Adventofcode.com day7 solution

package main

import (
    "bufio"
    "fmt"
    "os"
    "regexp"
    "strings"
)

func main() {
    fmt.Println("Day 7 for Advent of Code 2016")

    information := read_input()

    var count_tls, count_ssl int
    for i := 0; i < len(information); i++ {
        brackets := extract_brackets(information[i])
        supernet := information[i]
        for _, str := range brackets {
            supernet = strings.Replace(supernet, str, "", -1)
        }
        ABAs := get_abas(supernet)
        var BABs []string
        for _, str := range brackets {
            BABs = append(BABs, get_abas(str[1:len(str)-1])...)
        }
        if validate_abas(ABAs, BABs) {
            count_ssl += 1
        }
        if valid_brackets(brackets) {
            if has_abba(information[i]) {
                count_tls += 1
            }
        }
    }

    fmt.Printf("Part 1: %d IPs support TLS\n", count_tls)
    fmt.Printf("Part 2: %d IPs support SSL\n", count_ssl)
}

func get_abas(str string) []string {
    var abas []string
    for i := 1; i < len(str)-1; i++ {
        if str[i-1] == str[i+1] {
            abas = append(abas, str[i-1:i+2])
        }
    }
    return abas
}

func validate_abas(ABAs, BABs []string) bool {
    for _, aba := range ABAs {
        for _, bab := range BABs {
            if aba_match(aba, bab) {
                return true
            }
        }
    }
    return false
}

func aba_match(aba, bab string) bool {
    return aba[1] == bab[0] && aba[0] == bab[1]
}

func valid_brackets(b []string) bool {
    for _, str := range b {
        if has_abba(str) {
            return false
        }
    }
    return true
}

func has_abba(str string) bool {
    var a, b byte
    a, b = str[0], str[1]
    for i := 2; i < len(str)-1; i++ {
        if b == str[i] && a == str[i+1] && a != b {
            return true
        }
        a, b = str[i-1], str[i]
    }
    return false
}

func extract_brackets(str string) []string {
    re := regexp.MustCompile("\\[[[:alpha:]]+\\]")

    return re.FindAllString(str, -1)
}

func read_input() []string {
    f, err := os.Open("input")
    check(err)

    scanner := bufio.NewScanner(f)

    var data []string
    for scanner.Scan() {
        data = append(data, scanner.Text())
    }
    return data
}

func check(e error) {
    if e != nil {
        panic(e)
    }
}