# ABOUTME: Session detection — discovers available Wayland and X11 sessions.
# ABOUTME: Parses .desktop files from standard session directories.

import configparser
from collections.abc import Sequence
from dataclasses import dataclass
from pathlib import Path

DEFAULT_WAYLAND_DIRS = (Path("/usr/share/wayland-sessions"),)
DEFAULT_XSESSION_DIRS = (Path("/usr/share/xsessions"),)


@dataclass
class Session:
    """Represents an available login session."""

    name: str
    exec_cmd: str
    session_type: str  # "wayland" or "x11"


def _parse_desktop_file(path: Path, session_type: str) -> Session | None:
    """Parse a .desktop file and return a Session, or None if invalid."""
    config = configparser.ConfigParser(interpolation=None)
    config.read(path)

    section = "Desktop Entry"
    if not config.has_section(section):
        return None

    name = config.get(section, "Name", fallback=None)
    exec_cmd = config.get(section, "Exec", fallback=None)

    if not name or not exec_cmd:
        return None

    return Session(name=name, exec_cmd=exec_cmd, session_type=session_type)


def get_sessions(
    wayland_dirs: Sequence[Path] = DEFAULT_WAYLAND_DIRS,
    xsession_dirs: Sequence[Path] = DEFAULT_XSESSION_DIRS,
) -> list[Session]:
    """Discover available sessions from .desktop files."""
    sessions: list[Session] = []

    for directory in wayland_dirs:
        if not directory.exists():
            continue
        for desktop_file in sorted(directory.glob("*.desktop")):
            session = _parse_desktop_file(desktop_file, "wayland")
            if session:
                sessions.append(session)

    for directory in xsession_dirs:
        if not directory.exists():
            continue
        for desktop_file in sorted(directory.glob("*.desktop")):
            session = _parse_desktop_file(desktop_file, "x11")
            if session:
                sessions.append(session)

    return sessions