Asynchronous Validation in Vue with TypeScript

This challenge focuses on implementing asynchronous validation for a Vue.js form using TypeScript. Asynchronous validation is crucial when you need to validate data against an external source, such as an API, rather than relying solely on simple regular expressions or comparisons. This allows for more robust and dynamic form validation.

Problem Description

You are tasked with creating a Vue component that includes a form with an email input field. The email input should be asynchronously validated against a mock API endpoint to check if the email address is already registered. If the email is already registered, an error message should be displayed below the input field. If the email is valid (not registered), the error message should be cleared.

What needs to be achieved:

Create a Vue component with an email input field.
Implement asynchronous validation using a mock API endpoint.
Display an error message below the input field if the email is already registered.
Clear the error message if the email is valid.
Ensure the form submission is disabled until the validation is complete and successful.

Key Requirements:

Use Vue 3 and TypeScript.
Utilize async/await for asynchronous operations.
Handle loading states during validation.
Provide clear and informative error messages.
The component should be reusable and maintainable.

Expected Behavior:

When the user types in the email input field, the component should start validating the email address asynchronously.
While validating, a loading indicator (e.g., a spinner) should be displayed.
If the email is already registered, an error message like "Email is already registered" should be displayed below the input field, and the submit button should remain disabled.
If the email is valid, the error message should be cleared, and the submit button should be enabled.
If there's a network error during validation, display a generic error message like "Validation failed. Please try again."

Edge Cases to Consider:

Network errors during the API call.
Empty email input.
Invalid email format (although this can be handled with a regular expression, focus on the asynchronous part).
Slow API response times.

Examples

Example 1:

Input: Email input field contains "test@example.com" (which is registered in the mock API)
Output: Error message "Email is already registered" displayed below the input field. Submit button disabled.
Explanation: The asynchronous validation call returns a response indicating the email is registered, triggering the error display and disabling the submit button.

Example 2:

Input: Email input field contains "newemail@example.com" (which is not registered in the mock API)
Output: Error message cleared. Submit button enabled.
Explanation: The asynchronous validation call returns a response indicating the email is not registered, clearing the error message and enabling the submit button.

Example 3: (Network Error)

Input: Email input field contains "anyemail@example.com" and the API call fails due to a network error.
Output: Error message "Validation failed. Please try again." displayed below the input field. Submit button disabled.
Explanation: The asynchronous validation call throws an error, which is caught and displayed as a generic error message, disabling the submit button.

Constraints

The mock API endpoint will return a JSON response with a registered boolean property. true indicates the email is registered, false indicates it is not.
The API endpoint URL is https://your-mock-api.com/validate-email. (You will need to mock this endpoint locally for testing. See Notes.)
The validation process should not take longer than 2 seconds. If it does, consider displaying a timeout message.
The component should be well-structured and easy to understand.

Notes

You'll need to set up a mock API endpoint locally to simulate the email validation service. Tools like json-server or Mockoon can be helpful for this. A simple mock API could return {"registered": true} or {"registered": false} based on the email address provided.
Consider using Vue's reactivity system to efficiently update the UI when the validation status changes.
Think about how to handle loading states and error messages gracefully.
Focus on the asynchronous validation logic and error handling. Basic email format validation (e.g., using a regular expression) is not the primary focus of this challenge, but can be added for extra credit.
The submit button should be disabled during the validation process and only enabled when the validation is successful.
Provide a clear and concise implementation that demonstrates your understanding of asynchronous programming and Vue.js component development.