Remove outdated toc_pages.txt, add new Go modules for IHK Chemnitz PDF rendering including diagrams, tables, and TOC functionality.

diagram.go

@@ -0,0 +1,68 @@
+package main
+
+import (
+	"bytes"
+	"compress/zlib"
+	"crypto/sha256"
+	"encoding/base64"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"path/filepath"
+)
+
+// RenderDiagramViaKroki converts a diagram source (Mermaid, PlantUML, etc.)
+// to a PNG image using the Kroki.io public rendering service and caches the
+// result in the OS temp directory.
+//
+// The cache key is the SHA-256 hash of the diagram source, so unchanged
+// diagrams are not re-fetched between runs.
+//
+// Supported languages: "mermaid", "plantuml" / "puml"
+func RenderDiagramViaKroki(lang, code string) (string, error) {
+	if lang == "puml" {
+		lang = "plantuml"
+	}
+
+	// Kroki encoding: deflate (zlib) then base64url
+	var buf bytes.Buffer
+	w := zlib.NewWriter(&buf)
+	if _, err := w.Write([]byte(code)); err != nil {
+		return "", fmt.Errorf("zlib write: %w", err)
+	}
+	if err := w.Close(); err != nil {
+		return "", fmt.Errorf("zlib close: %w", err)
+	}
+	encoded := base64.URLEncoding.EncodeToString(buf.Bytes())
+	url := fmt.Sprintf("https://kroki.io/%s/png/%s", lang, encoded)
+
+	// Deterministic cache path based on content hash
+	hash := fmt.Sprintf("%x", sha256.Sum256([]byte(code)))
+	cachePath := filepath.Join(os.TempDir(), "ihk_kroki_"+hash+".png")
+
+	if _, err := os.Stat(cachePath); err == nil {
+		return cachePath, nil // cache hit
+	}
+
+	resp, err := http.Get(url) //nolint:gosec // URL is constructed from user content, acceptable here
+	if err != nil {
+		return "", fmt.Errorf("kroki request: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return "", fmt.Errorf("kroki returned HTTP %d", resp.StatusCode)
+	}
+
+	out, err := os.Create(cachePath)
+	if err != nil {
+		return "", fmt.Errorf("cache file create: %w", err)
+	}
+	defer out.Close()
+
+	if _, err = io.Copy(out, resp.Body); err != nil {
+		return "", fmt.Errorf("cache file write: %w", err)
+	}
+	return cachePath, nil
+}