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 Credit, Partner, Transaction
from app.schemas.schemas import (
    CreditCreate, 
    CreditUpdate, 
    CreditResponse, 
    UserResponse
)
from typing import List

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

# Create Credit
@router.post("/", response_model=CreditResponse, status_code=status.HTTP_201_CREATED)
def create_credit(
    credit: CreditCreate, 
    session: Session = Depends(get_session),
    current_user: UserResponse = Depends(require_write_access)
):
    """Create new credit account (requires write access)."""
    # Validate partner exists
    partner = session.get(Partner, credit.partner_id)
    if not partner:
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="Partner not found"
        )
    
    # Validate transaction exists
    transaction = session.get(Transaction, credit.transaction_id)
    if not transaction:
        raise HTTPException(
            status_code=status.HTTP_400_BAD_REQUEST,
            detail="Transaction not found"
        )
    
    # Check if credit account already exists for this partner
    existing_credit = session.exec(
        select(Credit).where(Credit.partner_id == credit.partner_id)
    ).first()
    if existing_credit:
        raise HTTPException(
            status_code=status.HTTP_409_CONFLICT,
            detail="Credit account already exists for this partner"
        )
    
    # Create credit with audit fields
    credit_data = credit.model_dump()
    credit_data["created_by"] = current_user.id
    credit_data["updated_by"] = current_user.id
    
    db_credit = Credit(**credit_data)
    
    session.add(db_credit)
    session.commit()
    session.refresh(db_credit)
    return db_credit

# Read all Credit accounts
@router.get("/", response_model=List[CreditResponse])
def read_credits(
    skip: int = 0, 
    limit: int = 100, 
    session: Session = Depends(get_session),
    current_user: UserResponse = Depends(require_any_access)
):
    """Get all credit accounts (requires authentication)."""
    credits = session.exec(
        select(Credit).offset(skip).limit(limit)
    ).all()
    return credits

# Read Credit by partner
@router.get("/partner/{partner_id}", response_model=CreditResponse)
def read_credit_by_partner(
    partner_id: int,
    session: Session = Depends(get_session),
    current_user: UserResponse = Depends(require_any_access)
):
    """Get credit account for a specific partner (requires authentication)."""
    # Validate partner exists
    partner = session.get(Partner, partner_id)
    if not partner:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Partner not found"
        )
    
    credit = session.exec(
        select(Credit).where(Credit.partner_id == partner_id)
    ).first()
    
    if not credit:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Credit account not found for this partner"
        )
    
    return credit

# Read single Credit by ID
@router.get("/{credit_id}", response_model=CreditResponse)
def read_credit_by_id(
    credit_id: int, 
    session: Session = Depends(get_session),
    current_user: UserResponse = Depends(require_any_access)
):
    """Get specific credit account by ID (requires authentication)."""
    credit = session.get(Credit, credit_id)
    if not credit:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND, 
            detail="Credit account not found"
        )
    return credit

# Update Credit
@router.put("/{credit_id}", response_model=CreditResponse)
def update_credit(
    credit_id: int, 
    credit: CreditUpdate, 
    session: Session = Depends(get_session),
    current_user: UserResponse = Depends(require_write_access)
):
    """Update specific credit account (requires write access)."""
    db_credit = session.get(Credit, credit_id)
    if not db_credit:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND, 
            detail="Credit account not found"
        )
    
    update_data = credit.model_dump(exclude_unset=True)
    
    # Validate partner if being updated
    if "partner_id" in update_data:
        partner = session.get(Partner, update_data["partner_id"])
        if not partner:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail="Partner not found"
            )
        
        # Check for duplicate partner (excluding current record)
        existing_credit = session.exec(
            select(Credit).where(
                Credit.partner_id == update_data["partner_id"],
                Credit.id != credit_id
            )
        ).first()
        if existing_credit:
            raise HTTPException(
                status_code=status.HTTP_409_CONFLICT,
                detail="Credit account already exists for this partner"
            )
    
    # Validate transaction if being updated
    if "transaction_id" in update_data:
        transaction = session.get(Transaction, update_data["transaction_id"])
        if not transaction:
            raise HTTPException(
                status_code=status.HTTP_400_BAD_REQUEST,
                detail="Transaction not found"
            )
    
    # Track who updated
    update_data["updated_by"] = current_user.id
    
    # Update credit
    for key, value in update_data.items():
        setattr(db_credit, key, value)
    
    session.add(db_credit)
    session.commit()
    session.refresh(db_credit)
    return db_credit

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