"""Celery tasks: invoice generation, PDF, email, overdue escalation."""
import logging
from datetime import date, timedelta, datetime, timezone

from app.worker import celery_app

logger = logging.getLogger(__name__)


def _make_session():
    import os
    from sqlalchemy import create_engine
    from sqlalchemy.orm import sessionmaker
    db_url = os.getenv("DATABASE_URL", "postgresql://postgres:postgres@db:5432/taptrack_hub")
    engine = create_engine(
        db_url.replace("postgresql+asyncpg://", "postgresql://"),
        pool_pre_ping=True,
    )
    return sessionmaker(bind=engine)()


def _hub_url() -> str:
    import os
    return os.getenv("HUB_BASE_URL", "http://localhost:8090")


@celery_app.task(name="billing.generate_monthly_invoices")
def generate_monthly_invoices():
    """On the 1st: create draft invoices for all active schools with a subscription."""
    from sqlalchemy import select, func
    from app.models.billing import Invoice, SchoolSubscription, InvoiceLineItem
    from app.models.school import School, SchoolStatus

    db = _make_session()
    try:
        today = date.today()
        period_start = date(today.year, today.month, 1)
        prev_month = period_start - timedelta(days=1)
        billing_start = date(prev_month.year, prev_month.month, 1)
        billing_end = period_start - timedelta(days=1)

        subs = db.execute(
            select(SchoolSubscription).where(SchoolSubscription.is_active == True)
        ).scalars().all()

        count = db.execute(select(func.count()).select_from(Invoice)).scalar_one()
        created = 0

        for sub in subs:
            school = db.get(School, sub.school_id)
            if not school or school.status != SchoolStatus.active:
                continue

            # Avoid duplicate invoices for the same period
            existing = db.execute(
                select(Invoice).where(
                    Invoice.school_id == sub.school_id,
                    Invoice.billing_period_start == billing_start,
                )
            ).scalar_one_or_none()
            if existing:
                continue

            total = float(sub.monthly_fee)
            inv_num = f"INV-{billing_start.strftime('%Y%m')}-{count + 1:04d}"
            count += 1
            created += 1

            inv = Invoice(
                school_id=sub.school_id,
                invoice_number=inv_num,
                billing_period_start=billing_start,
                billing_period_end=billing_end,
                subscription_amount=float(sub.monthly_fee),
                total_amount=total,
                due_date=period_start + timedelta(days=14),
            )
            db.add(inv)
            db.flush()

            db.add(InvoiceLineItem(
                invoice_id=inv.id,
                description=f"Monthly subscription — {school.name}",
                quantity=1,
                unit_price=float(sub.monthly_fee),
                amount=float(sub.monthly_fee),
            ))

            # Auto-send invoice email
            send_invoice_email_task.delay(inv.id)

        db.commit()
        logger.info("Generated %d invoices for %s", created, billing_start)
    except Exception as e:
        db.rollback()
        logger.error("generate_monthly_invoices error: %s", e)
    finally:
        db.close()


@celery_app.task(name="billing.generate_invoice_pdf")
def generate_invoice_pdf_task(invoice_id: str):
    """Generate PDF for a single invoice and update the pdf_path field."""
    from app.services.invoice_pdf import generate_invoice_pdf
    from app.models.billing import Invoice

    db = _make_session()
    try:
        path = generate_invoice_pdf(invoice_id, db)
        inv = db.get(Invoice, invoice_id)
        if inv:
            inv.pdf_path = path
            db.commit()
        logger.info("Invoice PDF generated: %s", path)
        return path
    except Exception as e:
        logger.error("generate_invoice_pdf_task error for %s: %s", invoice_id, e)
        raise
    finally:
        db.close()


@celery_app.task(name="billing.send_invoice_email")
def send_invoice_email_task(invoice_id: str):
    """Send invoice email to school billing contact and set status to 'sent'."""
    from app.models.billing import Invoice, InvoiceStatus
    from app.models.school import School
    from app.services.email import send_email

    db = _make_session()
    try:
        inv = db.get(Invoice, invoice_id)
        if not inv:
            return
        school = db.get(School, inv.school_id)
        if not school or not school.billing_email:
            return

        plain = (
            f"Dear {school.contact_name or school.name},\n\n"
            f"Your invoice {inv.invoice_number} for PHP {float(inv.total_amount):,.2f} "
            f"covering {inv.billing_period_start} to {inv.billing_period_end} is ready.\n"
            f"Due: {inv.due_date or 'Upon receipt'}\n\n"
            f"Log in: {_hub_url()}/portal/billing\n\nTapTrack Hub Team"
        )
        send_email(
            to=school.billing_email,
            subject=f"Invoice {inv.invoice_number} — TapTrack Hub",
            body=plain,
            template_name="email/invoice.html",
            context={
                "contact_name": school.contact_name or school.name,
                "school_name": school.name,
                "invoice_number": inv.invoice_number,
                "period_start": str(inv.billing_period_start),
                "period_end": str(inv.billing_period_end),
                "amount": f"{float(inv.total_amount):,.2f}",
                "due_date": str(inv.due_date) if inv.due_date else "Upon receipt",
            },
            email_type="invoice",
            school_id=school.id,
        )
        inv.email_sent_at = datetime.now(timezone.utc)
        if inv.status == InvoiceStatus.draft:
            inv.status = InvoiceStatus.sent
        db.commit()
    finally:
        db.close()


@celery_app.task(name="billing.check_overdue")
def check_overdue():
    """
    Daily task: mark overdue invoices and escalate.
    - sent + past due_date → overdue
    - overdue 7+ days → warning email
    - overdue 30+ days → suspend school + suspension email
    """
    from sqlalchemy import select, and_
    from app.models.billing import Invoice, InvoiceStatus
    from app.models.school import School, SchoolStatus
    from app.services.email import send_email

    db = _make_session()
    try:
        today = date.today()

        # 1. Mark newly overdue
        newly_overdue = db.execute(
            select(Invoice).where(
                and_(
                    Invoice.status == InvoiceStatus.sent,
                    Invoice.due_date != None,
                    Invoice.due_date < today,
                )
            )
        ).scalars().all()
        for inv in newly_overdue:
            inv.status = InvoiceStatus.overdue
        db.commit()
        logger.info("Marked %d invoices as overdue", len(newly_overdue))

        # 2. Warning email: overdue 7+ days (but not yet 30)
        warn_cutoff = today - timedelta(days=7)
        suspend_cutoff = today - timedelta(days=30)

        warn_invoices = db.execute(
            select(Invoice).where(
                and_(
                    Invoice.status == InvoiceStatus.overdue,
                    Invoice.due_date != None,
                    Invoice.due_date <= warn_cutoff,
                    Invoice.due_date > suspend_cutoff,
                )
            )
        ).scalars().all()

        for inv in warn_invoices:
            school = db.get(School, inv.school_id)
            if school and school.billing_email:
                days_overdue = (today - inv.due_date).days
                days_until_suspension = max(0, 30 - days_overdue)
                send_email(
                    to=school.billing_email,
                    subject=f"[TapTrack Hub] Overdue Invoice — {inv.invoice_number}",
                    body=(
                        f"Dear {school.contact_name or school.name},\n\n"
                        f"Invoice {inv.invoice_number} (PHP {float(inv.total_amount):,.2f}) "
                        f"was due on {inv.due_date} and is now overdue.\n"
                        f"Please settle immediately to avoid suspension.\n\n"
                        f"Portal: {_hub_url()}/portal/billing\n\nTapTrack Hub Team"
                    ),
                    template_name="email/overdue_warning.html",
                    context={
                        "contact_name": school.contact_name or school.name,
                        "school_name": school.name,
                        "invoice_number": inv.invoice_number,
                        "amount": f"{float(inv.total_amount):,.2f}",
                        "due_date": str(inv.due_date),
                        "days_overdue": days_overdue,
                        "days_until_suspension": days_until_suspension,
                    },
                    email_type="overdue_warning",
                    school_id=school.id,
                )
        logger.info("Sent %d overdue warning emails", len(warn_invoices))

        # 3. Suspend: overdue 30+ days
        suspend_invoices = db.execute(
            select(Invoice).where(
                and_(
                    Invoice.status == InvoiceStatus.overdue,
                    Invoice.due_date != None,
                    Invoice.due_date <= suspend_cutoff,
                )
            )
        ).scalars().all()

        suspended = 0
        for inv in suspend_invoices:
            school = db.get(School, inv.school_id)
            if school and school.status == SchoolStatus.active:
                school.status = SchoolStatus.suspended
                suspended += 1
                logger.warning(
                    "Suspended school %s — overdue invoice %s (30+ days)",
                    school.name, inv.invoice_number,
                )
                if school.billing_email:
                    send_email(
                        to=school.billing_email,
                        subject=f"[TapTrack Hub] Account Suspended — Invoice {inv.invoice_number}",
                        body=(
                            f"Your TapTrack account for {school.name} has been suspended.\n"
                            f"Invoice {inv.invoice_number} (PHP {float(inv.total_amount):,.2f}) "
                            f"was due on {inv.due_date} and remains unpaid.\n\n"
                            f"Contact support@taptrack.io to restore service."
                        ),
                        template_name="email/suspension.html",
                        context={
                            "contact_name": school.contact_name or school.name,
                            "school_name": school.name,
                            "invoice_number": inv.invoice_number,
                            "amount": f"{float(inv.total_amount):,.2f}",
                            "due_date": str(inv.due_date),
                        },
                        email_type="suspension",
                        school_id=school.id,
                    )

        db.commit()
        logger.info("Suspended %d schools for non-payment", suspended)

    except Exception as e:
        db.rollback()
        logger.error("check_overdue error: %s", e)
    finally:
        db.close()