// Package say says numbers in English.
package say
import (
	"math"
	"strings"
)
// names for powers of thousand
var thousandName = []string{
	"", " thousand", " million", " billion", " trillion",
}
// basic names, some could be concatenated, but does not worth the fuss
var tilTwenty = []string{
	"zero", "one", "two", "three", "four",
	"five", "six", "seven", "eight", "nine", "ten",
	"eleven", "twelve", "thirteen", "fourteen", "fifteen",
	"sixteen", "seventeen", "eighteen", "nineteen",
}
// names of tenth values
var tens = []string{
	"XXX", // placeholder
	"XXX", // placeholder
	"twenty", "thirty", "forty", "fifty",
	"sixty", "seventy", "eighty", "ninety",
}
func Say(input int64) (string, bool) {
	if input > 999_999_999_999 || input < 0 {
		return "", false
	}
	// split input to thousands
	// 12_453_132_981 -> [12 453 132 981]
	const maxThousands = 4
	split := make([]int, maxThousands)
	split[len(split)-1] = int(input) % 1000
	for i := len(split) - 1; i >= 0; i-- {
		split[len(split)-i-1] = int(input) / int(math.Pow10(i*3))
		input = input % int64(math.Pow10(i*3))
	}
	// write splits one-by-one
	var ret strings.Builder
	for i, s := range split {
		if s != 0 || // do not write empty thousands
			// for the last one write zero if nothing is written yet
			i == len(split)-1 && ret.Len() == 0 {
			if ret.Len() != 0 {
				ret.WriteRune(' ')
			}
			ret.WriteString(splitHandler(s) + thousandName[len(split)-i-1])
		}
	}
	return ret.String(), true
}
func splitHandler(in int) string {
	var ret strings.Builder
	// handle the hundreds
	if in > 99 {
		ret.WriteString(tilTwenty[in/100] + " hundred")
		if in%100 != 0 {
			// we want to connect to hundred what is left if it is more than zero
			ret.WriteRune(' ')
		}
	}
	// under hundred part > 19
	if in := in % 100; in > 19 {
		ret.WriteString(tens[in/10])
		if in%10 != 0 { // eg. twenty-two
			ret.WriteString("-" + tilTwenty[in%10])
		}
	} else {
		if in != 0 || ret.Len() == 0 { // non-zero or _only_ zero
			ret.WriteString(tilTwenty[in%100])
		}
	}
	return ret.String()
}