"""
SCAFFOLDED MODULE — NOT YET INTEGRATED

This file is intentionally scaffolded.
Structure, interfaces, and intent are defined,
but this module is not yet wired into the active runtime.

⚠️ Do NOT assume runtime execution.
⚠️ Do NOT extend behavior without integration work.

Status: SCAFFOLDED
"""

"""
APE Virtual Machine (v1.0.0 Scaffold)

Stack-based bytecode interpreter.

Author: David Van Aelst
Status: Scaffold - implementation pending
"""

from typing import Any, List, Dict, Optional
from dataclasses import dataclass, field


@dataclass
class StackFrame:
    """
    Execution stack frame for function calls.
    
    Contains local variables, instruction pointer, and operand stack.
    """
    variables: Dict[str, Any] = field(default_factory=dict)
    instruction_pointer: int = 0
    operand_stack: List[Any] = field(default_factory=list)
    return_address: Optional[int] = None


@dataclass
class ExecutionContext:
    """
    Complete execution context for VM.
    
    Contains call stack and global state.
    """
    call_stack: List[StackFrame] = field(default_factory=list)
    globals: Dict[str, Any] = field(default_factory=dict)
    halted: bool = False


class VirtualMachine:
    """
    APE bytecode virtual machine.
    
    Stack-based VM executing APE bytecode instructions.
    
    Features:
        - Stack-based operand handling
        - Call stack for function invocation
        - Deterministic execution
        - Safe sandboxed environment
    
    Example:
        vm = VirtualMachine()
        result = vm.execute(bytecode_program)
    
    TODO:
        - Implement instruction dispatch loop
        - Implement each opcode handler
        - Implement call stack management
        - Implement error handling
        - Implement execution tracing
    
    Author: David Van Aelst
    Status: v1.0.0 scaffold - implementation pending
    """
    
    def __init__(self, max_stack_depth: int = 1000):
        """
        Initialize virtual machine.
        
        Args:
            max_stack_depth: Maximum call stack depth (prevents infinite recursion)
        """
        self._max_stack_depth = max_stack_depth
        self._context: Optional[ExecutionContext] = None
    
    def execute(self, program: Any) -> Any:
        """
        Execute a bytecode program.
        
        Args:
            program: BytecodeProgram to execute
        
        Returns:
            Result of program execution
        
        TODO: Implement bytecode execution loop
        """
        raise NotImplementedError("VM execution not yet implemented")
    
    def step(self) -> bool:
        """
        Execute single instruction (for debugging/tracing).
        
        Returns:
            True if execution should continue, False if halted
        
        TODO: Implement single-step execution
        """
        raise NotImplementedError("VM step execution not yet implemented")
    
    def get_context(self) -> ExecutionContext:
        """
        Get current execution context (for debugging).
        
        Returns:
            Current ExecutionContext
        """
        if self._context is None:
            raise RuntimeError("No active execution context")
        return self._context
    
    def reset(self):
        """
        Reset VM state.
        
        TODO: Implement state reset
        """
        self._context = None


__all__ = ['VirtualMachine', 'StackFrame', 'ExecutionContext']
