feat: add file browser image previews

src/server/workspaces/imagePreviewService.ts

@@ -0,0 +1,46 @@
+import { createReadStream, type ReadStream } from "node:fs";
+import { stat } from "node:fs/promises";
+import { extname } from "node:path";
+import { MAX_IMAGE_PREVIEW_BYTES, MAX_IMAGE_PREVIEW_LABEL } from "../../shared/workspaceFiles.js";
+import { resolveInsideWorkspace } from "./pathSafety.js";
+
+const IMAGE_MIME_TYPES: Record<string, string | undefined> = {
+  ".avif": "image/avif",
+  ".bmp": "image/bmp",
+  ".gif": "image/gif",
+  ".ico": "image/x-icon",
+  ".jpeg": "image/jpeg",
+  ".jpg": "image/jpeg",
+  ".png": "image/png",
+  ".svg": "image/svg+xml",
+  ".webp": "image/webp",
+};
+
+export interface WorkspaceImagePreview {
+  path: string;
+  mimeType: string;
+  size: number;
+  modifiedAt: string;
+  stream: ReadStream;
+}
+
+export function imageMimeTypeForPath(path: string): string | undefined {
+  return IMAGE_MIME_TYPES[extname(path).toLowerCase()];
+}
+
+export async function readWorkspaceImagePreview(rootPath: string, path: string | undefined): Promise<WorkspaceImagePreview> {
+  if (path === undefined || path === "") throw new Error("path query parameter is required");
+  const { target, relativePath } = await resolveInsideWorkspace(rootPath, path);
+  const s = await stat(target);
+  if (!s.isFile()) throw new Error("Path is not a file");
+  const mimeType = imageMimeTypeForPath(relativePath);
+  if (mimeType === undefined) throw new Error("Image preview is not supported for this file type");
+  if (s.size > MAX_IMAGE_PREVIEW_BYTES) throw new Error(`Image is too large to preview (limit ${MAX_IMAGE_PREVIEW_LABEL})`);
+  return {
+    path: relativePath,
+    mimeType,
+    size: s.size,
+    modifiedAt: s.mtime.toISOString(),
+    stream: createReadStream(target),
+  };
+}