added score mechanism

crypto.js

@@ -1,4 +1,10 @@
 const chars = "abcdefghijklmnopqrstuvwxyz";
+import { chisquare } from "jstat"
+import {add, dotDivide, inv, pow, map, sum, multiply, square, subtract, divide} from "mathjs"
+let expected_prob = [0.08167, 0.01492, 0.02782, 0.04253, 0.12702, 0.02228, 0.02015,
+  0.06094, 0.06966, 0.00153, 0.00772, 0.04025, 0.02406, 0.06749, 0.07507,
+  0.01929, 0.00095, 0.05987, 0.06327, 0.09056, 0.02758, 0.00978, 0.02360,
+  0.00150, 0.01974, 0.00074]
 
 export const stoi = {};
 export const itos = {};
@@ -7,6 +13,7 @@ for (let i = 0; i < chars.length; i++) {
   stoi[ch] = i;
   itos[i] = ch;
 }
+
 export function ceaser_cipher(string, n = 0){
   string = string.replace(/[^a-zA-Z]/g, '').toLowerCase();
   let result = "";
@@ -16,4 +23,41 @@ export function ceaser_cipher(string, n = 0){
   }
   return result;
 }
+export function word_freq(string) {
+  /*
+    Given a string, return frequencies as a list 
+  */
+  let frequencies = new Array(26).fill(0);
+
+  for (let i = 0; i < string.length; i++) {
+    let char = string[i];
+
+    if (/[a-zA-Z]/.test(char)) {
+      char = char.toLowerCase();
+      let index = char.charCodeAt(0) - 'a'.charCodeAt(0);
+      frequencies[index]++;
+    }
+  }
+  return frequencies;
+}
 
+export function chi_squared(expected, observed){
+ let epsilon = 0.001
+ return sum(dotDivide(map(subtract(expected, observed), square) , 
+                      add(expected,epsilon)))
+}
+
+export function sentence_score(string){
+  /*
+    Given string return score of its likliness to be a english sentence
+  */
+  let len = string.length 
+
+  let freq = word_freq(string)
+  let exp_freq = multiply(expected_prob , len)
+  let chi_squared_value= chi_squared(exp_freq, freq)
+  const p_value = chisquare.cdf(chi_squared_value, 25);
+
+  return p_value 
+}
+console.log(sentence_score(""))

package.json

@@ -9,8 +9,10 @@
     "lint": "next lint"
   },
   "dependencies": {
+    "jstat": "^1.9.6",
+    "mathjs": "^12.2.1",
+    "next": "14.0.4",
     "react": "^18",
-    "react-dom": "^18",
-    "next": "14.0.4"
+    "react-dom": "^18"
   }
 }

pages/index.js

@@ -4,7 +4,7 @@ import Head from 'next/head'
 import Image from 'next/image'
 import {IBM_Plex_Mono, Inter} from 'next/font/google'
 import styles from '@/styles/Home.module.css'
-import {ceaser_cipher} from "../crypto.js"
+import {ceaser_cipher, sentence_score} from "../crypto.js"
 
 const inter = Inter({ subsets: ['latin'] })
 const ibm_plex = IBM_Plex_Mono({ subsets: ['latin'], weight:["100", "200", "300", "400", "500", "600", "700"] })
@@ -13,34 +13,39 @@ export default function Home() {
   function handle_message_change(event){
     set_message(event.target.value)
   } 
-  function encrypted_messages(message){
+  function encrypted_messages(message) {
     let enc_messages = [];
-    for (let i = 0; i<26; i++){
+    for (let i = 0; i < 26; i++) {
+      const encrypted = ceaser_cipher(message, i);
+      const score = sentence_score(encrypted).toFixed(2); // Limit to 2 decimal places
+
       enc_messages.push(
         <p key={i}>
-            +{i + " "}
-           {ceaser_cipher(message, i)}
+          +{i + " "}
+          {encrypted + " "}
+          {score}
         </p>
-        )
+      );
+
+
     }
     return enc_messages
-
   }
   return (
 
     <div className = {`${ibm_plex.className}`}>
       <h1>Break Ceaser Cipher</h1>
       <label>
       Message:
-      <input style={ {fontSize: 18 }}value={message} onChange={handle_message_change}/>
+      <input style = {{fontSize: 18 }}
+             value = {message} 
+             onChange = {handle_message_change}/>
       </label>
       <p>Striped message: {ceaser_cipher(message)}</p>
       <h2>Encrypted Messages:</h2>
       <ul>
-      {
-        encrypted_messages(message)
-      }
-     </ul>
+        {encrypted_messages(message)}
+      </ul>
     </div>
   )
 }