Replace flag with go-arg because flag sucks

This changes the command line arguments from -target-hour,
-target-minute, etc., to --hour, --minute, etc. and includes the short
forms as well (eg, -h and -m).

Also, added go.mod and go.sum.

go.mod

@@ -0,0 +1,8 @@
+module countdown
+
+go 1.19
+
+require (
+	github.com/alexflint/go-arg v1.4.3 // indirect
+	github.com/alexflint/go-scalar v1.1.0 // indirect
+)

go.sum

@@ -0,0 +1,12 @@
+github.com/alexflint/go-arg v1.4.3 h1:9rwwEBpMXfKQKceuZfYcwuc/7YY7tWJbFsgG5cAU/uo=
+github.com/alexflint/go-arg v1.4.3/go.mod h1:3PZ/wp/8HuqRZMUUgu7I+e1qcpUbvmS258mRXkFH4IA=
+github.com/alexflint/go-scalar v1.1.0 h1:aaAouLLzI9TChcPXotr6gUhq+Scr8rl0P9P4PnltbhM=
+github.com/alexflint/go-scalar v1.1.0/go.mod h1:LoFvNMqS1CPrMVltza4LvnGKhaSpc3oyLEBUZVhhS2o=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
+github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

main.go

@@ -1,13 +1,14 @@
 package main
 
 import (
-	"flag"
 	"fmt"
 	"os"
 	"strings"
 	"sync"
 	"time"
 	"text/template"
+
+	"github.com/alexflint/go-arg"
 )
 
 /*
@@ -19,82 +20,59 @@ import (
 
 */
 
+type Arguments struct {
+	Hour int   `arg:"--hour,-h" help:"Target hour" default:"-1"`
+	Minute int `arg:"--minute,-m" help:"Target minute" default:"-1"`
+	Year int   `arg:"--year" help:"Target year" default:"-1"`
+	Day int    `arg:"--day" help:"Target day" default:"-1"`
+	Month int  `arg:"--month" help:"Target month" default:"-1"`
+
+	Output string `arg:"--output,-o" help:"Output filename" default:"/tmp/countdown.txt"`
+	Done string   `arg:"--done,-d" help:"String to display when done" default:"MOVIE SIGN"`
+	Format string `arg:"--format,-f" help:"Format string for the countdown" default:"{{if .Hours}}{{.Hours}}h {{end}}{{if or .Minutes .Hours}}{{.Minutes}}m {{end}}{{.Seconds}}s"`
+}
+
 func main() {
+	args := &Arguments{}
+	arg.MustParse(args)
 
-	var filename string
-	var untilStr string
-	var targetTimeStr string
-	var doneStr string
-	var format string
-
-	flag.StringVar(&filename, "o", "/tmp/countdown.txt", "Output file to write the countdown to.")
-	flag.StringVar(&untilStr, "u", "", "Countdown duration")
-	flag.StringVar(&targetTimeStr, "t", "", "Countdown to time")
-	flag.StringVar(&doneStr, "d", "00:00:00", "String to display when done")
-	//flag.StringVar(&format, "f", "%H:%M:%S", "Format for the countdown")
-	flag.StringVar(&format, "f", "{{if .Hours}}{{.Hours}}h {{end}}{{if or .Minutes .Hours}}{{.Minutes}}m {{end}}{{.Seconds}}s", "Format for the countdown")
-
-	var targetYear int
-	var targetDay int
-	var targetMonth int
-
-	flag.IntVar(&targetYear, "target-year", -1, "")
-	flag.IntVar(&targetDay, "target-day", -1, "")
-	flag.IntVar(&targetMonth, "target-month", -1, "")
-
-	var targetHour int
-	var targetMinute int
-	var targetSecond int
-
-	flag.IntVar(&targetHour, "target-hour", -1, "")
-	flag.IntVar(&targetMinute, "target-minute", 0, "")
-	flag.IntVar(&targetSecond, "target-second", 0, "")
-
-	flag.Parse()
-
-	var until time.Time
 	now := time.Now()
 
-	if untilStr != "" {
-		untilDuration, err := time.ParseDuration(untilStr)
-		if err != nil {
-			fmt.Println(err)
-			os.Exit(1)
-		}
-		until = time.Now().Add(untilDuration)
-	} else {
-		if targetYear == -1 {
-			targetYear = now.Year()
-		}
-		if targetMonth == -1 {
-			targetMonth = int(now.Month())
-		}
-		if targetDay == -1 {
-			targetDay = now.Day()
+	if args.Hour == -1 {
+		args.Hour = now.Hour()
 	}
 
-		if targetHour == -1 {
-			targetHour = now.Hour()
-		}
-		if targetMinute == -1 {
-			targetMinute = now.Minute()
-		}
-		if targetSecond == -1 {
-			targetSecond = now.Second()
+	if args.Minute == -1 {
+		args.Minute = now.Minute()
 	}
 
-		until = time.Date(
-			targetYear, time.Month(targetMonth), targetDay,
-			targetHour, targetMinute, targetSecond,
-			0, time.Local,
+	if args.Year == -1 {
+		args.Year = now.Year()
+	}
+
+	if args.Month == -1 {
+		args.Month = int(now.Month())
+	}
+
+	if args.Day == -1 {
+		args.Day = now.Day()
+	}
+
+	until := time.Date(
+		args.Year, time.Month(args.Month), args.Day,
+		args.Hour, args.Minute, 0, 0, time.Local,
 	)
+
+	if now.After(until) {
+		fmt.Println("time is in the past!")
+		return
 	}
 
-	fmt.Printf("Output file: %s\nCountdown to: %s\n", filename, until)
+	fmt.Printf("Output file: %s\nCountdown to: %s\n", args.Output, until)
 
 	var err error
 	tp := template.New("time")
-	tp, err = tp.Parse(format)
+	tp, err = tp.Parse(args.Format)
 	if err != nil {
 		fmt.Println(err)
 		os.Exit(1)
@@ -121,7 +99,7 @@ func main() {
 				Seconds: s,
 			}
 
-			// Do I want to use this format as well as the complicated AF one?I want to use this format as well as the complicated AF template one?
+			// Do I want to use this format as well as the complicated AF one?
 			//str := format
 			//if hide && h == 0 {
 			//	str = strings.ReplaceAll(str, "%H", "")
@@ -144,7 +122,7 @@ func main() {
 				continue
 			}
 
-			err = os.WriteFile(filename, []byte(sb.String()), 0644)
+			err = os.WriteFile(args.Output, []byte(sb.String()), 0644)
 			if err != nil {
 				fmt.Println("unable to write file: %v\n", err)
 			}
@@ -155,7 +133,7 @@ func main() {
 
 	wg.Wait()
 
-	err = os.WriteFile(filename, []byte(doneStr), 0644)
+	err = os.WriteFile(args.Output, []byte(args.Done), 0644)
 	if err != nil {
 		fmt.Println("unable to write file: %v\n", err)
 	}