package main

import (
	"flag"
	"fmt"
	"time"
)

const (
	defaultFormat = "15:04"
	defaultGoal   = "8.3h"
)

func main() {
	format := flag.String("f", defaultFormat, "Set the input time format ")
	goalS := flag.String("g", defaultGoal, "Set the duration goal ")
	flag.Parse()

	goal, err := time.ParseDuration(*goalS)
	if err != nil {
		fmt.Printf("Error parsing \"%s\": %v", *goalS, err)
		eight := 8.3 * float64(time.Hour)
		goal = time.Duration(eight)
	}

	acc := time.Second * 0
	for i, arg := range flag.Args() {
		t, err := time.Parse(*format, arg)
		if err != nil {
			fmt.Printf("Error parsing \"%s\": %v", arg, err)
			continue
		}
		dur := time.Hour*time.Duration(t.Hour()) + time.Minute*time.Duration(t.Minute())

		if i%2 == 0 {
			acc -= dur
		} else {
			acc += dur
		}
	}
	if len(flag.Args())%2 != 0 {
		diff := goal - acc
		fmt.Printf("You reached your goal of %v at: %s\n", goal, time.Time{}.Add(diff).Format(*format))
	} else {
		fmt.Printf("With these hour's you have worked: %v\n", acc)
	}
}