From 518e240bca5bf7c36ecc40bf4b3934d7a5de8929 Mon Sep 17 00:00:00 2001
From: Ian Gulliver <git@flamingcow.io>
Date: Wed, 23 Sep 2026 21:14:00 -0700
Subject: [PATCH] PLS312 flag label sheet generator

---
 .gitignore |   1 +
 go.mod     |   3 ++
 main.go    | 145 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 149 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 go.mod
 create mode 100644 main.go

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..89f9ac0
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+out/
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..2437fe0
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,3 @@
+module labels
+
+go 1.26.7
diff --git a/main.go b/main.go
new file mode 100644
index 0000000..4567bba
--- /dev/null
+++ b/main.go
@@ -0,0 +1,145 @@
+package main
+
+import (
+	"bytes"
+	"encoding/xml"
+	"flag"
+	"fmt"
+	"log"
+	"math"
+	"os"
+	"os/exec"
+	"strconv"
+	"strings"
+)
+
+const (
+	pt             = 72.0
+	pageWidth      = 8.5
+	pageHeight     = 11.0
+	cols           = 7
+	rows           = 9
+	pitch          = 1.125
+	labelDiameter  = 1.0
+	leftMargin     = 0.375
+	topMargin      = 0.5
+	circleDiameter = 0.875
+	flagDiagonal   = 0.8
+)
+
+var rootOnlyAttrs = map[string]bool{
+	"width": true, "height": true, "x": true, "y": true, "viewBox": true,
+	"preserveAspectRatio": true, "version": true, "baseProfile": true,
+}
+
+type flagSVG struct {
+	viewBox [4]float64
+	nsAttrs string
+	gAttrs  string
+	inner   string
+}
+
+func main() {
+	stroke := flag.Bool("stroke", false, "draw a thin black stroke around each flag")
+	flag.Parse()
+	if flag.NArg() != 2 {
+		log.Fatal("usage: go run . [--stroke] flag.svg out.pdf")
+	}
+
+	data, err := os.ReadFile(flag.Arg(0))
+	if err != nil {
+		log.Fatal(err)
+	}
+	src := parseFlag(data)
+
+	aspect := src.viewBox[2] / src.viewBox[3]
+	flagH := flagDiagonal / math.Sqrt(1+aspect*aspect)
+	flagW := aspect * flagH
+
+	var b strings.Builder
+	fmt.Fprintf(&b, `<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"%s width="%gin" height="%gin" viewBox="0 0 %g %g">`+"\n", src.nsAttrs, pageWidth, pageHeight, pageWidth*pt, pageHeight*pt)
+	fmt.Fprintf(&b, `<defs><symbol id="labels-flag" viewBox="%g %g %g %g" preserveAspectRatio="none"><g%s>%s</g></symbol></defs>`+"\n", src.viewBox[0], src.viewBox[1], src.viewBox[2], src.viewBox[3], src.gAttrs, src.inner)
+	for r := 0; r < rows; r++ {
+		for c := 0; c < cols; c++ {
+			cx := (leftMargin + labelDiameter/2 + float64(c)*pitch) * pt
+			cy := (topMargin + labelDiameter/2 + float64(r)*pitch) * pt
+			fmt.Fprintf(&b, `<circle cx="%g" cy="%g" r="%g" fill="none" stroke="black" stroke-width="0.5" stroke-dasharray="2 1.5"/>`+"\n", cx, cy, circleDiameter/2*pt)
+			fmt.Fprintf(&b, `<use xlink:href="#labels-flag" x="%g" y="%g" width="%g" height="%g"/>`+"\n", cx-flagW/2*pt, cy-flagH/2*pt, flagW*pt, flagH*pt)
+			if *stroke {
+				fmt.Fprintf(&b, `<rect x="%g" y="%g" width="%g" height="%g" fill="none" stroke="black" stroke-width="0.25"/>`+"\n", cx-flagW/2*pt, cy-flagH/2*pt, flagW*pt, flagH*pt)
+			}
+		}
+	}
+	b.WriteString("</svg>\n")
+
+	cmd := exec.Command("rsvg-convert", "--format", "pdf", "--output", flag.Arg(1))
+	cmd.Stdin = strings.NewReader(b.String())
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	if err := cmd.Run(); err != nil {
+		log.Fatal(err)
+	}
+}
+
+func parseFlag(data []byte) flagSVG {
+	dec := xml.NewDecoder(bytes.NewReader(data))
+	for {
+		tok, err := dec.Token()
+		if err != nil {
+			log.Fatalf("[ERROR] no svg root element: %v", err)
+		}
+		start, ok := tok.(xml.StartElement)
+		if !ok {
+			continue
+		}
+
+		f := flagSVG{}
+		attrs := map[string]string{}
+		for _, a := range start.Attr {
+			switch {
+			case a.Name.Space == "xmlns" && a.Name.Local != "xlink":
+				f.nsAttrs += fmt.Sprintf(` xmlns:%s="%s"`, a.Name.Local, escape(a.Value))
+			case a.Name.Space == "" && a.Name.Local != "xmlns" && !rootOnlyAttrs[a.Name.Local]:
+				f.gAttrs += fmt.Sprintf(` %s="%s"`, a.Name.Local, escape(a.Value))
+			}
+			attrs[a.Name.Local] = a.Value
+		}
+
+		if vb, ok := attrs["viewBox"]; ok {
+			fields := strings.FieldsFunc(vb, func(r rune) bool { return r == ' ' || r == ',' })
+			if len(fields) != 4 {
+				log.Fatalf("[ERROR] bad viewBox %q", vb)
+			}
+			for i, s := range fields {
+				f.viewBox[i] = parseLength(s)
+			}
+		} else {
+			f.viewBox = [4]float64{0, 0, parseLength(attrs["width"]), parseLength(attrs["height"])}
+		}
+		if f.viewBox[2] <= 0 || f.viewBox[3] <= 0 {
+			log.Fatalf("[ERROR] bad svg size %v", f.viewBox)
+		}
+
+		innerStart := int(dec.InputOffset())
+		innerEnd := bytes.LastIndex(data, []byte("</"))
+		if innerEnd < innerStart {
+			log.Fatal("[ERROR] svg root element has no closing tag")
+		}
+		f.inner = string(data[innerStart:innerEnd])
+		return f
+	}
+}
+
+func parseLength(s string) float64 {
+	v, err := strconv.ParseFloat(strings.TrimRight(strings.TrimSpace(s), "abcdefghijklmnopqrstuvwxyz%"), 64)
+	if err != nil {
+		log.Fatalf("[ERROR] bad svg dimension %q", s)
+	}
+	return v
+}
+
+func escape(s string) string {
+	var b strings.Builder
+	xml.EscapeText(&b, []byte(s))
+	return b.String()
+}