main.go

// Threshold is a simple command line tool to monitor network usage and disable
// network interface automatically when specified threshold is exeeded.
// Copyright (C) 2025-2026 Enindu Alahapperuma
//
// Threshold is free software: you can redistribute it and/or modify it under
// the terms of the GNU General Public License as published by the Free Software
// Foundation, either version 3 of the License, or (at your option) any later
// version.
//
// Threshold is distributed in the hope that it will be useful, but WITHOUT ANY
// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License along with
// Threshold. If not, see <https://www.gnu.org/licenses/>.

// Threshold is a simple command line tool to monitor network usage and disable
// network interface automatically when specified threshold is exeeded.
//
// Usage:
//
//	threshold <command>:<subcommand> [arguments]
//	threshold [flags]
//
// Available commands:
//
//	daemon
//	device
//
// Available flags:
//
//	-v, --version # Display version message.
//	-h, --help    # Display help message.
//
// Use "threshold <command>:help" to see more information about commands.
package main

import (
	"context"
	"errors"
	"log"
	"os"
	"os/user"

	"github.com/enindu/palette"
	"github.com/enindu/threshold/commands/daemon"
	"github.com/enindu/threshold/commands/device"
)

var (
	errUserNoPermission    error = errors.New("User has no permission, run as \"root\".")
	errInstructionNotFound error = errors.New("Instruction is not found, use \"-h\" or \"--help\" to see help message.")
	errCommandInvalid      error = errors.New("Command is invalid, use \"-h\" or \"--help\" to see help message.")
)

var (
	reguPrinter *palette.Printer = palette.NewPrinterRegu()
	erroPrinter *palette.Printer = palette.NewPrinterErro()
)

func main() {
	current, err := user.Current()

	if err != nil {
		erroPrinter.Print("%s\n", err.Error())
		return
	}

	if current.Uid != "0" {
		erroPrinter.Print("%s\n", errUserNoPermission.Error())
		return
	}

	file, err := os.OpenFile("/var/log/threshold.log", os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0644)

	if err != nil {
		erroPrinter.Print("%s\n", err.Error())
		return
	}

	defer file.Close()

	logger := log.New(file, log.Prefix(), log.Flags())

	dispatchers := map[string]func([]string, context.Context, *log.Logger){
		"daemon:start":  daemon.Start,
		"daemon:stop":   daemon.Stop,
		"daemon:status": daemon.Status,
		"daemon:help":   daemon.Help,
		"device:up":     device.Up,
		"device:down":   device.Down,
		"device:usage":  device.Usage,
		"device:help":   device.Help,
	}

	inputs := os.Args

	if len(inputs) < 2 {
		erroPrinter.Print("%s\n", errInstructionNotFound.Error())
		return
	}

	instruction := inputs[1]

	switch instruction {
	case "-v", "--version":
		version()
		return
	case "-h", "--help":
		help()
		return
	}

	execute, ok := dispatchers[instruction]

	if !ok {
		erroPrinter.Print("%s\n", errCommandInvalid)
		return
	}

	ctx := context.Background()
	arguments := inputs[2:]

	execute(arguments, ctx, logger)
}