package utils

import (
	"bytes"
	"crypto/md5"
	"fmt"
	"io"
	"math"
	"os"
)

type UTCOffset struct {
	Name  string
	Value string
}

var UTC_OFFSETS = []UTCOffset{
	{Value: "-12 hours", Name: "UTC−12:00"},
	{Value: "-11 hours", Name: "UTC−11:00"},
	{Value: "-10 hours", Name: "UTC−10:00"},
	{Value: "-9.5 hours", Name: "UTC−09:30"},
	{Value: "-9 hours", Name: "UTC−09:00"},
	{Value: "-8 hours", Name: "UTC−08:00"},
	{Value: "-7 hours", Name: "UTC−07:00"},
	{Value: "-6 hours", Name: "UTC−06:00"},
	{Value: "-5 hours", Name: "UTC−05:00"},
	{Value: "-4 hours", Name: "UTC−04:00"},
	{Value: "-3.5 hours", Name: "UTC−03:30"},
	{Value: "-3 hours", Name: "UTC−03:00"},
	{Value: "-2 hours", Name: "UTC−02:00"},
	{Value: "-1 hours", Name: "UTC−01:00"},
	{Value: "0 hours", Name: "UTC±00:00"},
	{Value: "+1 hours", Name: "UTC+01:00"},
	{Value: "+2 hours", Name: "UTC+02:00"},
	{Value: "+3 hours", Name: "UTC+03:00"},
	{Value: "+3.5 hours", Name: "UTC+03:30"},
	{Value: "+4 hours", Name: "UTC+04:00"},
	{Value: "+4.5 hours", Name: "UTC+04:30"},
	{Value: "+5 hours", Name: "UTC+05:00"},
	{Value: "+5.5 hours", Name: "UTC+05:30"},
	{Value: "+5.75 hours", Name: "UTC+05:45"},
	{Value: "+6 hours", Name: "UTC+06:00"},
	{Value: "+6.5 hours", Name: "UTC+06:30"},
	{Value: "+7 hours", Name: "UTC+07:00"},
	{Value: "+8 hours", Name: "UTC+08:00"},
	{Value: "+8.75 hours", Name: "UTC+08:45"},
	{Value: "+9 hours", Name: "UTC+09:00"},
	{Value: "+9.5 hours", Name: "UTC+09:30"},
	{Value: "+10 hours", Name: "UTC+10:00"},
	{Value: "+10.5 hours", Name: "UTC+10:30"},
	{Value: "+11 hours", Name: "UTC+11:00"},
	{Value: "+12 hours", Name: "UTC+12:00"},
	{Value: "+12.75 hours", Name: "UTC+12:45"},
	{Value: "+13 hours", Name: "UTC+13:00"},
	{Value: "+14 hours", Name: "UTC+14:00"},
}

func GetUTCOffsets() []UTCOffset {
	return UTC_OFFSETS
}

func NiceSeconds(input int64) (result string) {
	if input == 0 {
		return "N/A"
	}

	days := math.Floor(float64(input) / 60 / 60 / 24)
	seconds := input % (60 * 60 * 24)
	hours := math.Floor(float64(seconds) / 60 / 60)
	seconds = input % (60 * 60)
	minutes := math.Floor(float64(seconds) / 60)
	seconds = input % 60

	if days > 0 {
		result += fmt.Sprintf("%dd ", int(days))
	}
	if hours > 0 {
		result += fmt.Sprintf("%dh ", int(hours))
	}
	if minutes > 0 {
		result += fmt.Sprintf("%dm ", int(minutes))
	}
	if seconds > 0 {
		result += fmt.Sprintf("%ds", int(seconds))
	}

	return
}

// Reimplemented KOReader Partial MD5 Calculation
func CalculatePartialMD5(filePath string) (string, error) {
	file, err := os.Open(filePath)
	if err != nil {
		return "", err
	}

	defer file.Close()

	var step int64 = 1024
	var size int64 = 1024
	var buf bytes.Buffer

	for i := -1; i <= 10; i++ {
		byteStep := make([]byte, size)

		var newShift int64 = int64(i * 2)
		var newOffset int64
		if i == -1 {
			newOffset = 0
		} else {
			newOffset = step << newShift
		}

		_, err := file.ReadAt(byteStep, newOffset)
		if err == io.EOF {
			break
		}
		buf.Write(byteStep)
	}

	allBytes := buf.Bytes()
	return fmt.Sprintf("%x", md5.Sum(allBytes)), nil
}
