Improve upload workflow with queue and progress states

[longobucco]

Description

Upgrade the document upload flow to properly support real course materials and repeated internal testing.

The workflow must support:

• multi-file upload
• per-file upload progress
• per-file backend processing state
• retry for failed uploads
• clear and actionable error messages

Scope

Implement a queue-based upload UI where each file is tracked independently.

Include:

• multi-file selection / drag-and-drop

• per-file client-side state (queued, uploading, uploaded, processing, indexed, failed)

• per-file upload progress bar

• per-file backend processing status polling

• per-file retry action

• clear distinction between:

  • upload failure
  • backend processing failure

Technical notes

• Model each file as an independent queue item
• Store backend documentId after successful upload
• Poll processing status only for uploaded/processing items
• Keep upload progress and processing status as two separate concepts
• Support limited upload concurrency (recommended: 2–3 files max)
• Validate files client-side before upload when possible

Suggested queue item shape

type UploadStatus =
  | "queued"
  | "uploading"
  | "uploaded"
  | "processing"
  | "indexed"
  | "failed";

Each queue item should track at least:

• local id
• file metadata
• upload progress
• status
• backend document id
• processing stage
• error message
• retry count

Deliverables

• working multi-file upload queue
• live per-file upload progress
• processing state updates in UI
• retry support for failed files
• clear error messages for validation, network, server, and processing failures

Acceptance criteria

• users can upload multiple files in one action
• each file is shown as an independent queue item
• each file displays upload progress
• each file displays backend processing state after upload
• failed files can be retried individually
• upload errors and processing errors are clearly distinguished
• one failed file does not break the rest of the queue

Why it helps

If you’re working with real PDFs/slides, this significantly improves team productivity during testing, debugging, and internal demos.