from __future__ import annotations

import json
from dataclasses import asdict, dataclass
from pathlib import Path


@dataclass(frozen=True)
class StoredSession:
    session_id: str
    messages: tuple[dict[str, object], ...]
    input_tokens: int
    output_tokens: int


DEFAULT_SESSION_DIR = Path('.port_sessions')


def save_session(session: StoredSession, directory: Path | None = None) -> Path:
    target_dir = directory or DEFAULT_SESSION_DIR
    target_dir.mkdir(parents=True, exist_ok=True)
    path = target_dir / f'{session.session_id}.json'
    path.write_text(json.dumps(asdict(session), indent=2))
    return path


def load_session(session_id: str, directory: Path | None = None) -> StoredSession:
    target_dir = directory or DEFAULT_SESSION_DIR
    data = json.loads((target_dir / f'{session_id}.json').read_text())
    return StoredSession(
        session_id=data['session_id'],
        messages=tuple(data['messages']),
        input_tokens=data['input_tokens'],
        output_tokens=data['output_tokens'],
    )
