"""Runtime UTF-8 guard for Korean-heavy KCSC tools.

Windows shells and MCP stdio clients can disagree about stream encodings.  The
project stores and exchanges Korean standards text, so every entrypoint should
pin process streams to UTF-8 before logging, JSON-RPC, or CLI output starts.
"""

from __future__ import annotations

import os
import sys
from typing import TextIO


UTF8 = "utf-8"


def _set_windows_console_utf8() -> None:
    """Best-effort console codepage switch for interactive Windows runs."""
    if os.name != "nt":
        return
    try:
        import ctypes

        kernel32 = ctypes.windll.kernel32
        kernel32.SetConsoleCP(65001)
        kernel32.SetConsoleOutputCP(65001)
    except Exception:
        # Headless MCP/CI processes often have no real console. Stream
        # reconfiguration below is the part that matters for those cases.
        return


def _reconfigure_stream(stream: TextIO | None, *, errors: str) -> bool:
    if stream is None:
        return False
    reconfigure = getattr(stream, "reconfigure", None)
    if not callable(reconfigure):
        return False
    try:
        reconfigure(encoding=UTF8, errors=errors)
        return True
    except (TypeError, ValueError, OSError):
        try:
            reconfigure(errors=errors)
            return True
        except (TypeError, ValueError, OSError):
            return False


def configure_utf8_stdio() -> dict[str, str | bool | None]:
    """Force Korean-safe UTF-8 stdio for CLI, MCP stdio, and REST entrypoints.

    Returns a small state dictionary for tests and diagnostics.  Environment
    variables are set for child Python processes; current streams are
    reconfigured directly because PYTHONUTF8/PYTHONIOENCODING are normally read
    only at interpreter startup.
    """
    os.environ.setdefault("PYTHONUTF8", "1")
    os.environ.setdefault("PYTHONIOENCODING", UTF8)

    _set_windows_console_utf8()
    stdin_ok = _reconfigure_stream(sys.stdin, errors="strict")
    stdout_ok = _reconfigure_stream(sys.stdout, errors="replace")
    stderr_ok = _reconfigure_stream(sys.stderr, errors="replace")

    return {
        "stdin_encoding": getattr(sys.stdin, "encoding", None),
        "stdout_encoding": getattr(sys.stdout, "encoding", None),
        "stderr_encoding": getattr(sys.stderr, "encoding", None),
        "stdin_reconfigured": stdin_ok,
        "stdout_reconfigured": stdout_ok,
        "stderr_reconfigured": stderr_ok,
        "PYTHONUTF8": os.environ.get("PYTHONUTF8"),
        "PYTHONIOENCODING": os.environ.get("PYTHONIOENCODING"),
    }