"""Server-side GST invoice PDF (reportlab). INR, 18% GST."""
import io
from datetime import datetime

from reportlab.lib import colors
from reportlab.lib.pagesizes import A4
from reportlab.lib.units import mm
from reportlab.pdfgen import canvas


def _inr(paise_or_rupees: int) -> str:
    return f"Rs. {paise_or_rupees:,.2f}"


def build_invoice_pdf(invoice: dict, org: dict) -> bytes:
    buf = io.BytesIO()
    c = canvas.Canvas(buf, pagesize=A4)
    w, h = A4
    y = h - 25 * mm

    # Header
    c.setFillColor(colors.HexColor("#0b1f4d"))
    c.setFont("Helvetica-Bold", 20)
    c.drawString(20 * mm, y, "VerifyPack")
    c.setFont("Helvetica", 9)
    c.setFillColor(colors.grey)
    c.drawString(20 * mm, y - 6 * mm, "Tax Invoice")
    c.setFont("Helvetica-Bold", 12)
    c.setFillColor(colors.black)
    c.drawRightString(w - 20 * mm, y, f"Invoice {invoice.get('invoice_number', '')}")
    c.setFont("Helvetica", 9)
    c.setFillColor(colors.grey)
    date = invoice.get("created_at")
    date_str = date.strftime("%d %b %Y") if isinstance(date, datetime) else str(date or "")
    c.drawRightString(w - 20 * mm, y - 6 * mm, f"Date: {date_str}")

    y -= 22 * mm
    c.setStrokeColor(colors.HexColor("#e2e8f0"))
    c.line(20 * mm, y, w - 20 * mm, y)

    # Billed to
    y -= 10 * mm
    c.setFillColor(colors.black)
    c.setFont("Helvetica-Bold", 10)
    c.drawString(20 * mm, y, "Billed To")
    c.setFont("Helvetica", 9)
    c.drawString(20 * mm, y - 5 * mm, org.get("name", ""))
    if org.get("gstin"):
        c.drawString(20 * mm, y - 10 * mm, f"GSTIN: {org['gstin']}")
    if org.get("address"):
        c.drawString(20 * mm, y - 15 * mm, org["address"][:60])

    c.setFont("Helvetica-Bold", 10)
    c.drawRightString(w - 20 * mm, y, "From")
    c.setFont("Helvetica", 9)
    c.drawRightString(w - 20 * mm, y - 5 * mm, "VerifyPack Technologies")
    c.drawRightString(w - 20 * mm, y - 10 * mm, "Bengaluru, Karnataka, India")

    # Line items table
    y -= 30 * mm
    c.setFillColor(colors.HexColor("#f1f5f9"))
    c.rect(20 * mm, y, w - 40 * mm, 8 * mm, fill=1, stroke=0)
    c.setFillColor(colors.HexColor("#334155"))
    c.setFont("Helvetica-Bold", 9)
    c.drawString(23 * mm, y + 2.5 * mm, "Description")
    c.drawRightString(w - 23 * mm, y + 2.5 * mm, "Amount")

    subtotal = invoice.get("subtotal", 0)
    gst = invoice.get("gst_amount", 0)
    total = invoice.get("total", 0)

    y -= 10 * mm
    c.setFillColor(colors.black)
    c.setFont("Helvetica", 9)
    period = invoice.get("period", "")
    c.drawString(23 * mm, y, f"{invoice.get('plan_name', 'Plan')} subscription {period}".strip())
    c.drawRightString(w - 23 * mm, y, _inr(subtotal))

    # Totals
    y -= 14 * mm
    c.line(w - 80 * mm, y + 6 * mm, w - 20 * mm, y + 6 * mm)
    c.setFont("Helvetica", 9)
    c.drawRightString(w - 55 * mm, y, "Subtotal")
    c.drawRightString(w - 23 * mm, y, _inr(subtotal))
    y -= 6 * mm
    c.drawRightString(w - 55 * mm, y, "GST (18%)")
    c.drawRightString(w - 23 * mm, y, _inr(gst))
    y -= 8 * mm
    c.setFont("Helvetica-Bold", 11)
    c.drawRightString(w - 55 * mm, y, "Total")
    c.drawRightString(w - 23 * mm, y, _inr(total))

    # Footer
    c.setFont("Helvetica", 8)
    c.setFillColor(colors.grey)
    c.drawString(20 * mm, 20 * mm, f"Place of supply: {invoice.get('place_of_supply', 'Karnataka')}")
    c.drawString(20 * mm, 15 * mm, "This is a computer-generated invoice and does not require a signature.")
    c.drawRightString(w - 20 * mm, 15 * mm, f"Status: {str(invoice.get('status', '')).upper()}")

    c.showPage()
    c.save()
    return buf.getvalue()