"""
APE Bytecode Specification (v1.0.0 Scaffold)

Bytecode format and encoding/decoding for APE VM.

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

from enum import IntEnum, auto
from dataclasses import dataclass
from typing import List, Any, Optional


class Opcode(IntEnum):
    """
    APE VM opcodes.
    
    Stack-based instruction set for APE virtual machine.
    """
    # Constants
    LOAD_CONST = auto()      # Push constant onto stack
    LOAD_NULL = auto()       # Push null onto stack
    
    # Variables
    LOAD_VAR = auto()        # Load variable value onto stack
    STORE_VAR = auto()       # Store top of stack to variable
    
    # Arithmetic
    ADD = auto()             # Pop 2 values, push sum
    SUB = auto()             # Pop 2 values, push difference
    MUL = auto()             # Pop 2 values, push product
    DIV = auto()             # Pop 2 values, push quotient
    MOD = auto()             # Pop 2 values, push remainder
    NEG = auto()             # Pop 1 value, push negation
    
    # Comparison
    EQ = auto()              # Pop 2 values, push equality result
    NE = auto()              # Pop 2 values, push inequality result
    LT = auto()              # Pop 2 values, push less-than result
    LE = auto()              # Pop 2 values, push less-or-equal result
    GT = auto()              # Pop 2 values, push greater-than result
    GE = auto()              # Pop 2 values, push greater-or-equal result
    
    # Logical
    AND = auto()             # Pop 2 values, push logical AND
    OR = auto()              # Pop 2 values, push logical OR
    NOT = auto()             # Pop 1 value, push logical NOT
    
    # Control flow
    JUMP = auto()            # Unconditional jump to address
    JUMP_IF_FALSE = auto()   # Jump if top of stack is false
    JUMP_IF_TRUE = auto()    # Jump if top of stack is true
    
    # Functions/Tasks
    CALL = auto()            # Call function with N args
    RETURN = auto()          # Return from function
    
    # Collections
    BUILD_LIST = auto()      # Build list from N stack items
    BUILD_MAP = auto()       # Build map from N key-value pairs
    INDEX = auto()           # Index into collection
    
    # Other
    POP = auto()             # Discard top of stack
    DUP = auto()             # Duplicate top of stack
    HALT = auto()            # Stop execution


@dataclass
class Instruction:
    """
    Single bytecode instruction.
    
    Example:
        Instruction(opcode=Opcode.LOAD_CONST, arg=42)
        Instruction(opcode=Opcode.ADD)
    """
    opcode: Opcode
    arg: Optional[Any] = None
    line: int = 0
    
    def __str__(self):
        if self.arg is not None:
            return f"{self.opcode.name} {self.arg}"
        return self.opcode.name


@dataclass
class BytecodeProgram:
    """
    Complete bytecode program with constants and instructions.
    """
    instructions: List[Instruction]
    constants: List[Any]
    variable_names: List[str]
    
    def __str__(self):
        lines = ["Bytecode Program:"]
        lines.append(f"  Constants: {self.constants}")
        lines.append(f"  Variables: {self.variable_names}")
        lines.append("  Instructions:")
        for i, instr in enumerate(self.instructions):
            lines.append(f"    {i:3d}  {instr}")
        return "\n".join(lines)


def encode(ast: Any) -> BytecodeProgram:
    """
    Encode AST into bytecode.
    
    Args:
        ast: Abstract syntax tree to compile
    
    Returns:
        BytecodeProgram ready for VM execution
    
    TODO: Implement AST to bytecode compiler
    
    Author: David Van Aelst
    Status: v1.0.0 scaffold - implementation pending
    """
    raise NotImplementedError("Bytecode encoding not yet implemented")


def decode(program: BytecodeProgram) -> Any:
    """
    Decode bytecode back to AST (for debugging/analysis).
    
    Args:
        program: BytecodeProgram to decode
    
    Returns:
        Reconstructed AST
    
    TODO: Implement bytecode to AST decoder
    
    Author: David Van Aelst
    Status: v1.0.0 scaffold - implementation pending
    """
    raise NotImplementedError("Bytecode decoding not yet implemented")


def disassemble(program: BytecodeProgram) -> str:
    """
    Disassemble bytecode to human-readable format.
    
    Args:
        program: BytecodeProgram to disassemble
    
    Returns:
        Human-readable assembly listing
    
    TODO: Implement bytecode disassembler
    
    Author: David Van Aelst
    Status: v1.0.0 scaffold - implementation pending
    """
    raise NotImplementedError("Bytecode disassembly not yet implemented")


__all__ = [
    'Opcode',
    'Instruction',
    'BytecodeProgram',
    'encode',
    'decode',
    'disassemble',
]
