package main

import (
	"fmt"
	"github.com/dariubs/percent"
	"io/ioutil"
	"sort"
	"strings"
)

type letter struct {
	upperCase string
	lowerCase string
	count     int
	frequency float64
}

type letterList []letter

func (l letterList) Len() int {
	return len(l)
}

func (l letterList) Less(i, j int) bool {
	return l[i].frequency > l[j].frequency
}

func (l letterList) Swap(i, j int) {
	l[i], l[j] = l[j], l[i]
}

var alphabet = []rune{
	'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
	'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
}
var letters = make([]letter, len(alphabet))

func initLetterStruct() {
	for index := range alphabet {
		letters[index].upperCase = string(alphabet[index])
		letters[index].lowerCase = string(alphabet[index] + 32)
	}
}

func readFile(relativePath string) string {
	content, err := ioutil.ReadFile(relativePath)
	if err != nil {
		fmt.Println(err)
	}
	return string(content)
}

func countLetters(inputText string) int {
	totalCount := 0
	for index := range alphabet {
		letters[index].count +=
			strings.Count(inputText, letters[index].lowerCase) +
				strings.Count(inputText, letters[index].upperCase)
		totalCount += letters[index].count
	}
	return totalCount
}

func calculateFrequency(totalCount int) {
	for index := range alphabet {
		letters[index].frequency = percent.PercentOf(letters[index].count, totalCount)
	}
}

func printResult() {
	for index := range alphabet {
		l := letters[index]
		fmt.Printf(
			"The letter %s (%s) occurs %d times in the text and the frequencyArray in percent is %0.2f\n",
			l.upperCase, l.lowerCase, l.count, l.frequency,
		)
	}
}

func main() {
	initLetterStruct()
	totalCount := countLetters(readFile("plaintext.txt"))
	calculateFrequency(totalCount)
	sort.Sort(letterList(letters))
	printResult()
}