Fixed-Size Ring Buffer

Design a class RingBuffer: a first-in-first-out queue of integers with a fixed capacity, backed by a fixed-size list (do not use collections.deque or list pop(0)).

• RingBuffer(capacity): create an empty buffer that can hold capacity items.
• enqueue(x): add x at the back; return True on success, False if the buffer is full.
• dequeue(): remove the front item and return True, or return False if the buffer is empty.
• front(): return the front item, or -1 if empty.
• rear(): return the back item, or -1 if empty.
• is_empty(), is_full(): return booleans.

Examples

Input:  ops  = ["RingBuffer", "enqueue", "enqueue", "enqueue", "enqueue", "rear", "is_full", "dequeue", "enqueue", "rear", "front"]
        args = [[3], [1], [2], [3], [4], [], [], [], [4], [], []]
Output: [None, True, True, True, False, 3, True, True, True, 4, 2]
Explanation: the fourth enqueue fails because the buffer holds 3; after removing 1 there is room for 4.

Constraints

• 1 <= capacity <= 1000
• At most 10**4 operations
• Target: O(1) per operation

Goals

• Implement a queue on top of a fixed-size list using head index and count
• Wrap indices around with modulo
• Distinguish the full and empty states