from typing import Optional

from fastapi import APIRouter, Depends, HTTPException, Query
from sqlmodel import Session, col, select

from app.auth import get_current_user
from app.db import get_session
from app.models.models import (
    Category,
    Transaction,
    TransactionCreate,
    TransactionRead,
    TransactionSource,
    TransactionUpdate,
)

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


def auto_categorize(merchant: str, session: Session) -> Optional[int]:
    categories = session.exec(select(Category)).all()
    merchant_lower = merchant.lower()
    for cat in categories:
        if cat.auto_match_patterns:
            patterns = [p.strip().lower() for p in cat.auto_match_patterns.split(",")]
            if any(p in merchant_lower for p in patterns if p):
                return cat.id
    return None


@router.get("/", response_model=list[TransactionRead])
def list_transactions(
    source: Optional[TransactionSource] = None,
    search: Optional[str] = None,
    category_id: Optional[int] = None,
    limit: int = Query(default=50, le=500),
    offset: int = 0,
    session: Session = Depends(get_session),
    _user: str = Depends(get_current_user),
):
    query = select(Transaction)
    if source:
        query = query.where(Transaction.source == source)
    if category_id:
        query = query.where(Transaction.category_id == category_id)
    if search:
        query = query.where(col(Transaction.merchant).ilike(f"%{search}%"))
    query = query.order_by(col(Transaction.date).desc()).offset(offset).limit(limit)
    return session.exec(query).all()


@router.get("/recent", response_model=list[TransactionRead])
def recent_transactions(
    limit: int = Query(default=5, le=20),
    session: Session = Depends(get_session),
    _user: str = Depends(get_current_user),
):
    query = (
        select(Transaction)
        .where(Transaction.source == TransactionSource.CREDIT_CARD)
        .order_by(col(Transaction.date).desc())
        .limit(limit)
    )
    return session.exec(query).all()


@router.post("/", response_model=TransactionRead, status_code=201)
def create_transaction(
    data: TransactionCreate,
    session: Session = Depends(get_session),
    _user: str = Depends(get_current_user),
):
    tx = Transaction.model_validate(data)
    if tx.category_id is None:
        tx.category_id = auto_categorize(tx.merchant, session)
    session.add(tx)
    session.commit()
    session.refresh(tx)
    return tx


@router.patch("/{transaction_id}", response_model=TransactionRead)
def update_transaction(
    transaction_id: int,
    data: TransactionUpdate,
    session: Session = Depends(get_session),
    _user: str = Depends(get_current_user),
):
    tx = session.get(Transaction, transaction_id)
    if not tx:
        raise HTTPException(status_code=404, detail="Transaction not found")
    update_data = data.model_dump(exclude_unset=True)
    for key, value in update_data.items():
        setattr(tx, key, value)
    session.add(tx)
    session.commit()
    session.refresh(tx)
    return tx


@router.delete("/{transaction_id}", status_code=204)
def delete_transaction(
    transaction_id: int,
    session: Session = Depends(get_session),
    _user: str = Depends(get_current_user),
):
    tx = session.get(Transaction, transaction_id)
    if not tx:
        raise HTTPException(status_code=404, detail="Transaction not found")
    session.delete(tx)
    session.commit()