Swift retry helper with capped exponential backoff

import Foundation

func retry<T>(attempts: Int = 4, base: TimeInterval = 0.2,
              operation: () throws -> T) throws -> T {
    var delay = base
    var lastError: Error?
    for attempt in 0..<attempts {
        do { return try operation() }
        catch {
            lastError = error
            if attempt < attempts - 1 {
                let jitter = Double.random(in: 0...delay)
                Thread.sleep(forTimeInterval: min(delay + jitter, 5))
            }
            delay = min(delay * 2, 5)
        }
    }
    throw lastError ?? CancellationError()
}