Add semantic block parser and PDF export

scripts/export-pdf.mjs

@@ -0,0 +1,64 @@
+import { existsSync, mkdirSync } from "node:fs";
+import path from "node:path";
+import { spawnSync } from "node:child_process";
+import { fileURLToPath } from "node:url";
+
+const repoRoot = path.resolve(fileURLToPath(new URL("..", import.meta.url)));
+const filterPath = path.join(repoRoot, "scripts", "pandoc-filters", "semantic-blocks.lua");
+const preamblePath = path.join(repoRoot, "scripts", "pandoc-templates", "semantic-preamble.tex");
+
+function usage() {
+  console.error("Usage: node scripts/export-pdf.mjs <post.md> [--out output.pdf]");
+}
+
+function parseArgs(argv) {
+  const args = [...argv];
+  const input = args.find((arg) => !arg.startsWith("--"));
+  const outIndex = args.indexOf("--out");
+  const output = outIndex >= 0 ? args[outIndex + 1] : "";
+  return { input, output };
+}
+
+const { input, output } = parseArgs(process.argv.slice(2));
+
+if (!input) {
+  usage();
+  process.exit(2);
+}
+
+const inputPath = path.resolve(input);
+if (!existsSync(inputPath)) {
+  console.error(`Input file not found: ${inputPath}`);
+  process.exit(2);
+}
+
+const outputPath = path.resolve(
+  output || path.join(path.dirname(inputPath), `${path.basename(inputPath, path.extname(inputPath))}.pdf`),
+);
+mkdirSync(path.dirname(outputPath), { recursive: true });
+
+const pandocArgs = [
+  inputPath,
+  "--from",
+  "markdown+fenced_code_attributes+tex_math_dollars+tex_math_single_backslash+footnotes+raw_html",
+  "--pdf-engine=lualatex",
+  "--lua-filter",
+  filterPath,
+  "--include-in-header",
+  preamblePath,
+  "--output",
+  outputPath,
+];
+
+const result = spawnSync("pandoc", pandocArgs, { stdio: "inherit" });
+
+if (result.error?.code === "ENOENT") {
+  console.error("pandoc is not installed or is not on PATH. Install pandoc and a LuaLaTeX distribution first.");
+  process.exit(127);
+}
+
+if (result.status !== 0) {
+  process.exit(result.status ?? 1);
+}
+
+console.log(`Wrote ${outputPath}`);