"""
Document parser for extracting text from various file formats.
Supports PDF, TXT, HTML, and detects document types.
"""

import re
import logging
from pathlib import Path
from typing import Dict, List, Optional, Tuple
import pdfplumber
from datetime import datetime

logger = logging.getLogger(__name__)


class DocumentParser:
    """Parse and extract text from various document formats."""

    # Document type detection patterns
    DOCUMENT_TYPES = {
        'whitepaper': [
            r'whitepaper', r'technical\s+paper', r'protocol\s+specification',
            r'tokenomics', r'blockchain\s+architecture'
        ],
        'regulation': [
            r'regulation\s+\(eu\)', r'securities\s+act', r'guidance\s+note',
            r'consultation\s+paper', r'policy\s+statement', r'final\s+rule'
        ],
        'business_plan': [
            r'business\s+plan', r'executive\s+summary', r'market\s+analysis',
            r'financial\s+projections', r'revenue\s+model'
        ],
        'license_application': [
            r'license\s+application', r'registration\s+form', r'compliance\s+declaration',
            r'fit\s+and\s+proper', r'aml\s+policy'
        ],
        'financial_statement': [
            r'balance\s+sheet', r'income\s+statement', r'cash\s+flow',
            r'financial\s+statements', r'audit\s+report'
        ],
        'legal_contract': [
            r'terms\s+of\s+service', r'user\s+agreement', r'smart\s+contract',
            r'memorandum\s+of\s+understanding', r'partnership\s+agreement'
        ]
    }

    def __init__(self):
        """Initialize document parser."""
        self.supported_formats = {'.pdf', '.txt', '.html', '.md'}

    def extract_text_from_pdf(self, file_path: str) -> str:
        """
        Extract text from a PDF file using pdfplumber.

        Args:
            file_path: Path to PDF file

        Returns:
            Extracted text as string

        Raises:
            FileNotFoundError: If file doesn't exist
            ValueError: If file is not a PDF
        """
        path = Path(file_path)

        if not path.exists():
            raise FileNotFoundError(f"PDF file not found: {file_path}")

        if path.suffix.lower() != '.pdf':
            raise ValueError(f"File is not a PDF: {file_path}")

        try:
            text_content = []

            with pdfplumber.open(file_path) as pdf:
                logger.info(f"Extracting text from PDF: {file_path} ({len(pdf.pages)} pages)")

                for page_num, page in enumerate(pdf.pages, 1):
                    page_text = page.extract_text()

                    if page_text:
                        text_content.append(page_text)
                    else:
                        logger.warning(f"No text extracted from page {page_num}")

            full_text = "\n\n".join(text_content)
            logger.info(f"Successfully extracted {len(full_text)} characters from PDF")

            return full_text

        except Exception as e:
            logger.error(f"Error extracting text from PDF {file_path}: {e}")
            raise

    def extract_text_from_file(self, file_path: str) -> str:
        """
        Extract text from any supported file format.

        Args:
            file_path: Path to file

        Returns:
            Extracted text

        Raises:
            ValueError: If file format not supported
        """
        path = Path(file_path)

        if not path.exists():
            raise FileNotFoundError(f"File not found: {file_path}")

        suffix = path.suffix.lower()

        if suffix not in self.supported_formats:
            raise ValueError(
                f"Unsupported file format: {suffix}. "
                f"Supported: {', '.join(self.supported_formats)}"
            )

        # PDF extraction
        if suffix == '.pdf':
            return self.extract_text_from_pdf(file_path)

        # Text-based formats
        try:
            with open(file_path, 'r', encoding='utf-8') as f:
                text = f.read()

            logger.info(f"Extracted {len(text)} characters from {file_path}")
            return text

        except UnicodeDecodeError:
            # Try with different encoding
            with open(file_path, 'r', encoding='latin-1') as f:
                text = f.read()

            logger.warning(f"Used latin-1 encoding for {file_path}")
            return text

    def clean_text(self, text: str) -> str:
        """
        Clean and normalize extracted text.

        Args:
            text: Raw text

        Returns:
            Cleaned text
        """
        if not text:
            return ""

        # Remove excessive whitespace
        text = re.sub(r'\s+', ' ', text)

        # Remove page numbers (common patterns)
        text = re.sub(r'\n\s*\d+\s*\n', '\n', text)

        # Remove headers/footers (repeated patterns)
        lines = text.split('\n')
        if len(lines) > 10:
            # Remove first/last lines if they appear to be headers/footers
            text = '\n'.join(lines[1:-1])

        # Normalize unicode characters
        text = text.replace('\u2019', "'")  # Smart quote
        text = text.replace('\u2018', "'")
        text = text.replace('\u201c', '"')
        text = text.replace('\u201d', '"')
        text = text.replace('\u2013', '-')  # En dash
        text = text.replace('\u2014', '-')  # Em dash

        # Remove excessive newlines
        text = re.sub(r'\n{3,}', '\n\n', text)

        return text.strip()

    def detect_document_type(self, text: str) -> Tuple[str, float]:
        """
        Detect the type of document based on content.

        Args:
            text: Document text

        Returns:
            Tuple of (document_type, confidence_score)
        """
        if not text:
            return "unknown", 0.0

        text_lower = text.lower()

        # Count matches for each document type
        type_scores = {}

        for doc_type, patterns in self.DOCUMENT_TYPES.items():
            matches = 0
            for pattern in patterns:
                matches += len(re.findall(pattern, text_lower, re.IGNORECASE))

            type_scores[doc_type] = matches

        # Find type with most matches
        if not any(type_scores.values()):
            return "unknown", 0.0

        best_type = max(type_scores.items(), key=lambda x: x[1])
        doc_type, match_count = best_type

        # Calculate confidence based on match density
        # More matches per 1000 words = higher confidence
        word_count = len(text_lower.split())
        match_density = (match_count / (word_count / 1000)) if word_count > 0 else 0
        confidence = min(match_density / 10, 1.0)  # Cap at 1.0

        logger.info(f"Detected document type: {doc_type} (confidence: {confidence:.2f})")

        return doc_type, confidence

    def extract_metadata(self, file_path: str) -> Dict:
        """
        Extract metadata from document.

        Args:
            file_path: Path to document

        Returns:
            Dictionary of metadata
        """
        path = Path(file_path)

        metadata = {
            'filename': path.name,
            'file_size': path.stat().st_size,
            'file_type': path.suffix.lower(),
            'modified_date': datetime.fromtimestamp(path.stat().st_mtime).isoformat()
        }

        # PDF-specific metadata
        if path.suffix.lower() == '.pdf':
            try:
                with pdfplumber.open(file_path) as pdf:
                    metadata['page_count'] = len(pdf.pages)

                    # Extract PDF metadata if available
                    if pdf.metadata:
                        metadata['pdf_metadata'] = {
                            'title': pdf.metadata.get('Title', ''),
                            'author': pdf.metadata.get('Author', ''),
                            'subject': pdf.metadata.get('Subject', ''),
                            'creator': pdf.metadata.get('Creator', ''),
                            'creation_date': pdf.metadata.get('CreationDate', '')
                        }
            except Exception as e:
                logger.warning(f"Could not extract PDF metadata: {e}")

        return metadata

    def parse_document(self, file_path: str) -> Dict:
        """
        Parse a document and extract all information.

        Args:
            file_path: Path to document

        Returns:
            Dictionary containing:
                - text: Cleaned text content
                - document_type: Detected type
                - confidence: Type detection confidence
                - metadata: File metadata
                - char_count: Character count
                - word_count: Word count
        """
        logger.info(f"Parsing document: {file_path}")

        # Extract raw text
        raw_text = self.extract_text_from_file(file_path)

        # Clean text
        cleaned_text = self.clean_text(raw_text)

        # Detect document type
        doc_type, confidence = self.detect_document_type(cleaned_text)

        # Extract metadata
        metadata = self.extract_metadata(file_path)

        # Calculate statistics
        char_count = len(cleaned_text)
        word_count = len(cleaned_text.split())

        result = {
            'text': cleaned_text,
            'document_type': doc_type,
            'type_confidence': confidence,
            'metadata': metadata,
            'char_count': char_count,
            'word_count': word_count,
            'extracted_at': datetime.now().isoformat()
        }

        logger.info(
            f"Parsed {metadata['filename']}: {word_count} words, "
            f"type={doc_type} ({confidence:.2f})"
        )

        return result

    def chunk_text(
        self,
        text: str,
        chunk_size: int = 1000,
        overlap: int = 200
    ) -> List[str]:
        """
        Split text into overlapping chunks for processing.
        Useful for handling long documents with LLMs.

        Args:
            text: Input text
            chunk_size: Maximum words per chunk
            overlap: Number of overlapping words between chunks

        Returns:
            List of text chunks
        """
        if not text:
            return []

        words = text.split()
        chunks = []

        if len(words) <= chunk_size:
            return [text]

        start = 0
        while start < len(words):
            end = start + chunk_size
            chunk_words = words[start:end]
            chunks.append(' '.join(chunk_words))

            # Move start forward, accounting for overlap
            start = end - overlap

            if start < 0:
                start = 0

        logger.info(f"Split text into {len(chunks)} chunks ({chunk_size} words each)")

        return chunks


# Convenience function for quick parsing
def parse_document(file_path: str) -> Dict:
    """
    Quick parse a document.

    Args:
        file_path: Path to document

    Returns:
        Parsed document dictionary
    """
    parser = DocumentParser()
    return parser.parse_document(file_path)


if __name__ == "__main__":
    # Example usage
    import sys

    if len(sys.argv) > 1:
        file_path = sys.argv[1]
        result = parse_document(file_path)

        print(f"\nDocument Type: {result['document_type']}")
        print(f"Confidence: {result['type_confidence']:.2f}")
        print(f"Words: {result['word_count']}")
        print(f"\nFirst 500 characters:")
        print(result['text'][:500])
    else:
        print("Usage: python document_parser.py <file_path>")