from fastapi import APIRouter, Depends, HTTPException, status
from sqlmodel import Session, select
from app.core.db import get_session
from app.core.auth import require_any_access, require_write_access, require_admin
from app.schemas.models import Inventory, Product
from app.schemas.schemas import (
    InventoryCreate, 
    InventoryUpdate, 
    InventoryResponse, 
    UserResponse
)
from typing import List

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

# Create Inventory
@router.post("/", response_model=InventoryResponse, status_code=status.HTTP_201_CREATED)
def create_inventory(
    inventory: InventoryCreate, 
    session: Session = Depends(get_session),
    current_user: UserResponse = Depends(require_write_access)
):
    """Create new inventory entry (requires write access)."""
    # Validate product exists
    product = session.get(Product, inventory.product_id)
    if not product:
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="Product not found"
        )
    
    # Check if inventory already exists for this product
    existing_inventory = session.exec(
        select(Inventory).where(Inventory.product_id == inventory.product_id)
    ).first()
    if existing_inventory:
        raise HTTPException(
            status_code=status.HTTP_409_CONFLICT,
            detail="Inventory entry already exists for this product"
        )
    
    # Create inventory
    inventory_data = inventory.model_dump()
    db_inventory = Inventory(**inventory_data)
    
    session.add(db_inventory)
    session.commit()
    session.refresh(db_inventory)
    return db_inventory

# Read all Inventory
@router.get("/", response_model=List[InventoryResponse])
def read_inventory(
    skip: int = 0, 
    limit: int = 100, 
    session: Session = Depends(get_session),
    current_user: UserResponse = Depends(require_any_access)
):
    """Get all inventory entries (requires authentication)."""
    inventory = session.exec(
        select(Inventory).offset(skip).limit(limit)
    ).all()
    return inventory

# Read Inventory by product
@router.get("/product/{product_id}", response_model=InventoryResponse)
def read_inventory_by_product(
    product_id: int,
    session: Session = Depends(get_session),
    current_user: UserResponse = Depends(require_any_access)
):
    """Get inventory for a specific product (requires authentication)."""
    # Validate product exists
    product = session.get(Product, product_id)
    if not product:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Product not found"
        )
    
    inventory = session.exec(
        select(Inventory).where(Inventory.product_id == product_id)
    ).first()
    
    if not inventory:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Inventory not found for this product"
        )
    
    return inventory

# Read single Inventory by ID
@router.get("/{inventory_id}", response_model=InventoryResponse)
def read_inventory_by_id(
    inventory_id: int, 
    session: Session = Depends(get_session),
    current_user: UserResponse = Depends(require_any_access)
):
    """Get specific inventory entry by ID (requires authentication)."""
    inventory = session.get(Inventory, inventory_id)
    if not inventory:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND, 
            detail="Inventory entry not found"
        )
    return inventory

# Update Inventory
@router.put("/{inventory_id}", response_model=InventoryResponse)
def update_inventory(
    inventory_id: int, 
    inventory: InventoryUpdate, 
    session: Session = Depends(get_session),
    current_user: UserResponse = Depends(require_write_access)
):
    """Update specific inventory entry (requires write access)."""
    db_inventory = session.get(Inventory, inventory_id)
    if not db_inventory:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND, 
            detail="Inventory entry not found"
        )
    
    update_data = inventory.model_dump(exclude_unset=True)
    
    # Validate product if being updated
    if "product_id" in update_data:
        product = session.get(Product, update_data["product_id"])
        if not product:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail="Product not found"
            )
        
        # Check for duplicate product (excluding current record)
        existing_inventory = session.exec(
            select(Inventory).where(
                Inventory.product_id == update_data["product_id"],
                Inventory.id != inventory_id
            )
        ).first()
        if existing_inventory:
            raise HTTPException(
                status_code=status.HTTP_409_CONFLICT,
                detail="Inventory entry already exists for this product"
            )
    
    # Update inventory
    for key, value in update_data.items():
        setattr(db_inventory, key, value)
    
    session.add(db_inventory)
    session.commit()
    session.refresh(db_inventory)
    return db_inventory

# Delete Inventory
@router.delete("/{inventory_id}", status_code=status.HTTP_204_NO_CONTENT)
def delete_inventory(
    inventory_id: int, 
    session: Session = Depends(get_session),
    current_user: UserResponse = Depends(require_admin)
):
    """Delete specific inventory entry (admin only)."""
    inventory = session.get(Inventory, inventory_id)
    if not inventory:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND, 
            detail="Inventory entry not found"
        )
    
    session.delete(inventory)
    session.commit()
    return None