package main

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

func renderYear() string {

	// Get Current time
	var ct time.Time
	var offset int
	ct, offset = getCurrentTime()

	// So what the following does is
	// Add one year to the current time (and call it next year)
	// Get the start of this year
	// Get the start of the next year

	// The New Year
	ny := ct.AddDate(1, 0, 0)

	// Get the start of this and next year
	t1 := startYear(ct.Year(), 1, 1)
	t2 := startYear(ny.Year(), 1, 1)

	// Subtract the current year in seconds from next year, in seconds.
	// This will leave us with the total year in seconds
	// I do this in case there is a leap-year,
	// or some dodgy science reason to add 30 seconds to a day.
	seconds := t2.Sub(t1).Seconds()

	// From the current time, subtract the start of this year, in seconds.
	// This should leave us with how far we are into the year, in seconds.
	tdiff := ct.Sub(t1).Seconds()

	// Calculate the percentages
	percentage := calcPercentageFloat64(seconds, tdiff+float64(offset))

	// Wrap things up
	var render string
	render = renderPercentage(percentage)
	render = render + fmt.Sprintf(" %.7f%%", percentage)

	return render
}

func renderDay() string {

	// Get Current time
	var ct time.Time
	var offset int
	ct, offset = getCurrentTime()

	// Get the Start of the Day
	sd := time.Date(ct.Year(), ct.Month(), ct.Day(), 0, 0, 0, 0, time.UTC)

	// Get the End of the Day
	ed := ct.AddDate(0, 0, 1)
	ed = time.Date(ed.Year(), ed.Month(), ed.Day(), 0, 0, 0, 0, time.UTC)

	// From the end of the day, subtract the end of the day to get the number of seconds.
	// Normally this would be 86400, thanks to science this may change.
	// Think Leap Seconds
	//
	// Get the current number of seconds into the day
	seconds_total := ed.Sub(sd).Seconds()
	seconds_tmp := ed.Sub(ct).Seconds()
	seconds_current := seconds_total - seconds_tmp

	// Calculate the percentages
	percentage := calcPercentageFloat64(seconds_total, seconds_current+float64(offset))

	// Wrap everything up
	var render string
	render = renderPercentage(percentage)
	render = render + fmt.Sprintf(" %.7f%%", percentage)

	return render
}

func renderCustom(t1 time.Time, t2 time.Time) string {

	var ct time.Time
	var offset int
	ct, offset = getCurrentTime()

	seconds := t2.Sub(t1).Seconds()
	tdiff := ct.Sub(t1).Seconds()

	percentage := calcPercentageFloat64(seconds, tdiff+float64(offset))

	var render string
	render = renderPercentage(percentage)
	render = render + fmt.Sprintf(" %.7f%%", percentage)

	return render

}

func getCurrentTime() (time.Time, int) {
	// Declarations
	var offset int
	var loc *time.Location
	var err error

	// Current Time
	ct := time.Now()

	// Get the offset from whatever the system timezone is
	_, offset = ct.Local().Zone()

	// Make sure that the time is in UTC, so the offset makes sense
	loc, err = time.LoadLocation("UTC")
	if err != nil {
		log.Fatal(err)
	}
	ct = ct.In(loc)

	// Return things
	return ct, offset
}

// displayPercentage Print a string of blocks simulating percentages
func renderPercentage(percentage float64) string {

	var counter int
	var balk string

	for percentage > 2 {
		balk = balk + "▓"
		percentage = percentage - 2
		counter++
	}

	if percentage < 2 {
		balk = balk + "▒"
		counter++
	}

	for counter < 50 {
		balk = balk + "░"
		counter++
	}

	return balk
}

// Get the percentages between two float64s
func calcPercentageFloat64(full float64, part float64) float64 {
	var percentage float64
	percentage = part / (full / 100)
	if percentage >= 100 {
		percentage = percentage - 100
	}
	return percentage
}

// Get the start of the year.
func startYear(year, month, day int) time.Time {
	return time.Date(year, time.Month(month), day, 0, 0, 0, 0, time.UTC)
}

func main() {

	var dayFlag = flag.Bool("day", true, "Display progress of the day.")
	var yearFlag = flag.Bool("year", true, "Display progress of this year.")

	var customFlag = flag.Bool("custom", false, "Display a custom range")
	var customStart = flag.String("custom-start", "", "Start of the custom range")
	var customStop = flag.String("custom-stop", "", "Start of the custom range")

	flag.Parse()

	if *dayFlag {
		fmt.Println(renderDay())
	}

	if *yearFlag {
		fmt.Println(renderYear())
	}

	if *customFlag {

		bt, err := time.Parse(time.RFC3339, *customStart)
		if err != nil {
			log.Fatalln("Error parsing start time: ", err)
		}

		pa, err := time.Parse(time.RFC3339, *customStop)
		if err != nil {
			log.Fatalln("Error parsing stop time: ", err)
		}

		fmt.Println(renderCustom(bt, pa))

	}

}