import Foundation

struct RetryPolicy {
    let maxAttempts: Int
    let baseDelay:   TimeInterval
    let maxDelay:    TimeInterval
    let shouldRetry: (Error) -> Bool

    static let fileSave = RetryPolicy(maxAttempts: 4, baseDelay: 0.25, maxDelay: 4.0) { _ in true }
    static let network  = RetryPolicy(maxAttempts: 3, baseDelay: 0.5,  maxDelay: 8.0) { error in
        let retryable: Set<Int> = [NSURLErrorTimedOut, NSURLErrorNetworkConnectionLost,
                                   NSURLErrorNotConnectedToInternet, NSURLErrorCannotConnectToHost]
        return retryable.contains((error as NSError).code)
    }
}

func withRetry<T>(policy: RetryPolicy, operation: @escaping () async throws -> T) async throws -> T {
    var lastError: Error?
    var delay = policy.baseDelay
    for attempt in 1...policy.maxAttempts {
        do { return try await operation() }
        catch {
            lastError = error
            guard policy.shouldRetry(error), attempt < policy.maxAttempts else { break }
            let jitter = Double.random(in: 0...0.3) * delay
            try? await Task.sleep(for: .seconds(min(delay + jitter, policy.maxDelay)))
            delay = min(delay * 2, policy.maxDelay)
        }
    }
    throw lastError ?? URLError(.unknown)
}