refactor: share trace, error boundary, and proxy http helpers

Lift the trace-to-shape geometry into @tts/mesh (traceToShape/
traceToUvBounds), parameterized by scale so the web token viewer and
@tts/tabletop share one implementation. Move the CORS proxy HTTP helpers
(assetUrl, resolveAssetUrl, traceImage) into a new @tts/http package, and
make @tts/tabletop's ErrorBoundary the single source used by the web app.

This removes the duplicated ErrorBoundary, assetUrl, tabletopHttp, and
trace-to-shape code from apps/web and packages/tabletop.

packages/http/package.json

@@ -0,0 +1,28 @@
+{
+  "name": "@tts/http",
+  "version": "0.0.0",
+  "private": true,
+  "type": "module",
+  "main": "./dist/index.js",
+  "types": "./dist/index.d.ts",
+  "exports": {
+    ".": {
+      "types": "./dist/index.d.ts",
+      "import": "./dist/index.js"
+    }
+  },
+  "scripts": {
+    "build": "tsc -p tsconfig.json",
+    "typecheck": "tsc -p tsconfig.json --noEmit",
+    "test": "vitest run",
+    "lint": "echo \"no lint configured\""
+  },
+  "dependencies": {
+    "@tts/shared": "workspace:*",
+    "bson": "^7.3.1"
+  },
+  "devDependencies": {
+    "typescript": "^5.7.2",
+    "vitest": "^4.1.10"
+  }
+}

packages/http/src/asset.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, it } from 'vitest';
-import { resolveAssetUrl } from './http.js';
+import { resolveAssetUrl } from './asset.js';
 
 describe('resolveAssetUrl', () => {
   it('passes absolute urls through unchanged', () => {

packages/http/src/asset.ts

@@ -0,0 +1,26 @@
+/**
+ * Asset URL helpers for the host app's CORS-safe asset proxy (`/asset`).
+ * Shared by the web viewers and `@tts/tabletop`, which both route external
+ * assets (textures, models) through the proxy so three.js can load them.
+ */
+
+/**
+ * Resolve a part's asset URL. Absolute URLs (http/https, data:, blob:) pass
+ * through unchanged; relative paths are resolved against `baseUrl` — the
+ * directory of the part's source file (the json/yaml/markdown that defined
+ * it). Without a `baseUrl`, a relative path is returned as-is.
+ */
+export function resolveAssetUrl(url: string, baseUrl?: string): string {
+  if (/^(https?:|data:|blob:)/i.test(url)) return url;
+  if (!baseUrl) return url;
+  // `baseUrl` is a path relative to the games root (no scheme), so join rather
+  // than resolve as a URL. A fake origin lets `new URL` normalize `./` and
+  // `../`; the origin is stripped from the result.
+  const resolved = new URL(url, `http://localhost/${baseUrl}`).pathname;
+  return resolved.replace(/^\/+/, '');
+}
+
+/** Route an external asset URL through the proxy so three.js can load it. */
+export function assetUrl(url: string): string {
+  return `/asset?url=${encodeURIComponent(url)}`;
+}

packages/http/src/index.ts

@@ -0,0 +1,3 @@
+export { resolveAssetUrl, assetUrl } from './asset.js';
+export { traceImage } from './trace.js';
+export type { TraceResult } from '@tts/shared';

packages/http/src/trace.ts

@@ -0,0 +1,27 @@
+/**
+ * Trace an image into a vector shape via the host app's proxy (`/trace`).
+ * Shared by the web token viewer and `@tts/tabletop`, which both trace an
+ * image's alpha channel into a silhouette for extrusion.
+ */
+import { deserialize } from 'bson';
+import type { TraceResult } from '@tts/shared';
+
+/**
+ * Trace an image into a vector shape, BSON-deserializing the proxy response.
+ * `mode` controls how the region is derived (`alpha`, `bw`, `color`); a
+ * non-zero `offset` insets (negative) or outsets (positive) the shape.
+ */
+export async function traceImage(
+  url: string,
+  mode: 'alpha' | 'bw' | 'color' = 'alpha',
+  offset?: number,
+): Promise<TraceResult> {
+  const params = new URLSearchParams({ url, mode });
+  if (offset !== undefined) params.set('offset', String(offset));
+  const res = await fetch(`/trace?${params.toString()}`);
+  if (!res.ok) {
+    const body = (await res.json().catch(() => null)) as { error?: string } | null;
+    throw new Error(body?.error ?? `Trace failed (${res.status})`);
+  }
+  return deserialize(new Uint8Array(await res.arrayBuffer())) as TraceResult;
+}

packages/http/tsconfig.json

@@ -0,0 +1,9 @@
+{
+  "extends": "../../tsconfig.base.json",
+  "compilerOptions": {
+    "outDir": "./dist",
+    "rootDir": "./src",
+    "lib": ["ES2022", "DOM"]
+  },
+  "include": ["src"]
+}

packages/http/vitest.config.ts

@@ -0,0 +1,7 @@
+import { defineConfig } from 'vitest/config';
+
+export default defineConfig({
+  test: {
+    include: ['src/**/*.test.ts'],
+  },
+});

packages/mesh/src/index.ts

@@ -2,4 +2,5 @@ export * from './types.js';
 export * from './shapes.js';
 export * from './tessellate.js';
 export * from './walls.js';
-export * from './extrude.js';
+export * from './extrude.js';
+export * from './trace.js';

packages/mesh/src/trace.test.ts

@@ -0,0 +1,45 @@
+import { describe, expect, it } from 'vitest';
+import { traceToShape, traceToUvBounds } from './trace.js';
+
+describe('traceToShape', () => {
+  it('flips y and centers the traced shape', () => {
+    const trace = {
+      shape: { outline: [[0, 0], [10, 0], [10, 10], [0, 10]] },
+      width: 10,
+      height: 10,
+    };
+    const shape = traceToShape(trace, 0.2);
+    // Centered at origin, scaled to fit the 2x2 box. The y-flip reverses
+    // winding, so the outline is normalized to CCW (order may differ).
+    expect(shape.outline).toHaveLength(4);
+    expect(shape.outline).toEqual(
+      expect.arrayContaining([
+        [-1, 1],
+        [1, 1],
+        [1, -1],
+        [-1, -1],
+      ]),
+    );
+  });
+
+  it('maps holes to clockwise winding', () => {
+    const trace = {
+      shape: {
+        outline: [[0, 0], [10, 0], [10, 10], [0, 10]],
+        holes: [[[2, 2], [2, 8], [8, 8], [8, 2]]],
+      },
+      width: 10,
+      height: 10,
+    };
+    const shape = traceToShape(trace, 0.2);
+    expect(shape.holes).toHaveLength(1);
+    expect(shape.holes![0]).toHaveLength(4);
+  });
+});
+
+describe('traceToUvBounds', () => {
+  it('maps the full image rectangle to the part box', () => {
+    const bounds = traceToUvBounds({ width: 10, height: 20 }, 0.2);
+    expect(bounds).toEqual({ minX: -1, minY: -2, maxX: 1, maxY: 2 });
+  });
+});

packages/mesh/src/trace.ts

@@ -0,0 +1,67 @@
+/**
+ * Trace-to-shape helpers: convert a proxy `/trace` result (image pixel coords,
+ * origin top-left, y-down) into a mesh `Shape` (y-up, centered at the origin).
+ *
+ * Shared by the web token viewer and `@tts/tabletop`, which both trace an
+ * image's alpha channel into a silhouette and extrude it. The only difference
+ * between consumers is the scale factor, so the transform is parameterized by
+ * `scale` and the callers compute it (fit-to-box vs fit-to-max-dimension).
+ */
+import type { Shape } from './shapes.js';
+import type { UVBounds } from './types.js';
+
+/** A traced image region, in image pixel coords (origin top-left, y-down). */
+export interface TraceInput {
+  shape: { outline: number[][]; holes?: number[][][] };
+  width: number;
+  height: number;
+}
+
+/**
+ * Convert a traced shape to a mesh `Shape` scaled by `scale`. Flips the y-axis
+ * (image y-down → mesh y-up), centers the result at the origin, and normalizes
+ * winding so the outline is counter-clockwise and holes are clockwise (as
+ * `@tts/mesh` expects).
+ */
+export function traceToShape(trace: TraceInput, scale: number): Shape {
+  const { shape, width, height } = trace;
+  const ox = (width * scale) / 2;
+  const oy = (height * scale) / 2;
+  const transform = (pts: number[][]) =>
+    pts.map(([x, y]) => [x! * scale - ox, (height - y!) * scale - oy]);
+  return {
+    outline: normalizeWinding(transform(shape.outline), true),
+    holes: shape.holes?.map((h) => normalizeWinding(transform(h), false)),
+  };
+}
+
+/**
+ * The full image rectangle, in mesh coordinates, used as the UV framing so the
+ * texture aligns with a traced silhouette (which may be smaller than the image
+ * when there is transparent padding).
+ */
+export function traceToUvBounds(
+  trace: { width: number; height: number },
+  scale: number,
+): UVBounds {
+  const ox = (trace.width * scale) / 2;
+  const oy = (trace.height * scale) / 2;
+  return { minX: -ox, minY: -oy, maxX: ox, maxY: oy };
+}
+
+/** Ensure a ring has the requested winding. `ccw` true yields CCW (outline). */
+function normalizeWinding(pts: number[][], ccw: boolean): number[][] {
+  const isCcw = signedArea(pts) > 0;
+  return isCcw === ccw ? pts : [...pts].reverse();
+}
+
+/** Signed area of a polygon; positive means counter-clockwise. */
+function signedArea(points: number[][]): number {
+  let area = 0;
+  for (let i = 0; i < points.length; i++) {
+    const [x1, y1] = points[i]!;
+    const [x2, y2] = points[(i + 1) % points.length]!;
+    area += x1! * y2! - x2! * y1!;
+  }
+  return area / 2;
+}

packages/tabletop/package.json

@@ -22,8 +22,8 @@
     "@react-three/fiber": "^9.7.0",
     "@react-three/postprocessing": "^3.0.4",
     "@tts/bgm": "workspace:*",
+    "@tts/http": "workspace:*",
     "@tts/mesh": "workspace:*",
-    "bson": "^7.3.1",
     "react": "^19.2.8",
     "three": "^0.185.1",
     "zustand": "^5.0.14"

packages/tabletop/src/http.ts

@@ -1,53 +1,7 @@
 /**
- * HTTP helpers for loading part assets. The only coupling to the host app's
- * HTTP surface: the asset proxy (`/asset`) and the trace endpoint (`/trace`).
- * Kept as plain functions so they're testable without react-three.
+ * HTTP helpers for loading part assets. Re-exported from `@tts/http`, the
+ * shared package for the host app's proxy (`/asset` and `/trace`) handlers.
+ * Kept as a thin re-export so the tabletop's public surface is unchanged.
  */
-import { deserialize } from 'bson';
-
-/**
- * Resolve a part's asset URL. Absolute URLs (http/https, data:, blob:) pass
- * through unchanged; relative paths are resolved against `baseUrl` — the
- * directory of the part's source file (the json/yaml/markdown that defined
- * it). Without a `baseUrl`, a relative path is returned as-is.
- */
-export function resolveAssetUrl(url: string, baseUrl?: string): string {
-  if (/^(https?:|data:|blob:)/i.test(url)) return url;
-  if (!baseUrl) return url;
-  // `baseUrl` is a path relative to the games root (no scheme), so join rather
-  // than resolve as a URL. A fake origin lets `new URL` normalize `./` and
-  // `../`; the origin is stripped from the result.
-  const resolved = new URL(url, `http://localhost/${baseUrl}`).pathname;
-  return resolved.replace(/^\/+/, '');
-}
-
-/** Route an external asset URL through the proxy so three.js can load it. */
-export function assetUrl(url: string): string {
-  return `/asset?url=${encodeURIComponent(url)}`;
-}
-
-export interface TraceResult {
-  width: number;
-  height: number;
-  shape?: { outline: number[][]; holes?: number[][][] };
-}
-
-/**
- * Trace an image into a vector shape, BSON-deserializing the proxy response.
- * `mode` controls how the region is derived (`alpha`, `bw`, `color`); a
- * non-zero `offset` insets (negative) or outsets (positive) the shape.
- */
-export async function traceImage(
-  url: string,
-  mode: 'alpha' | 'bw' | 'color' = 'alpha',
-  offset?: number,
-): Promise<TraceResult> {
-  const params = new URLSearchParams({ url, mode });
-  if (offset !== undefined) params.set('offset', String(offset));
-  const res = await fetch(`/trace?${params.toString()}`);
-  if (!res.ok) {
-    const body = (await res.json().catch(() => null)) as { error?: string } | null;
-    throw new Error(body?.error ?? `Trace failed (${res.status})`);
-  }
-  return deserialize(new Uint8Array(await res.arrayBuffer())) as TraceResult;
-}
+export { resolveAssetUrl, assetUrl, traceImage } from '@tts/http';
+export type { TraceResult } from '@tts/http';

packages/tabletop/src/part.ts

@@ -4,7 +4,13 @@
  * app's `cardResolution.ts`).
  */
 import type { Part, Crop } from '@tts/bgm';
-import { rectShape, roundedRectShape, type Shape } from '@tts/mesh';
+import {
+  rectShape,
+  roundedRectShape,
+  traceToShape as meshTraceToShape,
+  traceToUvBounds as meshTraceToUvBounds,
+  type Shape,
+} from '@tts/mesh';
 
 /** Scale from mm (the format's `size` unit) to world units. */
 export const MM_TO_WORLD = 1 / 30;
@@ -67,15 +73,8 @@ export function traceToShape(
   width: number,
   height: number,
 ): Shape {
-  const { shape, width: tw, height: th } = trace;
-  const scale = Math.min(width / tw, height / th);
-  const ox = (tw * scale) / 2;
-  const oy = (th * scale) / 2;
-  const transform = (pts: number[][]) => pts.map(([x, y]) => [x! * scale - ox, (th - y!) * scale - oy]);
-  return {
-    outline: normalizeWinding(transform(shape.outline), true),
-    holes: shape.holes?.map((h) => normalizeWinding(transform(h), false)),
-  };
+  const { width: tw, height: th } = trace;
+  return meshTraceToShape(trace, Math.min(width / tw, height / th));
 }
 
 /**
@@ -88,25 +87,5 @@ export function traceToUvBounds(
   width: number,
   height: number,
 ): { minX: number; minY: number; maxX: number; maxY: number } {
-  const scale = Math.min(width / trace.width, height / trace.height);
-  const ox = (trace.width * scale) / 2;
-  const oy = (trace.height * scale) / 2;
-  return { minX: -ox, minY: -oy, maxX: ox, maxY: oy };
-}
-
-/** Ensure a ring has the requested winding. `ccw` true yields CCW (outline). */
-function normalizeWinding(pts: number[][], ccw: boolean): number[][] {
-  const isCcw = signedArea(pts) > 0;
-  return isCcw === ccw ? pts : [...pts].reverse();
-}
-
-/** Signed area of a polygon; positive means counter-clockwise. */
-function signedArea(points: number[][]): number {
-  let area = 0;
-  for (let i = 0; i < points.length; i++) {
-    const [x1, y1] = points[i]!;
-    const [x2, y2] = points[(i + 1) % points.length]!;
-    area += x1! * y2! - x2! * y1!;
-  }
-  return area / 2;
+  return meshTraceToUvBounds(trace, Math.min(width / trace.width, height / trace.height));
 }