"""Engine, session plumbing, and shared column helpers.

DATA_DIR is resolved relative to this file; the db package lives one level
deeper than the old single-file module, hence the extra ``parent``.
"""

import json
import uuid
from datetime import datetime, timezone
from pathlib import Path
from typing import Any

from sqlalchemy.pool import StaticPool
from sqlmodel import Session, SQLModel, create_engine

DATA_DIR = Path(__file__).resolve().parent.parent.parent.parent.parent / "data"
DATA_DIR.mkdir(parents=True, exist_ok=True)
DATABASE_URL = f"sqlite:///{DATA_DIR / 'agenteval.db'}"
FILES_DIR = DATA_DIR / "files"
FILES_DIR.mkdir(parents=True, exist_ok=True)

engine = create_engine(
    DATABASE_URL,
    echo=False,
    connect_args={"check_same_thread": False},
    poolclass=StaticPool,
)


def utc_now() -> datetime:
    return datetime.now(timezone.utc)


def as_utc(dt: datetime) -> datetime:
    """Attach UTC tzinfo to a naive datetime.

    SQLite round-trips drop tzinfo; stored times are always UTC, so a naive
    value read back is restored as UTC before any comparison with utc_now().
    """
    return dt if dt.tzinfo is not None else dt.replace(tzinfo=timezone.utc)


def iso_utc(dt: datetime | None) -> str | None:
    """Serialize a datetime to ISO 8601 with UTC timezone suffix.

    Guarantees the output always ends with 'Z' or '+00:00' so JavaScript's
    Date.parse() interprets it correctly as UTC (no 8-hour local-time offset).
    """
    if dt is None:
        return None
    if dt.tzinfo is None:
        dt = dt.replace(tzinfo=timezone.utc)
    return dt.isoformat(timespec="seconds").replace("+00:00", "Z")


def new_uuid() -> str:
    return str(uuid.uuid4())


def _json_dumps(value: Any) -> str:
    """Serialize a JSON column value. ensure_ascii=False keeps CJK readable
    in the stored text — the single serialization口径 for all JSON columns."""
    return json.dumps(value, ensure_ascii=False)


def _json_loads(raw: str) -> Any:
    return json.loads(raw)


def init_db() -> None:
    SQLModel.metadata.create_all(engine)


def get_session() -> Session:
    return Session(engine)


def get_session_context():
    """Context manager that creates and properly closes a database session."""
    session = Session(engine)
    try:
        yield session
    finally:
        session.close()