From 38348f978f928e7868cae567cbf9a938db3fac1d Mon Sep 17 00:00:00 2001
From: derek mcquay <derekmcquay@gmail.com>
Date: Mon, 14 Mar 2016 12:50:45 -0700
Subject: [PATCH] implemented guess function for caesar cipher

---
 main.go         | 26 +++++++++++++++++++++++---
 psyfer/guess.go | 36 +++++++++++++++++++++++++-----------
 2 files changed, 48 insertions(+), 14 deletions(-)

diff --git a/main.go b/main.go
index 4a08bc9..fe434a8 100644
--- a/main.go
+++ b/main.go
@@ -13,6 +13,21 @@ import (
 	"github.com/spf13/cobra"
 )
 
+func clean(input string) string {
+	input = strings.ToUpper(strings.Replace(input, ",", "", -1))
+	input = strings.ToUpper(strings.Replace(input, ".", "", -1))
+	input = strings.ToUpper(strings.Replace(input, "'", "", -1))
+	input = strings.ToUpper(strings.Replace(input, "\"", "", -1))
+	input = strings.ToUpper(strings.Replace(input, "(", "", -1))
+	input = strings.ToUpper(strings.Replace(input, ")", "", -1))
+	input = strings.ToUpper(strings.Replace(input, ";", "", -1))
+	input = strings.ToUpper(strings.Replace(input, ":", "", -1))
+	input = strings.ToUpper(strings.Replace(input, "!", "", -1))
+	input = strings.ToUpper(strings.Replace(input, "?", "", -1))
+	input = strings.ToUpper(strings.Replace(input, "$", "", -1))
+	return input
+}
+
 func init() {
 	rand.Seed(time.Now().UnixNano())
 }
@@ -115,6 +130,7 @@ func main() {
 				os.Exit(1)
 			}
 			for _, arg := range args {
+				arg = clean(arg)
 				arg = strings.ToUpper(strings.Replace(arg, " ", "", -1))
 				key = strings.ToUpper(strings.Replace(key, " ", "", -1))
 				fmt.Printf("%v\n", psyfer.VigenereCipher(arg, key, decrypt))
@@ -124,14 +140,18 @@ func main() {
 
 	var guess = &cobra.Command{
 		Use:   "guess",
-		Short: "guess cipher",
-		Long:  `will try to guess ceasar cipher`,
+		Short: "guess caesar cipher",
+		Long:  `will try to guess a caesar cipher`,
 		Run: func(cmd *cobra.Command, args []string) {
 			if len(args) < 1 {
 				fmt.Println("missing input, see -h (--help) for more info")
 				os.Exit(1)
 			}
-			psyfer.Guess()
+			fmt.Println("Top 5 possibilities:")
+			for _, arg := range args {
+				arg = clean(arg)
+				psyfer.Guess(arg)
+			}
 		},
 	}
 
diff --git a/psyfer/guess.go b/psyfer/guess.go
index 2eb1738..67b4d41 100644
--- a/psyfer/guess.go
+++ b/psyfer/guess.go
@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"math"
 	"sort"
+	"strings"
 )
 
 var charFreq = []float64{
@@ -58,22 +59,35 @@ func (p allPhi) Len() int           { return len(p) }
 func (p allPhi) Swap(i, j int)      { p[i], p[j] = p[j], p[i] }
 func (p allPhi) Less(i, j int) bool { return p[i].value < p[j].value }
 
-func Guess() {
-	fmt.Println((6 - 7) % 26)
+func CharacterFrequency(input string) map[rune]float64 {
+	cf := make(map[rune]int)
+	freq := make(map[rune]float64)
+	for _, c := range input {
+		cf[c]++
+	}
+	l := len(input)
+	for c, n := range cf {
+		freq[c] = float64(n) / float64(l)
+	}
+	return freq
+}
+
+func Guess(input string) {
+	alphabet := "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+	input = strings.ToUpper(strings.Replace(input, " ", "", -1))
+	freq := CharacterFrequency(input)
 	total := []phi{}
 	for i := 0; i < 26; i++ {
 		a := 0.0
-		a += 0.1 * charFreq[pc(6, i)]
-		a += 0.1 * charFreq[pc(7, i)]
-		a += 0.1 * charFreq[pc(10, i)]
-		a += 0.3 * charFreq[pc(14, i)]
-		a += 0.2 * charFreq[pc(17, i)]
-		a += 0.1 * charFreq[pc(20, i)]
-		a += 0.1 * charFreq[pc(25, i)]
+		for c, n := range freq {
+			index := int(c - 'A')
+			a += n * charFreq[pc(index, i)]
+		}
 		p := phi{i, a}
 		total = append(total, p)
 	}
-	fmt.Println(total)
 	sort.Sort(allPhi(total))
-	fmt.Println(total)
+	for i := len(total) - 1; i > len(total)-6; i-- {
+		fmt.Println(VigenereCipher(input, string(alphabet[total[i].position]), true))
+	}
 }