"""Centralized error handling utility for the polymer classification app.
Provides consistent error logging and graceful UI error reporting"""

import streamlit as st 
import traceback

# Define a constant for error messages
ERROR = "[ERROR]"

class ErrorHandler:
    """Centralized error handler for the application"""

    @staticmethod
    def log_error(error: Exception, context: str = "", include_traceback: bool = False) -> None:
        """Log error to session state for display in UI"""
        if "log_messages" not in st.session_state:
            st.session_state["log_messages"] = []

        error_msg = f"{ERROR} {context}: {str(error)}" if context else f"{ERROR} {str(error)}"

        if include_traceback:
            error_msg += f"\nTraceback: {traceback.format_exc()}"

        st.session_state["log_messages"].append(error_msg)

    @staticmethod
    def log_warning(message: str, context: str = "") -> None:
        """Log warning to session state"""
        if "log_messages" not in st.session_state:
            st.session_state["log_messages"] = []
        
        warning_msg = f"[WARNING] {context}: {message}" if context else f"[WARNING] {message}"
        st.session_state["log_messages"].append(warning_msg)
    
    @staticmethod
    def log_info(message: str, context: str = "") -> None:
        """Log info message to session state"""
        if "log_messages" not in st.session_state:
            st.session_state["log_messages"] = []
        
        info_msg = f"[INFO] {context}: {message}" if context else f"[INFO] {message}"
        st.session_state["log_messages"].append(info_msg)
    
    @staticmethod
    def handle_file_error(filename: str, error: Exception) -> str:
        """Handle file processing errors and return user-friendly message"""
        ErrorHandler.log_error(error, f"File processing: {filename}")
        
        if isinstance(error, FileNotFoundError):
            return f"❌ File not found: {filename}"
        elif isinstance(error, PermissionError):
            return f"❌ Permission denied accessing: {filename}"
        elif isinstance(error, (ValueError, TypeError)):
            return f"❌ Invalid file format in: {filename}. Please ensure it contains wavenumber and intensity columns."
        else:
            return f"❌ Error processing file: {filename}. {str(error)}"
    
    @staticmethod
    def handle_inference_error(model_name: str, error: Exception) -> str:
        """Handle model inference errors and return user-friendly message"""
        ErrorHandler.log_error(error, f"Model inference: {model_name}")
        
        if "CUDA" in str(error) or "device" in str(error).lower():
            return f"❌ Device error with model {model_name}. Falling back to CPU."
        elif "shape" in str(error).lower() or "dimension" in str(error).lower():
            return f"❌ Input shape mismatch for model {model_name}. Please check spectrum data format."
        else:
            return f"❌ Inference failed for model {model_name}: {str(error)}"
    
    @staticmethod
    def handle_parsing_error(filename: str, error: Exception) -> str:
        """Handle spectrum parsing errors and return user-friendly message"""
        ErrorHandler.log_error(error, f"Spectrum parsing: {filename}")
        
        if "could not convert" in str(error).lower():
            return f"❌ Invalid data format in {filename}. Expected numeric wavenumber and intensity columns."
        elif "empty" in str(error).lower():
            return f"❌ File {filename} appears to be empty or contains no valid data."
        elif "columns" in str(error).lower():
            return f"❌ File {filename} must contain exactly 2 columns (wavenumber, intensity)."
        else:
            return f"❌ Failed to parse spectrum data from {filename}: {str(error)}"
    
    @staticmethod
    def clear_logs() -> None:
        """Clear all logged messages"""
        st.session_state["log_messages"] = []
    
    @staticmethod
    def get_logs() -> list[str]:
        """Get all logged messages"""
        return st.session_state.get("log_messages", [])
    
    @staticmethod
    def display_error_ui(error_message: str, show_details: bool = False) -> None:
        """Display error in Streamlit UI with optional details"""
        st.error(error_message)
        
        if show_details and st.session_state.get("log_messages"):
            with st.expander("Error Details", expanded=False):
                for msg in st.session_state["log_messages"][-5:]:  # Show last 5 log entries
                    st.text(msg)

def safe_execute(func, *args, error_context: str = "", show_error: bool = True, **kwargs):
    """
    Safely execute a function with error handling
    
    Args:
        func: Function to execute
        *args: Arguments for the function
        error_context: Context description for error logging
        show_error: Whether to show error in UI
        **kwargs: Keyword arguments for the function
    
    Returns:
        Tuple of (result, success_flag)
    """
    try:
        result = func(*args, **kwargs)
        return result, True
    except Exception as e:
        ErrorHandler.log_error(e, error_context)
        if show_error:
            error_msg = f"Error in {error_context}: {str(e)}" if error_context else str(e)
            st.error(error_msg)
        return None, False