# shellcheck shell=bash
#------------------------------------------
# lib/session.sh — display manager and graphical session wiring
#
# DM policy:
#   * A DE module leaves its native DM alone (GNOME→gdm, Plasma→sddm, XFCE→sddm).
#   * A TWM module enforces SDDM, because SDDM is the only DM that presents both
#     Wayland compositors and X11 sessions in one menu. One greeter, no surprises.
#------------------------------------------

if [[ -n "${_SB_SESSION_LOADED:-}" ]]; then
    return 0
fi
_SB_SESSION_LOADED=1

# Name of the active display manager ("sddm", "gdm", "lightdm"), or "" if none.
detect_display_manager() {
    local link=/etc/systemd/system/display-manager.service
    if [[ -L "$link" ]]; then
        basename "$(readlink "$link")" | sed 's/\.service$//'
    else
        echo ""
    fi
}

enable_graphical_target() {
    sudo systemctl set-default graphical.target
}

# Make $1 the display manager, disabling whatever is active now.
switch_display_manager() {
    local target="$1"
    local current
    current=$(detect_display_manager)

    if [[ "$current" == "$target" ]]; then
        ok "Display manager already $target."
    else
        if [[ -n "$current" ]]; then
            info "Disabling current display manager: $current"
            # disable may fail if the unit vanished; that is not fatal
            sudo systemctl disable "$current" 2>/dev/null || true
        fi
        info "Enabling display manager: $target"
        sudo systemctl enable "$target"
    fi

    enable_graphical_target
}

# Register a Wayland session so the DM can list it.
# $1 = identifier, $2 = display name, $3 = command
write_wayland_session() {
    local id="$1" name="$2" exec_cmd="$3"
    local file="/usr/share/wayland-sessions/${id}.desktop"
    if [[ -f "$file" ]]; then
        ok "Wayland session already registered: $id"
        return 0
    fi
    info "Registering Wayland session: $id"
    sudo mkdir -p "$(dirname "$file")"
    printf '[Desktop Entry]\nName=%s\nComment=%s\nExec=%s\nType=Application\nDesktopNames=%s\n' \
        "$name" "$name session" "$exec_cmd" "$id" | sudo tee "$file" >/dev/null
    sudo chmod 644 "$file"
}

# Register an X11 session so the DM can list it.
write_x11_session() {
    local id="$1" name="$2" exec_cmd="$3"
    local file="/usr/share/xsessions/${id}.desktop"
    if [[ -f "$file" ]]; then
        ok "X11 session already registered: $id"
        return 0
    fi
    info "Registering X11 session: $id"
    # A bare Fedora has no X session yet, so the directory may not exist.
    sudo mkdir -p "$(dirname "$file")"
    printf '[Desktop Entry]\nName=%s\nComment=%s\nExec=%s\nType=Application\n' \
        "$name" "$name session" "$exec_cmd" | sudo tee "$file" >/dev/null
    sudo chmod 644 "$file"
}

# Common login-time plumbing every Wayland compositor wants on a bare install.
install_session_prereqs() {
    install_packages \
        xdg-desktop-portal \
        polkit \
        polkit-gnome \
        pipewire \
        pipewire-pulseaudio \
        wireplumber

    # A bare compositor (niri, MangoWC, Hyprland) has NO polkit agent: without
    # one, anything needing privilege elevation (virt-manager's libvirt access,
    # disks, network settings) fails with "no polkit agent available to
    # authenticate". Autostart it for every graphical session via the XDG
    # autostart dir the session runs.
    local autostart="${XDG_AUTOSTART_DIR:-/etc/xdg/autostart}"
    local desktop_src="${POLKIT_AGENT_DESKTOP:-/usr/share/applications/polkit-gnome-authentication-agent-1.desktop}"
    if [[ -f "$desktop_src" ]] && [[ ! -e "$autostart/$(basename "$desktop_src")" ]]; then
        info "Enabling polkit agent for compositor sessions..."
        sudo mkdir -p "$autostart"
        sudo ln -sf "$desktop_src" "$autostart/$(basename "$desktop_src")"
    fi
}