"""
Document Loading and Chunking Module
"""
from typing import List, Dict, Optional
from datasets import load_dataset
import re


class DocumentLoader:
    """Loads and chunks documents for RAG system"""
    
    def __init__(self, chunk_size: int = 500, chunk_overlap: int = 50):
        self.chunk_size = chunk_size
        self.chunk_overlap = chunk_overlap
        self.documents = []
        self.chunks = []
        self.chunk_metadata = []
        
    def load_from_huggingface(
        self, 
        dataset_name: str, 
        split: str = "train",
        text_column: Optional[str] = None,
        max_docs: Optional[int] = None,
        hf_token: Optional[str] = None
    ):
        """Load documents from HuggingFace dataset"""
        print(f"Loading dataset: {dataset_name}")
        if hf_token:
            print("Using HuggingFace token for authentication")
        
        try:
            print("Using streaming mode for faster loading...")
            dataset = load_dataset(
                dataset_name, 
                split=split,
                streaming=True,
                token=hf_token if hf_token else None
            )
        except Exception as e:
            if "429" in str(e) or "rate limit" in str(e).lower():
                raise Exception(
                    f"Rate limit error: {str(e)}\n\n"
                    "To fix this:\n"
                    "1. Create a free HuggingFace account at https://huggingface.co/join\n"
                    "2. Get your token at https://huggingface.co/settings/tokens\n"
                    "3. Add it in the 'HuggingFace Token' field above"
                )
            raise
        
        documents = []
        count = 0
        for item in dataset:
            if max_docs and count >= max_docs:
                break
            if "chapters" in item and isinstance(item["chapters"], list):
                doc_text_parts = []
                
                if "title" in item and item["title"]:
                    doc_text_parts.append(item["title"])
                
                if "abstract" in item and item["abstract"]:
                    doc_text_parts.append(item["abstract"])
                
                for chapter in item["chapters"]:
                    if isinstance(chapter, dict):
                        if "head" in chapter and chapter["head"]:
                            doc_text_parts.append(chapter["head"])
                        
                        if "paragraphs" in chapter and isinstance(chapter["paragraphs"], list):
                            for para in chapter["paragraphs"]:
                                if isinstance(para, dict) and "text" in para and para["text"]:
                                    doc_text_parts.append(para["text"])
                
                full_text = "\n\n".join(doc_text_parts)
                if full_text.strip():
                    documents.append(full_text)
                    count += 1
                    if count % 10 == 0:
                        print(f"  Loaded {count} documents...")
            
            elif text_column and text_column in item:
                if isinstance(item[text_column], str):
                    documents.append(item[text_column])
                    count += 1
                elif isinstance(item[text_column], list):
                    documents.append("\n\n".join(str(p) for p in item[text_column]))
                    count += 1
            
            elif not text_column:
                for key in ["text", "content", "body", "context"]:
                    if key in item and isinstance(item[key], str):
                        documents.append(item[key])
                        count += 1
                        if count % 10 == 0:
                            print(f"  Loaded {count} documents...")
                        break
        
        self.documents = documents
        print(f"Loaded {len(self.documents)} documents from dataset")
        
    def load_from_texts(self, texts: List[str]):
        """Load documents from list of text strings"""
        self.documents = texts
        print(f"Loaded {len(self.documents)} documents")
    
    def _split_text(self, text: str) -> List[str]:
        """Split text into chunks with overlap"""
        sentences = re.split(r'(?<=[.!?])\s+', text)
        
        chunks = []
        current_chunk = ""
        
        for sentence in sentences:
            if len(current_chunk) + len(sentence) > self.chunk_size and current_chunk:
                chunks.append(current_chunk.strip())
                overlap_text = current_chunk[-self.chunk_overlap:] if len(current_chunk) > self.chunk_overlap else current_chunk
                current_chunk = overlap_text + " " + sentence
            else:
                current_chunk += " " + sentence if current_chunk else sentence
                
        if current_chunk.strip():
            chunks.append(current_chunk.strip())
            
        if not chunks and text.strip():
            chunks = [text.strip()]
            
        return chunks
        
    def _is_low_quality_chunk(self, chunk: str) -> bool:
        """Check if a chunk is low quality"""
        
        if len(chunk.strip()) < 50:
            return True
        
        if len(chunk.split()) < 10:
            return True
        
        return False
    
    def chunk_documents(self):
        """Chunk all loaded documents"""
        self.chunks = []
        self.chunk_metadata = []
        
        for doc_idx, doc in enumerate(self.documents):
            doc_chunks = self._split_text(doc)
            
            for chunk_idx, chunk in enumerate(doc_chunks):
                if not self._is_low_quality_chunk(chunk):
                    self.chunks.append(chunk)
                    self.chunk_metadata.append({
                        'doc_id': doc_idx,
                        'chunk_id': chunk_idx,
                        'total_chunks_in_doc': len(doc_chunks)
                    })
                
        print(f"Created {len(self.chunks)} chunks from {len(self.documents)} documents")
        
    def get_chunks(self) -> List[str]:
        """Get list of all chunks"""
        return self.chunks
        
    def get_chunk_metadata(self) -> List[Dict]:
        """Get metadata for all chunks"""
        return self.chunk_metadata