import os
from pathlib import Path
from typing import List, Optional
from core.exceptions import ValidationError, UnsupportedFileError, FileSizeError
from utils.constants import MAX_FILE_SIZE_MB, SUPPORTED_EXTENSIONS, LANGUAGES

class FileValidator:
    """Validator for file uploads and processing parameters"""
    
    @staticmethod
    def validate_file(file_path: Path) -> None:
        """
        Validate uploaded file
        
        Args:
            file_path: Path to the file to validate
            
        Raises:
            ValidationError: If file is invalid
            UnsupportedFileError: If file format is not supported
            FileSizeError: If file is too large
        """
        if not file_path.exists():
            raise ValidationError(f"File does not exist: {file_path}")
        
        if not file_path.is_file():
            raise ValidationError(f"Path is not a file: {file_path}")
        
        # Check file extension
        extension = file_path.suffix.lower()
        if extension not in SUPPORTED_EXTENSIONS:
            raise UnsupportedFileError(
                f"Unsupported file format: {extension}. "
                f"Supported formats: {', '.join(SUPPORTED_EXTENSIONS)}"
            )
        
        # Check file size
        file_size_mb = file_path.stat().st_size / (1024 * 1024)
        if file_size_mb > MAX_FILE_SIZE_MB:
            raise FileSizeError(
                f"File too large: {file_size_mb:.1f}MB. "
                f"Maximum allowed size: {MAX_FILE_SIZE_MB}MB"
            )
        
        # Check if file is readable
        try:
            with open(file_path, 'rb') as f:
                f.read(1024)  # Try to read first KB
        except Exception as e:
            raise ValidationError(f"Cannot read file: {str(e)}")
    
    @staticmethod
    def validate_language(language: str) -> str:
        """
        Validate and normalize language input
        
        Args:
            language: Language name or code
            
        Returns:
            Normalized language name
            
        Raises:
            ValidationError: If language is not supported
        """
        if not language:
            raise ValidationError("Language cannot be empty")
        
        # Check if it's a valid language name
        if language in LANGUAGES:
            return language
        
        # Check if it's a valid language code
        for name, code in LANGUAGES.items():
            if code == language:
                return name
        
        raise ValidationError(
            f"Unsupported language: {language}. "
            f"Supported languages: {', '.join(LANGUAGES.keys())}"
        )
    
    @staticmethod
    def validate_api_key(api_key: str, provider: str) -> None:
        """
        Validate API key format
        
        Args:
            api_key: API key to validate
            provider: API provider name
            
        Raises:
            ValidationError: If API key is invalid
        """
        if not api_key or not api_key.strip():
            raise ValidationError("API key cannot be empty")
        
        api_key = api_key.strip()
        
        if provider == "ChatGPT":
            if not api_key.startswith('sk-'):
                raise ValidationError("OpenAI API key must start with 'sk-'")
            if len(api_key) < 20:
                raise ValidationError("OpenAI API key appears too short")
        
        elif provider == "DeepSeek":
            if len(api_key) < 10:
                raise ValidationError("DeepSeek API key appears too short")
        
        else:
            raise ValidationError(f"Unknown provider: {provider}")
    
    @staticmethod
    def validate_translation_params(
        source_lang: str,
        target_lang: str,
        api_provider: str,
        api_key: str
    ) -> tuple[str, str]:
        """
        Validate all translation parameters
        
        Args:
            source_lang: Source language
            target_lang: Target language  
            api_provider: API provider name
            api_key: API key
            
        Returns:
            Tuple of normalized (source_lang, target_lang)
            
        Raises:
            ValidationError: If any parameter is invalid
        """
        # Validate languages
        norm_source = FileValidator.validate_language(source_lang)
        norm_target = FileValidator.validate_language(target_lang)
        
        if norm_source == norm_target:
            raise ValidationError("Source and target languages cannot be the same")
        
        # Validate API provider
        if api_provider not in ["ChatGPT", "DeepSeek"]:
            raise ValidationError(f"Unsupported API provider: {api_provider}")
        
        # Validate API key
        FileValidator.validate_api_key(api_key, api_provider)
        
        return norm_source, norm_target
    
    @staticmethod
    def sanitize_filename(filename: str) -> str:
        """
        Sanitize filename for safe file operations
        
        Args:
            filename: Original filename
            
        Returns:
            Sanitized filename
        """
        # Remove or replace unsafe characters
        unsafe_chars = '<>:"/\\|?*'
        for char in unsafe_chars:
            filename = filename.replace(char, '_')
        
        # Remove leading/trailing spaces and dots
        filename = filename.strip(' .')
        
        # Ensure filename is not empty
        if not filename:
            filename = "translated_document"
        
        return filename