a naive typoglycemia generator

random.go

package main

import (
    "fmt"
    "math/rand"
    "io/ioutil"
    "os"
    "bytes"
    "unicode"
)


func main() {
    input, _ := ioutil.ReadAll(os.Stdin)
    fmt.Printf("\n\n%v", string(shuffleWords(input)))
}

func shuffleWords(input []byte) []byte {
    words := bytes.Fields(input)

    if len(words) == 0 { return input }
    lenOfSeeds := len(words[0])
    seeds := rand.Perm(lenOfSeeds) // [0, lenOfSeeds)

    for _, word := range words {
        lenOfWord := len(word)

        if lenOfWord <= 3 { continue }
        if lenOfWord > lenOfSeeds {
            lenOfSeeds = lenOfWord
            seeds = rand.Perm(lenOfSeeds)
        }

        lastAlphaIndex := findLastAlpha(word, lenOfWord - 1)
        if lastAlphaIndex == -1 || lastAlphaIndex <= 2 { continue }

        shuffleWord(word, seeds, 1, lastAlphaIndex - 1)
    }

    return bytes.Join(words, []byte(" "))
}

func shuffleWord(word []byte, seeds []int, start, end int) {
    for i := start; i <= end; i++ {
        j := seeds[i]
        if j == 0 || j > end { continue }
        word[i], word[j] = word[j], word[i]
    }
}

func findLastAlpha(str []byte, lastIndex int) int {
    for i := lastIndex; i > 1; i-- {
        if unicode.IsLetter(rune(str[i])) { return i }
    }
    return -1
}