#!/bin/bash

# =============================================
# Graphical Environment Manager Script
# Disables/enables graphical environment to save RAM
# Must be run with sudo!
#
# Usage:
#   ./gui_manager.sh [enable|disable|status]
#   GUI_ACTION=enable|disable ./gui_manager.sh
# =============================================

# --- Configuration ---
LOG_FILE="/var/log/gui_manager.log"

# --- Functions ---

# Function to check if system uses systemd
is_systemd() {
    [ -d /run/systemd/system ] && return 0 || return 1
}

# Function to get current display manager
get_display_manager() {
    if [ -f /etc/X11/default-display-manager ]; then
        cat /etc/X11/default-display-manager
    elif systemctl list-units --type=service | grep -q "gdm"; then
        echo "/usr/sbin/gdm3"
    elif systemctl list-units --type=service | grep -q "lightdm"; then
        echo "/usr/sbin/lightdm"
    elif systemctl list-units --type=service | grep -q "sddm"; then
        echo "/usr/sbin/sddm"
    elif systemctl list-units --type=service | grep -q "lxdm"; then
        echo "/usr/sbin/lxdm"
    else
        echo "unknown"
    fi
}

# Function to get current target
get_current_target() {
    if is_systemd; then
        systemctl get-default
    else
        echo "System doesn't use systemd"
    fi
}

# Function to show GUI status
show_gui_status() {
    if ! is_systemd; then
        echo "$(date): System doesn't use systemd" | tee -a "$LOG_FILE"
        return 1
    fi

    current_target=$(get_current_target)
    dm=$(get_display_manager)

    echo "$(date): Current system target: $current_target" | tee -a "$LOG_FILE"
    echo "$(date): Display Manager: $(basename "$dm")" | tee -a "$LOG_FILE"

    if [ "$current_target" = "graphical.target" ]; then
        echo "$(date): Graphical environment is ENABLED" | tee -a "$LOG_FILE"
    else
        echo "$(date): Graphical environment is DISABLED" | tee -a "$LOG_FILE"
    fi

    # Show memory usage
    echo "$(date): Memory usage:" | tee -a "$LOG_FILE"
    free -h | awk '/^Mem:/ {print "  Total: " $2 ", Used: " $3 ", Free: " $4}' | tee -a "$LOG_FILE"
}

# Function to disable graphical environment
disable_gui() {
    if ! is_systemd; then
        echo "$(date): Error: This system doesn't use systemd" | tee -a "$LOG_FILE"
        return 1
    fi

    current_target=$(get_current_target)
    if [ "$current_target" != "graphical.target" ]; then
        echo "$(date): Graphical environment is already disabled" | tee -a "$LOG_FILE"
        return 0
    fi

    echo "$(date): Disabling graphical environment..." | tee -a "$LOG_FILE"

    # Get current display manager
    dm=$(get_display_manager)
    if [ "$dm" = "unknown" ]; then
        echo "$(date): Error: Could not determine display manager" | tee -a "$LOG_FILE"
        return 1
    fi

    # Show memory usage before
    echo "$(date): Memory usage before disabling GUI:" | tee -a "$LOG_FILE"
    free -h | awk '/^Mem:/ {print "  Total: " $2 ", Used: " $3 ", Free: " $4}' | tee -a "$LOG_FILE"

    # Stop display manager
    echo "$(date): Stopping display manager $(basename "$dm")..." | tee -a "$LOG_FILE"
    systemctl stop "$(basename "$dm")"

    # Disable graphical target
    echo "$(date): Setting default target to multi-user.target..." | tee -a "$LOG_FILE"
    systemctl set-default multi-user.target

    # Show memory usage after
    echo "$(date): Memory usage after disabling GUI:" | tee -a "$LOG_FILE"
    free -h | awk '/^Mem:/ {print "  Total: " $2 ", Used: " $3 ", Free: " $4}' | tee -a "$LOG_FILE"

    echo "$(date): Graphical environment disabled successfully" | tee -a "$LOG_FILE"
    return 0
}

# Function to enable graphical environment
enable_gui() {
    if ! is_systemd; then
        echo "$(date): Error: This system doesn't use systemd" | tee -a "$LOG_FILE"
        return 1
    fi

    current_target=$(get_current_target)
    if [ "$current_target" = "graphical.target" ]; then
        echo "$(date): Graphical environment is already enabled" | tee -a "$LOG_FILE"
        return 0
    fi

    echo "$(date): Enabling graphical environment..." | tee -a "$LOG_FILE"

    # Get current display manager
    dm=$(get_display_manager)
    if [ "$dm" = "unknown" ]; then
        echo "$(date): Error: Could not determine display manager" | tee -a "$LOG_FILE"
        return 1
    fi

    # Enable graphical target
    echo "$(date): Setting default target to graphical.target..." | tee -a "$LOG_FILE"
    systemctl set-default graphical.target

    # Start display manager
    echo "$(date): Starting display manager $(basename "$dm")..." | tee -a "$LOG_FILE"
    systemctl start "$(basename "$dm")"

    echo "$(date): Graphical environment enabled successfully" | tee -a "$LOG_FILE"
    return 0
}

# --- Main Execution ---

# Create log directory if it doesn't exist
mkdir -p /var/log

# Determine action based on parameters or environment variable
ACTION=""

# Check for command line parameter
if [ $# -gt 0 ]; then
    ACTION="$1"
fi

# Check for environment variable if no parameter provided
if [ -z "$ACTION" ] && [ -n "$GUI_ACTION" ]; then
    ACTION="$GUI_ACTION"
fi

# Default to status if no action specified
if [ -z "$ACTION" ]; then
    ACTION="status"
fi

# Execute the appropriate action
case "$ACTION" in
    disable)
        disable_gui
        ;;
    enable)
        enable_gui
        ;;
    status)
        show_gui_status
        ;;
    *)
        echo "Usage: $0 [enable|disable|status]"
        echo "Or: GUI_ACTION=enable|disable $0"
        echo "Invalid action: $ACTION"
        exit 1
        ;;
esac