refactor: excalidraw-app/

1 files changed, 222 insertions, 0 deletions

diff --git a/excalidraw-app/ExcalidrawPlusIframeExport.tsx b/excalidraw-app/ExcalidrawPlusIframeExport.tsx
new file mode 100644
index 0000000..1f9cd63
--- /dev/null
+++ b/excalidraw-app/ExcalidrawPlusIframeExport.tsx
@@ -0,0 +1,222 @@
+import { useLayoutEffect, useRef } from "react";
+import { STORAGE_KEYS } from "./app_constants";
+import { LocalData } from "./data/LocalData";
+import type {
+  FileId,
+  OrderedExcalidrawElement,
+} from "@excalidraw/excalidraw/element/types";
+import type { AppState, BinaryFileData } from "@excalidraw/excalidraw/types";
+import { ExcalidrawError } from "@excalidraw/excalidraw/errors";
+import { base64urlToString } from "@excalidraw/excalidraw/data/encode";
+
+const EVENT_REQUEST_SCENE = "REQUEST_SCENE";
+
+const EXCALIDRAW_PLUS_ORIGIN = import.meta.env.VITE_APP_PLUS_APP;
+
+// -----------------------------------------------------------------------------
+// outgoing message
+// -----------------------------------------------------------------------------
+type MESSAGE_REQUEST_SCENE = {
+  type: "REQUEST_SCENE";
+  jwt: string;
+};
+
+type MESSAGE_FROM_PLUS = MESSAGE_REQUEST_SCENE;
+
+// incoming messages
+// -----------------------------------------------------------------------------
+type MESSAGE_READY = { type: "READY" };
+type MESSAGE_ERROR = { type: "ERROR"; message: string };
+type MESSAGE_SCENE_DATA = {
+  type: "SCENE_DATA";
+  elements: OrderedExcalidrawElement[];
+  appState: Pick<AppState, "viewBackgroundColor">;
+  files: { loadedFiles: BinaryFileData[]; erroredFiles: Map<FileId, true> };
+};
+
+type MESSAGE_FROM_EDITOR = MESSAGE_ERROR | MESSAGE_SCENE_DATA | MESSAGE_READY;
+// -----------------------------------------------------------------------------
+
+const parseSceneData = async ({
+  rawElementsString,
+  rawAppStateString,
+}: {
+  rawElementsString: string | null;
+  rawAppStateString: string | null;
+}): Promise<MESSAGE_SCENE_DATA> => {
+  if (!rawElementsString || !rawAppStateString) {
+    throw new ExcalidrawError("Elements or appstate is missing.");
+  }
+
+  try {
+    const elements = JSON.parse(
+      rawElementsString,
+    ) as OrderedExcalidrawElement[];
+
+    if (!elements.length) {
+      throw new ExcalidrawError("Scene is empty, nothing to export.");
+    }
+
+    const appState = JSON.parse(rawAppStateString) as Pick<
+      AppState,
+      "viewBackgroundColor"
+    >;
+
+    const fileIds = elements.reduce((acc, el) => {
+      if ("fileId" in el && el.fileId) {
+        acc.push(el.fileId);
+      }
+      return acc;
+    }, [] as FileId[]);
+
+    const files = await LocalData.fileStorage.getFiles(fileIds);
+
+    return {
+      type: "SCENE_DATA",
+      elements,
+      appState,
+      files,
+    };
+  } catch (error: any) {
+    throw error instanceof ExcalidrawError
+      ? error
+      : new ExcalidrawError("Failed to parse scene data.");
+  }
+};
+
+const verifyJWT = async ({
+  token,
+  publicKey,
+}: {
+  token: string;
+  publicKey: string;
+}) => {
+  try {
+    if (!publicKey) {
+      throw new ExcalidrawError("Public key is undefined");
+    }
+
+    const [header, payload, signature] = token.split(".");
+
+    if (!header || !payload || !signature) {
+      throw new ExcalidrawError("Invalid JWT format");
+    }
+
+    // JWT is using Base64URL encoding
+    const decodedPayload = base64urlToString(payload);
+    const decodedSignature = base64urlToString(signature);
+
+    const data = `${header}.${payload}`;
+    const signatureArrayBuffer = Uint8Array.from(decodedSignature, (c) =>
+      c.charCodeAt(0),
+    );
+
+    const keyData = publicKey.replace(/-----\w+ PUBLIC KEY-----/g, "");
+    const keyArrayBuffer = Uint8Array.from(atob(keyData), (c) =>
+      c.charCodeAt(0),
+    );
+
+    const key = await crypto.subtle.importKey(
+      "spki",
+      keyArrayBuffer,
+      { name: "RSASSA-PKCS1-v1_5", hash: "SHA-256" },
+      true,
+      ["verify"],
+    );
+
+    const isValid = await crypto.subtle.verify(
+      "RSASSA-PKCS1-v1_5",
+      key,
+      signatureArrayBuffer,
+      new TextEncoder().encode(data),
+    );
+
+    if (!isValid) {
+      throw new Error("Invalid JWT");
+    }
+
+    const parsedPayload = JSON.parse(decodedPayload);
+
+    // Check for expiration
+    const currentTime = Math.floor(Date.now() / 1000);
+    if (parsedPayload.exp && parsedPayload.exp < currentTime) {
+      throw new Error("JWT has expired");
+    }
+  } catch (error) {
+    console.error("Failed to verify JWT:", error);
+    throw new Error(error instanceof Error ? error.message : "Invalid JWT");
+  }
+};
+
+export const ExcalidrawPlusIframeExport = () => {
+  const readyRef = useRef(false);
+
+  useLayoutEffect(() => {
+    const handleMessage = async (event: MessageEvent<MESSAGE_FROM_PLUS>) => {
+      if (event.origin !== EXCALIDRAW_PLUS_ORIGIN) {
+        throw new ExcalidrawError("Invalid origin");
+      }
+
+      if (event.data.type === EVENT_REQUEST_SCENE) {
+        if (!event.data.jwt) {
+          throw new ExcalidrawError("JWT is missing");
+        }
+
+        try {
+          try {
+            await verifyJWT({
+              token: event.data.jwt,
+              publicKey: import.meta.env.VITE_APP_PLUS_EXPORT_PUBLIC_KEY,
+            });
+          } catch (error: any) {
+            console.error(`Failed to verify JWT: ${error.message}`);
+            throw new ExcalidrawError("Failed to verify JWT");
+          }
+
+          const parsedSceneData: MESSAGE_SCENE_DATA = await parseSceneData({
+            rawAppStateString: localStorage.getItem(
+              STORAGE_KEYS.LOCAL_STORAGE_APP_STATE,
+            ),
+            rawElementsString: localStorage.getItem(
+              STORAGE_KEYS.LOCAL_STORAGE_ELEMENTS,
+            ),
+          });
+
+          event.source!.postMessage(parsedSceneData, {
+            targetOrigin: EXCALIDRAW_PLUS_ORIGIN,
+          });
+        } catch (error) {
+          const responseData: MESSAGE_ERROR = {
+            type: "ERROR",
+            message:
+              error instanceof ExcalidrawError
+                ? error.message
+                : "Failed to export scene data",
+          };
+          event.source!.postMessage(responseData, {
+            targetOrigin: EXCALIDRAW_PLUS_ORIGIN,
+          });
+        }
+      }
+    };
+
+    window.addEventListener("message", handleMessage);
+
+    // so we don't send twice in StrictMode
+    if (!readyRef.current) {
+      readyRef.current = true;
+      const message: MESSAGE_FROM_EDITOR = { type: "READY" };
+      window.parent.postMessage(message, EXCALIDRAW_PLUS_ORIGIN);
+    }
+
+    return () => {
+      window.removeEventListener("message", handleMessage);
+    };
+  }, []);
+
+  // Since this component is expected to run in a hidden iframe on Excaildraw+,
+  // it doesn't need to render anything. All the data we need is available in
+  // LocalStorage and IndexedDB. It only needs to handle the messaging between
+  // the parent window and the iframe with the relevant data.
+  return null;
+};