import json

from fastapi import APIRouter, Depends, HTTPException
from pydantic import BaseModel
from sqlalchemy.orm import Session

from core.db import get_db
from core.redis_client import redis_client
from core.security import get_current_user_id

from .models import Cart, CartItem

router = APIRouter()


class AddItemIn(BaseModel):
    product_id: int
    qty: int = 1


class UpdateItemIn(BaseModel):
    qty: int


class CartItemOut(BaseModel):
    product_id: int
    qty: int
    name: dict = {}
    price: float = 0.0
    image_url: str = ""
    line_total: float = 0.0


class CartOut(BaseModel):
    items: list[CartItemOut]
    subtotal: float


def _get_or_create_cart(db: Session, user_id: int) -> Cart:
    cart = db.query(Cart).filter_by(user_id=user_id).first()
    if not cart:
        cart = Cart(user_id=user_id)
        db.add(cart)
        db.commit()
        db.refresh(cart)
    return cart


def _cart_to_out(cart: Cart) -> CartOut:
    items: list[CartItemOut] = []
    subtotal = 0.0
    for it in cart.items:
        raw = redis_client.get(f"product:{it.product_id}")
        if not raw:
            continue
        p = json.loads(raw)
        line = round(float(p["price"]) * it.qty, 2)
        subtotal += line
        items.append(
            CartItemOut(
                product_id=it.product_id,
                qty=it.qty,
                name=p.get("name", {}),
                price=float(p["price"]),
                image_url=p.get("image_url", ""),
                line_total=line,
            )
        )
    return CartOut(items=items, subtotal=round(subtotal, 2))


@router.get("", response_model=CartOut)
def get_cart(user_id: int = Depends(get_current_user_id), db: Session = Depends(get_db)):
    return _cart_to_out(_get_or_create_cart(db, user_id))


@router.post("/items", response_model=CartOut)
def add_item(
    body: AddItemIn,
    user_id: int = Depends(get_current_user_id),
    db: Session = Depends(get_db),
):
    if body.qty < 1:
        raise HTTPException(400, "qty must be >= 1")
    if not redis_client.get(f"product:{body.product_id}"):
        raise HTTPException(404, "Product not found or inactive")
    cart = _get_or_create_cart(db, user_id)
    existing = db.query(CartItem).filter_by(cart_id=cart.id, product_id=body.product_id).first()
    if existing:
        existing.qty += body.qty
    else:
        db.add(CartItem(cart_id=cart.id, product_id=body.product_id, qty=body.qty))
    db.commit()
    db.refresh(cart)
    return _cart_to_out(cart)


@router.put("/items/{product_id}", response_model=CartOut)
def update_item(
    product_id: int,
    body: UpdateItemIn,
    user_id: int = Depends(get_current_user_id),
    db: Session = Depends(get_db),
):
    cart = _get_or_create_cart(db, user_id)
    item = db.query(CartItem).filter_by(cart_id=cart.id, product_id=product_id).first()
    if not item:
        raise HTTPException(404, "Not in cart")
    if body.qty < 1:
        db.delete(item)
    else:
        item.qty = body.qty
    db.commit()
    db.refresh(cart)
    return _cart_to_out(cart)


@router.delete("/items/{product_id}", response_model=CartOut)
def remove_item(
    product_id: int,
    user_id: int = Depends(get_current_user_id),
    db: Session = Depends(get_db),
):
    cart = _get_or_create_cart(db, user_id)
    item = db.query(CartItem).filter_by(cart_id=cart.id, product_id=product_id).first()
    if item:
        db.delete(item)
        db.commit()
    db.refresh(cart)
    return _cart_to_out(cart)


@router.delete("", response_model=CartOut)
def clear_cart(user_id: int = Depends(get_current_user_id), db: Session = Depends(get_db)):
    cart = _get_or_create_cart(db, user_id)
    for it in list(cart.items):
        db.delete(it)
    db.commit()
    db.refresh(cart)
    return _cart_to_out(cart)