import Foundation

/// User-facing text for every failure the app can produce.
///
/// The relay work is what forced this out of `ConnectionProbe`: with one hop there was one thing
/// that could go wrong, and "请求失败" was an acceptable summary. With two hops there are four
/// distinct situations that call for four different actions, and a message that cannot tell them
/// apart is the difference between a five-second fix and a support thread.
public enum ErrorMessage {
    public static let network = "暂时无法连接实例，请稍后重试。"
    public static let unauthorized = "实例登录状态已失效，请重新登录。"

    // MARK: - Relay mode

    /// Describes a relay-mode failure in terms of what the user should do next.
    public static func describe(_ error: UpstreamError, nodeName: String) -> String {
        switch error {
        case .relayUnreachable:
            return "无法连接中继服务器。请检查网络，或确认中继是否在运行。"
        case .relayTimeout:
            return "中继响应超时。稍后重试；如果反复出现，请检查中继负载。"
        case .relayRejectedDevice:
            return "中继已不再接受这台设备的凭据，需要在节点上重新配对。"
        case .relayNodeUnknown:
            return "中继不认识节点 \(nodeName)。可能节点已离线并被移出，或这台手机未与该节点配对。"
        case .agentOffline:
            return "节点 \(nodeName) 的 agent 当前未连接到中继。等它上线后重试。"
        case .nodeBusy:
            return "节点 \(nodeName) 正在处理其它请求，稍后重试。"
        case .agentTimeout:
            // The one message that must not invite a blind retry: the node may have executed it.
            return "节点 \(nodeName) 未在时限内应答。该操作可能已经执行，请先确认结果再决定是否重试。"
        case .relayBadEnvelope:
            return "中继拒绝了发往节点 \(nodeName) 的请求信封。这通常意味着两端版本不一致。"
        case .relayRateLimited:
            return "对节点 \(nodeName) 的请求过于频繁，已被中继限流。稍后再试。"
        case .relayPolicyDenied:
            return "节点 \(nodeName) 的 agent 不允许该操作。该路径不在它的授权范围内。"
        case .confirmationRejected:
            return "节点 \(nodeName) 拒绝了这次确认：确认信息与请求不匹配，操作未执行。请重新发起。"
        case .envelopeExpired:
            return "对节点 \(nodeName) 的请求已过期或重复。请重新发起；如果反复出现，请检查手机与节点的时钟。"
        case .nodeRateLimited:
            return "节点 \(nodeName) 限制了危险写操作频率，稍后再试。"
        case .nodeAuthFailed:
            return "节点 \(nodeName) 的 agent 无法登录本机 SimAdmin。需要在节点上修正 agent 的密码配置。"
        case .payloadTooLarge:
            return "请求内容超过节点 \(nodeName) 允许的大小。"
        case .relayResponseUnverifiable:
            return "节点 \(nodeName) 的应答未通过签名校验，已丢弃。这可能是中继被篡改或密钥不匹配。"
        case .relayResponseMismatch:
            return "中继返回了与请求不匹配的应答，已丢弃。"
        case .envelopeRejected:
            return "节点 \(nodeName) 拒绝了该请求的签名或格式。可能需要在节点上重新配对。"
        case .unauthorized:
            return unauthorized
        case .timeout, .transportFailed:
            return network
        default:
            return "请求失败：\(error)"
        }
    }
}