"""Kategorie-Gruppen und Kategorien (zweistufig). Alles owner-gescoped.

Eine Kategorie erbt ihre Art (Einnahme/Ausgabe) von ihrer Gruppe.
"""

from fastapi import APIRouter, Depends, HTTPException, status
from sqlalchemy import func
from sqlalchemy.orm import Session

from ..database import get_db
from ..deps import get_current_user, get_owned
from ..models import Account, CategorizationRule, Category, CategoryGroup, MatchField, RuleSource, User
from ..schemas import (
    CategoryCreate,
    CategoryGroupCreate,
    CategoryGroupOut,
    CategoryGroupUpdate,
    CategoryOut,
    CategoryUpdate,
    FlaggedKeywordOut,
    KeywordCreate,
    KeywordOut,
    KeywordUpdate,
    TransferKeywordCreate,
    TransferKeywordOut,
)
from ..services.csv_import import normalize_text

router = APIRouter(prefix="/categories", tags=["categories"])

# Ab wann ein manuelles Schlagwort als „stimmt vielleicht nicht" markiert wird:
# mindestens so viele Anwendungen UND mindestens dieser Anteil wegkorrigiert.
FLAG_MIN_APPLIED = 5
FLAG_RATIO_DEN = 3  # >= 1/3 (jede dritte)


def group_out(g: CategoryGroup, keyword_counts: dict[int, int] | None = None) -> CategoryGroupOut:
    cats = sorted(g.categories, key=lambda c: (c.position, c.name.lower()))
    out = []
    for c in cats:
        eintrag = CategoryOut.model_validate(c)
        if keyword_counts is not None:
            eintrag.keyword_count = keyword_counts.get(c.id, 0)
        out.append(eintrag)
    return CategoryGroupOut(
        id=g.id,
        name=g.name,
        kind=g.kind,
        icon=g.icon,
        color=g.color,
        position=g.position,
        is_builtin=g.is_builtin,
        categories=out,
    )


def _keyword_counts(db: Session, user: User) -> dict[int, int]:
    """Schlagwörter je Kategorie – eine Abfrage für die ganze Liste.

    Die Übersicht markiert damit die Kategorien, für die schon etwas hinterlegt
    ist; ein Abruf je Kategorie waere dafuer unverhaeltnismaessig."""
    zeilen = (
        db.query(CategorizationRule.category_id, func.count(CategorizationRule.id))
        .filter(
            CategorizationRule.owner_id == user.id,
            CategorizationRule.source == RuleSource.manual,
            CategorizationRule.is_transfer.is_(False),
            CategorizationRule.category_id.isnot(None),
        )
        .group_by(CategorizationRule.category_id)
        .all()
    )
    return {cat_id: anzahl for cat_id, anzahl in zeilen}


def _next_position(db: Session, model, **filters) -> int:
    q = db.query(model.position)
    for k, v in filters.items():
        q = q.filter(getattr(model, k) == v)
    row = q.order_by(model.position.desc()).first()
    return (row[0] + 1) if row else 0


@router.get("", response_model=list[CategoryGroupOut])
def list_categories(db: Session = Depends(get_db), user: User = Depends(get_current_user)):
    groups = (
        db.query(CategoryGroup)
        .filter(CategoryGroup.owner_id == user.id)
        .order_by(CategoryGroup.position, CategoryGroup.name)
        .all()
    )
    counts = _keyword_counts(db, user)
    return [group_out(g, counts) for g in groups]


# --- Gruppen ---------------------------------------------------------------


@router.post("/groups", response_model=CategoryGroupOut, status_code=status.HTTP_201_CREATED)
def create_group(
    payload: CategoryGroupCreate, db: Session = Depends(get_db), user: User = Depends(get_current_user)
):
    g = CategoryGroup(
        owner_id=user.id,
        name=payload.name.strip(),
        kind=payload.kind,
        icon=payload.icon,
        color=payload.color,
        position=_next_position(db, CategoryGroup, owner_id=user.id),
    )
    db.add(g)
    db.commit()
    db.refresh(g)
    return group_out(g)


@router.patch("/groups/{group_id}", response_model=CategoryGroupOut)
def update_group(
    group_id: int,
    payload: CategoryGroupUpdate,
    db: Session = Depends(get_db),
    user: User = Depends(get_current_user),
):
    g = get_owned(db, CategoryGroup, group_id, user)
    for key, value in payload.model_dump(exclude_unset=True).items():
        if value is not None:
            setattr(g, key, value)
    db.commit()
    db.refresh(g)
    return group_out(g)


@router.delete("/groups/{group_id}", status_code=status.HTTP_204_NO_CONTENT)
def delete_group(
    group_id: int, db: Session = Depends(get_db), user: User = Depends(get_current_user)
):
    g = get_owned(db, CategoryGroup, group_id, user)
    db.delete(g)
    db.commit()


# --- Kategorien ------------------------------------------------------------


@router.post("", response_model=CategoryOut, status_code=status.HTTP_201_CREATED)
def create_category(
    payload: CategoryCreate, db: Session = Depends(get_db), user: User = Depends(get_current_user)
):
    group = get_owned(db, CategoryGroup, payload.group_id, user)
    cat = Category(
        owner_id=user.id,
        group_id=group.id,
        name=payload.name.strip(),
        type=group.kind,  # erbt die Art der Gruppe
        icon=payload.icon,
        color=payload.color,
        position=_next_position(db, Category, owner_id=user.id, group_id=group.id),
    )
    db.add(cat)
    db.commit()
    db.refresh(cat)
    return CategoryOut.model_validate(cat)


@router.patch("/{category_id}", response_model=CategoryOut)
def update_category(
    category_id: int,
    payload: CategoryUpdate,
    db: Session = Depends(get_db),
    user: User = Depends(get_current_user),
):
    cat = get_owned(db, Category, category_id, user)
    data = payload.model_dump(exclude_unset=True)
    new_group_id = data.pop("group_id", None)
    if new_group_id is not None:
        group = get_owned(db, CategoryGroup, new_group_id, user)
        cat.group_id = group.id
        cat.type = group.kind  # Art an die neue Gruppe angleichen
    for key, value in data.items():
        if value is not None or key == "is_archived":
            setattr(cat, key, value)
    db.commit()
    db.refresh(cat)
    return CategoryOut.model_validate(cat)


@router.delete("/{category_id}", status_code=status.HTTP_204_NO_CONTENT)
def delete_category(
    category_id: int, db: Session = Depends(get_db), user: User = Depends(get_current_user)
):
    cat = get_owned(db, Category, category_id, user)
    db.delete(cat)
    db.commit()


# --- Schlagwörter je Kategorie (manuelle Regeln, Feld = Empfänger ODER Zweck) ---


def _keyword_out(rule: CategorizationRule) -> KeywordOut:
    return KeywordOut(id=rule.id, category_id=rule.category_id, word=rule.pattern, amount_cents=rule.amount_cents)


def _owned_manual_rule(db: Session, rule_id: int, user: User) -> CategorizationRule:
    rule = db.get(CategorizationRule, rule_id)
    if rule is None or rule.owner_id != user.id or rule.source != RuleSource.manual:
        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Nicht gefunden")
    return rule


def _conflict(db: Session, clash: CategorizationRule) -> HTTPException:
    """Klare Meldung, wenn ein Schlagwort schon woanders (Kategorie/Transfer) hängt."""
    if clash.is_transfer:
        wo = "als Transfer-Regel"
    else:
        cat = db.get(Category, clash.category_id)
        wo = f"der Kategorie „{cat.name if cat else '?'}“"
    return HTTPException(
        status_code=status.HTTP_409_CONFLICT,
        detail=f"Schlagwort ist bereits {wo} zugeordnet.",
    )


def _find_any_rule(
    db: Session, user: User, pattern: str, kind: str,
    amount_cents: int | None = None, exclude_id: int | None = None,
):
    """Sucht ein manuelles Schlagwort gleicher Art (kind) UND gleichen Betrags.

    Dasselbe Wort darf je einmal für Ausgabe, Einnahme und Transfer existieren –
    und innerhalb einer Art mehrfach mit verschiedenen Beträgen: Im Personal-
    restaurant zahlt man mal 5.00, mal 7.50. Ohne Betrag ist es der Auffang für
    alle übrigen Beträge."""
    q = db.query(CategorizationRule).filter(
        CategorizationRule.owner_id == user.id,
        CategorizationRule.match_field == MatchField.any,
        CategorizationRule.pattern == pattern,
        CategorizationRule.kind == kind,
    )
    q = q.filter(
        CategorizationRule.amount_cents.is_(None) if amount_cents is None
        else CategorizationRule.amount_cents == amount_cents
    )
    if exclude_id is not None:
        q = q.filter(CategorizationRule.id != exclude_id)
    return q.first()


@router.get("/keywords/flagged", response_model=list[FlaggedKeywordOut])
def list_flagged_keywords(db: Session = Depends(get_db), user: User = Depends(get_current_user)):
    """Manuelle Schlagwörter, die auffällig oft wegkorrigiert werden."""
    rules = (
        db.query(CategorizationRule)
        .filter(
            CategorizationRule.owner_id == user.id,
            CategorizationRule.source == RuleSource.manual,
            CategorizationRule.confirmed.is_(False),
            CategorizationRule.applied_count >= FLAG_MIN_APPLIED,
            CategorizationRule.overridden_count * FLAG_RATIO_DEN >= CategorizationRule.applied_count,
        )
        .order_by(CategorizationRule.overridden_count.desc())
        .all()
    )
    names = {c.id: c.name for c in db.query(Category).filter(Category.owner_id == user.id)}
    return [
        FlaggedKeywordOut(
            id=r.id, category_id=r.category_id,
            category_name="→ Transfer" if r.is_transfer else names.get(r.category_id, "?"),
            word=r.pattern, applied_count=r.applied_count, overridden_count=r.overridden_count,
        )
        for r in rules
    ]


@router.post("/keywords/{rule_id}/confirm", status_code=status.HTTP_204_NO_CONTENT)
def confirm_keyword(rule_id: int, db: Session = Depends(get_db), user: User = Depends(get_current_user)):
    """„Behalten" – nicht mehr nachfragen, obwohl korrigiert wird."""
    rule = _owned_manual_rule(db, rule_id, user)
    rule.confirmed = True
    db.commit()


@router.patch("/keywords/{rule_id}", response_model=KeywordOut)
def update_keyword(
    rule_id: int,
    payload: KeywordUpdate,
    db: Session = Depends(get_db),
    user: User = Depends(get_current_user),
):
    """Schlagwort ändern – Wort und optional Betrag. Ändert sich das Muster,
    werden die Korrektur-Zähler zurückgesetzt."""
    rule = _owned_manual_rule(db, rule_id, user)
    pattern = normalize_text(payload.word)[:255]
    if not pattern:
        raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail="Leeres Schlagwort")
    neuer_betrag = (
        payload.amount_cents if "amount_cents" in payload.model_fields_set else rule.amount_cents
    )
    if pattern != rule.pattern or neuer_betrag != rule.amount_cents:
        clash = _find_any_rule(db, user, pattern, rule.kind, neuer_betrag, exclude_id=rule.id)
        if clash is not None:
            raise _conflict(db, clash)
    if pattern != rule.pattern:
        rule.pattern = pattern
        rule.applied_count = 0
        rule.overridden_count = 0
        rule.confirmed = False
    # Betrag nur anfassen, wenn er mitgeschickt wurde. Ausdrücklich null löscht
    # ihn (das leere Betragsfeld im Popup), ein Weglassen lässt ihn stehen.
    if "amount_cents" in payload.model_fields_set:
        rule.amount_cents = payload.amount_cents
    db.commit()
    db.refresh(rule)
    return _keyword_out(rule)


@router.delete("/keywords/{rule_id}", status_code=status.HTTP_204_NO_CONTENT)
def delete_keyword(rule_id: int, db: Session = Depends(get_db), user: User = Depends(get_current_user)):
    rule = _owned_manual_rule(db, rule_id, user)
    db.delete(rule)
    db.commit()


@router.get("/{category_id}/keywords", response_model=list[KeywordOut])
def list_keywords(category_id: int, db: Session = Depends(get_db), user: User = Depends(get_current_user)):
    cat = get_owned(db, Category, category_id, user)
    rules = (
        db.query(CategorizationRule)
        .filter(
            CategorizationRule.owner_id == user.id,
            CategorizationRule.source == RuleSource.manual,
            CategorizationRule.category_id == cat.id,
        )
        .order_by(CategorizationRule.pattern)
        .all()
    )
    return [_keyword_out(r) for r in rules]


@router.post("/{category_id}/keywords", response_model=KeywordOut, status_code=status.HTTP_201_CREATED)
def add_keyword(
    category_id: int,
    payload: KeywordCreate,
    db: Session = Depends(get_db),
    user: User = Depends(get_current_user),
):
    cat = get_owned(db, Category, category_id, user)
    pattern = normalize_text(payload.word)[:255]
    if not pattern:
        raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail="Leeres Schlagwort")
    kind = cat.type.value  # "expense" | "income" – Konflikt nur innerhalb derselben Art
    # Konflikt nur bei gleichem Wort UND gleichem Betrag: „sv = 5.00" und
    # „sv = 7.50" sind zwei gültige Regeln derselben Kategorie.
    existing = _find_any_rule(db, user, pattern, kind, payload.amount_cents)
    if existing is not None:
        if not existing.is_transfer and existing.category_id == cat.id:
            return _keyword_out(existing)  # schon identisch vorhanden – unverändert zurück
        raise _conflict(db, existing)
    rule = CategorizationRule(
        owner_id=user.id, match_field=MatchField.any, pattern=pattern,
        category_id=cat.id, amount_cents=payload.amount_cents, kind=kind,
        source=RuleSource.manual, priority=10,
    )
    db.add(rule)
    db.commit()
    db.refresh(rule)
    return _keyword_out(rule)


# --- Transfer-Schlagwörter (Text -> Transfer, Zielkonto aus Konto-Texten) ------


def _transfer_keyword_out(rule: CategorizationRule) -> TransferKeywordOut:
    return TransferKeywordOut(
        id=rule.id, word=rule.pattern, amount_cents=rule.amount_cents,
        target_account_id=rule.target_account_id,
    )


@router.get("/transfer-keywords", response_model=list[TransferKeywordOut])
def list_transfer_keywords(db: Session = Depends(get_db), user: User = Depends(get_current_user)):
    rules = (
        db.query(CategorizationRule)
        .filter(
            CategorizationRule.owner_id == user.id,
            CategorizationRule.source == RuleSource.manual,
            CategorizationRule.is_transfer.is_(True),
        )
        .order_by(CategorizationRule.pattern)
        .all()
    )
    return [_transfer_keyword_out(r) for r in rules]


@router.post("/transfer-keywords", response_model=TransferKeywordOut, status_code=status.HTTP_201_CREATED)
def add_transfer_keyword(
    payload: TransferKeywordCreate, db: Session = Depends(get_db), user: User = Depends(get_current_user)
):
    pattern = normalize_text(payload.word)[:255]
    if not pattern:
        raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail="Leeres Schlagwort")
    target_id = None
    if payload.target_account_id is not None:
        target_id = get_owned(db, Account, payload.target_account_id, user).id
    # Gleiches Wort existiert schon als Transfer-Regel -> aktualisieren (Betrag/Zielkonto).
    existing = _find_any_rule(db, user, pattern, "transfer", payload.amount_cents)
    if existing is not None:
        existing.amount_cents = payload.amount_cents
        existing.target_account_id = target_id
        db.commit()
        db.refresh(existing)
        return _transfer_keyword_out(existing)
    rule = CategorizationRule(
        owner_id=user.id, match_field=MatchField.any, pattern=pattern,
        category_id=None, amount_cents=payload.amount_cents, is_transfer=True,
        target_account_id=target_id, kind="transfer", source=RuleSource.manual, priority=10,
    )
    db.add(rule)
    db.commit()
    db.refresh(rule)
    return _transfer_keyword_out(rule)