291 lines
10 KiB
Swift
291 lines
10 KiB
Swift
import Foundation
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/// 网络请求封装 - 对应 Android 版 OkGo
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class NetworkManager {
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/// 全局共享实例。
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static let shared = NetworkManager()
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/// 默认最大重试次数（不含首次请求）。
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static let defaultMaxRetries = 2
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/// 重试基础延迟（秒），实际延迟 = base * 2^attempt + jitter。
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private static let retryBaseDelay: TimeInterval = 0.5
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/// 重试最大延迟上限（秒）。
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private static let retryMaxDelay: TimeInterval = 8.0
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/// 兜底字符集名称列表（按常见中文资源站编码优先级排序）。
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private static let fallbackCharsetNames: [String] = [
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"utf-8",
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"gb18030",
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"gbk",
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"gb2312",
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"utf-16",
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"utf-16le",
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"utf-16be",
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"utf-32",
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"windows-1252",
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"iso-8859-1"
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]
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/// 兜底字符串编码列表（与字符集列表互补）。
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private static let fallbackStringEncodings: [String.Encoding] = [
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.utf8,
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.utf16,
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.utf16LittleEndian,
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.utf16BigEndian,
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.utf32,
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.utf32LittleEndian,
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.utf32BigEndian,
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.windowsCP1252,
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.isoLatin1
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]
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/// 内部会话对象，统一超时与连接上限配置。
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private let session: URLSession
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/// JSON 解码器。
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private let decoder = JSONDecoder()
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/// 私有初始化，防止外部创建多个请求管理器。
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private init() {
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let config = URLSessionConfiguration.default
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config.timeoutIntervalForRequest = 15
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config.timeoutIntervalForResource = 30
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config.httpMaximumConnectionsPerHost = 5
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config.waitsForConnectivity = true
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self.session = URLSession(configuration: config)
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}
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/// GET 请求获取字符串，支持自动重试。
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func getString(
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from urlString: String,
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headers: [String: String]? = nil,
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maxRetries: Int = NetworkManager.defaultMaxRetries
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) async throws -> String {
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guard let url = URL(string: urlString.trimmingCharacters(in: .whitespacesAndNewlines)) else {
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throw NetworkError.invalidURL(urlString)
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}
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var request = URLRequest(url: url)
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request.httpMethod = "GET"
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headers?.forEach { request.setValue($1, forHTTPHeaderField: $0) }
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let (data, httpResponse) = try await performRequest(request, maxRetries: maxRetries)
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guard let str = Self.decodeString(data: data, response: httpResponse) else {
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throw NetworkError.decodingError("文本解码失败")
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}
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return str
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}
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/// GET 请求解码 JSON，支持自动重试。
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func getJSON<T: Decodable>(
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from urlString: String,
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type: T.Type,
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headers: [String: String]? = nil,
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maxRetries: Int = NetworkManager.defaultMaxRetries
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) async throws -> T {
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let str = try await getString(from: urlString, headers: headers, maxRetries: maxRetries)
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guard let data = str.data(using: .utf8) else {
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throw NetworkError.decodingError("字符串转 Data 失败")
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}
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return try decoder.decode(T.self, from: data)
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}
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/// GET 请求获取原始 Data，支持自动重试和 HTTP 状态码校验。
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func getData(
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from urlString: String,
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maxRetries: Int = NetworkManager.defaultMaxRetries
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) async throws -> Data {
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guard let url = URL(string: urlString.trimmingCharacters(in: .whitespacesAndNewlines)) else {
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throw NetworkError.invalidURL(urlString)
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}
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let request = URLRequest(url: url)
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let (data, _) = try await performRequest(request, maxRetries: maxRetries)
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return data
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}
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// MARK: - 带重试的核心请求方法
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/// 执行 HTTP 请求，遇到可重试错误时自动指数退避重试。
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private func performRequest(
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_ request: URLRequest,
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maxRetries: Int
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) async throws -> (Data, HTTPURLResponse) {
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var lastError: Error = NetworkError.invalidResponse
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let totalAttempts = max(1, maxRetries + 1)
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for attempt in 0..<totalAttempts {
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do {
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try Task.checkCancellation()
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let (data, response) = try await session.data(for: request)
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guard let httpResponse = response as? HTTPURLResponse else {
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throw NetworkError.invalidResponse
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}
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guard (200...299).contains(httpResponse.statusCode) else {
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let error = NetworkError.httpError(httpResponse.statusCode)
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if Self.isRetryableHTTPStatus(httpResponse.statusCode) && attempt < totalAttempts - 1 {
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lastError = error
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try await retryDelay(attempt: attempt)
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continue
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}
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throw error
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}
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return (data, httpResponse)
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} catch is CancellationError {
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throw CancellationError()
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} catch {
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lastError = error
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if Self.isRetryableError(error) && attempt < totalAttempts - 1 {
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try await retryDelay(attempt: attempt)
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continue
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}
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throw error
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}
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}
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throw lastError
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}
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/// 指数退避延迟 + 随机抖动，避免多请求同时重试造成惊群效应。
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private func retryDelay(attempt: Int) async throws {
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let base = Self.retryBaseDelay * pow(2.0, Double(attempt))
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let jitter = Double.random(in: 0...0.5)
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let delay = min(base + jitter, Self.retryMaxDelay)
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try await Task.sleep(nanoseconds: UInt64(delay * 1_000_000_000))
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}
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/// 判断 HTTP 状态码是否值得重试（仅服务端临时错误）。
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private static func isRetryableHTTPStatus(_ statusCode: Int) -> Bool {
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switch statusCode {
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case 408, 429, 500, 502, 503, 504: return true
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default: return false
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}
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}
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/// 判断错误是否为可重试的瞬态网络错误。
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private static func isRetryableError(_ error: Error) -> Bool {
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if error is CancellationError { return false }
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if let networkError = error as? NetworkError {
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if case .httpError(let code) = networkError {
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return isRetryableHTTPStatus(code)
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}
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if case .invalidURL = networkError { return false }
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if case .decodingError = networkError { return false }
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}
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let nsError = error as NSError
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if nsError.domain == NSURLErrorDomain {
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switch nsError.code {
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case NSURLErrorTimedOut,
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NSURLErrorCannotFindHost,
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NSURLErrorCannotConnectToHost,
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NSURLErrorNetworkConnectionLost,
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NSURLErrorDNSLookupFailed,
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NSURLErrorNotConnectedToInternet,
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NSURLErrorSecureConnectionFailed,
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NSURLErrorDataNotAllowed:
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return true
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default:
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return false
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}
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}
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return false
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}
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/// 文本解码策略：
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/// 1) 先用响应头声明字符集；
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/// 2) 再按常见字符集与编码顺序尝试；
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/// 3) 最后用 UTF-8 宽容解码兜底。
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private static func decodeString(data: Data, response: HTTPURLResponse) -> String? {
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// 优先使用服务端声明的字符集（如 gbk / gb2312 / gb18030）
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if let charset = response.textEncodingName,
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let declaredEncoding = encoding(fromIANACharset: charset),
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let value = String(data: data, encoding: declaredEncoding) {
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return value
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}
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for charset in fallbackCharsetNames {
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if let encoding = encoding(fromIANACharset: charset),
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let value = String(data: data, encoding: encoding) {
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return value
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}
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}
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for encoding in fallbackStringEncodings {
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if let value = String(data: data, encoding: encoding) {
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return value
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}
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}
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// 最后兜底，避免单纯因编码不一致直接报错
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if !data.isEmpty {
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return String(decoding: data, as: UTF8.self)
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}
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return nil
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}
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/// IANA 字符集名转 `String.Encoding`。
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private static func encoding(fromIANACharset charset: String) -> String.Encoding? {
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let cfEncoding = CFStringConvertIANACharSetNameToEncoding(charset as CFString)
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guard cfEncoding != kCFStringEncodingInvalidId else {
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return nil
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}
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let nsEncoding = CFStringConvertEncodingToNSStringEncoding(cfEncoding)
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return String.Encoding(rawValue: nsEncoding)
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}
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}
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/// 网络层错误定义。
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enum NetworkError: LocalizedError {
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case invalidURL(String)
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case invalidResponse
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case httpError(Int)
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case decodingError(String)
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/// 面向 UI/日志的错误描述。
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var errorDescription: String? {
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switch self {
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case .invalidURL(let url): return "无效的URL: \(url)"
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case .invalidResponse: return "无效的响应"
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case .httpError(let code): return "HTTP 错误: \(code)"
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case .decodingError(let msg): return "解码错误: \(msg)"
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}
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}
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/// 是否为网络不可用导致的错误（供 UI 层判断是否显示网络提示）。
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var isNetworkUnavailable: Bool {
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if case .httpError = self { return false }
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return true
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}
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}
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extension Error {
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/// 判断是否为网络连接类错误（超时、断网、DNS 失败等）。
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var isNetworkConnectionError: Bool {
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if self is CancellationError { return false }
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let nsError = self as NSError
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if nsError.domain == NSURLErrorDomain {
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switch nsError.code {
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case NSURLErrorTimedOut,
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NSURLErrorCannotFindHost,
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NSURLErrorCannotConnectToHost,
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NSURLErrorNetworkConnectionLost,
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NSURLErrorDNSLookupFailed,
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NSURLErrorNotConnectedToInternet,
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NSURLErrorDataNotAllowed:
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return true
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default:
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return false
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}
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}
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return false
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}
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}
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