This document outlines a solution for a GUI for building a tree that represents a system, where the frontend is built using React and an existing backend that uses a REST API. The system allows for various state changes, node removal, and serialization of the state.
Important aspects of this strategy for efficient communication between the frontend and backend, which involves using an event-driven architecture to handle user actions and updates to the tree. To ensure high consistency between the frontend and backend, we introduced a version control system that tracks changes and enables undo and redo functionalities. We also proposed several React components and TypeScript interfaces to model the various parts of the system.
The tree data model described in this solution is a hierarchical data structure composed of nodes, each of which can have zero or more child nodes.* Each node can contain data and have any number of child nodes. The tree is represented in the system by a TypeScript class that contains methods for adding, removing, and querying nodes, as well as serializing and deserializing the tree for storage or transmission. Each node in the tree has a unique identifier, and nodes can be accessed by their ID or by their position in the tree.
Type Interface
/** A serializable interface containing tree data */
interface TreeNode {
id: number; // Unique identifier for the node
name: string; // Name of the node
type: string; // Type of the node
children?: TreeNode[]; // Array of child nodes. Optional for leaf nodes.
parent?: TreeNode; // Reference to the parent node. Optional for root node.
metadata?: Record<string, any>; // Object for storing additional data about the node. Optional.
}
/** An interface describing the class that operates on the data. */
interface Tree {
rootNode: TreeNode; // The root node of the tree
addNode(parentNode: TreeNode, newNode: TreeNode): void; // Method for adding a node to the tree
removeNode(node: TreeNode): void; // Method for removing a node from the tree
queryNode(id: number): TreeNode | undefined; // Method for querying a node by its ID
serializeTree(): string; // Method for serializing the tree
deserializeTree(treeString: string): void; // Method for deserializing a serialized tree
}*The Tree data model for this application differs from the problem statement description. In the description, the Tree that is described is a binary tree. Whereas the Tree structure described in this solution has more than one leave node. We'll treat this approaches a request to the Backend.
The strategy for efficient communication between the front-end and back-end involves the use of websockets and aggregating event changes. websockets allow for real-time communication between the front-end and back-end, reducing the need for frequent HTTP requests.
To efficiently aggregate event changes and avoid too many queries to the database, we will use the Event Sourcing pattern. The event-sourcing design pattern is implemented in this solution by having the frontend send events to the backend via websockets. The backend aggregates events into a list of changes and stores them in a database. When changes occur, the EditorComponent updates its internal state by applying the changes to the current state using the EventDispatcher class, which tracks a history of changes and allows for undo and redo functionality.
Here is what a type interface could looks like:
// Interface for the EventDispatcher class
interface EventDispatcher<T extends Event> {
dispatch: (event: T) => void; // A method for dispatching events
addListener: (listener: EventListener<T>) => void; // A method for adding an event listener
removeListener: (listener: EventListener<T>) => void; // A method for removing an event listener
clearListeners: () => void; // A method for removing all event listeners
getHistory: () => T[]; // A method for retrieving the event history
undo: () => void; // A method for undoing the last event
redo: () => void; // A method for redoing the last undone event
}The various events that can be dispatched by the EditorComponent, such as NodeAddedEvent and NodeRemovedEvent, all inherit from a base Event interface. The Event interface includes a type property that identifies the type of event and a timestamp property that indicates when the event occurred. The child event interfaces includes various
// Base interface for all events
interface Event {
type: string; // A string representing the type of event
timestamp: string; // ISO timestamp at time of event
}
// Interface for the node added event
interface NodeAddedEvent extends Event {
type: "nodeAdded"; // Specifies this event type as "nodeAdded"
nodeId: string; // The ID of the newly added node
parentId: string; // The ID of the parent node where the new node was added
}
// Interface for the node removed event
interface NodeRemovedEvent extends Event {
type: "nodeRemoved"; // Specifies this event type as "nodeRemoved"
nodeId: string; // The ID of the removed node
}
// Interface for the node updated event
interface NodeUpdatedEvent extends Event {
type: "nodeUpdated"; // Specifies this event type as "nodeUpdated"
nodeId: string; // The ID of the updated node
updates: Partial<TreeNode>; // An object containing the updated properties of the node
}
// Interface for the focus changed event
interface FocusChangedEvent extends Event {
type: "focusChanged"; // Specifies this event type as "focusChanged"
nodeId: string | null; // The ID of the node that is currently focused, or null if no node is focused
}
// Interface for the zoom changed event
interface ZoomChangedEvent extends Event {
type: "zoomChanged"; // Specifies this event type as "zoomChanged"
zoomLevel: number; // The current zoom level of the editor
}Overall, this event-sourcing design pattern allows for efficient communication between the frontend and backend, as well as robust handling of changes and undo/redo functionality in the EditorComponent.
There will likely require several React components to build the complete UI. As such, we will focus on the functional requirements for the editor as described by the problem statement.
Description: The NodeComponentProps interface defines the props for rendering a node in the tree editor. The entire tree (from the root to the leaves) can be recursively rendered using this component.
Interface
interface NodeComponentProps {
node: TreeNode; // In this interface, node is the TreeNode object that the component is rendering.
onRenameNode: (newName: string) => void; // A callback that is triggered when the user renames the node.
onRemoveNode: () => void; // A callback that is triggered when the user renames the node.
onSelectNode: () => void; // A callback that is triggered when the user selects the node.
onZoomToNode: () => void; // A callback that is triggered when the user zooms to the node.
isFocused: boolean; // A flag indicating whether the node is currently focused or not.
isZoomed: boolean; // A flag indicating whether the node is currently zoomed in or not.
}Description: An EditorComponent is a top-level component that renders the entire editor UI. It contains all other components and provides a high-level API for managing the state of the tree and responding to user actions. The EditorComponent interfaces with the backend to fetch and update the tree data model, and communicates with other components via props and event callbacks.
Interface
interface EditorComponentProps {
tree: TreeNode; // The root node of the tree data model
onNodeFocus: (nodeId: string) => void; // Callback when a node is focused
onNodeUnfocus: () => void; // Callback when a node is unfocused
onNodeSelect: (nodeId: string) => void; // Callback when a node is selected
onNodeEdit: (nodeId: string, value: string) => void; // Callback when a node is edited
onNodeCreate: (parentId: string) => void; // Callback when a new node is created
onNodeDelete: (nodeId: string) => void; // Callback when a node is deleted
onUndo: () => void; // Callback when the undo action is triggered
onRedo: () => void; // Callback when the redo action is triggered
}Some other components worth mentioning:
- ToolbarComponent: A component responsible for displaying various tools and actions that can be performed on the tree, such as adding nodes, deleting nodes, and undo/redo actions.
- ModalComponent: A component responsible for displaying modals, such as confirmation dialogs or error messages.
- ZoomComponent: A component responsible for providing an interface for zooming in and out of the tree view.
A possible strategy for handling a mismatch between frontend and backend versions is detected, the user should be warned that they are not using the latest version of the application. The warning should inform them that there is a newer version available and provide them with the option to update their local version or fork their tree based on their local changes.
If they choose to update, the frontend should download the latest version from the backend and merge it with their local changes. If they choose to fork, a new copy of the tree will be created based on their local changes and they will be prompted to enter a new name for the tree. In both cases, the user's local changes will be preserved.
To handle poor internet connectivity in the client app, we can implement an offline caching strategy. One approach is to use a service worker to cache resources and enable the app to work offline. We can also use client-side storage, such as local storage or indexedDB, to store data that the user can access when offline.
To enable editing when offline, the user's changes are immediately reflected on the client side, even if the changes have not yet been sent to the server. When connectivity is restored, we can send the changes to the server and update the UI with the server's response.
In addition to these techniques, we can also use websockets to provide real-time updates when connectivity is restored. When the client reconnects to the server, the server can send any changes that were made by other users while the client was offline.
To implement these strategies, we can implement the EventDispatcher to include offline support. We can use client-side storage to store a queue of changes that have not yet been sent to the server, and then send these changes when connectivity is restored. We can also use websockets to receive real-time updates from the server when connectivity is restored.
This system provides a strong basis for supporting additional features such as:
- Collaboration features: Add real-time collaborative editing to enable multiple users to work on the same tree simultaneously.
- Access control: Implement different user roles and permissions to control who can edit or view the tree.
- Advanced search: Add advanced search functionality, such as filtering by node properties or searching for nodes with specific patterns.
- Rich text editing: Allow users to format node text using rich text editing tools, such as bold, italic, or underline.
In conclusion, the solution we have designed provides a robust and scalable approach to building a tree editor application. Leveraging event-sourcing architecture, efficient communication strategies between the frontend and backend, and offline caching to improve the user experience, our solution provides a solid foundation for building a production-ready application. Overall, our solution provides a powerful set of tools for building a collaborative editor, and we believe it is a strong starting point for future development.