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

#import "Segmenter.h"

@interface Segmenter ()

@property(nonatomic, strong) NSMutableString *buffer;
@property(nonatomic, strong) NSMutableArray<NSString *> *readySegments;

@end

@implementation Segmenter

- (instancetype)init {
  self = [super init];
  if (self) {
    _buffer = [[NSMutableString alloc] init];
    _readySegments = [[NSMutableArray alloc] init];
    _maxCharacterThreshold = 30;
  }
  return self;
}

#pragma mark - Public Methods

- (void)appendToken:(NSString *)token {
  if (!token || token.length == 0) {
    return;
  }

  [self.buffer appendString:token];

  // 检查是否需要切分
  [self checkAndSplit];
}

- (NSArray<NSString *> *)popReadySegments {
  NSArray *segments = [self.readySegments copy];
  [self.readySegments removeAllObjects];
  return segments;
}

- (NSString *)flushRemainingSegment {
  NSString *remaining = [self.buffer copy];
  [self.buffer setString:@""];

  // 去除首尾空白
  remaining = [remaining
      stringByTrimmingCharactersInSet:[NSCharacterSet
                                          whitespaceAndNewlineCharacterSet]];

  return remaining.length > 0 ? remaining : nil;
}

- (void)reset {
  [self.buffer setString:@""];
  [self.readySegments removeAllObjects];
}

#pragma mark - Private Methods

- (void)checkAndSplit {
  // 句子结束标点
  NSCharacterSet *sentenceEnders =
      [NSCharacterSet characterSetWithCharactersInString:@"。！？\n"];

  while (YES) {
    NSString *currentBuffer = self.buffer;

    // 查找第一个句子结束标点
    NSRange range = [currentBuffer rangeOfCharacterFromSet:sentenceEnders];

    if (range.location != NSNotFound) {
      // 找到结束标点，切分
      NSUInteger endIndex = range.location + 1;
      NSString *segment = [currentBuffer substringToIndex:endIndex];
      segment = [segment stringByTrimmingCharactersInSet:
                             [NSCharacterSet whitespaceAndNewlineCharacterSet]];

      if (segment.length > 0) {
        [self.readySegments addObject:segment];
      }

      // 移除已切分的部分
      [self.buffer deleteCharactersInRange:NSMakeRange(0, endIndex)];
    } else if (currentBuffer.length >= self.maxCharacterThreshold) {
      // 未找到标点，但超过阈值，强制切分
      // 尝试在空格或逗号处切分
      NSRange breakRange = [self findBestBreakPoint:currentBuffer];

      if (breakRange.location != NSNotFound) {
        NSString *segment =
            [currentBuffer substringToIndex:breakRange.location + 1];
        segment =
            [segment stringByTrimmingCharactersInSet:
                         [NSCharacterSet whitespaceAndNewlineCharacterSet]];

        if (segment.length > 0) {
          [self.readySegments addObject:segment];
        }

        [self.buffer
            deleteCharactersInRange:NSMakeRange(0, breakRange.location + 1)];
      } else {
        // 无法找到合适的断点，直接切分
        NSString *segment =
            [currentBuffer substringToIndex:self.maxCharacterThreshold];
        segment =
            [segment stringByTrimmingCharactersInSet:
                         [NSCharacterSet whitespaceAndNewlineCharacterSet]];

        if (segment.length > 0) {
          [self.readySegments addObject:segment];
        }

        [self.buffer
            deleteCharactersInRange:NSMakeRange(0, self.maxCharacterThreshold)];
      }
    } else {
      // 未达到切分条件
      break;
    }
  }
}

- (NSRange)findBestBreakPoint:(NSString *)text {
  // 优先在逗号、分号等处断开
  NSCharacterSet *breakChars =
      [NSCharacterSet characterSetWithCharactersInString:@"，,、；;：: "];

  // 从后往前查找，尽可能多包含内容
  for (NSInteger i = text.length - 1; i >= self.maxCharacterThreshold / 2;
       i--) {
    unichar c = [text characterAtIndex:i];
    if ([breakChars characterIsMember:c]) {
      return NSMakeRange(i, 1);
    }
  }

  return NSMakeRange(NSNotFound, 0);
}

@end