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/frontmatter/frontmatter.go

@@ -0,0 +1,77 @@
+// Package frontmatter parses the key: value front-matter block that may
+// open a mopac-pdf markdown input (delimited by --- lines).
+package frontmatter
+
+import (
+	"fmt"
+	"strings"
+)
+
+// Meta is the parsed front-matter. The well-known keys mopac-pdf templates
+// consume are Title, Subtitle, Author, Date, Classification and Template;
+// anything else found in the block is kept in Extra (never an error: the
+// currency of this stack is loose markdown).
+type Meta struct {
+	Title          string
+	Subtitle       string
+	Author         string
+	Date           string
+	Classification string
+	Template       string
+	Extra          map[string]string
+}
+
+// Split separates an optional front-matter block from the markdown body and
+// parses it. Input without a leading --- line is all body, empty Meta.
+func Split(input string) (Meta, string, error) {
+	var meta Meta
+	first, rest, ok := strings.Cut(input, "\n")
+	if strings.TrimRight(first, "\r") != "---" || !ok {
+		return meta, input, nil
+	}
+	end := -1
+	var block []string
+	for i, line := range strings.Split(rest, "\n") {
+		trimmed := strings.TrimRight(line, "\r")
+		if trimmed == "---" || trimmed == "..." {
+			end = i
+			break
+		}
+		block = append(block, trimmed)
+	}
+	if end < 0 {
+		return meta, input, fmt.Errorf("frontmatter: opening --- without closing ---")
+	}
+	body := strings.Join(strings.Split(rest, "\n")[end+1:], "\n")
+	body = strings.TrimPrefix(body, "\n")
+	meta.Extra = map[string]string{}
+	for _, line := range block {
+		line = strings.TrimSpace(line)
+		if line == "" || strings.HasPrefix(line, "#") {
+			continue
+		}
+		key, value, ok := strings.Cut(line, ":")
+		if !ok {
+			return meta, "", fmt.Errorf("frontmatter: not a key: value line: %q", line)
+		}
+		key = strings.TrimSpace(key)
+		value = strings.Trim(strings.TrimSpace(value), `"'`)
+		switch strings.ToLower(key) {
+		case "title":
+			meta.Title = value
+		case "subtitle":
+			meta.Subtitle = value
+		case "author":
+			meta.Author = value
+		case "date":
+			meta.Date = value
+		case "classification":
+			meta.Classification = value
+		case "template":
+			meta.Template = value
+		default:
+			meta.Extra[key] = value
+		}
+	}
+	return meta, body, nil
+}