date-picker.txt

5. Your SaaS platform uses a design system to maintain consistency across its interface. 
You’re tasked with creating a reusable date-picker component that supports multiple date formats, 
time zones, and custom styling options. 

How would you approach building this component to ensure it is scalable, accessible, and easy 
to integrate with existing applications?

1. Requirements Analysis
* Date Formats: Support multiple formats (e.g., YYYY-MM-DD, MM/DD/YYYY).
* Time Zones: Handle user-specified or system-detected time zones.
* Custom Styling: Allow theme overrides and component-level styling.
* Accessibility: Adhere to WAI-ARIA guidelines.
* Scalability: Ensure the component is modular and extendable for future features like 
  calender, range selection.
* Integration: Easy to plug into any project using the design system.

2. technical/Design Decisions
* Framework: Use react.js.
* Base Libraries:
  Use date-fns or Day.js for date manipulation.
  Optionally, integrate Intl.DateTimeFormat for internationalization.
* Styling:
  Use CSS-in-JS solutions like Emotion or Styled Components for theme support.
  Expose a className or style prop for custom styles.

*Configuration Options:
  Props for format, timeZone, minDate, maxDate, and disabledDates.
  Support controlled and uncontrolled modes (value and defaultValue).

4. Development Process
  a. Setup and Configuration
    Create a TypeScript-based component for better type safety.
    Set up a story in Storybook to demonstrate variations and test edge cases.
  b. Input Field
    Accept a user-provided placeholder or auto-generate based on the selected date format.
    Show a clear button to reset the value.
  c. Calendar Pop-up
    Display a grid with weekdays, dates, and navigation controls.
    Highlight the current date and selected date.
    Allow multi-date selection (optional for scalability).
  d. Time Zone Handling
    Use the Intl API to detect and set the default time zone.
    Provide a dropdown to switch time zones dynamically.
  e. Styling
    Use tokens from the design system (e.g., colors, spacing, typography).
    Allow customization via theme context or props like styles or className.
  f. Testing
    Write unit tests for:
    Date parsing and formatting.  
    Boundary conditions like min/max dates.
    End-to-end tests for user interactions (e.g., Cypress).
    Accessibility testing using tools like Axe or Lighthouse.