"""
@router AdminInvoiceRouter (Backend/app/api/v1/routers/AdminInvoiceRouter.py)
@purpose CRM Admin endpoint controllers to query, generate, and print standard PDF and 80mm thermal roll GST invoices on-the-fly.
"""
from fastapi import APIRouter, Depends, HTTPException, status, Response
from sqlalchemy.orm import Session
from pydantic import BaseModel
from typing import List, Optional
from datetime import datetime
import ulid
import io
import zipfile

from app.core.database.db_session import get_db
from app.core.permissions.RoleChecker import get_current_user
from app.models.UserModel import User
from app.models.InvoiceModel import Invoice
from app.models.OrderModel import Order, OrderItem
from app.models.EcomCustomerModel import EcomCustomer
from app.core.invoice_generator import generate_invoice_pdf, generate_thermal_invoice_pdf

router = APIRouter(prefix="/api/v1/admin/invoices", tags=["Admin CRM Customer Invoices"])

# --- Schemas ---

class AdminInvoiceResponse(BaseModel):
    invoice_id: str
    invoice_no: str
    order_id: Optional[str] = None
    customer_id: str
    customer_email: Optional[str] = None
    subtotal: float
    discount_amount: float
    cgst: float
    sgst: float
    igst: float
    total_amount: float
    status: str
    pdf_url: Optional[str] = None
    created_at: datetime

# --- Endpoints ---

@router.get("", response_model=List[AdminInvoiceResponse])
def list_all_invoices(
    current_user: User = Depends(get_current_user),
    db: Session = Depends(get_db)
):
    """
    List all generated GST invoices in the system.
    """
    invoices = db.query(Invoice).order_by(Invoice.created_at.desc()).all()
    
    result = []
    for inv in invoices:
        cust_email = None
        customer = db.query(EcomCustomer).filter(EcomCustomer.customer_id == inv.customer_id).first()
        if customer:
            cust_email = customer.email
            
        pdf_url = f"/api/v1/admin/invoices/{inv.invoice_id}/download"
        
        result.append(
            AdminInvoiceResponse(
                invoice_id=inv.invoice_id,
                invoice_no=inv.invoice_no,
                order_id=inv.order_id,
                customer_id=inv.customer_id,
                customer_email=cust_email,
                subtotal=float(inv.subtotal),
                discount_amount=float(inv.discount_amount),
                cgst=float(inv.cgst),
                sgst=float(inv.sgst),
                igst=float(inv.igst),
                total_amount=float(inv.total_amount),
                status=inv.status,
                pdf_url=pdf_url,
                created_at=inv.created_at
            )
        )
    return result

@router.post("/generate/{order_id}", response_model=AdminInvoiceResponse)
def generate_invoice_for_order(
    order_id: str,
    current_user: User = Depends(get_current_user),
    db: Session = Depends(get_db)
):
    """
    Generate a new GST invoice for a confirmed order.
    """
    # Check if invoice already exists
    existing = db.query(Invoice).filter(Invoice.order_id == order_id).first()
    if existing:
        cust_email = None
        customer = db.query(EcomCustomer).filter(EcomCustomer.customer_id == existing.customer_id).first()
        if customer:
            cust_email = customer.email
        return AdminInvoiceResponse(
            invoice_id=existing.invoice_id,
            invoice_no=existing.invoice_no,
            order_id=existing.order_id,
            customer_id=existing.customer_id,
            customer_email=cust_email,
            subtotal=float(existing.subtotal),
            discount_amount=float(existing.discount_amount),
            cgst=float(existing.cgst),
            sgst=float(existing.sgst),
            igst=float(existing.igst),
            total_amount=float(existing.total_amount),
            status=existing.status,
            pdf_url=f"/api/v1/admin/invoices/{existing.invoice_id}/download",
            created_at=existing.created_at
        )

    # Fetch order details
    order = db.query(Order).filter(Order.order_id == order_id).first()
    if not order:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Order not found"
        )

    # GST calculation matching order details
    subtotal = float(order.total_amount)
    discount = float(order.discount_amount)
    tax_amount = float(order.tax_amount)
    cgst = round(tax_amount / 2, 2)
    sgst = round(tax_amount / 2, 2)
    igst = 0.0
    total = float(order.final_amount)

    # Allocate a 16-char GST invoice number
    # Format: C1P2-26-SEQ
    today = datetime.now()
    fy = today.strftime("%y") # financial year seq, e.g. 26
    last_inv = db.query(Invoice).order_by(Invoice.created_at.desc()).first()
    if not last_inv:
        seq = 1
    else:
        try:
            seq = int(last_inv.invoice_no.split("-")[-1]) + 1
        except Exception:
            seq = 1
    invoice_no = f"C1P1-{fy}-{seq:06d}"

    invoice = Invoice(
        invoice_id=str(ulid.ULID()),
        invoice_no=invoice_no,
        order_id=order.order_id,
        customer_id=order.customer_id,
        subtotal=subtotal,
        discount_amount=discount,
        cgst=cgst,
        sgst=sgst,
        igst=igst,
        total_amount=total,
        pdf_path=f"uploads/invoices/{invoice_no}.pdf" # virtual pointer path
    )
    db.add(invoice)
    db.commit()
    db.refresh(invoice)

    cust_email = None
    if order.customer:
        cust_email = order.customer.email

    return AdminInvoiceResponse(
        invoice_id=invoice.invoice_id,
        invoice_no=invoice.invoice_no,
        order_id=invoice.order_id,
        customer_id=invoice.customer_id,
        customer_email=cust_email,
        subtotal=float(invoice.subtotal),
        discount_amount=float(invoice.discount_amount),
        cgst=float(invoice.cgst),
        sgst=float(invoice.sgst),
        igst=float(invoice.igst),
        total_amount=float(invoice.total_amount),
        status=invoice.status,
        pdf_url=f"/api/v1/admin/invoices/{invoice.invoice_id}/download",
        created_at=invoice.created_at
    )

@router.get("/{invoice_id}/download")
def download_invoice_pdf(
    invoice_id: str,
    db: Session = Depends(get_db)
):
    """
    Generate and serve standard Letter-sized PDF GST Invoice on-the-fly.
    """
    invoice = db.query(Invoice).filter(Invoice.invoice_id == invoice_id).first()
    if not invoice:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Invoice not found"
        )

    order = db.query(Order).filter(Order.order_id == invoice.order_id).first()
    if not order:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Sales order record missing, cannot generate PDF invoice"
        )

    customer = db.query(EcomCustomer).filter(EcomCustomer.customer_id == invoice.customer_id).first()
    order_items = db.query(OrderItem).filter(OrderItem.order_id == invoice.order_id).all()

    try:
        pdf_bytes = generate_invoice_pdf(order, customer, order_items, db=db)
        return Response(
            content=pdf_bytes,
            media_type="application/pdf",
            headers={"Content-Disposition": f"inline; filename={invoice.invoice_no}.pdf"}
        )
    except Exception as e:
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail=f"Failed to compile PDF on-the-fly: {str(e)}"
        )

@router.get("/{invoice_id}/thermal-download")
def download_thermal_invoice_pdf(
    invoice_id: str,
    db: Session = Depends(get_db)
):
    """
    Generate and serve compact 80mm thermal receipt PDF on-the-fly.
    """
    invoice = db.query(Invoice).filter(Invoice.invoice_id == invoice_id).first()
    if not invoice:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Invoice not found"
        )

    order = db.query(Order).filter(Order.order_id == invoice.order_id).first()
    if not order:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail="Sales order record missing, cannot generate PDF invoice"
        )

    customer = db.query(EcomCustomer).filter(EcomCustomer.customer_id == invoice.customer_id).first()
    order_items = db.query(OrderItem).filter(OrderItem.order_id == invoice.order_id).all()

    try:
        pdf_bytes = generate_thermal_invoice_pdf(order, customer, order_items)
        return Response(
            content=pdf_bytes,
            media_type="application/pdf",
            headers={"Content-Disposition": f"inline; filename=thermal_{invoice.invoice_no}.pdf"}
        )
    except Exception as e:
        raise HTTPException(
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            detail=f"Failed to compile thermal receipt PDF: {str(e)}"
        )

@router.get("/export/excel")
def export_invoices_excel(
    start_date: Optional[str] = None,
    end_date: Optional[str] = None,
    db: Session = Depends(get_db)
):
    invoices = db.query(Invoice).order_by(Invoice.created_at.desc()).all()
    csv_data = "Invoice No,Order ID,Customer ID,Subtotal,CGST,SGST,Total Amount,Created At\n"
    for inv in invoices:
        csv_data += f"{inv.invoice_no},{inv.order_id},{inv.customer_id},{inv.subtotal},{inv.cgst},{inv.sgst},{inv.total_amount},{inv.created_at}\n"
    
    return Response(
        content=csv_data,
        media_type="text/csv",
        headers={"Content-Disposition": "attachment; filename=invoices_export.csv"}
    )

@router.get("/export/zip")
def export_invoices_zip(
    start_date: Optional[str] = None,
    end_date: Optional[str] = None,
    db: Session = Depends(get_db)
):
    invoices = db.query(Invoice).order_by(Invoice.created_at.desc()).all()
    
    zip_buffer = io.BytesIO()
    with zipfile.ZipFile(zip_buffer, "w", zipfile.ZIP_DEFLATED) as zip_file:
        summary = "Invoice No,Order ID,Customer ID,Total Amount\n"
        for inv in invoices:
            summary += f"{inv.invoice_no},{inv.order_id},{inv.customer_id},{inv.total_amount}\n"
        zip_file.writestr("summary.csv", summary)
        zip_file.writestr("read_me.txt", "Sassynest CRM invoice bulk dump package.")
        
    zip_buffer.seek(0)
    return Response(
        content=zip_buffer.getvalue(),
        media_type="application/zip",
        headers={"Content-Disposition": "attachment; filename=invoices_export.zip"}
    )