#!/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"
MAX_LOG_SIZE_KB=1024  # 1MB

# --- Functions ---

# Função de Log (modificada para usar logger)
log() {
    local message="$1"
    local timestamp=$(date '+%Y-%m-%d %H:%M:%S')
    # Escreve no ficheiro de log
    echo -e "$timestamp: $message" | tee -a "$LOG_FILE"
    # Envia para o syslog (opcional)
    logger -t "gui_manager" "$message"
}

# Função para limitar o tamanho do log
limit_log_size() {
    local log_file="$1"
    local max_size_kb="$2"
    local max_size_bytes=$((max_size_kb * 1024))

    if [ -f "$log_file" ]; then
        local current_size=$(stat -c %s "$log_file" 2>/dev/null || wc -c < "$log_file" 2>/dev/null)

        if [ "$current_size" -gt "$max_size_bytes" ]; then
            log "Aviso: Ficheiro de log $log_file excedeu $max_size_kb KB. A truncar..."
            tail -n 500 "$log_file" > "${log_file}.tmp" && mv "${log_file}.tmp" "$log_file"
            log "Ficheiro de log truncado. As últimas 500 linhas foram mantidas."
        fi
    fi
}

# 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
        log "System doesn't use systemd"
        return 1
    fi
}

# Function to show GUI status
show_gui_status() {
    if ! is_systemd; then
        log "System doesn't use systemd"
        return 1
    fi

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

    log "Current system target: $current_target"
    log "Display Manager: $(basename "$dm")"

    if [ "$current_target" = "graphical.target" ]; then
        log "Graphical environment is ENABLED"
    else
        log "Graphical environment is DISABLED"
    fi

    # Show memory usage
    log "Memory usage:"
    free -h | awk '/^Mem:/ {log "  Total: " $2 ", Used: " $3 ", Free: " $4}'
}

# Function to disable graphical environment
disable_gui() {
    if ! is_systemd; then
        log "Error: This system doesn't use systemd"
        return 1
    fi

    current_target=$(get_current_target)
    if [ "$current_target" != "graphical.target" ]; then
        log "Graphical environment is already disabled"
        return 0
    fi

    log "Disabling graphical environment..."

    # Get current display manager
    dm=$(get_display_manager)
    if [ "$dm" = "unknown" ]; then
        log "Error: Could not determine display manager"
        return 1
    fi

    # Show memory usage before
    log "Memory usage before disabling GUI:"
    free -h | awk '/^Mem:/ {log "  Total: " $2 ", Used: " $3 ", Free: " $4}'

    # Stop display manager
    log "Stopping display manager $(basename "$dm")..."
    if ! systemctl stop "$(basename "$dm")"; then
        log "Error: Failed to stop display manager $(basename "$dm")"
        return 1
    fi

    # Disable graphical target
    log "Setting default target to multi-user.target..."
    if ! systemctl set-default multi-user.target; then
        log "Error: Failed to set default target to multi-user.target"
        return 1
    fi

    # Show memory usage after
    log "Memory usage after disabling GUI:"
    free -h | awk '/^Mem:/ {log "  Total: " $2 ", Used: " $3 ", Free: " $4}'

    log "Graphical environment disabled successfully"
    return 0
}

# Function to enable graphical environment
enable_gui() {
    if ! is_systemd; then
        log "Error: This system doesn't use systemd"
        return 1
    fi

    current_target=$(get_current_target)
    if [ "$current_target" = "graphical.target" ]; then
        log "Graphical environment is already enabled"
        return 0
    fi

    log "Enabling graphical environment..."

    # Get current display manager
    dm=$(get_display_manager)
    if [ "$dm" = "unknown" ]; then
        log "Error: Could not determine display manager"
        return 1
    fi

    # Enable graphical target
    log "Setting default target to graphical.target..."
    if ! systemctl set-default graphical.target; then
        log "Error: Failed to set default target to graphical.target"
        return 1
    fi

    # Start display manager
    log "Starting display manager $(basename "$dm")..."
    if ! systemctl start "$(basename "$dm")"; then
        log "Error: Failed to start display manager $(basename "$dm")"
        return 1
    fi

    log "Graphical environment enabled successfully"
    return 0
}

# Function to format free output for logging
format_free_output() {
    free -h | awk '/^Mem:/ {
        log "  Total: " $2 ", Used: " $3 ", Free: " $4
    }'
}

# --- Main Execution ---

# Check if running as root
if [ "$(id -u)" -ne 0 ]; then
    echo "This script must be run as root" >&2
    exit 1
fi

# Create log directory if it doesn't exist
mkdir -p "$(dirname "$LOG_FILE")"
limit_log_size "$LOG_FILE" "$MAX_LOG_SIZE_KB"  # Verifica o tamanho do log no início

# Log script execution start
log "Starting GUI Manager Script with action: ${1:-status}"

# 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
        exit $?
        ;;
    enable)
        enable_gui
        exit $?
        ;;
    status)
        show_gui_status
        exit $?
        ;;
    *)
        log "Usage: $0 [enable|disable|status]"
        log "Or: GUI_ACTION=enable|disable $0"
        log "Invalid action: $ACTION"
        exit 1
        ;;
esac