"""
APE VM Instruction Specifications (v1.0.0 Scaffold)

Detailed specifications for VM instructions.

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

from typing import Dict
from dataclasses import dataclass


# Re-export for convenience
from .vm import StackFrame, ExecutionContext


@dataclass
class InstructionSpec:
    """
    Specification for a VM instruction.
    
    Describes stack effects and semantics.
    """
    name: str
    opcode: int
    stack_effect: int  # Net change to operand stack depth
    has_arg: bool
    description: str


# Instruction specifications (for documentation and validation)
INSTRUCTION_SPECS: Dict[int, InstructionSpec] = {
    # TODO: Populate with complete instruction specifications
    # Example:
    # Opcode.ADD: InstructionSpec(
    #     name="ADD",
    #     opcode=Opcode.ADD,
    #     stack_effect=-1,  # Pops 2, pushes 1
    #     has_arg=False,
    #     description="Pop two values, push their sum"
    # )
}


def validate_instruction_sequence(instructions: list) -> bool:
    """
    Validate that instruction sequence is well-formed.
    
    Checks:
        - Stack balance
        - Valid jump targets
        - Valid variable references
    
    TODO: Implement instruction validation
    
    Author: David Van Aelst
    Status: v1.0.0 scaffold - implementation pending
    """
    raise NotImplementedError("Instruction validation not yet implemented")


__all__ = [
    'StackFrame',
    'ExecutionContext',
    'InstructionSpec',
    'INSTRUCTION_SPECS',
    'validate_instruction_sequence',
]
