Angular Entity Adapter Implementation

This challenge focuses on implementing an Entity Adapter in Angular, a powerful pattern for managing and querying normalized data. Entity Adapters are particularly useful when dealing with data fetched from APIs, allowing you to efficiently store and retrieve entities by their IDs, simplifying data manipulation and improving performance. Your task is to create a reusable Entity Adapter that can handle adding, updating, and removing entities from a normalized data store.

Problem Description

You need to create a generic EntityAdapter class in Angular that can be used with any entity type. This adapter should provide methods for:

• addOne(entity: T): Adds a new entity to the store. If an entity with the same ID already exists, it should update the existing entity.
• updateOne(entity: T): Updates an existing entity in the store. If an entity with the same ID doesn't exist, it should add it.
• removeOne(id: string): Removes an entity from the store based on its ID.
• getAll(): Returns an array of all entities in the store.
• getOne(id: string): Returns a single entity based on its ID, or undefined if not found.

The adapter should internally maintain a normalized data store, where entities are stored as an object keyed by their ID. The id property of each entity is assumed to be a string.

Key Requirements:

• The EntityAdapter should be generic, accepting a type parameter T representing the entity type.
• The adapter should use a private entities object to store the normalized data.
• All methods should modify the internal entities store and return the updated entity (for addOne and updateOne) or void for removeOne. getAll should return an array of entities. getOne should return the entity or undefined.
• The adapter should handle cases where an entity with the given ID already exists.

Expected Behavior:

The adapter should correctly add, update, and remove entities based on their IDs, maintaining the integrity of the normalized data store. The getAll() method should return all entities in the order they were added (or in any consistent order).

Edge Cases to Consider:

• What happens if the entity doesn't have an id property? (Assume the id property always exists and is a string. No error handling for missing id is required.)
• What happens if you try to remove an entity that doesn't exist? (No error handling is required; simply do nothing.)
• What happens if you try to add or update an entity with a duplicate ID? (The existing entity should be overwritten.)

Examples

Example 1:

Input:
adapter = new EntityAdapter<MyEntity>();
adapter.addOne({ id: '1', name: 'Alice' });
adapter.addOne({ id: '2', name: 'Bob' });
Output:
adapter.getAll() // Returns: [{ id: '1', name: 'Alice' }, { id: '2', name: 'Bob' }]

Explanation: Two entities are added to the store. getAll() returns them in the order they were added.

Example 2:

Input:
adapter = new EntityAdapter<MyEntity>();
adapter.addOne({ id: '1', name: 'Alice' });
adapter.updateOne({ id: '1', name: 'Alicia' });
Output:
adapter.getAll() // Returns: [{ id: '1', name: 'Alicia' }]
adapter.getOne('1') // Returns: { id: '1', name: 'Alicia' }

Explanation: An entity is added, then updated. getAll() returns the updated entity. getOne returns the updated entity.

Example 3:

Input:
adapter = new EntityAdapter<MyEntity>();
adapter.addOne({ id: '1', name: 'Alice' });
adapter.removeOne('1');
Output:
adapter.getAll() // Returns: []
adapter.getOne('1') // Returns: undefined

Explanation: An entity is added, then removed. getAll() returns an empty array. getOne returns undefined.

Constraints

• The id property of each entity must be a string.
• The adapter must be generic and reusable for different entity types.
• The adapter should be implemented as a class.
• Performance is not a primary concern for this challenge; focus on correctness and clarity.

Notes

• Consider using a private entities object (e.g., private entities: { [id: string]: T }) to store the normalized data.
• Think about how to handle updates efficiently.
• This is a foundational building block for more complex state management solutions.
• The MyEntity type used in the examples is just for illustration. You don't need to define it explicitly in your solution. It represents any object with an id property of type string.