package config

import (
	"math"
	"regexp"
)

func anyRegexMatch(f string, res []*regexp.Regexp) bool {
	for _, re := range res {
		if regexMatched(f, re) {
			return true
		}
	}
	return false
}

func regexMatched(f string, re *regexp.Regexp) bool {
	if re == nil {
		return false
	}
	if re.FindString(f) != "" {
		return true
	}
	return false
}

func containsDigit(s string) bool {
	for _, c := range s {
		switch c {
		case '1', '2', '3', '4', '5', '6', '7', '8', '9':
			return true
		}

	}
	return false
}

// shannonEntropy calculates the entropy of data using the formula defined here:
// https://en.wiktionary.org/wiki/Shannon_entropy
// Another way to think about what this is doing is calculating the number of bits
// needed to on average encode the data. So, the higher the entropy, the more random the data, the
// more bits needed to encode that data.
func shannonEntropy(data string) (entropy float64) {
	if data == "" {
		return 0
	}

	charCounts := make(map[rune]int)
	for _, char := range data {
		charCounts[char]++
	}

	invLength := 1.0 / float64(len(data))
	for _, count := range charCounts {
		freq := float64(count) * invLength
		entropy -= freq * math.Log2(freq)
	}

	return entropy
}