule(
        id=uuid.uuid4(),
        user_id=user_id,
        name=payload.name,
        priority=payload.priority,
        enabled=payload.enabled,
        stop=payload.stop,
        matchers=payload.matchers,
        actions=payload.actions,
    )
    db.add(rule)
    db.commit()
    return rule


def update_rule(db: Session, user_id: int, rule_id: uuid.UUID, payload: Any) -> FinRule:
    rule = get_rule(db, user_id, rule_id)
    data = payload.model_dump(exclude_unset=True)
    matchers = data.get("matchers", rule.matchers)
    actions = data.get("actions", rule.actions)
    _validate_rule_payload(db, user_id, matchers, actions)
    for key, value in data.items():
        setattr(rule, key, value)
    db.commit()
    return rule


def delete_rule(db: Session, user_id: int, rule_id: uuid.UUID) -> None:
    rule = get_rule(db, user_id, rule_id)
    db.delete(rule)
    db.commit()


def reorder_rules(db: Session, user_id: int, ordered_ids: list[uuid.UUID]) -> None:
    rules = {rule.id: rule for rule in list_rules(db, user_id)}
    for index, rule_id in enumerate(ordered_ids):
        rule = rules.get(rule_id)
        if rule is None:
            raise NotFoundError("Règle introuvable.")
        rule.priority = index * 10
    db.commit()


# ---------------------------------------------------------------------------
# Budgets (§9.5)
# ---------------------------------------------------------------------------


def get_budget(db: Session, user_id: int, budget_id: uuid.UUID) -> FinBudget:
    budget = db.get(FinBudget, budget_id)
    if budget is None or budget.user_id != user_id:
        raise NotFoundError("Budget introuvable.")
    return budget


def _check_budget_overlap(
    db: Session,
    user_id: int,
    category_id: uuid.UUID,
    start_month: date,
    end_month: date | None,
    exclude_id: uuid.UUID | None = None,
) -> None:
    stmt = select(FinBudget).where(
        FinBudget.user_id == user_id, FinBudget.category_id == category_id
    )
    if exclude_id is not None:
        stmt = stmt.where(FinBudget.id != exclude_id)
    for other in db.scalars(stmt).all():
        starts_after_other_ends = (
            other.end_month is not None and start_month > other.end_month
        )
        ends_before_other_starts = (
            end_month is not None and end_month < other.start_month
        )
        if not starts_after_other_ends and not ends_before_other_starts:
            raise ConflictError(
                "Un budget existe déjà pour cette catégorie sur cette période."
            )


def list_budgets(
    db: Session, user_id: int, month: date, account_ids: list[uuid.UUID] | None = None
) -> list[dict[str, Any]]:
    progress = stats_service.budget_progress(
        db, user_id, month, account_ids=account_ids
    )
    by_id = {item["budget_id"]: item for item in progress["items"]}
    budgets = db.scalars(
        select(FinBudget)
        .where(
            FinBudget.user_id == user_id,
            FinBudget.start_month <= month.replace(day=1),
            or_(
                FinBudget.end_month.is_(None),
                FinBudget.end_month >= month.replace(day=1),
            ),
        )
        .order_by(FinBudget.start_month.asc())
    ).all()
    out: list[dict[str, Any]] = []
    for budget in budgets:
        item = by_id.get(budget.id, {})
        out.append(
            {
                "id": budget.id,
                "category_id": budget.category_id,
                "category_name": item.get("category_name"),
                "category_color": item.get("category_color"),
                "monthly_amount": budget.monthly_amount,
                "start_month": budget.start_month,
                "end_month": budget.end_month,
                "actual": item.get("actual", Decimal("0.00")),
                "remaining": item.get(
                    "remaining", stats_service.money(budget.monthly_amount)
                ),
                "progress_pct": item.get("progress_pct", 0.0),
                "projected_eom": item.get("projected_eom"),
                "status": item.get("status", "ok"),
            }
        )
    return out


def create_budget(db: Session, user_id: int, payload: Any) -> FinBudget:
    category = get_category(db, user_id, payload.category_id)
    if category.kind != CategoryKind.EXPENSE:
        raise DomainValidationError(
            "Un budget ne peut cibler qu'une catégorie de dépense."
        )
    if payload.end_month is not None and payload.end_month < payload.start_month:
        raise DomainValidationError(
            "Le mois de fin doit être postérieur au mois de début."
        )
    _check_budget_overlap(
        db, user_id, payload.category_id, payload.start_month, payload.end_month
    )
    budget = FinBudget(
        id=uuid.uuid4(),
        user_id=user_id,
        category_id=payload.category_id,
        monthly_amount=payload.monthly_amount,
        start_month=payload.start_month,
        end_month=payload.end_month,
    )
    db.add(budget)
    db.commit()
    return budget


def update_budget(
    db: Session, user_id: int, budget_id: uuid.UUID, payload: Any
) -> list[FinBudget]:
    budget = get_budget(db, user_id, budget_id)
    data = payload.model_dump(exclude_unset=True)
    effective_from = data.pop("effective_from", None)
    if effective_from is not None:
        # Close the current budget and open a new one from `effective_from`.
        amount = data.get("monthly_amount", budget.monthly_amount)
        if effective_from <= budget.start_month:
            budget.monthly_amount = amount
            db.commit()
            return [budget]
        budget.end_month = add_months(effective_from, -1)
        successor = FinBudget(
            id=uuid.uuid4(),
            user_id=user_id,
            category_id=budget.category_id,
            monthly_amount=amount,
            start_month=effective_from,
            end_month=data.get("end_month"),
        )
        db.add(successor)
        db.commit()
        return [budget, successor]
    if "end_month" in data:
        _check_budget_overlap(
            db,
            user_id,
            budget.category_id,
            budget.start_month,
            data["end_month"],
            exclude_id=budget.id,
        )
    for key, value in data.items():
        setattr(budget, key, value)
    db.commit()
    return [budget]


def delete_budget(db: Session, user_id: int, budget_id: uuid.UUID) -> None:
    budget = get_budget(db, user_id, budget_id)
    db.delete(budget)
    db.commit()


# ---------------------------------------------------------------------------
# Import runs (§9.6)
# ---------------------------------------------------------------------------


def import_runs_query(user_id: int) -> Select:
    return (
        select(FinImportRun)
        .where(FinImportRun.user_id == user_id)
        .order_by(FinImportRun.started_at.desc(), FinImportRun.id.desc())
    )


def get_import_run(db: Session, user_id: int, run_id: uuid.UUID) -> FinImportRun:
    run = db.get(FinImportRun, run_id)
    if run is None or run.user_id != user_id:
        raise NotFoundError("Import introuvable.")
    return run


def rollback_import(
    db: Session, user_id: int, run_id: uuid.UUID, force: bool = False
) -> None:
    """Delete the central run: transactions vanish through ON DELETE CASCADE."""
    run = get_import_run(db, user_id, run_id)
    if not force:
        touched = db.scalar(
            select(func.count())
            .select_from(FinTransaction)
            .where(
                FinTransaction.import_run_id == run.import_run_id,
                or_(
                    FinTransaction.category_source == CategorySource.USER,
                    FinTransaction.notes.is_not(None),
                ),
            )
        )
        if touched:
            raise ConflictError(
                "Des transactions de cet import ont été modifiées "
                "manuellement. Relancez avec force=true pour les supprimer "
                "malgré tout."
            )
    central = db.get(ImportRun, run.import_run_id)
    if central is not None:
        db.delete(central)
    else:
        db.delete(run)
    db.commit()


def resolve_profile(
    db: Session, user_id: int, profile_id: uuid.UUID | None
) -> FinSourceProfile:
    if profile_id is not None:
        return get_source_profile(db, user_id, profile_id)
    profile = find_profile_by_name(db, "CSV générique")
    if profile is None:
        raise NotFoundError("Profil de source introuvable.")
    return profile


def current_month(today: date) -> date:
    return today.replace(day=1)


def parse_month_param(value: str | None, today: date) -> date:
    if not value:
        return current_month(today)
    try:
        year, month = value.split("-")
        return date(int(year), int(month), 1)
    except (ValueError, TypeError) as exc:
        raise DomainValidationError(
            f"Mois invalide : « {value} » (format attendu AAAA-MM)."
        ) from exc


def transfer_category(db: Session, user_id: int) -> FinCategory | None:
    return db.scalars(
        select(FinCategory).where(
            FinCategory.user_id == user_id,
            FinCategory.name == TRANSFER_CATEGORY_NAME,
        )
    ).first()


def account_for_source_kind(
    db: Session, user_id: int, kind: str, label: str
) -> FinAccount:
    """Default target account used by the generic `POST /api/imports` route."""
    account = db.scalars(
        select(FinAccount).where(
            FinAccount.user_id == user_id, FinAccount.name == label
        )
    ).first()
    if account is not None:
        return account
    account = FinAccount(
        id=uuid.uuid4(),
        user_id=user_id,
        name=label,
        kind=AccountKind.PAYPAL
        if kind == SourceKind.PAYPAL_CSV
        else AccountKind.CHECKING,
        currency="EUR",
        institution=None,
        initial_balance=Decimal("0.00"),
    )
    db.add(account)
    db.flush()
    return account


def month_label(value: date) -> str:
    return month_str(value)