//
//  LLMStreamClient.m
//  keyBoard
//
//  Created by Mac on 2026/1/15.
//

#import "LLMStreamClient.h"

@interface LLMStreamClient () <NSURLSessionDataDelegate>

@property(nonatomic, strong) NSURLSession *urlSession;
@property(nonatomic, strong) NSURLSessionDataTask *dataTask;
@property(nonatomic, strong) dispatch_queue_t networkQueue;
@property(nonatomic, assign) BOOL generating;
@property(nonatomic, strong) NSMutableString *buffer; // SSE 数据缓冲

@end

@implementation LLMStreamClient

- (instancetype)init {
  self = [super init];
  if (self) {
    _networkQueue = dispatch_queue_create("com.keyboard.aitalk.llm.network",
                                          DISPATCH_QUEUE_SERIAL);
    _buffer = [[NSMutableString alloc] init];
    // TODO: 替换为实际的 LLM 服务器地址
    _serverURL = @"https://your-llm-server.com/api/chat/stream";
  }
  return self;
}

- (void)dealloc {
  [self cancel];
}

#pragma mark - Public Methods

- (void)sendUserText:(NSString *)text
      conversationId:(NSString *)conversationId {
  dispatch_async(self.networkQueue, ^{
    [self cancelInternal];

    self.generating = YES;
    [self.buffer setString:@""];

    // 创建请求
    NSURL *url = [NSURL URLWithString:self.serverURL];
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
    request.HTTPMethod = @"POST";
    [request setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
    [request setValue:@"text/event-stream" forHTTPHeaderField:@"Accept"];

    if (self.apiKey) {
      [request setValue:[NSString stringWithFormat:@"Bearer %@", self.apiKey]
          forHTTPHeaderField:@"Authorization"];
    }

    // 请求体
    NSDictionary *body = @{
      @"message" : text,
      @"conversationId" : conversationId,
      @"stream" : @YES
    };

    NSError *jsonError = nil;
    NSData *jsonData = [NSJSONSerialization dataWithJSONObject:body
                                                       options:0
                                                         error:&jsonError];
    if (jsonError) {
      [self reportError:jsonError];
      return;
    }
    request.HTTPBody = jsonData;

    // 创建会话
    NSURLSessionConfiguration *config =
        [NSURLSessionConfiguration defaultSessionConfiguration];
    config.timeoutIntervalForRequest = 60;
    config.timeoutIntervalForResource = 300;

    self.urlSession = [NSURLSession sessionWithConfiguration:config
                                                    delegate:self
                                               delegateQueue:nil];

    self.dataTask = [self.urlSession dataTaskWithRequest:request];
    [self.dataTask resume];

    NSLog(@"[LLMStreamClient] Started request for conversation: %@",
          conversationId);
  });
}

- (void)cancel {
  dispatch_async(self.networkQueue, ^{
    [self cancelInternal];
  });
}

#pragma mark - Private Methods

- (void)cancelInternal {
  self.generating = NO;

  if (self.dataTask) {
    [self.dataTask cancel];
    self.dataTask = nil;
  }

  if (self.urlSession) {
    [self.urlSession invalidateAndCancel];
    self.urlSession = nil;
  }

  [self.buffer setString:@""];
}

- (void)reportError:(NSError *)error {
  self.generating = NO;
  dispatch_async(dispatch_get_main_queue(), ^{
    if ([self.delegate respondsToSelector:@selector(llmClientDidFail:)]) {
      [self.delegate llmClientDidFail:error];
    }
  });
}

- (void)reportComplete {
  self.generating = NO;
  dispatch_async(dispatch_get_main_queue(), ^{
    if ([self.delegate respondsToSelector:@selector(llmClientDidComplete)]) {
      [self.delegate llmClientDidComplete];
    }
  });
}

- (void)reportToken:(NSString *)token {
  dispatch_async(dispatch_get_main_queue(), ^{
    if ([self.delegate
            respondsToSelector:@selector(llmClientDidReceiveToken:)]) {
      [self.delegate llmClientDidReceiveToken:token];
    }
  });
}

#pragma mark - SSE Parsing

- (void)parseSSEData:(NSData *)data {
  NSString *string = [[NSString alloc] initWithData:data
                                           encoding:NSUTF8StringEncoding];
  if (!string)
    return;

  [self.buffer appendString:string];

  // SSE 格式：每个事件以 \n\n 分隔
  NSArray *events = [self.buffer componentsSeparatedByString:@"\n\n"];

  // 保留最后一个可能不完整的事件
  if (events.count > 1) {
    [self.buffer setString:events.lastObject];

    for (NSUInteger i = 0; i < events.count - 1; i++) {
      [self handleSSEEvent:events[i]];
    }
  }
}

- (void)handleSSEEvent:(NSString *)event {
  if (event.length == 0)
    return;

  // 解析 SSE 事件
  // 格式: data: {...}
  NSArray *lines = [event componentsSeparatedByString:@"\n"];

  for (NSString *line in lines) {
    if ([line hasPrefix:@"data: "]) {
      NSString *dataString = [line substringFromIndex:6];

      // 检查是否是结束标志
      if ([dataString isEqualToString:@"[DONE]"]) {
        [self reportComplete];
        return;
      }

      // 解析 JSON
      NSData *jsonData = [dataString dataUsingEncoding:NSUTF8StringEncoding];
      NSError *jsonError = nil;
      NSDictionary *json = [NSJSONSerialization JSONObjectWithData:jsonData
                                                           options:0
                                                             error:&jsonError];

      if (jsonError) {
        NSLog(@"[LLMStreamClient] Failed to parse SSE data: %@", dataString);
        continue;
      }

      // 提取 token（根据实际 API 格式调整）
      // 常见格式: {"token": "..."} 或 {"choices": [{"delta": {"content":
      // "..."}}]}
      NSString *token = json[@"token"];
      if (!token) {
        // OpenAI 格式
        NSArray *choices = json[@"choices"];
        if (choices.count > 0) {
          NSDictionary *delta = choices[0][@"delta"];
          token = delta[@"content"];
        }
      }

      if (token && token.length > 0) {
        [self reportToken:token];
      }
    }
  }
}

#pragma mark - NSURLSessionDataDelegate

- (void)URLSession:(NSURLSession *)session
          dataTask:(NSURLSessionDataTask *)dataTask
    didReceiveData:(NSData *)data {
  [self parseSSEData:data];
}

- (void)URLSession:(NSURLSession *)session
                    task:(NSURLSessionTask *)task
    didCompleteWithError:(NSError *)error {
  if (error) {
    if (error.code != NSURLErrorCancelled) {
      [self reportError:error];
    }
  } else {
    // 处理缓冲区中剩余的数据
    if (self.buffer.length > 0) {
      [self handleSSEEvent:self.buffer];
      [self.buffer setString:@""];
    }
    [self reportComplete];
  }
}

@end