import Foundation

/// 上传桥接协议常量与 registerTask 参数解析（P3 计划 Task 8）。
///
/// 与 Android 侧 `UploadProtocol.kt` 逐字对齐：通道名、方法名、事件名、
/// 失败码完全一致；Dart 侧 `lib/features/uploads/native_transport.dart`
/// 的 [UploadBridgeChannels] 为同一协议的单源镜像。
enum UploadBridge {
    /// 命令通道（registerTask / cancelTask / queryTask / ackEvents）。
    static let methodChannel = "photolive/uploads"

    /// 事件流（progress / completed / needsRenew / failed，带单调 seq）。
    static let eventChannel = "photolive/uploads/events"

    static let methodRegister = "registerTask"
    static let methodCancel = "cancelTask"
    static let methodQuery = "queryTask"
    static let methodAck = "ackEvents"

    static let eventProgress = "progress"
    static let eventCompleted = "completed"
    static let eventNeedsRenew = "needsRenew"
    static let eventFailed = "failed"

    /// 网络不可达/超时（重试上限耗尽后上报）。
    static let failNetwork = "NETWORK"

    /// 4xx 客户端错误（status 随事件携带；403 单独走 needsRenew）。
    static let failHttp4xx = "HTTP_4XX"

    /// 5xx 服务端错误（重试上限耗尽后上报）。
    static let failServerError = "SERVER_ERROR"

    /// 源文件缺失（受管副本被清理，不可恢复）。
    static let failSourceMissing = "SOURCE_MISSING"

    /// 后台 URLSession 标识（App 重启后系统按此重联会话）。
    static let sessionIdentifier = "com.photolive.photo_live.uploads"
}

/// registerTask 参数（Dart → 原生），字段与 Kotlin `UploadRegisterSpec` 一致。
struct UploadRegisterSpec {
    let taskId: String
    let url: String
    let method: String
    let headers: [String: String]
    let filePath: String
    let uploadId: String?
    let attempt: Int
}

/// 参数形状不符（插件层转 bad_args 错误，镜像 Kotlin IllegalArgumentException）。
struct UploadBridgeBadArgsError: Error {
    let message: String
}

/// registerTask 参数解析（纯函数；与 Kotlin `parseRegisterSpec` 同语义）。
///
/// 通道解码所得字典为 [String: Any]（Flutter 标准编解码 null → NSNull），
/// 显式 null 与类型不符同样归为 bad_args。
func parseRegisterSpec(_ args: [String: Any]) throws -> UploadRegisterSpec {
    func str(_ key: String) throws -> String {
        guard let v = args[key] as? String else {
            throw UploadBridgeBadArgsError(
                message: args[key] == nil ? "missing '\(key)'" : "'\(key)' must be a String"
            )
        }
        return v
    }
    let taskId = try str("taskId")
    let url = try str("url")
    let methodRaw = try str("method")
    let method = methodRaw.isEmpty ? "PUT" : methodRaw
    let filePath = try str("filePath")
    var headers: [String: String] = [:]
    if let raw = args["headers"] as? [String: Any] {
        for (k, v) in raw {
            guard let value = v as? String else {
                throw UploadBridgeBadArgsError(message: "'headers' must be Map<String, String>")
            }
            headers[k] = value
        }
    } else if args["headers"] != nil {
        throw UploadBridgeBadArgsError(message: "'headers' must be a Map")
    }
    var uploadId: String?
    var attempt = 0
    if let metadata = args["metadata"] as? [String: Any] {
        uploadId = metadata["uploadId"] as? String
        if let v = metadata["attempt"] as? NSNumber {
            attempt = v.intValue
        } else if let v = metadata["attempt"] as? Int {
            attempt = v
        } else if metadata["attempt"] != nil {
            throw UploadBridgeBadArgsError(message: "'metadata.attempt' must be an int")
        }
    }
    return UploadRegisterSpec(
        taskId: taskId,
        url: url,
        method: method,
        headers: headers,
        filePath: filePath,
        uploadId: uploadId,
        attempt: attempt
    )
}