"""JSON-line protocol reader/writer over stdin/stdout."""

from __future__ import annotations

import json
import sys
from typing import Any

from voice_to_notes.ipc.messages import IPCMessage


def read_message() -> IPCMessage | None:
    """Read a single JSON-line message from stdin. Returns None on EOF."""
    try:
        line = sys.stdin.readline()
        if not line:
            return None  # EOF
        line = line.strip()
        if not line:
            return None
        data = json.loads(line)
        return IPCMessage.from_dict(data)
    except json.JSONDecodeError as e:
        _log(f"Invalid JSON: {e}")
        return None
    except Exception as e:
        _log(f"Read error: {e}")
        return None


def write_message(msg: IPCMessage) -> None:
    """Write a JSON-line message to stdout."""
    line = json.dumps(msg.to_dict(), separators=(",", ":"))
    sys.stdout.write(line + "\n")
    sys.stdout.flush()


def write_dict(data: dict[str, Any]) -> None:
    """Write a raw dict as a JSON-line message to stdout."""
    line = json.dumps(data, separators=(",", ":"))
    sys.stdout.write(line + "\n")
    sys.stdout.flush()


def _log(message: str) -> None:
    """Log to stderr (stdout is reserved for IPC)."""
    print(f"[sidecar] {message}", file=sys.stderr, flush=True)