feat(app): support pasting images into prompt attachments

packages/app/src/utils/image-attachments-from-files.ts

@@ -0,0 +1,67 @@
+export interface ClipboardItemLike {
+  kind?: string;
+  type?: string;
+  getAsFile?: () => File | null;
+}
+
+export interface ClipboardDataLike {
+  items?: ArrayLike<ClipboardItemLike> | null;
+}
+
+export interface ImageAttachmentFromFile {
+  uri: string;
+  mimeType: string;
+}
+
+function toBase64(buffer: ArrayBuffer): string {
+  const bytes = new Uint8Array(buffer);
+  const chunkSize = 0x8000;
+  let binary = "";
+
+  for (let index = 0; index < bytes.length; index += chunkSize) {
+    const chunk = bytes.subarray(index, index + chunkSize);
+    binary += String.fromCharCode(...chunk);
+  }
+
+  return btoa(binary);
+}
+
+export function collectImageFilesFromClipboardData(
+  clipboardData?: ClipboardDataLike | null
+): File[] {
+  if (!clipboardData?.items) {
+    return [];
+  }
+
+  const files: File[] = [];
+  for (const item of Array.from(clipboardData.items)) {
+    if (item?.kind !== "file") {
+      continue;
+    }
+    if (!item.type?.startsWith("image/")) {
+      continue;
+    }
+    const file = item.getAsFile?.();
+    if (!file) {
+      continue;
+    }
+    files.push(file);
+  }
+
+  return files;
+}
+
+export async function filesToImageAttachments(
+  files: readonly File[]
+): Promise<ImageAttachmentFromFile[]> {
+  return Promise.all(
+    files.map(async (file) => {
+      const mimeType = file.type || "image/jpeg";
+      const base64 = toBase64(await file.arrayBuffer());
+      return {
+        uri: `data:${mimeType};base64,${base64}`,
+        mimeType,
+      };
+    })
+  );
+}