Editor: font-size presets + image insert/export support

Two editor features that were in flight alongside the sound work:
- FontSize TipTap extension (rides on textStyle) with Small/Normal/Large/
  Title presets in the toolbar; StatusBar + CSS support
- Image handling: internal/images handler, upload route + config, client
  API, EditorCore wiring, and md/html/docx export support for images

Claude-Session: https://claude.ai/code/session_016Yr6jELuRc7hyzYLccQKZd

internal/images/handler.go

@@ -0,0 +1,132 @@
+// Package images implements a tiny content-addressed image store: writers upload
+// images from the editor, they're saved to disk under the configured directory,
+// and served back by hashed filename. Content addressing means the same image
+// pasted twice is stored once, and URLs are stable and cacheable forever.
+package images
+
+import (
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"io"
+	"net/http"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/go-chi/chi/v5"
+)
+
+// maxUploadBytes caps a single image at 10 MiB — generous for a writing tool,
+// small enough to keep a careless paste from filling the disk.
+const maxUploadBytes = 10 << 20
+
+// extByContentType maps the image types we accept to a canonical extension. The
+// allowlist doubles as validation: anything not here is rejected.
+var extByContentType = map[string]string{
+	"image/png":     ".png",
+	"image/jpeg":    ".jpg",
+	"image/gif":     ".gif",
+	"image/webp":    ".webp",
+	"image/svg+xml": ".svg",
+}
+
+// Handler serves the upload + fetch endpoints, backed by a directory on disk.
+type Handler struct {
+	dir string
+}
+
+// New constructs a Handler, ensuring the storage directory exists.
+func New(dir string) (*Handler, error) {
+	if err := os.MkdirAll(dir, 0o755); err != nil {
+		return nil, err
+	}
+	return &Handler{dir: dir}, nil
+}
+
+// Routes mounts the image endpoints. Mount under "/images" so the full paths are
+// POST /api/images (upload) and GET /api/images/{name} (fetch).
+func (h *Handler) Routes() chi.Router {
+	r := chi.NewRouter()
+	r.Post("/", h.upload)
+	r.Get("/{name}", h.serve)
+	return r
+}
+
+// upload accepts a single multipart "image" field, sniffs and validates its
+// type, and writes it under a content hash so identical images dedupe. Responds
+// with the served URL the editor inserts.
+func (h *Handler) upload(w http.ResponseWriter, r *http.Request) {
+	r.Body = http.MaxBytesReader(w, r.Body, maxUploadBytes)
+	file, _, err := r.FormFile("image")
+	if err != nil {
+		http.Error(w, "expected an 'image' file field", http.StatusBadRequest)
+		return
+	}
+	defer file.Close()
+
+	data, err := io.ReadAll(file)
+	if err != nil {
+		http.Error(w, "could not read upload", http.StatusBadRequest)
+		return
+	}
+
+	// Trust a sniff over the client-declared type. SVG isn't reliably sniffable
+	// (DetectContentType returns text/plain or text/xml), so fall back to a
+	// lightweight tag check for it.
+	ct := http.DetectContentType(data)
+	ext, ok := extByContentType[ct]
+	if !ok {
+		if looksLikeSVG(data) {
+			ext, ok = ".svg", true
+		}
+	}
+	if !ok {
+		http.Error(w, "unsupported image type", http.StatusUnsupportedMediaType)
+		return
+	}
+
+	sum := sha256.Sum256(data)
+	name := hex.EncodeToString(sum[:])[:32] + ext
+	path := filepath.Join(h.dir, name)
+
+	// Skip the write if this exact content is already stored.
+	if _, statErr := os.Stat(path); errors.Is(statErr, os.ErrNotExist) {
+		if err := os.WriteFile(path, data, 0o644); err != nil {
+			http.Error(w, "could not store image", http.StatusInternalServerError)
+			return
+		}
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	_ = json.NewEncoder(w).Encode(map[string]string{"url": "/api/images/" + name})
+}
+
+// serve returns a stored image by its hashed filename. The filename is validated
+// to be a bare name (no path separators) so it can't escape the storage dir, and
+// served with a long-lived cache header since content-addressed URLs never change.
+func (h *Handler) serve(w http.ResponseWriter, r *http.Request) {
+	name := chi.URLParam(r, "name")
+	if name == "" || name != filepath.Base(name) || strings.ContainsAny(name, `/\`) {
+		http.NotFound(w, r)
+		return
+	}
+	path := filepath.Join(h.dir, filepath.Base(name))
+	if _, err := os.Stat(path); err != nil {
+		http.NotFound(w, r)
+		return
+	}
+	w.Header().Set("Cache-Control", "public, max-age=31536000, immutable")
+	http.ServeFile(w, r, path)
+}
+
+// looksLikeSVG does a cheap check for an <svg root tag near the start of the
+// file, since DetectContentType doesn't recognize SVG.
+func looksLikeSVG(data []byte) bool {
+	head := data
+	if len(head) > 512 {
+		head = head[:512]
+	}
+	return strings.Contains(strings.ToLower(string(head)), "<svg")
+}

internal/images/handler_test.go

@@ -0,0 +1,97 @@
+package images
+
+import (
+	"bytes"
+	"encoding/json"
+	"mime/multipart"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+)
+
+// a 1x1 transparent PNG.
+var pngBytes = []byte{
+	0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a, 0x00, 0x00, 0x00, 0x0d, 0x49, 0x48, 0x44, 0x52,
+	0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x01, 0x08, 0x06, 0x00, 0x00, 0x00, 0x1f, 0x15, 0xc4,
+	0x89, 0x00, 0x00, 0x00, 0x0d, 0x49, 0x44, 0x41, 0x54, 0x78, 0x9c, 0x62, 0x00, 0x01, 0x00, 0x00,
+	0x05, 0x00, 0x01, 0x0d, 0x0a, 0x2d, 0xb4, 0x00, 0x00, 0x00, 0x00, 0x49, 0x45, 0x4e, 0x44, 0xae,
+	0x42, 0x60, 0x82,
+}
+
+func uploadReq(t *testing.T, field string, data []byte) *http.Request {
+	t.Helper()
+	var buf bytes.Buffer
+	mw := multipart.NewWriter(&buf)
+	fw, err := mw.CreateFormFile(field, "x.png")
+	if err != nil {
+		t.Fatal(err)
+	}
+	fw.Write(data)
+	mw.Close()
+	req := httptest.NewRequest(http.MethodPost, "/", &buf)
+	req.Header.Set("Content-Type", mw.FormDataContentType())
+	return req
+}
+
+func TestUploadAndServe(t *testing.T) {
+	h, err := New(t.TempDir())
+	if err != nil {
+		t.Fatal(err)
+	}
+	r := h.Routes()
+
+	// Upload a PNG → expect a JSON url under /api/images/.
+	rec := httptest.NewRecorder()
+	r.ServeHTTP(rec, uploadReq(t, "image", pngBytes))
+	if rec.Code != http.StatusOK {
+		t.Fatalf("upload code=%d body=%s", rec.Code, rec.Body)
+	}
+	var resp struct{ URL string }
+	if err := json.Unmarshal(rec.Body.Bytes(), &resp); err != nil {
+		t.Fatal(err)
+	}
+	if !strings.HasPrefix(resp.URL, "/api/images/") || !strings.HasSuffix(resp.URL, ".png") {
+		t.Fatalf("unexpected url %q", resp.URL)
+	}
+
+	// The same content uploaded again dedupes to the same URL.
+	rec2 := httptest.NewRecorder()
+	r.ServeHTTP(rec2, uploadReq(t, "image", pngBytes))
+	var resp2 struct{ URL string }
+	json.Unmarshal(rec2.Body.Bytes(), &resp2)
+	if resp2.URL != resp.URL {
+		t.Fatalf("expected dedup to same url, got %q vs %q", resp2.URL, resp.URL)
+	}
+
+	// Fetch it back.
+	name := strings.TrimPrefix(resp.URL, "/api/images/")
+	rec3 := httptest.NewRecorder()
+	r.ServeHTTP(rec3, httptest.NewRequest(http.MethodGet, "/"+name, nil))
+	if rec3.Code != http.StatusOK {
+		t.Fatalf("serve code=%d", rec3.Code)
+	}
+	if !bytes.Equal(rec3.Body.Bytes(), pngBytes) {
+		t.Fatal("served bytes differ from uploaded")
+	}
+}
+
+func TestUploadRejectsNonImage(t *testing.T) {
+	h, _ := New(t.TempDir())
+	r := h.Routes()
+	rec := httptest.NewRecorder()
+	r.ServeHTTP(rec, uploadReq(t, "image", []byte("this is plainly not an image at all")))
+	if rec.Code != http.StatusUnsupportedMediaType {
+		t.Fatalf("expected 415, got %d", rec.Code)
+	}
+}
+
+func TestServeMissing(t *testing.T) {
+	h, _ := New(t.TempDir())
+	r := h.Routes()
+	rec := httptest.NewRecorder()
+	r.ServeHTTP(rec, httptest.NewRequest(http.MethodGet, "/deadbeef.png", nil))
+	if rec.Code != http.StatusNotFound {
+		t.Fatalf("expected 404, got %d", rec.Code)
+	}
+}