package main

import (
	"strconv"

	"golang.org/x/exp/slices"
)

// Attempts to identify if we can convert to a int
func CanInt(text string) bool {
	negative := false
	numbers := []rune{'0', '1', '2', '3', '4', '5', '6', '7', '8', '9'}
	for _, c := range text {
		if !negative && c == '-' {
			negative = true
			continue
		} else if negative && c == '-' {
			return false
		}
		if !slices.Contains(numbers, c) {
			return false
		}
	}
	return true
}

// Attempts to identify if we can convert to a float
//
// Requires encountering only 1 '.', if multiple found (it's not a float), if none found (it's not a float)
func CanFloat(text string) bool {
	found_dot := false
	negative := false
	numbers := []rune{'0', '1', '2', '3', '4', '5', '6', '7', '8', '9'}
	for _, c := range text {
		if !found_dot && c == '.' {
			found_dot = true
			continue
		} else if found_dot && c == '.' {
			return false
		}
		if !negative && c == '-' {
			negative = true
			continue
		} else if negative && c == '-' {
			return false
		}
		if !slices.Contains(numbers, c) {
			return false
		}
	}
	return found_dot
}

// https://stackoverflow.com/questions/13020308/how-to-fmt-printf-an-integer-with-thousands-comma/31046325#31046325
//
// This should take 1234567 and put it as 1,234,567
func FormatCredit(n int64) string {
	in := strconv.FormatInt(n, 10)
	numOfDigits := len(in)
	if n < 0 {
		numOfDigits-- // First character is the - sign (not a digit)
	}
	numOfCommas := (numOfDigits - 1) / 3

	out := make([]byte, len(in)+numOfCommas)
	if n < 0 {
		in, out[0] = in[1:], '-'
	}

	for i, j, k := len(in)-1, len(out)-1, 0; ; i, j = i-1, j-1 {
		out[j] = in[i]
		if i == 0 {
			return string(out)
		}
		if k++; k == 3 {
			j, k = j-1, 0
			out[j] = ','
		}
	}
}