args.go

package main

import (
	"flag"
	"fmt"
	"os"
	"sort"
	"strings"
)

func parseArguments() {
	showError := func(msg string) {
		fmt.Println(msg)
		flag.Usage()
		os.Exit(1)
	}
	helpAlgos := func() string {
		as := make([]string, len(algos))
		i := 0
		for k := range algos {
			as[i] = fmt.Sprintf("%q", string(k))
			i++
		}
		sort.Strings(as)
		return strings.Join(as, ", ")
	}

	var showHelp bool
	var _algorithm string
	var _windowWidth int
	var _windowHeight int

	flag.BoolVar(&showHelp, "help", false, "Show usage info")
	flag.BoolVar(&showHelp, "h", false, "Show usage info")
	flag.IntVar(&_windowWidth, "width", 800, "Window's width")
	flag.IntVar(&_windowHeight, "height", 600, "Window's height")
	flag.IntVar(&size, "size", 100, "Size of the array to sort")
	flag.IntVar(&speed, "speed", 2, "Step duration in milliseconds")
	flag.IntVar(&startDelay, "delay", 0, "Initial delay before running the animation")
	flag.BoolVar(&debug, "debug", false, "Enable debug info")
	flag.BoolVar(&dataAsc, "asc", false, "Data set is already sorted")
	flag.BoolVar(&dataDesc, "desc", false, "Data set is in descending")
	flag.Int64Var(&dataRndSeed, "seed", 0, "Random seed to generate the data set. 0 means autogenerated")
	flag.StringVar(&_algorithm, "algo", string(quickSort), "One of: "+helpAlgos())

	flag.Parse()

	if showHelp {
		flag.Usage()
		os.Exit(0)
	}

	if _windowWidth <= 0 {
		showError("Window's width must be positive")
	}
	windowWidth = float64(_windowWidth)
	if _windowHeight <= 0 {
		showError("Window0s height must be positive")
	}
	if size <= 1 {
		showError("Size bust be at least 2")
	}
	if dataRndSeed < 0 {
		showError("Random seed must be non negative")
	}
	if dataRndSeed > 0 && (dataAsc || dataDesc) || (dataAsc && dataDesc) {
		showError("You can't combine ascending, descending options and random seed")
	}
	windowHeight = float64(_windowHeight)
	algorithm = algo(_algorithm)
	if _, found := algos[algorithm]; !found {
		showError(fmt.Sprintf("Unknown algorithm %q", _algorithm))
	}

}