"""Session service for active session management."""

import json
from datetime import datetime
from pathlib import Path
from typing import Optional

from ..models import Session


_ACTIVE_SESSION_FILE = ".active_session.json"


def get_active_session_path() -> Path:
    """Return the path to the active session file in projects/ directory."""
    return Path("projects") / _ACTIVE_SESSION_FILE


def get_active_session() -> Optional[Session]:
    """Load and return the currently active session, or None if none exists."""
    path = get_active_session_path()
    if not path.exists():
        return None

    with open(path, "r", encoding="utf-8") as f:
        data = json.load(f)

    # Convert started_at string back to datetime
    data["started_at"] = datetime.fromisoformat(data["started_at"])
    if data.get("ended_at"):
        data["ended_at"] = datetime.fromisoformat(data["ended_at"])

    return Session(**data)


def set_active_session(session: Session) -> None:
    """Save the given session as the active session."""
    path = get_active_session_path()
    path.parent.mkdir(parents=True, exist_ok=True)

    data = session.model_dump(mode="json")
    # Serialize datetime objects to ISO format
    data["started_at"] = session.started_at.isoformat()
    if session.ended_at:
        data["ended_at"] = session.ended_at.isoformat()

    with open(path, "w", encoding="utf-8") as f:
        json.dump(data, f, indent=2, ensure_ascii=False)


def clear_active_session() -> None:
    """Remove the active session file."""
    path = get_active_session_path()
    if path.exists():
        path.unlink()


def validate_no_other_active_session(project_slug: str) -> bool:
    """
    Check if there is an active session for a different project.
    Returns True if no conflict exists (i.e., either no active session
    or the active session belongs to the same project).
    """
    active = get_active_session()
    if active is None:
        return True
    return active.project_slug == project_slug