mopac-pdf v0: markdown to beautiful PDFs via digest-pinned typst

Go CLI that turns the markdown currency of this stack (Redmine notes,
Discourse posts, briefing output) into typeset PDFs: two embedded typst
templates (report with title page/TOC/headers, dense brief), front-matter
(title/subtitle/author/date/classification/template), GFM tables, and
bar charts rendered in pure Go (go-chart) from fenced chart data blocks.
Engine is a prebuilt typst 0.15.1 container pinned by digest and run
--network none; PDF bytes to stdout or -o. Exit codes 0/1/2.

All dev in docker (dev.sh/Makefile); unit tests + golden typst fixtures
plus a host-side smoke against the real engine container.

Generated with Crush

Assisted-by: Crush:glm-5.2

internal/chart/chart.go

@@ -0,0 +1,61 @@
+// Package chart renders ```chart data blocks into PNG assets using the
+// permissive go-chart library (pure Go). v0 proves one chart type end to
+// end: bar.
+package chart
+
+import (
+	"bytes"
+	"fmt"
+
+	"github.com/wcharczuk/go-chart/v2"
+	"github.com/wcharczuk/go-chart/v2/drawing"
+
+	"ukrrs.com/mopac/pdf/internal/markdown"
+)
+
+// accent matches the shipped templates (#1f4e79).
+var accent = drawing.Color{R: 31, G: 78, B: 121, A: 255}
+
+// Bar renders a bar chart to PNG bytes. Unknown chart types are an error:
+// v0 is deliberately one type, proven end to end.
+func Bar(c *markdown.Chart) ([]byte, error) {
+	if c == nil || len(c.Labels) == 0 {
+		return nil, fmt.Errorf("chart: no data points")
+	}
+	if c.Type != "bar" {
+		return nil, fmt.Errorf("chart: unsupported type %q (v0: bar only)", c.Type)
+	}
+	values := make([]chart.Value, len(c.Labels))
+	for i, label := range c.Labels {
+		values[i] = chart.Value{
+			Value: c.Values[i],
+			Label: label,
+			Style: chart.Style{FillColor: accent, StrokeColor: accent, StrokeWidth: 0.5},
+		}
+	}
+	yfmt := chart.ValueFormatter(chart.FloatValueFormatter)
+	if c.Unit != "" {
+		unit := c.Unit
+		yfmt = func(v interface{}) string {
+			return chart.FloatValueFormatter(v) + " " + unit
+		}
+	}
+	graph := chart.BarChart{
+		Title: c.Title,
+		Background: chart.Style{
+			Padding: chart.Box{Top: 24, Left: 12, Right: 12, Bottom: 8},
+		},
+		XAxis:      chart.Style{FontSize: 9, FontColor: drawing.Color{R: 60, G: 60, B: 60, A: 255}},
+		YAxis:      chart.YAxis{ValueFormatter: yfmt, Style: chart.Style{FontSize: 8}},
+		BarWidth:   48,
+		BarSpacing: 26,
+		Height:     320,
+		Width:      260 + len(values)*74,
+		Bars:       values,
+	}
+	var buf bytes.Buffer
+	if err := graph.Render(chart.PNG, &buf); err != nil {
+		return nil, fmt.Errorf("chart: render: %w", err)
+	}
+	return buf.Bytes(), nil
+}

internal/chart/chart_test.go

@@ -0,0 +1,52 @@
+package chart
+
+import (
+	"bytes"
+	"image"
+	_ "image/png"
+	"testing"
+
+	"ukrrs.com/mopac/pdf/internal/markdown"
+)
+
+func TestBarPNG(t *testing.T) {
+	c := &markdown.Chart{
+		Type:   "bar",
+		Title:  "Revenue",
+		Unit:   "$K",
+		Labels: []string{"Q1", "Q2", "Q3"},
+		Values: []float64{10, 20, 15},
+	}
+	png, err := Bar(c)
+	if err != nil {
+		t.Fatalf("render: %v", err)
+	}
+	if !bytes.HasPrefix(png, []byte{0x89, 'P', 'N', 'G'}) {
+		t.Fatalf("not a PNG: % x", png[:4])
+	}
+	img, _, err := image.Decode(bytes.NewReader(png))
+	if err != nil {
+		t.Fatalf("decode: %v", err)
+	}
+	b := img.Bounds()
+	if b.Dx() < 300 || b.Dy() < 200 {
+		t.Fatalf("unexpected dimensions %dx%d", b.Dx(), b.Dy())
+	}
+}
+
+func TestBarRejectsUnknownType(t *testing.T) {
+	c := &markdown.Chart{Type: "pie", Labels: []string{"a"}, Values: []float64{1}}
+	if _, err := Bar(c); err == nil {
+		t.Fatal("pie must be rejected in v0")
+	}
+}
+
+func TestBarRejectsEmpty(t *testing.T) {
+	if _, err := Bar(nil); err == nil {
+		t.Fatal("nil chart must be rejected")
+	}
+	c := &markdown.Chart{Type: "bar"}
+	if _, err := Bar(c); err == nil {
+		t.Fatal("chart without data must be rejected")
+	}
+}