Added PDF Generation

go.mod

@@ -2,10 +2,12 @@ module printer.backend
 
 go 1.26.3
 
-require github.com/spf13/cobra v1.10.2
+require (
+	github.com/google/uuid v1.6.0
+	github.com/spf13/cobra v1.10.2
+)
 
 require (
-	github.com/google/uuid v1.6.0 // indirect
 	github.com/inconshreveable/mousetrap v1.1.0 // indirect
 	github.com/spf13/pflag v1.0.9 // indirect
 )

internal/layout/layout.go

@@ -4,25 +4,14 @@ import (
 	"printer.backend/internal/model"
 )
 
-// Footprint returns the physical width and height one item occupies on the plate (mm).
-// Includes bleed on all sides and the item's margin as a safe zone.
-func Footprint(spec model.ItemSpec) (width, height float64) {
-	w := spec.SizeMM + 2*spec.BleedMM + 2*spec.MarginMM
-	return w, w
-}
-
-// CellPitch returns width and height of one grid cell (footprint + spacing between items).
-func CellPitch(spec model.ItemSpec, spacingMM float64) (width, height float64) {
-	fw, fh := Footprint(spec)
-	return fw + spacingMM, fh + spacingMM
-}
-
 // Pack computes the maximum grid of items that fit on the plate.
+// Item spacing uses the SVG viewport size (spec.SizeMM); bleed/margin/padding live inside the template.
 func Pack(plate model.Plate, spec model.ItemSpec, spacingMM float64) model.LayoutPreview {
 	pw := plate.PrintableWidth()
 	ph := plate.PrintableHeight()
-	fw, fh := Footprint(spec)
+	itemW := spec.SizeMM
-	cw, ch := CellPitch(spec, spacingMM)
+	cw := itemW + spacingMM
+	ch := itemW + spacingMM
 
 	cols, rows := gridCount(pw, ph, cw, ch)
 	count := cols * rows
@@ -49,8 +38,8 @@ func Pack(plate model.Plate, spec model.ItemSpec, spacingMM float64) model.Layou
 		PrintableHMM:  ph,
 		CellWidthMM:   cw,
 		CellHeightMM:  ch,
-		FootprintWMM:  fw,
+		FootprintWMM:  itemW,
-		FootprintHMM:  fh,
+		FootprintHMM:  itemW,
 		SpacingMM:     spacingMM,
 		Columns:       cols,
 		Rows:          rows,

internal/layout/layout_test.go

@@ -16,20 +16,22 @@ func TestPack(t *testing.T) {
 		MarginLeft:   10,
 	}
 	spec := model.ItemSpec{SizeMM: 80, BleedMM: 2, MarginMM: 5}
-	// footprint = 80+4+10 = 94, cell = 94+2 = 96
+	// viewport 80mm, cell = 80+2 = 82, printable 280x380 -> cols=3, rows=4 -> 12
-	// printable 280x380 -> cols=2, rows=3 -> 6
 	preview := Pack(plate, spec, 2)
-	if preview.Columns != 2 {
+	if preview.Columns != 3 {
-		t.Fatalf("columns: got %d want 2", preview.Columns)
+		t.Fatalf("columns: got %d want 3", preview.Columns)
 	}
-	if preview.Rows != 3 {
+	if preview.Rows != 4 {
-		t.Fatalf("rows: got %d want 3", preview.Rows)
+		t.Fatalf("rows: got %d want 4", preview.Rows)
 	}
-	if preview.Count != 6 {
+	if preview.Count != 12 {
-		t.Fatalf("count: got %d want 6", preview.Count)
+		t.Fatalf("count: got %d want 12", preview.Count)
 	}
-	if len(preview.Positions) != 6 {
+	if preview.FootprintWMM != 80 {
-		t.Fatalf("positions: got %d want 6", len(preview.Positions))
+		t.Fatalf("footprint width: got %v want 80", preview.FootprintWMM)
+	}
+	if len(preview.Positions) != 12 {
+		t.Fatalf("positions: got %d want 12", len(preview.Positions))
 	}
 	if preview.Positions[0].XMM != 10 || preview.Positions[0].YMM != 10 {
 		t.Fatalf("first position: got (%v,%v)", preview.Positions[0].XMM, preview.Positions[0].YMM)

internal/platepdf/composite.go

@@ -0,0 +1,50 @@
+package platepdf
+
+import (
+	"bytes"
+	"encoding/base64"
+	"fmt"
+
+	"printer.backend/internal/model"
+)
+
+const renderDPI = 300
+
+// BuildCompositeSVG assembles a plate-sized SVG by embedding each item as a PNG
+// rendered by rsvg-convert (identical to the standalone item file).
+func BuildCompositeSVG(plate model.Plate, spec model.ItemSpec, itemSVG []byte, preview model.LayoutPreview) ([]byte, error) {
+	itemW, itemH, err := svgViewportMM(itemSVG)
+	if err != nil {
+		return nil, err
+	}
+	if itemW <= 0 || itemH <= 0 {
+		itemW, itemH = spec.SizeMM, spec.SizeMM
+	}
+
+	itemPNG, err := svgToPNGViaRsvg(itemSVG, renderDPI)
+	if err != nil {
+		return nil, fmt.Errorf("render item: %w", err)
+	}
+	itemB64 := base64.StdEncoding.EncodeToString(itemPNG)
+
+	var b bytes.Buffer
+	fmt.Fprintf(&b, `<?xml version="1.0" encoding="UTF-8"?>
+<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="0 0 %.4f %.4f" width="%.4fmm" height="%.4fmm">
+  <rect width="%.4f" height="%.4f" fill="#ffffff"/>
+  <rect x="%.4f" y="%.4f" width="%.4f" height="%.4f" fill="none" stroke="#cccccc" stroke-width="0.2"/>
+`,
+		plate.WidthMM, plate.HeightMM, plate.WidthMM, plate.HeightMM,
+		plate.WidthMM, plate.HeightMM,
+		preview.PrintableXMM, preview.PrintableYMM, preview.PrintableWMM, preview.PrintableHMM,
+	)
+
+	for _, pos := range preview.Positions {
+		fmt.Fprintf(&b,
+			`<image x="%.4f" y="%.4f" width="%.4f" height="%.4f" href="data:image/png;base64,%s"/>`,
+			pos.XMM, pos.YMM, itemW, itemH, itemB64,
+		)
+	}
+
+	b.WriteString("\n</svg>")
+	return b.Bytes(), nil
+}

internal/platepdf/platepdf.go

@@ -0,0 +1,32 @@
+package platepdf
+
+import (
+	"fmt"
+	"os"
+
+	"printer.backend/internal/model"
+)
+
+// Generate builds a PDF of the plate layout using the item's SVG template.
+// Requires rsvg-convert on PATH.
+func Generate(plate model.Plate, spec model.ItemSpec, itemSVGPath string, preview model.LayoutPreview) ([]byte, error) {
+	if !rsvgAvailable() {
+		return nil, fmt.Errorf("rsvg-convert not found in PATH (required for PDF export)")
+	}
+
+	itemSVG, err := os.ReadFile(itemSVGPath)
+	if err != nil {
+		return nil, fmt.Errorf("read item svg: %w", err)
+	}
+
+	composite, err := BuildCompositeSVG(plate, spec, itemSVG, preview)
+	if err != nil {
+		return nil, err
+	}
+
+	pdf, err := svgToPDFViaRsvg(composite, plate.WidthMM, plate.HeightMM)
+	if err != nil {
+		return nil, fmt.Errorf("render plate pdf: %w", err)
+	}
+	return pdf, nil
+}

internal/platepdf/platepdf_test.go

@@ -0,0 +1,106 @@
+package platepdf
+
+import (
+	"bytes"
+	"os"
+	"strings"
+	"testing"
+
+	"printer.backend/internal/layout"
+	"printer.backend/internal/model"
+	"printer.backend/internal/svgtemplate"
+)
+
+const sampleItemSVG = `<?xml version="1.0" encoding="UTF-8"?>
+<svg xmlns="http://www.w3.org/2000/svg" width="80mm" height="80mm" viewBox="-13 -13 106 106">
+  <defs>
+    <clipPath id="item-mask">
+      <rect x="0" y="0" width="80" height="80" rx="5" ry="5" />
+    </clipPath>
+  </defs>
+  <rect x="-13" y="-13" width="106" height="106" fill="#f9f9f9" />
+  <g clip-path="url(#item-mask)">
+    <rect x="-2" y="-2" width="84" height="84" fill="#00ff00" opacity="0.7" />
+  </g>
+</svg>`
+
+func requireRsvg(t *testing.T) {
+	t.Helper()
+	if !rsvgAvailable() {
+		t.Skip("rsvg-convert not available")
+	}
+}
+
+func TestBuildCompositeSVG(t *testing.T) {
+	requireRsvg(t)
+
+	plate := model.Plate{
+		WidthMM: 300, HeightMM: 400,
+		MarginTop: 10, MarginRight: 10, MarginBottom: 10, MarginLeft: 10,
+	}
+	spec := model.ItemSpec{SizeMM: 80, BleedMM: 2, MarginMM: 5, PaddingMM: 3}
+	preview := layout.Pack(plate, spec, 2)
+
+	out, err := BuildCompositeSVG(plate, spec, []byte(sampleItemSVG), preview)
+	if err != nil {
+		t.Fatal(err)
+	}
+	s := string(out)
+	if !strings.Contains(s, `viewBox="0 0 300`) {
+		t.Fatalf("expected plate viewBox, got: %s", s[:min(200, len(s))])
+	}
+	if preview.Count > 0 && !strings.Contains(s, `<image `) {
+		t.Fatal("expected embedded item images")
+	}
+	if preview.Count > 0 && !strings.Contains(s, `x="10.0000"`) {
+		t.Fatal("expected items at plate margin (footprint origin)")
+	}
+}
+
+func TestBuildCompositeSVGInvalid(t *testing.T) {
+	requireRsvg(t)
+
+	_, err := BuildCompositeSVG(model.Plate{}, model.ItemSpec{}, []byte("not svg"), model.LayoutPreview{})
+	if err == nil {
+		t.Fatal("expected error for invalid svg")
+	}
+}
+
+func TestGeneratePDF(t *testing.T) {
+	requireRsvg(t)
+
+	plate := model.Plate{
+		WidthMM: 200, HeightMM: 200,
+		MarginLeft: 10, MarginTop: 10, MarginRight: 10, MarginBottom: 10,
+	}
+	spec := model.ItemSpec{SizeMM: 80, BleedMM: 2, MarginMM: 5, PaddingMM: 3}
+	preview := layout.Pack(plate, spec, 2)
+
+	var buf bytes.Buffer
+	if err := svgtemplate.Write(&buf, svgtemplate.Build(spec.SizeMM, spec.BleedMM, spec.MarginMM, spec.PaddingMM)); err != nil {
+		t.Fatal(err)
+	}
+
+	path := t.TempDir() + "/item.svg"
+	if err := os.WriteFile(path, buf.Bytes(), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	pdf, err := Generate(plate, spec, path, preview)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(pdf) < 4 || string(pdf[:4]) != "%PDF" {
+		t.Fatalf("expected PDF header, got %d bytes", len(pdf))
+	}
+}
+
+func TestGenerateRequiresRsvg(t *testing.T) {
+	if rsvgAvailable() {
+		t.Skip("rsvg-convert is available")
+	}
+	_, err := Generate(model.Plate{}, model.ItemSpec{}, "/nonexistent", model.LayoutPreview{})
+	if err == nil || !strings.Contains(err.Error(), "rsvg-convert") {
+		t.Fatalf("expected rsvg error, got: %v", err)
+	}
+}

internal/platepdf/rsvg.go

@@ -0,0 +1,62 @@
+package platepdf
+
+import (
+	"bytes"
+	"fmt"
+	"os/exec"
+)
+
+// rsvgAvailable returns true when rsvg-convert is found in PATH.
+func rsvgAvailable() bool {
+	_, err := exec.LookPath("rsvg-convert")
+	return err == nil
+}
+
+// svgToPDFViaRsvg converts an SVG byte slice to a PDF using rsvg-convert.
+// widthMM / heightMM set the output page size so the PDF is exactly that physical size.
+func svgToPDFViaRsvg(svg []byte, widthMM, heightMM float64) ([]byte, error) {
+	args := []string{
+		"-f", "pdf",
+		"--page-width", fmt.Sprintf("%.4fmm", widthMM),
+		"--page-height", fmt.Sprintf("%.4fmm", heightMM),
+		"-", // read from stdin
+	}
+	cmd := exec.Command("rsvg-convert", args...)
+	cmd.Stdin = bytes.NewReader(svg)
+
+	var stdout, stderr bytes.Buffer
+	cmd.Stdout = &stdout
+	cmd.Stderr = &stderr
+
+	err := cmd.Run()
+	// rsvg-convert exits non-zero when writing to a non-terminal stdout; treat
+	// a non-empty PDF output as success regardless of exit code.
+	if stdout.Len() > 4 && string(stdout.Bytes()[:4]) == "%PDF" {
+		return stdout.Bytes(), nil
+	}
+	if err != nil {
+		return nil, fmt.Errorf("rsvg-convert: %w: %s", err, stderr.String())
+	}
+	return stdout.Bytes(), nil
+}
+
+// svgToPNGViaRsvg converts SVG to PNG at the given DPI using rsvg-convert.
+func svgToPNGViaRsvg(svg []byte, dpi float64) ([]byte, error) {
+	args := []string{
+		"-f", "png",
+		"-d", fmt.Sprintf("%.0f", dpi),
+		"-p", fmt.Sprintf("%.0f", dpi),
+		"-",
+	}
+	cmd := exec.Command("rsvg-convert", args...)
+	cmd.Stdin = bytes.NewReader(svg)
+	out, err := cmd.Output()
+	if err != nil {
+		var stderr []byte
+		if ee, ok := err.(*exec.ExitError); ok {
+			stderr = ee.Stderr
+		}
+		return nil, fmt.Errorf("rsvg-convert: %w: %s", err, stderr)
+	}
+	return out, nil
+}

internal/platepdf/svgparse.go

@@ -0,0 +1,54 @@
+package platepdf
+
+import (
+	"fmt"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+var svgAttrRE = regexp.MustCompile(`(?i)(\w+)\s*=\s*"([^"]*)"`)
+
+func svgAttrValue(openTag, name string) string {
+	for _, m := range svgAttrRE.FindAllStringSubmatch(openTag, -1) {
+		if strings.EqualFold(m[1], name) {
+			return m[2]
+		}
+	}
+	return ""
+}
+
+// svgViewportMM reads width/height from the root <svg> element (supports mm suffix).
+func svgViewportMM(data []byte) (widthMM, heightMM float64, err error) {
+	s := string(data)
+	open := strings.Index(s, "<svg")
+	if open < 0 {
+		return 0, 0, fmt.Errorf("invalid svg: missing root element")
+	}
+	tagEnd := strings.Index(s[open:], ">")
+	if tagEnd < 0 {
+		return 0, 0, fmt.Errorf("invalid svg: malformed root element")
+	}
+	tagEnd += open
+
+	w, err := parseLengthMM(svgAttrValue(s[open:tagEnd], "width"))
+	if err != nil {
+		return 0, 0, err
+	}
+	h, err := parseLengthMM(svgAttrValue(s[open:tagEnd], "height"))
+	if err != nil {
+		return 0, 0, err
+	}
+	return w, h, nil
+}
+
+func parseLengthMM(s string) (float64, error) {
+	s = strings.TrimSpace(s)
+	if s == "" {
+		return 0, fmt.Errorf("empty length")
+	}
+	if strings.HasSuffix(s, "mm") {
+		return strconv.ParseFloat(strings.TrimSuffix(s, "mm"), 64)
+	}
+	return strconv.ParseFloat(s, 64)
+}

internal/platepdf/svgparse_test.go

@@ -0,0 +1,13 @@
+package platepdf
+
+import "testing"
+
+func TestSVGViewportMM(t *testing.T) {
+	w, h, err := svgViewportMM([]byte(`<svg width="80mm" height="80mm" viewBox="0 0 1 1"></svg>`))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if w != 80 || h != 80 {
+		t.Fatalf("got %v×%v want 80×80", w, h)
+	}
+}

internal/server/admin/static/index.html

@@ -68,6 +68,13 @@
     }
     button:hover { filter: brightness(1.1); }
     button:disabled { opacity: 0.5; cursor: not-allowed; }
+    button.secondary {
+      background: transparent;
+      border: 1px solid var(--accent);
+      color: var(--accent);
+    }
+    button.secondary:hover { background: rgba(59, 130, 246, 0.12); filter: none; }
+    .btn-row { display: flex; flex-wrap: wrap; gap: 0.5rem; margin-top: 1rem; }
     button.danger {
       background: transparent;
       border: 1px solid var(--err);
@@ -364,9 +371,15 @@
               <input type="number" step="0.1" min="0" x-model.number="configForm.spacing_mm" @input="refreshLayoutPreview()">
             </div>
           </div>
-          <button type="submit" :disabled="configSaving || !configForm.plate_id || !configForm.item_id">
+          <div class="btn-row">
-            <span x-text="configSaving ? 'Speichere…' : 'Konfiguration speichern'"></span>
+            <button type="submit" :disabled="configSaving || !configForm.plate_id || !configForm.item_id">
-          </button>
+              <span x-text="configSaving ? 'Speichere…' : 'Konfiguration speichern'"></span>
+            </button>
+            <button type="button" class="secondary" @click="downloadLayoutPDF()"
+              :disabled="pdfGenerating || !layoutPreview || !configForm.plate_id || !configForm.item_id">
+              <span x-text="pdfGenerating ? 'PDF…' : 'PDF-Vorschau'"></span>
+            </button>
+          </div>
           <p class="msg-err" x-show="configError" x-text="configError"></p>
           <p class="msg-ok" x-show="configSuccess" x-text="configSuccess"></p>
         </form>
@@ -377,7 +390,7 @@
             <div class="layout-stats">
               <span><strong x-text="layoutPreview.count"></strong> Items passen</span>
               <span><strong x-text="layoutPreview.columns + ' × ' + layoutPreview.rows"></strong> Raster</span>
-              <span>Fußabdruck <strong x-text="layoutPreview.footprint_width_mm.toFixed(1) + ' mm'"></strong></span>
+              <span>Item <strong x-text="layoutPreview.footprint_width_mm.toFixed(1) + ' mm'"></strong></span>
               <span>Zellenabstand <strong x-text="layoutPreview.cell_width_mm.toFixed(1) + ' mm'"></strong></span>
               <span>Druckfläche <strong x-text="layoutPreview.printable_width_mm.toFixed(1) + ' × ' + layoutPreview.printable_height_mm.toFixed(1) + ' mm'"></strong></span>
             </div>
@@ -399,7 +412,13 @@
                   <h3 x-text="c.name || ('Konfiguration ' + c.id.slice(0, 8))"></h3>
                   <p class="muted" x-text="configSummary(c)"></p>
                 </div>
-                <button type="button" class="danger" @click="deleteConfiguration(c.id)">Löschen</button>
+                <div class="row-actions">
+                  <button type="button" class="secondary" @click="downloadConfigurationPDF(c.id)"
+                    :disabled="pdfGenerating || !!c.preview_error" x-show="c.preview && !c.preview_error">
+                    PDF
+                  </button>
+                  <button type="button" class="danger" @click="deleteConfiguration(c.id)">Löschen</button>
+                </div>
               </header>
               <p class="msg-err" x-show="c.preview_error" x-text="c.preview_error"></p>
               <div class="layout-preview-wrap" x-show="c.preview && !c.preview_error">
@@ -486,6 +505,7 @@
         },
         layoutPreview: null,
         layoutLoading: false,
+        pdfGenerating: false,
         _layoutTimer: null,
 
         apiUrl(path) {
@@ -714,6 +734,46 @@
           }
         },
 
+        async downloadBlob(path, filename) {
+          this.pdfGenerating = true;
+          this.configError = '';
+          try {
+            const res = await fetch(this.apiUrl(path));
+            if (!res.ok) {
+              let msg = res.statusText;
+              try {
+                const err = await res.json();
+                if (err.error) msg = err.error;
+              } catch (_) {}
+              throw new Error(msg);
+            }
+            const blob = await res.blob();
+            const url = URL.createObjectURL(blob);
+            const a = document.createElement('a');
+            a.href = url;
+            a.download = filename;
+            a.click();
+            URL.revokeObjectURL(url);
+          } catch (e) {
+            this.configError = String(e.message || e);
+          } finally {
+            this.pdfGenerating = false;
+          }
+        },
+
+        downloadLayoutPDF() {
+          const q = new URLSearchParams({
+            plate_id: this.configForm.plate_id,
+            item_id: this.configForm.item_id,
+            spacing_mm: String(Number(this.configForm.spacing_mm) || 0),
+          });
+          this.downloadBlob('/layout/pdf?' + q, 'layout-preview.pdf');
+        },
+
+        downloadConfigurationPDF(id) {
+          this.downloadBlob('/configurations/' + id + '/pdf', 'configuration-' + id.slice(0, 8) + '.pdf');
+        },
+
         async deleteConfiguration(id) {
           if (!confirm('Konfiguration wirklich löschen?')) return;
           this.configError = '';

internal/server/api/configuration.go

@@ -18,6 +18,7 @@ func registerConfigurationRoutes(mux *http.ServeMux, configs *store.Configuratio
 	mux.HandleFunc("DELETE /configurations/{id}", deleteConfiguration(configs))
 	mux.HandleFunc("GET /configurations/{id}/preview", previewConfiguration(configs, plates, items))
 	mux.HandleFunc("GET /layout/preview", layoutPreview(plates, items))
+	registerPDFRoutes(mux, configs, plates, items)
 }
 
 type configurationResponse struct {

internal/server/api/pdf.go

@@ -0,0 +1,120 @@
+package api
+
+import (
+	"errors"
+	"fmt"
+	"net/http"
+
+	"printer.backend/internal/model"
+	"printer.backend/internal/platepdf"
+	"printer.backend/internal/store"
+)
+
+func registerPDFRoutes(mux *http.ServeMux, configs *store.ConfigurationStore, plates *store.PlateStore, items *store.ItemStore) {
+	mux.HandleFunc("GET /layout/pdf", layoutPDF(plates, items))
+	mux.HandleFunc("GET /configurations/{id}/pdf", configurationPDF(configs, plates, items))
+}
+
+func layoutPDF(plates *store.PlateStore, items *store.ItemStore) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		plateID := r.URL.Query().Get("plate_id")
+		itemID := r.URL.Query().Get("item_id")
+		if plateID == "" || itemID == "" {
+			writeError(w, http.StatusBadRequest, errors.New("plate_id and item_id query params are required"))
+			return
+		}
+		spacing, err := parseSpacing(r.URL.Query().Get("spacing_mm"))
+		if err != nil {
+			writeError(w, http.StatusBadRequest, err)
+			return
+		}
+
+		plate, item, preview, svgPath, err := resolveLayoutPDF(plates, items, plateID, itemID, spacing)
+		if err != nil {
+			writeError(w, http.StatusBadRequest, err)
+			return
+		}
+
+		pdf, err := platepdf.Generate(plate, item.Spec, svgPath, preview)
+		if err != nil {
+			writeError(w, http.StatusInternalServerError, err)
+			return
+		}
+		servePDF(w, pdf, "layout-preview.pdf")
+	}
+}
+
+func configurationPDF(configs *store.ConfigurationStore, plates *store.PlateStore, items *store.ItemStore) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		id := r.PathValue("id")
+		c, err := configs.Get(id)
+		if err != nil {
+			writeError(w, http.StatusNotFound, err)
+			return
+		}
+
+		plate, item, preview, svgPath, err := resolveLayoutPDF(plates, items, c.PlateID, c.ItemID, c.SpacingMM)
+		if err != nil {
+			writeError(w, http.StatusBadRequest, err)
+			return
+		}
+
+		pdf, err := platepdf.Generate(plate, item.Spec, svgPath, preview)
+		if err != nil {
+			writeError(w, http.StatusInternalServerError, err)
+			return
+		}
+		name := c.Name
+		if name == "" {
+			name = "configuration-" + id[:8]
+		}
+		servePDF(w, pdf, sanitizeFilename(name)+".pdf")
+	}
+}
+
+func resolveLayoutPDF(plates *store.PlateStore, items *store.ItemStore, plateID, itemID string, spacingMM float64) (
+	plate model.Plate, item model.Item, preview model.LayoutPreview, svgPath string, err error,
+) {
+	plate, err = findPlate(plates, plateID)
+	if err != nil {
+		return plate, item, preview, "", err
+	}
+	item, err = items.Get(itemID)
+	if err != nil {
+		return plate, item, preview, "", err
+	}
+	svgPath, err = items.SVGPath(itemID)
+	if err != nil {
+		return plate, item, preview, "", err
+	}
+	preview, err = buildPreview(plates, items, plateID, itemID, spacingMM)
+	if err != nil {
+		return plate, item, preview, "", err
+	}
+	preview.PlateID = plateID
+	preview.ItemID = itemID
+	return plate, item, preview, svgPath, nil
+}
+
+func servePDF(w http.ResponseWriter, pdf []byte, filename string) {
+	w.Header().Set("Content-Type", "application/pdf")
+	w.Header().Set("Content-Disposition", fmt.Sprintf(`attachment; filename="%s"`, filename))
+	w.Header().Set("Cache-Control", "no-cache")
+	_, _ = w.Write(pdf)
+}
+
+func sanitizeFilename(name string) string {
+	var b []byte
+	for i := 0; i < len(name); i++ {
+		c := name[i]
+		if (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || (c >= '0' && c <= '9') || c == '-' || c == '_' {
+			b = append(b, c)
+		} else if c == ' ' {
+			b = append(b, '_')
+		}
+	}
+	if len(b) == 0 {
+		return "preview"
+	}
+	return string(b)
+}