from datetime import datetime, date, timedelta, timezone
from decimal import Decimal
from typing import Optional
from calendar import monthrange
from .models import Invoice, InvoiceLineItem, PricingConfig, UserSubscription
from .usage_tracker import UsageTracker
from .stripe_client import StripeClient
from ..models import User


class InvoiceGenerator:
    @staticmethod
    async def generate_monthly_invoice(
        user: User, year: int, month: int
    ) -> Optional[Invoice]:
        period_start = date(year, month, 1)
        days_in_month = monthrange(year, month)[1]
        period_end = date(year, month, days_in_month)

        usage = await UsageTracker.get_monthly_usage(user, year, month)

        pricing = await PricingConfig.all()
        pricing_dict = {p.config_key: p.config_value for p in pricing}

        storage_price_per_gb = pricing_dict.get(
            "storage_per_gb_month", Decimal("0.0045")
        )
        bandwidth_price_per_gb = pricing_dict.get(
            "bandwidth_egress_per_gb", Decimal("0.009")
        )
        free_storage_gb = pricing_dict.get("free_tier_storage_gb", Decimal("15"))
        free_bandwidth_gb = pricing_dict.get("free_tier_bandwidth_gb", Decimal("15"))
        tax_rate = pricing_dict.get("tax_rate_default", Decimal("0"))

        storage_gb = Decimal(str(usage["storage_gb_avg"]))
        bandwidth_gb = Decimal(str(usage["bandwidth_down_gb"]))

        billable_storage = max(Decimal("0"), storage_gb - free_storage_gb)
        billable_bandwidth = max(Decimal("0"), bandwidth_gb - free_bandwidth_gb)

        import math

        billable_storage_rounded = Decimal(math.ceil(float(billable_storage)))
        billable_bandwidth_rounded = Decimal(math.ceil(float(billable_bandwidth)))

        storage_cost = billable_storage_rounded * storage_price_per_gb
        bandwidth_cost = billable_bandwidth_rounded * bandwidth_price_per_gb

        subtotal = storage_cost + bandwidth_cost

        if subtotal <= 0:
            return None

        tax_amount = subtotal * tax_rate
        total = subtotal + tax_amount

        invoice_number = f"INV-{user.id:06d}-{year}{month:02d}"

        subscription = await UserSubscription.get_or_none(user=user)

        invoice = await Invoice.create(
            user=user,
            invoice_number=invoice_number,
            period_start=period_start,
            period_end=period_end,
            subtotal=subtotal,
            tax=tax_amount,
            total=total,
            currency="USD",
            status="draft",
            due_date=period_end + timedelta(days=7),
            metadata={
                "usage": usage,
                "pricing": {
                    "storage_per_gb": float(storage_price_per_gb),
                    "bandwidth_per_gb": float(bandwidth_price_per_gb),
                },
            },
        )

        if billable_storage_rounded > 0:
            await InvoiceLineItem.create(
                invoice=invoice,
                description=f"Storage usage for {period_start.strftime('%B %Y')} (Average: {storage_gb:.2f} GB, Billable: {billable_storage_rounded} GB)",
                quantity=billable_storage_rounded,
                unit_price=storage_price_per_gb,
                amount=storage_cost,
                item_type="storage",
                metadata={
                    "avg_gb": float(storage_gb),
                    "free_gb": float(free_storage_gb),
                },
            )

        if billable_bandwidth_rounded > 0:
            await InvoiceLineItem.create(
                invoice=invoice,
                description=f"Bandwidth usage for {period_start.strftime('%B %Y')} (Total: {bandwidth_gb:.2f} GB, Billable: {billable_bandwidth_rounded} GB)",
                quantity=billable_bandwidth_rounded,
                unit_price=bandwidth_price_per_gb,
                amount=bandwidth_cost,
                item_type="bandwidth",
                metadata={
                    "total_gb": float(bandwidth_gb),
                    "free_gb": float(free_bandwidth_gb),
                },
            )

        if subscription and subscription.stripe_customer_id:
            try:
                line_items = await invoice.line_items.all()
                stripe_line_items = [
                    {
                        "amount": item.amount,
                        "currency": "usd",
                        "description": item.description,
                        "metadata": item.metadata or {},
                    }
                    for item in line_items
                ]

                stripe_invoice = await StripeClient.create_invoice(
                    customer_id=subscription.stripe_customer_id,
                    description=f"MyWebdav Usage Invoice for {period_start.strftime('%B %Y')}",
                    line_items=stripe_line_items,
                    metadata={"mywebdav_invoice_id": str(invoice.id)},
                )

                invoice.stripe_invoice_id = stripe_invoice.id
                await invoice.save()
            except Exception as e:
                print(f"Failed to create Stripe invoice: {e}")

        return invoice

    @staticmethod
    async def finalize_invoice(invoice: Invoice) -> Invoice:
        if invoice.status != "draft":
            raise ValueError("Only draft invoices can be finalized")

        invoice.status = "open"
        await invoice.save()

        if invoice.stripe_invoice_id:
            try:
                await StripeClient.finalize_invoice(invoice.stripe_invoice_id)
            except Exception as e:
                print(f"Failed to finalize Stripe invoice: {e}")

        # Send invoice email
        from ..mail import queue_email

        line_items = await invoice.line_items.all()
        items_text = "\n".join(
            [f"- {item.description}: ${item.amount}" for item in line_items]
        )
        body = f"""Dear {invoice.user.username},

Your invoice {invoice.invoice_number} for the period {invoice.period_start} to {invoice.period_end} is now available.

Invoice Details:
{items_text}

Subtotal: ${invoice.subtotal}
Tax: ${invoice.tax}
Total: ${invoice.total}

Due Date: {invoice.due_date}

You can view and pay your invoice at: {invoice.user.email}  # Placeholder, should be a link to invoice page

Best regards,
The MyWebdav Team
"""
        html = f"""
<h2>Invoice {invoice.invoice_number}</h2>
<p>Dear {invoice.user.username},</p>
<p>Your invoice for the period {invoice.period_start} to {invoice.period_end} is now available.</p>
<table border="1">
<tr><th>Description</th><th>Amount</th></tr>
{"".join([f"<tr><td>{item.description}</td><td>${item.amount}</td></tr>" for item in line_items])}
<tr><td><strong>Subtotal</strong></td><td><strong>${invoice.subtotal}</strong></td></tr>
<tr><td><strong>Tax</strong></td><td><strong>${invoice.tax}</strong></td></tr>
<tr><td><strong>Total</strong></td><td><strong>${invoice.total}</strong></td></tr>
</table>
<p>Due Date: {invoice.due_date}</p>
<p>You can view and pay your invoice at: <a href="#">Invoice Link</a></p>
<p>Best regards,<br>The MyWebdav Team</p>
"""
        queue_email(
            to_email=invoice.user.email,
            subject=f"Your MyWebdav Invoice {invoice.invoice_number}",
            body=body,
            html=html,
        )

        return invoice

    @staticmethod
    async def mark_invoice_paid(invoice: Invoice) -> Invoice:
        invoice.status = "paid"
        invoice.paid_at = datetime.now(timezone.utc)
        await invoice.save()
        return invoice