feat: setup the attachment to the passenger clients

apps/edr-passenger-web/backoffice/src/features/support/useAttachmentDraft.ts

@@ -0,0 +1,123 @@
+'use client';
+
+import {
+  isSupportAttachmentAllowed,
+  isSupportAttachmentImage,
+  SUPPORT_ATTACHMENT_MAX_BYTES,
+  SUPPORT_ATTACHMENT_MAX_PER_MESSAGE,
+} from '@edr/types';
+import { useCallback, useEffect, useRef, useState } from 'react';
+
+/** A file staged in the composer, not yet sent. */
+export interface PendingAttachment {
+  /** Local-only id; the server id doesn't exist until the message is sent. */
+  id: string;
+  file: File;
+  /** Object URL, images only. Revoked when the entry goes away. */
+  previewUrl?: string;
+}
+
+let nextId = 0;
+
+/**
+ * Staging area for files being attached to a message.
+ *
+ * Files are held client-side until send, then posted alongside the text in one
+ * multipart request — there's no upload-then-reference step, so nothing to
+ * garbage-collect if the agent changes their mind.
+ *
+ * Object URLs for image previews are revoked on removal and unmount; without
+ * that, pasting screenshots into a long-lived chat page leaks the full bytes of
+ * every image for the life of the tab.
+ */
+export function useAttachmentDraft(onReject?: (reason: string) => void) {
+  const [attachments, setAttachments] = useState<PendingAttachment[]>([]);
+  const rejectRef = useRef(onReject);
+  rejectRef.current = onReject;
+
+  // Read from a ref in the unmount cleanup so it doesn't re-run (and revoke
+  // still-live URLs) on every change to the list.
+  const attachmentsRef = useRef(attachments);
+  attachmentsRef.current = attachments;
+  useEffect(
+    () => () => {
+      for (const a of attachmentsRef.current) {
+        if (a.previewUrl) URL.revokeObjectURL(a.previewUrl);
+      }
+    },
+    [],
+  );
+
+  const add = useCallback((files: File[]) => {
+    if (files.length === 0) return;
+    setAttachments((current) => {
+      const accepted: PendingAttachment[] = [];
+      for (const file of files) {
+        if (current.length + accepted.length >= SUPPORT_ATTACHMENT_MAX_PER_MESSAGE) {
+          rejectRef.current?.(`Up to ${SUPPORT_ATTACHMENT_MAX_PER_MESSAGE} files per message.`);
+          break;
+        }
+        if (!isSupportAttachmentAllowed(file.type)) {
+          rejectRef.current?.(`${file.name}: that file type isn't supported.`);
+          continue;
+        }
+        if (file.size > SUPPORT_ATTACHMENT_MAX_BYTES) {
+          rejectRef.current?.(
+            `${file.name} is over the ${SUPPORT_ATTACHMENT_MAX_BYTES / (1024 * 1024)}MB limit.`,
+          );
+          continue;
+        }
+        accepted.push({
+          id: `pending-${nextId++}`,
+          file,
+          previewUrl: isSupportAttachmentImage(file.type) ? URL.createObjectURL(file) : undefined,
+        });
+      }
+      return accepted.length ? [...current, ...accepted] : current;
+    });
+  }, []);
+
+  const remove = useCallback((id: string) => {
+    setAttachments((current) => {
+      const target = current.find((a) => a.id === id);
+      if (target?.previewUrl) URL.revokeObjectURL(target.previewUrl);
+      return current.filter((a) => a.id !== id);
+    });
+  }, []);
+
+  const clear = useCallback(() => {
+    setAttachments((current) => {
+      for (const a of current) {
+        if (a.previewUrl) URL.revokeObjectURL(a.previewUrl);
+      }
+      return [];
+    });
+  }, []);
+
+  /**
+   * Pull files off a paste. Returns true if anything was taken, so the caller
+   * can suppress the default paste — otherwise pasting a screenshot also drops
+   * its filename (or nothing) into the textarea.
+   *
+   * Copying an image in most apps puts BOTH the bitmap and some text/html on
+   * the clipboard, so check for files first and only then let the text through.
+   */
+  const addFromPaste = useCallback(
+    (clipboard: DataTransfer | null): boolean => {
+      const files = Array.from(clipboard?.files ?? []);
+      if (files.length === 0) return false;
+      add(files);
+      return true;
+    },
+    [add],
+  );
+
+  return {
+    attachments,
+    files: attachments.map((a) => a.file),
+    add,
+    addFromPaste,
+    remove,
+    clear,
+  };
+}