fix: serve map sprites globally instead of per-map duplicates (#285)

* fix: serve map sprites globally instead of per-map duplicates

Sprites (icon sheets for MapLibre vector styles) were generated per-map
and stored in each map's styles/ directory. The content is identical for
every map since it comes from embedded icons. This caused wasted disk
I/O during import/restyle and made sprite URLs per-map when they should
be global (like fonts already are).

Backend:
- Add GenerateSpriteBytes() for in-memory sprite generation
- Add GET /images/maps/sprites/:name handler with sync.Once lazy init
- Remove WriteSpriteFiles calls from pipeline and restyle stages
- Remove StylesPrefix from StyleConfig (only used for sprites)
- Style JSON sprite path now "images/maps/sprites/sprite" (global)

Frontend:
- Replace transformStyle with fetchStyle that fetches style JSON and
  patches sprite/glyphs URLs to absolute before passing to MapLibre.
  leaflet-maplibre-gl doesn't forward transformStyle to the underlying
  Map constructor's setStyle call, so it never actually ran.

* fix: surface sprite generation errors instead of swallowing them

Author: fank

internal/maptool/metadata.go

@@ -104,11 +104,9 @@ func NewGenerateStylesStage() Stage {
 
 			mapBase := "images/maps/" + worldName
 			tilesPrefix := mapBase
-			stylesPrefix := mapBase
 			stylesDir := job.OutputDir
 			if job.SubDirs {
 				tilesPrefix = mapBase + "/tiles"
-				stylesPrefix = mapBase + "/styles"
 				stylesDir = job.StylesOutputDir()
 				if err := os.MkdirAll(stylesDir, 0755); err != nil {
 					return fmt.Errorf("create styles dir: %w", err)
@@ -118,7 +116,6 @@ func NewGenerateStylesStage() Stage {
 			styleCfg := StyleConfig{
 				WorldName:      worldName,
 				URLPrefix:      tilesPrefix,
-				StylesPrefix:   stylesPrefix,
 				VectorLayers:   job.VectorLayers,
 				HasSatellite:   true,
 				HasHeightmap:   job.HasHeightmap,
@@ -146,10 +143,6 @@ func NewGenerateStylesStage() Stage {
 			}
 			job.HasMaplibre = true
 
-			if err := WriteSpriteFiles(stylesDir); err != nil {
-				return fmt.Errorf("write sprites: %w", err)
-			}
-
 			return nil
 		},
 	}

internal/maptool/metadata_test.go

@@ -136,9 +136,6 @@ func TestNewGenerateStylesStage(t *testing.T) {
 		_, err := os.Stat(filepath.Join(dir, name))
 		assert.NoError(t, err, "expected %s to exist", name)
 	}
-	// Verify sprites exist
-	_, err = os.Stat(filepath.Join(dir, "sprite.json"))
-	assert.NoError(t, err)
 }
 
 func TestNewGenerateStylesStage_SubDirs(t *testing.T) {

internal/maptool/restyle.go

@@ -43,7 +43,6 @@ func RestyleWorld(mapsDir, worldName string) error {
 	styleCfg := StyleConfig{
 		WorldName:      meta.WorldName,
 		URLPrefix:      mapBase + "/tiles",
-		StylesPrefix:   mapBase + "/styles",
 		VectorLayers:   meta.FeatureLayers,
 		HasSatellite:   hasFile("satellite.pmtiles"),
 		HasHeightmap:   hasFile("heightmap.pmtiles"),
@@ -80,10 +79,5 @@ func RestyleWorld(mapsDir, worldName string) error {
 		}
 	}
 
-	// 5. Regenerate sprites
-	if err := WriteSpriteFiles(stylesDir); err != nil {
-		return fmt.Errorf("write sprites: %w", err)
-	}
-
 	return nil
 }

internal/maptool/restyle_test.go

@@ -94,10 +94,4 @@ func TestRestyleWorld_ProbesTileFiles(t *testing.T) {
 		require.NoError(t, err, "expected %s to exist", name)
 		assert.Greater(t, info.Size(), int64(0))
 	}
-
-	// Should have generated sprites
-	for _, name := range []string{"sprite.json", "sprite.png", "sprite-dark.json", "sprite-dark.png"} {
-		_, err := os.Stat(filepath.Join(worldDir, "styles", name))
-		assert.NoError(t, err, "expected %s to exist", name)
-	}
 }

internal/maptool/sprite.go

@@ -143,6 +143,34 @@ func GenerateSprite(blacken bool) (*image.NRGBA, map[string]spriteEntry) {
 	return sheet, manifest
 }
 
+// GenerateSpriteBytes returns all sprite files as in-memory byte slices.
+// Keys: "sprite.json", "sprite.png", "sprite-dark.json", "sprite-dark.png".
+func GenerateSpriteBytes() (map[string][]byte, error) {
+	result := make(map[string][]byte, 4)
+	for _, v := range []struct {
+		prefix  string
+		blacken bool
+	}{
+		{"sprite", true},
+		{"sprite-dark", false},
+	} {
+		img, manifest := GenerateSprite(v.blacken)
+
+		data, err := json.MarshalIndent(manifest, "", "  ")
+		if err != nil {
+			return nil, fmt.Errorf("marshal %s.json: %w", v.prefix, err)
+		}
+		result[v.prefix+".json"] = data
+
+		var buf bytes.Buffer
+		if err := png.Encode(&buf, img); err != nil {
+			return nil, fmt.Errorf("encode %s.png: %w", v.prefix, err)
+		}
+		result[v.prefix+".png"] = buf.Bytes()
+	}
+	return result, nil
+}
+
 // WriteSpriteFiles generates sprite sheets at native 64px and writes to dir:
 //   - sprite.json, sprite.png (blackened — for light themes)
 //   - sprite-dark.json, sprite-dark.png (original — for dark themes)

internal/maptool/styles.go

@@ -1157,7 +1157,6 @@ const (
 type StyleConfig struct {
 	WorldName        string
 	URLPrefix        string // e.g. "images/maps/stratis/tiles" — base for tile sources
-	StylesPrefix     string // e.g. "images/maps/stratis/styles" — base for sprite files
 	VectorLayers     []string
 	HasSatellite     bool
 	HasHeightmap     bool
@@ -1214,7 +1213,7 @@ func GenerateStyleDocument(cfg StyleConfig, variant StyleVariant) map[string]int
 		"name":    cfg.WorldName + "-" + string(variant),
 		"sources": sources,
 		"layers":  layers,
-		"sprite":  assetPath(cfg.StylesPrefix, spriteName),
+		"sprite":  "images/maps/sprites/" + spriteName,
 		"glyphs":  cfg.GlyphsURL,
 	}
 	return doc

internal/maptool/styles_test.go

@@ -203,7 +203,6 @@ func TestGenerateStyleDocument_Structure(t *testing.T) {
 	cfg := StyleConfig{
 		WorldName:    "altis",
 		URLPrefix:    "images/maps/altis/tiles",
-		StylesPrefix: "images/maps/altis/styles",
 		VectorLayers: []string{"sea", "road", "namecity"},
 		HasSatellite: true,
 		GlyphsURL:    "images/maps/fonts/{fontstack}/{range}.pbf",
@@ -215,7 +214,7 @@ func TestGenerateStyleDocument_Structure(t *testing.T) {
 	assert.Equal(t, "altis-color-relief", doc["name"])
 	assert.NotNil(t, doc["sources"])
 	assert.NotNil(t, doc["layers"])
-	assert.Equal(t, "images/maps/altis/styles/sprite", doc["sprite"])
+	assert.Equal(t, "images/maps/sprites/sprite", doc["sprite"])
 	assert.Equal(t, "images/maps/fonts/{fontstack}/{range}.pbf", doc["glyphs"])
 }
 

internal/server/handler.go

@@ -15,6 +15,7 @@ import (
 	"path/filepath"
 	"strconv"
 	"strings"
+	"sync"
 	"time"
 
 	"github.com/OCAP2/web/internal/maptool"
@@ -50,6 +51,10 @@ type Handler struct {
 	openIDCache       openid.DiscoveryCache
 	openIDNonceStore  openid.NonceStore
 	steamAPIBaseURL   string // override for testing; empty uses default
+
+	spriteOnce    sync.Once
+	spriteFiles   map[string][]byte
+	spriteInitErr error
 }
 
 // HandlerOption configures the Handler
@@ -157,6 +162,11 @@ func NewHandler(
 		hdlr.GetFont,
 		hdlr.cacheControl(CacheDuration),
 	)
+	g.GET(
+		"/images/maps/sprites/:name",
+		hdlr.GetSprite,
+		hdlr.cacheControl(CacheDuration),
+	)
 	g.GET(
 		"/images/maps/*",
 		hdlr.GetMapTitle,
@@ -442,6 +452,27 @@ func (h *Handler) GetMarker(c echo.Context) error {
 	return c.Stream(http.StatusOK, ct, img)
 }
 
+func (h *Handler) GetSprite(c echo.Context) error {
+	h.spriteOnce.Do(func() {
+		h.spriteFiles, h.spriteInitErr = maptool.GenerateSpriteBytes()
+	})
+	if h.spriteInitErr != nil {
+		return fmt.Errorf("generate sprites: %w", h.spriteInitErr)
+	}
+
+	name := c.Param("name")
+	data, ok := h.spriteFiles[name]
+	if !ok {
+		return echo.ErrNotFound
+	}
+
+	ct := "application/json"
+	if strings.HasSuffix(name, ".png") {
+		ct = "image/png"
+	}
+	return c.Blob(http.StatusOK, ct, data)
+}
+
 func (h *Handler) GetFont(c echo.Context) error {
 	fontstack := filepath.Base(c.Param("fontstack"))
 	rangeParam := filepath.Base(c.Param("range"))

internal/server/handler_admin_test.go

@@ -19,7 +19,7 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
-func setupAdminTest(t *testing.T) (Handler, *Operation) {
+func setupAdminTest(t *testing.T) (*Handler, *Operation) {
 	t.Helper()
 	dir := t.TempDir()
 	repo, err := NewRepoOperation(filepath.Join(dir, "test.db"))
@@ -34,7 +34,7 @@ func setupAdminTest(t *testing.T) (Handler, *Operation) {
 	}
 	require.NoError(t, repo.Store(t.Context(), op))
 
-	hdlr := Handler{
+	hdlr := &Handler{
 		repoOperation: repo,
 		setting:       Setting{Secret: "test-secret", Data: dir},
 		jwt:           NewJWTManager("test-secret", time.Hour),
@@ -391,7 +391,7 @@ func TestAdminFlow_LoginEditDelete(t *testing.T) {
 	jwtMgr := NewJWTManager("test-secret", time.Hour)
 
 	e := echo.New()
-	hdlr := Handler{
+	hdlr := &Handler{
 		repoOperation: repo,
 		setting:       setting,
 		jwt:           jwtMgr,

internal/server/handler_test.go

@@ -1518,6 +1518,44 @@ func TestGetFont(t *testing.T) {
 	assert.Equal(t, http.StatusOK, rec.Code)
 }
 
+func TestGetSprite(t *testing.T) {
+	hdlr := Handler{}
+
+	e := echo.New()
+
+	tests := []struct {
+		name        string
+		wantStatus  int
+		wantType    string
+	}{
+		{"sprite.json", http.StatusOK, "application/json"},
+		{"sprite.png", http.StatusOK, "image/png"},
+		{"sprite-dark.json", http.StatusOK, "application/json"},
+		{"sprite-dark.png", http.StatusOK, "image/png"},
+		{"nonexistent.json", http.StatusNotFound, ""},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			req := httptest.NewRequest(http.MethodGet, "/images/maps/sprites/"+tt.name, nil)
+			rec := httptest.NewRecorder()
+			c := e.NewContext(req, rec)
+			c.SetParamNames("name")
+			c.SetParamValues(tt.name)
+
+			err := hdlr.GetSprite(c)
+			if tt.wantStatus == http.StatusNotFound {
+				assert.Error(t, err)
+			} else {
+				assert.NoError(t, err)
+				assert.Equal(t, tt.wantStatus, rec.Code)
+				assert.Contains(t, rec.Header().Get("Content-Type"), tt.wantType)
+				assert.Greater(t, rec.Body.Len(), 0)
+			}
+		})
+	}
+}
+
 func TestWithMapTool(t *testing.T) {
 	jm := maptool.NewJobManager(t.TempDir(), func() *maptool.Pipeline {
 		return maptool.NewPipeline(nil)