"""A printable A4 poster with a QR code that opens the bot (for dorm walls, class boards, cafeterias).
Latin text only (standard PDF fonts), so it needs no font files."""
import io

from reportlab.graphics import renderPDF
from reportlab.graphics.barcode.qr import QrCodeWidget
from reportlab.graphics.shapes import Drawing
from reportlab.lib.pagesizes import A4
from reportlab.pdfgen import canvas

BLUE = (0.10, 0.30, 0.60)


def make_poster_pdf(link: str, bot_username: str, channel_url: str, headline: str = "DBU Freshman Central") -> bytes:
    w, h = A4
    buf = io.BytesIO()
    c = canvas.Canvas(buf, pagesize=A4)
    c.setTitle(headline)

    c.setFillColorRGB(*BLUE)
    c.rect(0, h - 190, w, 190, stroke=0, fill=1)  # header band
    c.setFillColorRGB(1, 1, 1)
    c.setFont("Helvetica-Bold", 40)
    c.drawCentredString(w / 2, h - 95, headline)
    c.setFont("Helvetica", 18)
    c.drawCentredString(w / 2, h - 135, "Debre Berhan University")

    c.setFillColorRGB(0.1, 0.1, 0.1)
    c.setFont("Helvetica-Bold", 28)
    c.drawCentredString(w / 2, h - 255, "Free study materials, one tap away")
    c.setFont("Helvetica", 20)
    for i, line in enumerate(("Lecture slides", "Past exams", "Course modules", "Weekly student ranking")):
        c.drawCentredString(w / 2, h - 300 - i * 28, "-  " + line + "  -")

    qr = QrCodeWidget(link)
    x0, y0, x1, y1 = qr.getBounds()
    size = 235
    drawing = Drawing(size, size, transform=[size / (x1 - x0), 0, 0, size / (y1 - y0), 0, 0])
    drawing.add(qr)
    qx, qy = (w - size) / 2, 185
    c.setFillColorRGB(1, 1, 1)
    c.setStrokeColorRGB(*BLUE)
    c.setLineWidth(3)
    c.roundRect(qx - 16, qy - 16, size + 32, size + 32, 14, stroke=1, fill=1)
    renderPDF.draw(drawing, c, qx, qy)

    c.setFillColorRGB(*BLUE)
    c.setFont("Helvetica-Bold", 24)
    c.drawCentredString(w / 2, 128, "Scan with your phone camera")
    c.setFont("Helvetica", 18)
    c.drawCentredString(w / 2, 98, f"or search  @{bot_username}  on Telegram")
    c.setFont("Helvetica", 14)
    c.drawCentredString(w / 2, 56, channel_url.replace("https://", ""))
    c.showPage()
    c.save()
    return buf.getvalue()