fix network

2026-03-10 21:37:51 +08:00
parent 76ed32ccf3
commit fac70d7496
7 changed files with 383 additions and 37 deletions
@@ -5,6 +5,13 @@ class NetworkManager {
    /// 全局共享实例。
    static let shared = NetworkManager()
    
+    /// 默认最大重试次数（不含首次请求）。
+    static let defaultMaxRetries = 2
+    /// 重试基础延迟（秒），实际延迟 = base * 2^attempt + jitter。
+    private static let retryBaseDelay: TimeInterval = 0.5
+    /// 重试最大延迟上限（秒）。
+    private static let retryMaxDelay: TimeInterval = 8.0
+    
    /// 兜底字符集名称列表（按常见中文资源站编码优先级排序）。
    private static let fallbackCharsetNames: [String] = [
        "utf-8",
@@ -43,11 +50,16 @@ class NetworkManager {
        config.timeoutIntervalForRequest = 15
        config.timeoutIntervalForResource = 30
        config.httpMaximumConnectionsPerHost = 5
+        config.waitsForConnectivity = true
        self.session = URLSession(configuration: config)
    }
    
-    /// GET 请求获取字符串
-    func getString(from urlString: String, headers: [String: String]? = nil) async throws -> String {
+    /// GET 请求获取字符串，支持自动重试。
+    func getString(
+        from urlString: String,
+        headers: [String: String]? = nil,
+        maxRetries: Int = NetworkManager.defaultMaxRetries
+    ) async throws -> String {
        guard let url = URL(string: urlString.trimmingCharacters(in: .whitespacesAndNewlines)) else {
            throw NetworkError.invalidURL(urlString)
        }
@@ -56,17 +68,8 @@ class NetworkManager {
        request.httpMethod = "GET"
        headers?.forEach { request.setValue($1, forHTTPHeaderField: $0) }
        
-        let (data, response) = try await session.data(for: request)
+        let (data, httpResponse) = try await performRequest(request, maxRetries: maxRetries)
        
-        guard let httpResponse = response as? HTTPURLResponse else {
-            throw NetworkError.invalidResponse
-        }
-        
-        guard (200...299).contains(httpResponse.statusCode) else {
-            throw NetworkError.httpError(httpResponse.statusCode)
-        }
-        
-        // 统一走字符集探测 + 多编码兜底，降低跨源乱码概率。
        guard let str = Self.decodeString(data: data, response: httpResponse) else {
            throw NetworkError.decodingError("文本解码失败")
        }
@@ -74,24 +77,127 @@ class NetworkManager {
        return str
    }
    
-    /// GET 请求解码 JSON
-    func getJSON<T: Decodable>(from urlString: String, type: T.Type, headers: [String: String]? = nil) async throws -> T {
-        let str = try await getString(from: urlString, headers: headers)
+    /// GET 请求解码 JSON，支持自动重试。
+    func getJSON<T: Decodable>(
+        from urlString: String,
+        type: T.Type,
+        headers: [String: String]? = nil,
+        maxRetries: Int = NetworkManager.defaultMaxRetries
+    ) async throws -> T {
+        let str = try await getString(from: urlString, headers: headers, maxRetries: maxRetries)
        guard let data = str.data(using: .utf8) else {
            throw NetworkError.decodingError("字符串转 Data 失败")
        }
        return try decoder.decode(T.self, from: data)
    }
    
-    /// GET 请求获取原始 Data
-    func getData(from urlString: String) async throws -> Data {
+    /// GET 请求获取原始 Data，支持自动重试和 HTTP 状态码校验。
+    func getData(
+        from urlString: String,
+        maxRetries: Int = NetworkManager.defaultMaxRetries
+    ) async throws -> Data {
        guard let url = URL(string: urlString.trimmingCharacters(in: .whitespacesAndNewlines)) else {
            throw NetworkError.invalidURL(urlString)
        }
-        let (data, _) = try await session.data(from: url)
+        let request = URLRequest(url: url)
+        let (data, _) = try await performRequest(request, maxRetries: maxRetries)
        return data
    }
    
+    // MARK: - 带重试的核心请求方法
+    
+    /// 执行 HTTP 请求，遇到可重试错误时自动指数退避重试。
+    private func performRequest(
+        _ request: URLRequest,
+        maxRetries: Int
+    ) async throws -> (Data, HTTPURLResponse) {
+        var lastError: Error = NetworkError.invalidResponse
+        let totalAttempts = max(1, maxRetries + 1)
+        
+        for attempt in 0..<totalAttempts {
+            do {
+                try Task.checkCancellation()
+                
+                let (data, response) = try await session.data(for: request)
+                
+                guard let httpResponse = response as? HTTPURLResponse else {
+                    throw NetworkError.invalidResponse
+                }
+                
+                guard (200...299).contains(httpResponse.statusCode) else {
+                    let error = NetworkError.httpError(httpResponse.statusCode)
+                    if Self.isRetryableHTTPStatus(httpResponse.statusCode) && attempt < totalAttempts - 1 {
+                        lastError = error
+                        try await retryDelay(attempt: attempt)
+                        continue
+                    }
+                    throw error
+                }
+                
+                return (data, httpResponse)
+            } catch is CancellationError {
+                throw CancellationError()
+            } catch {
+                lastError = error
+                if Self.isRetryableError(error) && attempt < totalAttempts - 1 {
+                    try await retryDelay(attempt: attempt)
+                    continue
+                }
+                throw error
+            }
+        }
+        
+        throw lastError
+    }
+    
+    /// 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。
+    private func retryDelay(attempt: Int) async throws {
+        let base = Self.retryBaseDelay * pow(2.0, Double(attempt))
+        let jitter = Double.random(in: 0...0.5)
+        let delay = min(base + jitter, Self.retryMaxDelay)
+        try await Task.sleep(nanoseconds: UInt64(delay * 1_000_000_000))
+    }
+    
+    /// 判断 HTTP 状态码是否值得重试（仅服务端临时错误）。
+    private static func isRetryableHTTPStatus(_ statusCode: Int) -> Bool {
+        switch statusCode {
+        case 408, 429, 500, 502, 503, 504: return true
+        default: return false
+        }
+    }
+    
+    /// 判断错误是否为可重试的瞬态网络错误。
+    private static func isRetryableError(_ error: Error) -> Bool {
+        if error is CancellationError { return false }
+        
+        if let networkError = error as? NetworkError {
+            if case .httpError(let code) = networkError {
+                return isRetryableHTTPStatus(code)
+            }
+            if case .invalidURL = networkError { return false }
+            if case .decodingError = networkError { return false }
+        }
+        
+        let nsError = error as NSError
+        if nsError.domain == NSURLErrorDomain {
+            switch nsError.code {
+            case NSURLErrorTimedOut,
+                 NSURLErrorCannotFindHost,
+                 NSURLErrorCannotConnectToHost,
+                 NSURLErrorNetworkConnectionLost,
+                 NSURLErrorDNSLookupFailed,
+                 NSURLErrorNotConnectedToInternet,
+                 NSURLErrorSecureConnectionFailed,
+                 NSURLErrorDataNotAllowed:
+                return true
+            default:
+                return false
+            }
+        }
+        
+        return false
+    }
+    
    /// 文本解码策略：
    /// 1) 先用响应头声明字符集；
    /// 2) 再按常见字符集与编码顺序尝试；
@@ -152,4 +258,33 @@ enum NetworkError: LocalizedError {
        case .decodingError(let msg): return "解码错误: \(msg)"
        }
    }
+    
+    /// 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）。
+    var isNetworkUnavailable: Bool {
+        if case .httpError = self { return false }
+        return true
+    }
+}
+
+extension Error {
+    /// 判断是否为网络连接类错误（超时、断网、DNS 失败等）。
+    var isNetworkConnectionError: Bool {
+        if self is CancellationError { return false }
+        let nsError = self as NSError
+        if nsError.domain == NSURLErrorDomain {
+            switch nsError.code {
+            case NSURLErrorTimedOut,
+                 NSURLErrorCannotFindHost,
+                 NSURLErrorCannotConnectToHost,
+                 NSURLErrorNetworkConnectionLost,
+                 NSURLErrorDNSLookupFailed,
+                 NSURLErrorNotConnectedToInternet,
+                 NSURLErrorDataNotAllowed:
+                return true
+            default:
+                return false
+            }
+        }
+        return false
+    }
 }