"""
PDF Parser Service for RAG Chatbot
Extracts text from PDF and splits into chunks for indexing
"""

import pypdfium2 as pdfium
from typing import List, Dict, Optional
import re
from dataclasses import dataclass


@dataclass
class PDFChunk:
    """Represents a chunk of text from PDF"""
    text: str
    page_number: int
    chunk_index: int
    metadata: Dict


class PDFParser:
    """Parse PDF files and prepare for RAG indexing"""

    def __init__(
        self,
        chunk_size: int = 500,  # words per chunk
        chunk_overlap: int = 50,  # words overlap between chunks
        min_chunk_size: int = 50  # minimum words in a chunk
    ):
        self.chunk_size = chunk_size
        self.chunk_overlap = chunk_overlap
        self.min_chunk_size = min_chunk_size

    def extract_text_from_pdf(self, pdf_path: str) -> Dict[int, str]:
        """
        Extract text from PDF file

        Args:
            pdf_path: Path to PDF file

        Returns:
            Dictionary mapping page number to text content
        """
        pdf_text = {}

        try:
            pdf = pdfium.PdfDocument(pdf_path)

            for page_num in range(len(pdf)):
                page = pdf[page_num]
                textpage = page.get_textpage()
                text = textpage.get_text_range()

                # Clean text
                text = self._clean_text(text)
                pdf_text[page_num + 1] = text  # 1-indexed pages

            return pdf_text

        except Exception as e:
            raise Exception(f"Error reading PDF: {str(e)}")

    def _clean_text(self, text: str) -> str:
        """Clean extracted text"""
        # Remove excessive whitespace
        text = re.sub(r'\s+', ' ', text)

        # Remove special characters that might cause issues
        text = text.replace('\x00', '')

        return text.strip()

    def chunk_text(self, text: str, page_number: int) -> List[PDFChunk]:
        """
        Split text into overlapping chunks

        Args:
            text: Text to chunk
            page_number: Page number this text came from

        Returns:
            List of PDFChunk objects
        """
        # Split into words
        words = text.split()

        if len(words) < self.min_chunk_size:
            # Text too short, return as single chunk
            if len(words) > 0:
                return [PDFChunk(
                    text=text,
                    page_number=page_number,
                    chunk_index=0,
                    metadata={'page': page_number, 'chunk': 0}
                )]
            return []

        chunks = []
        chunk_index = 0
        start = 0

        while start < len(words):
            # Get chunk
            end = min(start + self.chunk_size, len(words))
            chunk_words = words[start:end]
            chunk_text = ' '.join(chunk_words)

            chunks.append(PDFChunk(
                text=chunk_text,
                page_number=page_number,
                chunk_index=chunk_index,
                metadata={
                    'page': page_number,
                    'chunk': chunk_index,
                    'start_word': start,
                    'end_word': end
                }
            ))

            chunk_index += 1

            # Move start position with overlap
            start = end - self.chunk_overlap

            # Avoid infinite loop
            if start >= len(words) - self.min_chunk_size:
                break

        return chunks

    def parse_pdf(
        self,
        pdf_path: str,
        document_metadata: Optional[Dict] = None
    ) -> List[PDFChunk]:
        """
        Parse entire PDF into chunks

        Args:
            pdf_path: Path to PDF file
            document_metadata: Additional metadata for the document

        Returns:
            List of all chunks from the PDF
        """
        # Extract text from all pages
        pages_text = self.extract_text_from_pdf(pdf_path)

        # Chunk each page
        all_chunks = []
        for page_num, text in pages_text.items():
            chunks = self.chunk_text(text, page_num)

            # Add document metadata
            if document_metadata:
                for chunk in chunks:
                    chunk.metadata.update(document_metadata)

            all_chunks.extend(chunks)

        return all_chunks

    def parse_pdf_bytes(
        self,
        pdf_bytes: bytes,
        document_metadata: Optional[Dict] = None
    ) -> List[PDFChunk]:
        """
        Parse PDF from bytes (for uploaded files)

        Args:
            pdf_bytes: PDF file as bytes
            document_metadata: Additional metadata

        Returns:
            List of chunks
        """
        import tempfile
        import os

        # Save to temp file
        with tempfile.NamedTemporaryFile(delete=False, suffix='.pdf') as tmp:
            tmp.write(pdf_bytes)
            tmp_path = tmp.name

        try:
            chunks = self.parse_pdf(tmp_path, document_metadata)
            return chunks
        finally:
            # Clean up temp file
            if os.path.exists(tmp_path):
                os.unlink(tmp_path)

    def get_pdf_info(self, pdf_path: str) -> Dict:
        """
        Get basic info about PDF

        Args:
            pdf_path: Path to PDF file

        Returns:
            Dictionary with PDF information
        """
        try:
            pdf = pdfium.PdfDocument(pdf_path)

            info = {
                'num_pages': len(pdf),
                'file_path': pdf_path,
            }

            return info

        except Exception as e:
            raise Exception(f"Error reading PDF info: {str(e)}")


class PDFIndexer:
    """Index PDF chunks into RAG system"""

    def __init__(self, embedding_service, qdrant_service, documents_collection):
        self.embedding_service = embedding_service
        self.qdrant_service = qdrant_service
        self.documents_collection = documents_collection
        self.parser = PDFParser()

    def index_pdf(
        self,
        pdf_path: str,
        document_id: str,
        document_metadata: Optional[Dict] = None
    ) -> Dict:
        """
        Index entire PDF into RAG system

        Args:
            pdf_path: Path to PDF file
            document_id: Unique ID for this document
            document_metadata: Additional metadata (title, author, etc.)

        Returns:
            Indexing results
        """
        # Parse PDF
        chunks = self.parser.parse_pdf(pdf_path, document_metadata)

        # Index each chunk
        indexed_count = 0
        chunk_ids = []

        for chunk in chunks:
            # Generate unique ID for chunk
            chunk_id = f"{document_id}_p{chunk.page_number}_c{chunk.chunk_index}"

            # Generate embedding
            embedding = self.embedding_service.encode_text(chunk.text)

            # Prepare metadata
            metadata = {
                'text': chunk.text,
                'document_id': document_id,
                'page': chunk.page_number,
                'chunk_index': chunk.chunk_index,
                'source': 'pdf',
                **chunk.metadata
            }

            # Index to Qdrant
            self.qdrant_service.index_data(
                doc_id=chunk_id,
                embedding=embedding,
                metadata=metadata
            )

            chunk_ids.append(chunk_id)
            indexed_count += 1

        # Save document info to MongoDB
        doc_info = {
            'document_id': document_id,
            'type': 'pdf',
            'file_path': pdf_path,
            'num_chunks': indexed_count,
            'chunk_ids': chunk_ids,
            'metadata': document_metadata or {},
            'pdf_info': self.parser.get_pdf_info(pdf_path)
        }
        self.documents_collection.insert_one(doc_info)

        return {
            'success': True,
            'document_id': document_id,
            'chunks_indexed': indexed_count,
            'chunk_ids': chunk_ids[:5]  # Return first 5 as sample
        }

    def index_pdf_bytes(
        self,
        pdf_bytes: bytes,
        document_id: str,
        filename: str,
        document_metadata: Optional[Dict] = None
    ) -> Dict:
        """
        Index PDF from bytes (for uploaded files)

        Args:
            pdf_bytes: PDF file as bytes
            document_id: Unique ID for this document
            filename: Original filename
            document_metadata: Additional metadata

        Returns:
            Indexing results
        """
        # Parse PDF
        metadata = document_metadata or {}
        metadata['filename'] = filename

        chunks = self.parser.parse_pdf_bytes(pdf_bytes, metadata)

        # Index each chunk
        indexed_count = 0
        chunk_ids = []

        for chunk in chunks:
            # Generate unique ID for chunk
            chunk_id = f"{document_id}_p{chunk.page_number}_c{chunk.chunk_index}"

            # Generate embedding
            embedding = self.embedding_service.encode_text(chunk.text)

            # Prepare metadata
            metadata = {
                'text': chunk.text,
                'document_id': document_id,
                'page': chunk.page_number,
                'chunk_index': chunk.chunk_index,
                'source': 'pdf',
                'filename': filename,
                **chunk.metadata
            }

            # Index to Qdrant
            self.qdrant_service.index_data(
                doc_id=chunk_id,
                embedding=embedding,
                metadata=metadata
            )

            chunk_ids.append(chunk_id)
            indexed_count += 1

        # Save document info to MongoDB
        doc_info = {
            'document_id': document_id,
            'type': 'pdf',
            'filename': filename,
            'num_chunks': indexed_count,
            'chunk_ids': chunk_ids,
            'metadata': metadata
        }
        self.documents_collection.insert_one(doc_info)

        return {
            'success': True,
            'document_id': document_id,
            'filename': filename,
            'chunks_indexed': indexed_count,
            'chunk_ids': chunk_ids[:5]
        }