"""
Document Reader for page-level document access.
"""

import os
import json
from typing import List, Optional, Dict, Union
from pathlib import Path
import logging

logger = logging.getLogger(__name__)


class DocumentReader:
    def __init__(self, pages_dir: Optional[Path] = None):
        """Initialize the document reader."""
        self.pages_dir = pages_dir or Path(__file__).parent.parent / "pages"
        self.document_index = self._load_document_index()
    
    def _load_document_index(self) -> Dict:
        """Load document index if available."""
        index_path = self.pages_dir / "document_index.json"
        if index_path.exists():
            try:
                with open(index_path, 'r') as f:
                    return json.load(f)
            except Exception as e:
                logger.error(f"Error loading document index: {e}")
        return {}
    
    def _normalize_document_name(self, document_name: str) -> str:
        """Normalize document name for consistent file matching."""
        # Remove common prefixes/suffixes
        name = document_name.strip()
        name = name.replace(" ", "_")
        name = name.replace(".", "_")
        
        # Handle different formats
        if not name.endswith(("UserGuide", "InstallationGuide", "QuickStartGuide")):
            # Try to identify the document type
            if "user" in name.lower() and "guide" in name.lower():
                if not name.endswith("UserGuide"):
                    name = name.replace("User_Guide", "UserGuide")
            elif "installation" in name.lower() and "guide" in name.lower():
                if not name.endswith("InstallationGuide"):
                    name = name.replace("Installation_Guide", "InstallationGuide")
            elif "quick" in name.lower() and "start" in name.lower():
                if not name.endswith("QuickStartGuide"):
                    name = name.replace("Quick_Start_Guide", "QuickStartGuide")
        
        return name
    
    def get_table_of_contents(self, document_name: str) -> Optional[str]:
        """Get the table of contents for a document."""
        normalized_name = self._normalize_document_name(document_name)
        toc_filename = f"{normalized_name}_TOC.txt"
        toc_path = self.pages_dir / toc_filename
        
        if not toc_path.exists():
            # Try alternative naming conventions
            alternatives = [
                f"{document_name}_TOC.txt",
                f"{document_name.replace(' ', '_')}_TOC.txt",
                f"{document_name.replace('.', '_')}_TOC.txt"
            ]
            
            for alt in alternatives:
                alt_path = self.pages_dir / alt
                if alt_path.exists():
                    toc_path = alt_path
                    break
        
        if toc_path.exists():
            try:
                with open(toc_path, 'r', encoding='utf-8') as f:
                    return f.read()
            except Exception as e:
                logger.error(f"Error reading TOC file {toc_path}: {e}")
                return None
        
        logger.warning(f"TOC file not found for document: {document_name}")
        return None
    
    def read_pages(self, document_name: str, page_numbers: Optional[List[int]] = None) -> Union[str, Dict[int, str]]:
        """
        Read specific pages from a document.
        If page_numbers is None, returns the table of contents.
        """
        if page_numbers is None:
            # Return table of contents
            toc = self.get_table_of_contents(document_name)
            if toc:
                return f"Table of Contents for {document_name}:\n\n{toc}"
            else:
                return f"Table of contents not found for document: {document_name}"
        
        # Read specific pages
        normalized_name = self._normalize_document_name(document_name)
        pages_content = {}
        
        for page_num in page_numbers:
            page_filename = f"{normalized_name}_page_{page_num:03d}.txt"
            page_path = self.pages_dir / page_filename
            
            if not page_path.exists():
                # Try alternative formats
                alternatives = [
                    f"{document_name}_page_{page_num:03d}.txt",
                    f"{document_name.replace(' ', '_')}_page_{page_num:03d}.txt",
                    f"{document_name.replace('.', '_')}_page_{page_num:03d}.txt"
                ]
                
                for alt in alternatives:
                    alt_path = self.pages_dir / alt
                    if alt_path.exists():
                        page_path = alt_path
                        break
            
            if page_path.exists():
                try:
                    with open(page_path, 'r', encoding='utf-8') as f:
                        pages_content[page_num] = f.read()
                except Exception as e:
                    logger.error(f"Error reading page {page_num} from {document_name}: {e}")
                    pages_content[page_num] = f"Error reading page {page_num}"
            else:
                pages_content[page_num] = f"Page {page_num} not found"
        
        # Format the output
        if len(pages_content) == 1:
            page_num = list(pages_content.keys())[0]
            return f"Page {page_num} of {document_name}:\n\n{pages_content[page_num]}"
        else:
            formatted_pages = []
            for page_num in sorted(pages_content.keys()):
                formatted_pages.append(f"=== Page {page_num} ===\n{pages_content[page_num]}")
            return f"Pages from {document_name}:\n\n" + "\n\n".join(formatted_pages)
    
    def list_available_documents(self) -> List[str]:
        """List all available documents."""
        documents = set()
        
        # Scan for TOC files
        for toc_file in self.pages_dir.glob("*_TOC.txt"):
            doc_name = toc_file.stem.replace("_TOC", "")
            documents.add(doc_name)
        
        # Also check document index
        if self.document_index:
            documents.update(self.document_index.keys())
        
        return sorted(list(documents))
    
    def get_document_info(self, document_name: str) -> Dict[str, any]:
        """Get information about a document (number of pages, etc.)."""
        normalized_name = self._normalize_document_name(document_name)
        info = {
            "name": document_name,
            "normalized_name": normalized_name,
            "has_toc": False,
            "page_count": 0,
            "available_pages": []
        }
        
        # Check for TOC
        toc_path = self.pages_dir / f"{normalized_name}_TOC.txt"
        info["has_toc"] = toc_path.exists()
        
        # Count pages
        page_pattern = f"{normalized_name}_page_*.txt"
        page_files = list(self.pages_dir.glob(page_pattern))
        
        if not page_files:
            # Try alternative patterns
            for alt_pattern in [f"{document_name}_page_*.txt", 
                              f"{document_name.replace(' ', '_')}_page_*.txt"]:
                page_files = list(self.pages_dir.glob(alt_pattern))
                if page_files:
                    break
        
        if page_files:
            page_numbers = []
            for page_file in page_files:
                try:
                    # Extract page number from filename
                    page_num_str = page_file.stem.split("_page_")[-1]
                    page_num = int(page_num_str)
                    page_numbers.append(page_num)
                except:
                    pass
            
            info["page_count"] = len(page_numbers)
            info["available_pages"] = sorted(page_numbers)
        
        return info