package beer
import (
	"fmt"
	"strconv"
	"strings"
)
func Verse(i int) (string, error) {
	if i < 0 {
		return "", fmt.Errorf("input must be positive")
	}
	if i > 99 {
		return "", fmt.Errorf("input must be below 99")
	}
	if i == 0 {
		return `No more bottles of beer on the wall, no more bottles of beer.
Go to the store and buy some more, 99 bottles of beer on the wall.
`, nil
	}
	var ret strings.Builder
	ret.WriteString(btl(i))
	ret.WriteString("of beer on the wall, ")
	ret.WriteString(btl(i))
	ret.WriteString("of beer.\nTake")
	ret.WriteString(one(i))
	ret.WriteString("down and pass it around, ")
	ret.WriteString(btl(i - 1))
	ret.WriteString("of beer on the wall.\n")
	return ret.String(), nil
}
func one(i int) string {
	if i == 1 {
		return " it "
	}
	return " one "
}
func btl(i int) string {
	switch i {
	case 0:
		return "no more bottles "
	case 1:
		return strconv.Itoa(i) + " bottle "
	default:
		return strconv.Itoa(i) + " bottles "
	}
}
func Verses(upper, lower int) (string, error) {
	if lower > upper {
		return "", fmt.Errorf("lower should be lower than upper")
	}
	var ret strings.Builder
	for i := upper; i >= lower; i-- {
		v, err := Verse(i)
		if err != nil {
			return "", err
		}
		ret.WriteString(v)
		ret.WriteByte('\n')
	}
	return ret.String(), nil
}
func Song() string {
	s, _ := Verses(99, 0)
	return s
}