Product Vision & Core Features

Our platform aims to be the go-to tool for teams creating and sharing knowledge. The rich text editor is central to this, offering a delightful, powerful, and collaborative writing experience. Key features include:

• Basic Text Formatting: Bold, italic, underline, strikethrough, code, links.
• Structural Elements: Headings (H1-H6), bulleted lists, numbered lists, blockquotes, code blocks.
• Inline Comments: Ability to highlight text and add comments, visible to collaborators.
• Custom Block Embeds: Support for easily adding new types of content blocks (e.g., simple tables, custom widgets, external embeds like YouTube videos or Figma frames).
• Real-time Multi-user Collaboration: Display of other users' cursors, selections, and instantaneous changes.
• Comprehensive Undo/Redo History: A global undo/redo stack that accounts for changes made by multiple collaborators.
• Copy/Paste Fidelity: Maintain rich text formatting when pasting from external sources and within the editor.

User Stories

• As a user, I want to edit a document with my teammates in real-time and see their changes instantly, including their cursor positions.
• As a user, I want to be able to revert my own or others' mistakes using undo/redo, even if multiple people have contributed to the document.
• As a developer, I want to easily add new custom content blocks (e.g., a poll widget or a diagram) to the editor without modifying its core codebase.
• As a user, I want to keep working on my document and save changes locally, even if my internet connection temporarily drops, with changes synchronizing upon reconnection.
• As a user, I expect the editor to feel fast and responsive, with no noticeable lag while typing or applying formatting.

Scale & Performance Targets

While individual documents have a moderate size limit, the overall platform will host millions of documents. The editor must remain responsive under various conditions:

• Smooth Typing: Zero perceived latency between keypress and character appearance.
• Efficient Rendering: Complex documents with many formatting nodes and custom blocks should render quickly without flickering or excessive reflows.
• Resource Usage: Minimize CPU and memory footprint, especially with multiple active collaborators.

Technical Requirements

Real-time Collaboration

• The editor must support concurrent edits from multiple users without data loss or perceived conflicts.
• Design the mechanism for synchronizing changes, considering strategies like Operational Transformation (OT) or Conflict-free Replicated Data Types (CRDTs).
• Visual indicators for collaborators (cursors, selections) are required.

Undo/Redo System

• Implement a robust, global undo/redo stack that handles interleaved changes from multiple users correctly.
• Consider how to represent and apply undo/redo operations in a collaborative context.

Extensibility Model

• The editor needs a clear and well-defined plugin architecture.
• Plugins should be able to:
  • Introduce new custom content blocks (e.g., a PollBlock or DiagramBlock).
  • Add new toolbar buttons or menu items.
  • Modify editor behavior (e.g., custom paste handlers).
• The core editor should remain stable and extensible without requiring frequent modifications for new features.

Offline Support

• Design a mechanism for local caching of document content and changes.
• Allow users to continue editing offline.
• Define the synchronization strategy for merging offline changes with the remote state upon reconnection, ensuring data integrity.

Performance & Accessibility

• Discuss strategies for optimizing initial load time (e.g., code splitting, lazy loading).
• Explain how to maintain a high frame rate and smooth user experience during active editing (e.g., virtualized rendering, efficient DOM updates).
• Detail how the editor will ensure WCAG 2.1 AA compliance for keyboard navigation, focus management, and screen reader support.

API Considerations

Assume the following API endpoints and real-time channel exist:

• GET /documents/{id}: Fetches the initial document content (e.g., as a JSON object representing the document's structure).
• POST /documents/{id}/save: Persists the current state of the document. This could be a full snapshot or a series of deltas/operations.
• WebSocket /documents/{id}/collaborate: A persistent connection for real-time communication. This channel will be used to send and receive operational transformations or CRDT messages between collaborators and the server.

Data Model

• Propose an internal data representation for the rich text content. This could be a flat string with markers, an Abstract Syntax Tree (AST), a specific library's JSON format (e.g., ProseMirror JSON), or a CRDT-specific data type (e.g., Yjs types).
• Justify your choice based on requirements for collaboration, extensibility, performance, and persistence.

UI/UX Considerations

• The editor must be responsive and adapt to different screen sizes.
• The toolbar should be intuitive and easily discoverable.
• Clear visual indicators for collaborators (avatars, colored cursors) are essential.

Key Decision Points & Trade-offs

Be prepared to discuss the trade-offs involved in your design choices, such as:

• Choosing between different underlying editor frameworks (e.g., ProseMirror, Lexical, Slate.js, custom).
• The implications of using Operational Transformation (OT) versus Conflict-free Replicated Data Types (CRDTs) for collaboration.
• Strategies for balancing bundle size, feature richness, and performance.
• Approaches to offline synchronization and potential conflict resolution scenarios.