import hashlib
import os
from typing import List, Tuple

def get_file_hash(file_path: str) -> str:
    """Calculate MD5 hash of a file"""
    hash_md5 = hashlib.md5()
    with open(file_path, "rb") as f:
        for chunk in iter(lambda: f.read(4096), b""):
            hash_md5.update(chunk)
    return hash_md5.hexdigest()

def detect_encoding(file_path: str) -> str:
    """Detect file encoding"""
    # Try to import chardet, if not available use fallback
    chardet = None
    try:
        import chardet as chardet_module
        chardet = chardet_module
    except ImportError:
        pass
    
    if chardet:
        with open(file_path, "rb") as f:
            raw_data = f.read()
            result = chardet.detect(raw_data)
            encoding = result["encoding"]
            
            # Priority: UTF-8 > GBK > others
            if encoding and encoding.lower().startswith("utf-8"):
                return "utf-8"
            elif encoding and encoding.lower() == "gbk":
                return "gbk"
            else:
                return encoding
    else:
        # Fallback if chardet is not available
        return "utf-8"

def read_text_file(file_path: str) -> str:
    """Read text file with automatic encoding detection"""
    try:
        encoding = detect_encoding(file_path)
        if not encoding:
            raise ValueError("无法识别文件编码")
            
        with open(file_path, "r", encoding=encoding) as f:
            return f.read()
    except UnicodeDecodeError:
        # Fallback to utf-8 with error handling
        with open(file_path, "r", encoding="utf-8", errors="ignore") as f:
            return f.read()
    except Exception as e:
        raise ValueError(f"文件读取失败: {str(e)}")

def split_into_paragraphs(text: str) -> List[str]:
    """Split text into paragraphs with improved logic"""
    import re
    
    # 首先尝试按标题分割
    # 查找标题模式（以数字或汉字开头，后跟顿号、点或空格）
    title_pattern = r'(?:^|\n)([一二三四五六七八九十\d]+[\.、 ]+.*?)(?=\n[一二三四五六七八九十\d]+[\.、 ]+|$)'
    title_matches = re.findall(title_pattern, text)
    
    if title_matches:
        # 按标题分割
        sections = re.split(title_pattern, text)
        # 移除空字符串并重新组织
        sections = [s.strip() for s in sections if s.strip()]
        return sections
    
    # 然后尝试按双换行符分割（段落）
    paragraphs = text.split("\n\n")
    
    # 如果段落太少，尝试按句子分割
    if len(paragraphs) <= 2:
        # 使用更复杂的句子分割逻辑
        sentence_endings = r'[。！？.!?;；]'
        sentences = re.split(sentence_endings, text)
        sentences = [s.strip() for s in sentences if s.strip()]
        
        # 组合短句子
        combined_sentences = []
        current_sentence = ""
        
        for sentence in sentences:
            if not sentence:
                continue
                
            # 添加标点符号（除了最后一个句子）
            if sentence != sentences[-1]:
                sentence += text[text.find(sentence) + len(sentence)] if text.find(sentence) + len(sentence) < len(text) else "。"
            
            current_sentence += sentence
            
            # 如果当前句子足够长或者遇到明显的句子结束符
            if len(current_sentence) > 50 or re.search(r'[。！？.!?]$', sentence):
                combined_sentences.append(current_sentence)
                current_sentence = ""
        
        # 添加剩余的句子
        if current_sentence:
            combined_sentences.append(current_sentence)
            
        return combined_sentences
    
    # 过滤空段落
    return [p.strip() for p in paragraphs if p.strip()]

def clean_text(text: str) -> str:
    """Clean text by removing noise"""
    lines = text.split("\n")
    cleaned_lines = []
    
    # Remove header/footer patterns
    skip_patterns = [r"第\d+页", r"^\s*$"]
    
    import re
    for line in lines:
        # Skip lines with header/footer patterns
        if any(re.search(pattern, line) for pattern in skip_patterns):
            continue
            
        # Skip lines with乱码 (garbled text)
        if "锘" in line or "???" in line:
            continue
            
        cleaned_lines.append(line)
    
    # Remove consecutive duplicate lines (3 or more)
    final_lines = []
    prev_line = ""
    repeat_count = 0
    
    for line in cleaned_lines:
        if line == prev_line:
            repeat_count += 1
            if repeat_count < 3:  # Keep up to 2 duplicates
                final_lines.append(line)
        else:
            repeat_count = 0
            final_lines.append(line)
            prev_line = line
    
    return "\n".join(final_lines)