"""
File Service - Handles file processing and chunked text analysis
"""
import os
import uuid
from typing import Dict, Any, List, Tuple
from werkzeug.utils import secure_filename
from flask import current_app

from .tokenizer_service import tokenizer_service
from .stats_service import stats_service


class FileService:
    """Service for handling file uploads and processing."""
    
    # Allowed file extensions for security
    ALLOWED_EXTENSIONS = {'.txt', '.md', '.py', '.js', '.html', '.css', '.json', '.csv', '.log'}
    
    @staticmethod
    def is_allowed_file(filename: str) -> bool:
        """Check if the uploaded file has an allowed extension."""
        if not filename:
            return False
        _, ext = os.path.splitext(filename.lower())
        return ext in FileService.ALLOWED_EXTENSIONS
    
    @staticmethod
    def generate_secure_filename(original_filename: str) -> str:
        """Generate a secure filename with UUID prefix."""
        if not original_filename:
            return f"{uuid.uuid4().hex}.txt"
        
        # Secure the filename and add UUID prefix to avoid conflicts
        secure_name = secure_filename(original_filename)
        name, ext = os.path.splitext(secure_name)
        return f"{uuid.uuid4().hex}_{name}{ext}"
    
    @staticmethod
    def save_uploaded_file(uploaded_file, upload_folder: str) -> str:
        """
        Save uploaded file to the upload folder with a secure filename.
        
        Returns:
            str: Path to the saved file
        """
        # Ensure upload folder exists
        os.makedirs(upload_folder, exist_ok=True)
        
        # Generate secure filename
        secure_filename_str = FileService.generate_secure_filename(uploaded_file.filename)
        file_path = os.path.join(upload_folder, secure_filename_str)
        
        # Save the file
        uploaded_file.save(file_path)
        return file_path
    
    @staticmethod
    def process_file_for_tokenization(
        file_path: str, 
        model_id_or_name: str,
        preview_char_limit: int = 8096,
        max_display_tokens: int = 50000,
        chunk_size: int = 1024 * 1024
    ) -> Dict[str, Any]:
        """
        Process a file for tokenization with chunked processing for large files.
        
        Args:
            file_path: Path to the file to process
            model_id_or_name: Tokenizer model to use
            preview_char_limit: Character limit for preview display
            max_display_tokens: Maximum tokens to display
            chunk_size: Size of chunks for processing large files
            
        Returns:
            Dict containing tokenization results
        """
        # Load tokenizer
        tokenizer, tokenizer_info, error = tokenizer_service.load_tokenizer(model_id_or_name)
        
        if error:
            raise Exception(error)
        
        # Read the preview for display
        with open(file_path, 'r', errors='replace') as f:
            preview_text = f.read(preview_char_limit)
        
        # Tokenize preview for display
        preview_tokens = tokenizer.tokenize(preview_text)
        display_tokens = preview_tokens[:max_display_tokens]
        
        # Process full file for stats in chunks to avoid memory issues
        total_tokens = []
        token_set = set()
        total_length = 0
        
        with open(file_path, 'r', errors='replace') as f:
            while True:
                chunk = f.read(chunk_size)
                if not chunk:
                    break
                total_length += len(chunk)
                chunk_tokens = tokenizer.tokenize(chunk)
                total_tokens.extend(chunk_tokens)
                token_set.update(chunk_tokens)
        
        # Calculate stats using approximation for original text
        stats = stats_service.get_token_stats(total_tokens, ' ' * total_length)
        
        # Format tokens for display
        token_data = stats_service.format_tokens_for_display(display_tokens, tokenizer)
        
        return {
            'tokens': token_data,
            'stats': stats,
            'display_limit_reached': len(total_tokens) > max_display_tokens,
            'total_tokens': len(total_tokens),
            'is_full_file': True,
            'preview_only': True,
            'tokenizer_info': tokenizer_info
        }
    
    @staticmethod
    def process_text_for_tokenization(
        text: str,
        model_id_or_name: str,
        is_preview: bool = False,
        preview_char_limit: int = 8096,
        max_display_tokens: int = 50000
    ) -> Dict[str, Any]:
        """
        Process regular text input for tokenization.
        
        Args:
            text: Input text to tokenize
            model_id_or_name: Tokenizer model to use
            is_preview: Whether this is a preview of a larger text
            preview_char_limit: Character limit for preview
            max_display_tokens: Maximum tokens to display
            
        Returns:
            Dict containing tokenization results
        """
        # Load tokenizer
        tokenizer, tokenizer_info, error = tokenizer_service.load_tokenizer(model_id_or_name)
        
        if error:
            raise Exception(error)
        
        # Tokenize full text for stats
        all_tokens = tokenizer.tokenize(text)
        total_token_count = len(all_tokens)
        
        # For display: if it's a preview, only take first preview_char_limit chars
        preview_text = text[:preview_char_limit] if is_preview else text
        preview_tokens = tokenizer.tokenize(preview_text)
        display_tokens = preview_tokens[:max_display_tokens]
        
        # Calculate stats on full text
        stats = stats_service.get_token_stats(all_tokens, text)
        
        # Format tokens for display
        token_data = stats_service.format_tokens_for_display(display_tokens, tokenizer)
        
        return {
            'tokens': token_data,
            'stats': stats,
            'display_limit_reached': total_token_count > max_display_tokens and not is_preview,
            'total_tokens': total_token_count,
            'is_full_file': False,
            'preview_only': is_preview,
            'tokenizer_info': tokenizer_info
        }
    
    @staticmethod
    def cleanup_file(file_path: str):
        """Safely remove a file if it exists."""
        try:
            if os.path.exists(file_path):
                os.remove(file_path)
        except OSError:
            pass  # Ignore errors during cleanup


# Global instance
file_service = FileService()