Implement sliding-window timestamped average

Problem

Implement a class that maintains a time-based sliding window of records and can return the average score within the current window.

Requirements

• The class is initialized with an integer window_size (a duration in the same units as timestamp, e.g., seconds).
• Each record is a pair (timestamp, score).
• The class exposes two methods:

1. insert_record(timestamp, score): insert a new record.
2. get_average(current_time): return the average of all score values whose timestamp is within the current window.

Window definition

At any operation time T (i.e., during insert_record or get_average), records are considered valid if:

• timestamp is in the range [T - window_size, T] (inclusive), and
• any record older than T - window_size must be evicted before proceeding.

Additional notes / assumptions

• get_average should return a sensible value when there are no valid records (define behavior, e.g., return 0 or null).
• Timestamps may be non-decreasing across calls (state and use this assumption if needed), or you may design to handle out-of-order timestamps.

Deliverables

Describe/implement the class and its methods with appropriate time and space complexity considerations.