//
//  XUDPServer.m
//  xcmd
//
//  Created by mac on 2025/2/17.
//

#import <Foundation/Foundation.h>
#include <complex.h>
#import <sys/socket.h>


#import "XUDPServer.h"
#import "UDPHandler.h"


#define FALLBACK_PORT_START 6001
#define FALLBACK_PORT_END 7000

#define PORT 6001

@interface XUDPServer() {
@private 
    GCDAsyncUdpSocket *serverSocket;
    dispatch_queue_t serverQueue;  // 专用队列
    dispatch_source_t restartTimer;  // 重用的定时器
    NSUInteger restartAttempts;
    uint16_t currentPort;
}

@end

@implementation XUDPServer

+(instancetype)sharedInstance
{
    static XUDPServer* _sharedInstance = nil;
    static dispatch_once_t oncePredicate;
    dispatch_once (&oncePredicate, ^{
        _sharedInstance = [[XUDPServer alloc] init];
    });
    return _sharedInstance;
}

-(instancetype)init {
    if (self = [super init]) {
        restartAttempts = 0;
        // 创建串行队列，避免并发问题
        currentPort = PORT;
        serverQueue = dispatch_queue_create("com.xudpserver.queue", DISPATCH_QUEUE_SERIAL);
        return self;
    }
    return nil;
}

- (void)start {
    // 使用专用队列，确保操作串行化
    dispatch_async(serverQueue, ^{
        [self _startInternal];
    });
}

- (uint16_t) udp_port {
    return currentPort;
}

- (void) _startInternal {
    NSLog(@"XS- start udp server");
    // 避免重复创建
    if (serverSocket && !serverSocket.isClosed) {
        NSLog(@"UDP server already running");
        return;
    }
    
     [self _stopInternal];
    
    serverSocket = [[GCDAsyncUdpSocket alloc] initWithDelegate:self 
                                                 delegateQueue:serverQueue];
    // ⭐️ 关键修复:启用地址重用
    NSError *error = nil;
    if (![serverSocket enableReusePort:YES error:&error]) {
        NSLog(@"❌ Error enabling reuse port: %@", error);
    }
    // ⭐️ 设置 SO_REUSEADDR
    int reuseOn = 1;
    if (setsockopt([serverSocket socketFD], SOL_SOCKET, SO_REUSEADDR, 
                   &reuseOn, sizeof(reuseOn)) == -1) {
        NSLog(@"❌ Error setting SO_REUSEADDR");
    }
    if (![serverSocket bindToPort:currentPort error:&error]) {
        NSLog(@"❌ Error binding to port %d: %@", currentPort, error);
        
        // ⭐️ 绑定失败后清理 socket
        [serverSocket close];
        serverSocket = nil;
        
        if (error.code == 48) { // EADDRINUSE
            NSLog(@"⚠️ Port %d is in use (possibly TIME_WAIT)", currentPort);
            [self _tryFallbackPorts];
            return;
        }
        
        [self _scheduleRestartWithBackoff];
        return;
    }
    
    if (![serverSocket beginReceiving:&error]) {
            NSLog(@"❌ Error starting server (recv): %@", error);
            
            // ⭐️ 接收失败后清理 socket
            [serverSocket close];
            serverSocket = nil;
            
            [self _scheduleRestartWithBackoff];
            return;
        }

    restartAttempts = 0;  // 重置重试计数
    NSLog(@"✅ UDP server started successfully on port %d", currentPort);

}
- (void)stop {
    dispatch_async(serverQueue, ^{
        [self _stopInternal];
    });
}

- (void)_stopInternal {
   [self _cancelRestartTimer];
    
    if (serverSocket) {
        NSLog(@"Stopping UDP server on port %d", currentPort);
        
        // ⭐️ 确保完全关闭
        if (!serverSocket.isClosed) {
            [serverSocket close];
        }
        
        serverSocket = nil;
    }
}
#pragma mark - Restart Logic with Backoff

- (void)_cancelRestartTimer {
    if (restartTimer) {
        dispatch_source_cancel(restartTimer);
        restartTimer = nil;
    }
}

- (void)_scheduleRestartWithBackoff {
    // 取消之前的定时器
    [self _cancelRestartTimer];
    
    // 限制重试次数
    const NSUInteger maxAttempts = 10;
    if (restartAttempts >= maxAttempts) {
        NSLog(@"❌ Maximum restart attempts (%lu) reached, giving up", 
              (unsigned long)maxAttempts);
        return;
    }
    
    restartAttempts++;
    
    // 指数退避：1s, 2s, 4s, 8s, 16s, 最大60s
    NSTimeInterval delay = MIN(pow(2, restartAttempts - 1), 60.0);
    
    NSLog(@"⏰ Scheduling restart attempt %lu in %.1f seconds", 
          (unsigned long)restartAttempts, delay);
    
    // 使用 dispatch_source 创建可取消的定时器
    restartTimer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, serverQueue);
    
    dispatch_source_set_timer(restartTimer, 
                             dispatch_time(DISPATCH_TIME_NOW, delay * NSEC_PER_SEC),
                             DISPATCH_TIME_FOREVER, 
                             0.1 * NSEC_PER_SEC);
    
    dispatch_source_set_event_handler(restartTimer, ^{
        [self _startInternal];
    });
    
    dispatch_resume(restartTimer);
}

- (void)_tryFallbackPorts {
   
   for (uint16_t port = FALLBACK_PORT_START; port <= FALLBACK_PORT_END; port++) {
        GCDAsyncUdpSocket *testSocket = [[GCDAsyncUdpSocket alloc] initWithDelegate:nil 
                                                                       delegateQueue:serverQueue];
        
        NSError *error = nil;
        if ([testSocket bindToPort:port error:&error]) {
            [testSocket close];
            
            // 找到可用端口
            serverSocket = [[GCDAsyncUdpSocket alloc] initWithDelegate:self 
                                                         delegateQueue:serverQueue];
            
            if ([serverSocket bindToPort:port error:&error] && 
                [serverSocket beginReceiving:&error]) {
                currentPort = port;
                restartAttempts = 0;
                NSLog(@"✅ UDP server started on fallback port %d", currentPort);
                return;
            }
        }
        [testSocket close];
    } 
    NSLog(@"❌ No available ports found");
    [self _scheduleRestartWithBackoff];
}



- (void)scheduleRestart {
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(5.0 * NSEC_PER_SEC)), 
                   serverQueue, ^{
        [self start];
    });
}


// 网络连接成功后  自动回调
- (void)udpSocket:(GCDAsyncUdpSocket *)sock didConnectToAddress:(NSData *)address
{
   NSLog(@"已连接到用户:ip:%@",[[NSString alloc]initWithData:address encoding:NSUTF8StringEncoding]);
}

-(void)udpSocket:(GCDAsyncUdpSocket *)sock didReceiveData:(NSData *)data fromAddress:(NSData *)address withFilterContext:(id)filterContext
{
    @autoreleasepool {
        // 安全的字符串转换
        NSString *datastr = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
        if (!datastr) {
            NSLog(@"Failed to decode received data");
            return;
        }
        
        NSLog(@"XS- UDP Request>>>> %@", datastr);
        
        UDPHandler *handle = [UDPHandler sharedInstance];
        NSString *res = [handle handle:datastr];
        
        if (res) {
            NSData *responseData = [res dataUsingEncoding:NSUTF8StringEncoding];
            [sock sendData:responseData toAddress:address withTimeout:10.0 tag:300];
        }
    }
}


- (void)udpSocket:(GCDAsyncUdpSocket *)sock didNotConnect:(NSError * _Nullable)error
{
    NSLog(@"didNotConnect:%@", error);
}


- (void)udpSocket:(GCDAsyncUdpSocket *)sock didSendDataWithTag:(long)tag
{
    NSLog(@"didSendDataWithTag:%ld", tag);
}


- (void)udpSocket:(GCDAsyncUdpSocket *)sock didNotSendDataWithTag:(long)tag dueToError:(NSError * _Nullable)error
{
    NSLog(@"didNotSendDataWithTag:%@", error);
}


- (void)udpSocketDidClose:(GCDAsyncUdpSocket *)sock withError:(NSError  * _Nullable)error
{
    NSLog(@"withError:%@", error);
    if (error) {
        [self scheduleRestart]; // 自动重连
    }
}

- (void)dealloc {
    [self _cancelRestartTimer];
    [self _stopInternal];
}

@end