from threading import Lock
from typing import Callable, List

from .io_buffer import IOBuffer

class WebIOBuffer(IOBuffer):
    """
    Thread-safe WebIOBuffer that maintains the synchronous IOBuffer interface.
    Uses threading primitives instead of asyncio for synchronization.
    """
    def __init__(self):
        self._stdin_buffer = ""
        self._stdout_buffer = ""
        self._stdout_change_handlers: List[Callable[[str], None]] = []
    
    def add_stdout_change_handler(self, handler: Callable[[str], None]) -> None:
        """
        Add a callback for stdout changes.
        """
        if handler not in self._stdout_change_handlers:
            self._stdout_change_handlers.append(handler)
    
    def read(self) -> str:
        """Thread-safe read from stdin buffer."""
        content = self._stdin_buffer
        self._stdin_buffer = ""
        return content
            
    def write(self, content: str) -> None:
        """Thread-safe write to stdout buffer."""
        self._stdout_buffer += content
        for handler in self._stdout_change_handlers:
            handler(self._stdout_buffer)
            
    def buffer_length(self) -> int:
        """
        Get the current length of the stdin buffer.
        
        Returns:
            int: Number of characters in the stdin buffer
        """
        return len(self._stdin_buffer)
        
    def append_stdin(self, content: str) -> None:
        """
        Append content to the stdin buffer.
        
        Args:
            content: String content to append to the stdin buffer
        """
        self._stdin_buffer += content
            
    def get_stdout(self) -> str:
        """Thread-safe get stdout content."""
        return self._stdout_buffer
            
    def clear_stdout(self) -> None:
        """Thread-safe clear stdout buffer."""
        self._stdout_buffer = ""
        for handler in self._stdout_change_handlers:
            handler(self._stdout_buffer)