Ruby Coding Challenge: Smart Cache Implementation

Overview

This coding challenge is designed to assess your Ruby programming skills, understanding of data structures, and ability to implement efficient algorithms.

The Challenge

Implement a SmartCache class that provides an efficient way to store and retrieve data with the following requirements:

1. The cache has a configurable maximum size.

2. When the cache reaches its maximum size, it should remove the least recently used item.

3. The cache should support the following operations:

   • get(key): Retrieve an item from the cache by key. Return nil if not found.
   • set(key, value): Add or update an item in the cache.
   • delete(key): Remove an item from the cache.
   • clear(): Remove all items from the cache.
   • size(): Return the current number of items in the cache.
   • keys(): Return an array of all keys in the cache.

4. Bonus: Implement a get_with_expiry(key, expiry_seconds) method that retrieves an item only if it hasn't expired.

Requirements

• All operations should have optimal time complexity.
• Your solution should include proper error handling.
• Your code should be well-documented with comments explaining your approach.
• You must implement the solution in a single file named smart_cache.rb.

Testing

• Run the tests with ruby smart_cache_test.rb
• All tests should pass for your solution to be considered complete.

Evaluation Criteria

Your solution will be evaluated based on:

1. Correctness and completeness
2. Code quality and organization
3. Performance and efficiency
4. Error handling
5. Documentation

Good luck!