Rebalance Shard Ranges Across Nodes in Python

import random
from dataclasses import dataclass

@dataclass
class Shard:
    id: int
    start: int
    end: int

def rebalance_shards(shards: list[Shard], node_count: int) -> dict[int, list[Shard]]:
    """Mock rebalancing of shard ranges across nodes."""
    all_ranges = [(s.start, s.end) for s in shards]
    random.shuffle(all_ranges)
    
    assignments = {i: [] for i in range(node_count)}
    for idx, (start, end) in enumerate(all_ranges):
        node_id = idx % node_count
        assignments[node_id].append(Shard(idx, start, end))
    
    return assignments

if __name__ == "__main__":
    shards = [
        Shard(0, 1, 100),
        Shard(1, 101, 200),
        Shard(2, 201, 300),
        Shard(3, 301, 400),
        Shard(4, 401, 500),
        Shard(5, 501, 600),
    ]
    
    result = rebalance_shards(shards, node_count=3)
    
    for node, shard_list in sorted(result.items()):
        print(f"Node {node}:")
        for shard in shard_list:
            print(f"  Shard {shard.id}: [{shard.start}-{shard.end}]")