"""Billing and invoice endpoints."""
from datetime import date, datetime, timezone
from typing import Optional
from fastapi import APIRouter, Depends, HTTPException, Query
from pydantic import BaseModel
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy import select, func, desc

from app.auth.dependencies import require_super_admin, get_current_user
from app.database import get_db
from app.models.user import HubUser, UserRole
from app.models.billing import Invoice, InvoiceStatus, InvoiceLineItem, SchoolSubscription, BillingCycle

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

class InvoiceCreate(BaseModel):
    school_id: str
    billing_period_start: date
    billing_period_end: date
    subscription_amount: float = 0.0
    sms_credit_amount: float = 0.0
    other_amount: float = 0.0
    due_date: Optional[date] = None
    notes: Optional[str] = None
    line_items: list[dict] = []

class InvoiceUpdate(BaseModel):
    status: Optional[InvoiceStatus] = None
    paid_at: Optional[datetime] = None
    payment_method: Optional[str] = None
    payment_reference: Optional[str] = None
    notes: Optional[str] = None

class SubscriptionUpsert(BaseModel):
    monthly_fee: float
    sms_cost_per_message: float = 1.0
    cycle: BillingCycle = BillingCycle.monthly
    next_billing_date: Optional[date] = None

def _inv_out(inv: Invoice) -> dict:
    return {
        "id": inv.id, "school_id": inv.school_id, "invoice_number": inv.invoice_number,
        "status": inv.status.value,
        "billing_period_start": inv.billing_period_start.isoformat(),
        "billing_period_end": inv.billing_period_end.isoformat(),
        "subscription_amount": float(inv.subscription_amount),
        "sms_credit_amount": float(inv.sms_credit_amount),
        "other_amount": float(inv.other_amount),
        "total_amount": float(inv.total_amount),
        "currency": inv.currency,
        "due_date": inv.due_date.isoformat() if inv.due_date else None,
        "paid_at": inv.paid_at.isoformat() if inv.paid_at else None,
        "payment_method": inv.payment_method,
        "payment_reference": inv.payment_reference,
        "email_sent_at": inv.email_sent_at.isoformat() if inv.email_sent_at else None,
        "created_at": inv.created_at.isoformat(),
        "notes": inv.notes,
    }

def _next_invoice_number(existing_count: int) -> str:
    from datetime import date
    return f"INV-{date.today().strftime('%Y%m')}-{existing_count + 1:04d}"

@router.get("/invoices")
async def list_invoices(
    school_id: Optional[str] = Query(None),
    status: Optional[InvoiceStatus] = Query(None),
    page: int = Query(1, ge=1),
    per_page: int = Query(25),
    current_user: HubUser = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
):
    stmt = select(Invoice).order_by(desc(Invoice.created_at))
    if current_user.role != UserRole.super_admin:
        stmt = stmt.where(Invoice.school_id == current_user.school_id)
    elif school_id:
        stmt = stmt.where(Invoice.school_id == school_id)
    if status:
        stmt = stmt.where(Invoice.status == status)
    total = (await db.execute(select(func.count()).select_from(stmt.subquery()))).scalar_one()
    invoices = (await db.execute(stmt.offset((page - 1) * per_page).limit(per_page))).scalars().all()
    return {"items": [_inv_out(i) for i in invoices], "total": total, "page": page, "per_page": per_page}

@router.post("/invoices", status_code=201)
async def create_invoice(
    body: InvoiceCreate,
    _admin: HubUser = Depends(require_super_admin),
    db: AsyncSession = Depends(get_db),
):
    total = body.subscription_amount + body.sms_credit_amount + body.other_amount
    count = (await db.execute(select(func.count()).select_from(Invoice))).scalar_one()
    inv = Invoice(
        school_id=body.school_id,
        invoice_number=_next_invoice_number(count),
        billing_period_start=body.billing_period_start,
        billing_period_end=body.billing_period_end,
        subscription_amount=body.subscription_amount,
        sms_credit_amount=body.sms_credit_amount,
        other_amount=body.other_amount,
        total_amount=total,
        due_date=body.due_date,
        notes=body.notes,
    )
    db.add(inv)
    await db.flush()
    for item in body.line_items:
        db.add(InvoiceLineItem(
            invoice_id=inv.id,
            description=item.get("description", ""),
            quantity=item.get("quantity", 1),
            unit_price=item.get("unit_price", 0),
            amount=item.get("amount", 0),
        ))
    await db.commit()
    return _inv_out(inv)

@router.put("/invoices/{invoice_id}")
async def update_invoice(
    invoice_id: str,
    body: InvoiceUpdate,
    _admin: HubUser = Depends(require_super_admin),
    db: AsyncSession = Depends(get_db),
):
    inv = (await db.execute(select(Invoice).where(Invoice.id == invoice_id))).scalar_one_or_none()
    if not inv:
        raise HTTPException(404, "Invoice not found")
    for field, value in body.model_dump(exclude_none=True).items():
        setattr(inv, field, value)
    await db.commit()
    return _inv_out(inv)

@router.post("/invoices/{invoice_id}/send-email")
async def send_invoice_email(
    invoice_id: str,
    _admin: HubUser = Depends(require_super_admin),
    db: AsyncSession = Depends(get_db),
):
    from app.tasks.billing import send_invoice_email_task
    inv = (await db.execute(select(Invoice).where(Invoice.id == invoice_id))).scalar_one_or_none()
    if not inv:
        raise HTTPException(404, "Invoice not found")
    send_invoice_email_task.delay(invoice_id)
    return {"message": "Email queued"}

@router.get("/subscriptions/{school_id}")
async def get_subscription(
    school_id: str,
    current_user: HubUser = Depends(get_current_user),
    db: AsyncSession = Depends(get_db),
):
    if current_user.role != UserRole.super_admin and current_user.school_id != school_id:
        raise HTTPException(403)
    sub = (await db.execute(select(SchoolSubscription).where(SchoolSubscription.school_id == school_id))).scalar_one_or_none()
    if not sub:
        raise HTTPException(404, "No subscription found")
    return {
        "id": sub.id, "school_id": sub.school_id, "cycle": sub.cycle.value,
        "monthly_fee": float(sub.monthly_fee), "sms_cost_per_message": float(sub.sms_cost_per_message),
        "next_billing_date": sub.next_billing_date.isoformat() if sub.next_billing_date else None,
        "is_active": sub.is_active,
    }

@router.put("/subscriptions/{school_id}")
async def upsert_subscription(
    school_id: str,
    body: SubscriptionUpsert,
    _admin: HubUser = Depends(require_super_admin),
    db: AsyncSession = Depends(get_db),
):
    sub = (await db.execute(select(SchoolSubscription).where(SchoolSubscription.school_id == school_id))).scalar_one_or_none()
    if sub:
        sub.monthly_fee = body.monthly_fee
        sub.sms_cost_per_message = body.sms_cost_per_message
        sub.cycle = body.cycle
        if body.next_billing_date:
            sub.next_billing_date = body.next_billing_date
    else:
        sub = SchoolSubscription(school_id=school_id, **body.model_dump())
        db.add(sub)
    await db.commit()
    return {"monthly_fee": float(sub.monthly_fee), "cycle": sub.cycle.value}