"""
AgentDebuggerEnv — Sandboxed Code Execution
============================================
Isolated execution environment for user-submitted code, providing
security through AST-based import filtering, subprocess isolation,
and runtime constraints.
"""

import subprocess
import tempfile
import os
import time
import ast
from typing import Tuple

BLOCKED_IMPORTS = [
    "os", "sys", "subprocess", "socket", "importlib", "shutil",
    "pathlib", "glob", "pickle", "shelve", "dbm", "sqlite3",
    "ftplib", "http", "urllib", "requests", "httpx", "asyncio",
    "multiprocessing", "threading",
    "ctypes", "cffi", "resource", "signal", "mmap", "gc"
]

EXECUTION_TIMEOUT_SECONDS = 10
MEMORY_LIMIT_MB = 256


def _build_import_checker(blocked: list[str]) -> str:
    """Build a Python script snippet that checks for blocked imports using AST parsing."""
    blocked_repr = repr(blocked)
    return f'''
import ast as _ast
import sys as _sys

_BLOCKED = {blocked_repr}
_source_to_check = open(__file__).read()

# Find the marker line and only check code after it
_marker = "# --- USER CODE START ---"
_marker_pos = _source_to_check.find(_marker)
if _marker_pos != -1:
    _source_to_check = _source_to_check[_marker_pos + len(_marker):]

try:
    _tree = _ast.parse(_source_to_check)
except SyntaxError:
    pass  # Let the actual execution catch syntax errors
else:
    for _node in _ast.walk(_tree):
        if isinstance(_node, _ast.Import):
            for _alias in _node.names:
                _top = _alias.name.split(".")[0]
                if _top in _BLOCKED:
                    print(f"BLOCKED IMPORT: '{{_alias.name}}' is not allowed in the sandbox.")
                    _sys.exit(1)
        elif isinstance(_node, _ast.ImportFrom):
            if _node.module:
                _top = _node.module.split(".")[0]
                if _top in _BLOCKED:
                    print(f"BLOCKED IMPORT: '{{_node.module}}' is not allowed in the sandbox.")
                    _sys.exit(1)

# Also block dangerous builtins
import builtins as _builtins
_original_import = _builtins.__import__

def _restricted_import(name, *args, **kwargs):
    _top = name.split(".")[0]
    if _top in _BLOCKED:
        raise ImportError(f"BLOCKED IMPORT: '{{name}}' is not allowed in the sandbox.")
    return _original_import(name, *args, **kwargs)

_builtins.__import__ = _restricted_import
'''


def execute_code(code: str, test_code: str, allow_threading: bool = False) -> Tuple[str, bool, int]:
    """
    Execute code + test_code in a sandboxed subprocess.

    Returns:
        (output: str, timed_out: bool, execution_time_ms: int)

    The output contains both stdout and stderr merged, exactly as a developer
    would see in their terminal.
    """
    # Build the blocked imports list, optionally allowing threading
    blocked = [b for b in BLOCKED_IMPORTS if not (b == "threading" and allow_threading)]

    # Build the full script: import checker + user code + test code
    import_checker = _build_import_checker(blocked)
    full_script = import_checker + "\n# --- USER CODE START ---\n" + code + "\n" + test_code

    tmp_path = None
    try:
        # Write to a temporary file
        with tempfile.NamedTemporaryFile(
            mode='w', suffix='.py', prefix='sandbox_',
            delete=False, dir=tempfile.gettempdir()
        ) as tmp:
            tmp.write(full_script)
            tmp_path = tmp.name

        # Run in subprocess with timeout
        start_time = time.time()
        try:
            result = subprocess.run(
                ["python3", tmp_path],
                capture_output=True,
                text=True,
                timeout=EXECUTION_TIMEOUT_SECONDS,
                env={
                    "PATH": os.environ.get("PATH", "/usr/bin:/usr/local/bin"),
                    "HOME": os.environ.get("HOME", "/tmp"),
                    "PYTHONDONTWRITEBYTECODE": "1",
                }
            )
            elapsed_ms = int((time.time() - start_time) * 1000)
            output = result.stdout + result.stderr
            return (output.strip(), False, elapsed_ms)

        except subprocess.TimeoutExpired:
            elapsed_ms = int((time.time() - start_time) * 1000)
            return (
                f"TIMEOUT: Code execution exceeded {EXECUTION_TIMEOUT_SECONDS} second limit and was killed.",
                True,
                elapsed_ms
            )

    except Exception as e:
        return (f"SANDBOX ERROR: {str(e)}", False, 0)

    finally:
        # Always clean up temp files
        if tmp_path and os.path.exists(tmp_path):
            try:
                os.unlink(tmp_path)
            except OSError:
                pass