From a7ccad8e1eb5a15ca27a6bb5344ec4487cf63b19 Mon Sep 17 00:00:00 2001
From: KKlochko <KKlochko@protonmail.com>
Date: Fri, 15 Sep 2023 21:30:37 +0300
Subject: [PATCH] Add the caesar-analyzers to get the plaintext from a
 ciphertext.

---
 .../caesar_analyzers.clj                      | 34 +++++++++++++++++++
 1 file changed, 34 insertions(+)
 create mode 100644 src/cipher_analytical_machine/caesar_analyzers.clj

diff --git a/src/cipher_analytical_machine/caesar_analyzers.clj b/src/cipher_analytical_machine/caesar_analyzers.clj
new file mode 100644
index 0000000..7b6d572
--- /dev/null
+++ b/src/cipher_analytical_machine/caesar_analyzers.clj
@@ -0,0 +1,34 @@
+(ns cipher-analytical-machine.caesar-analyzers
+  (:require [cipher-analytical-machine.caesar :as caesar]
+            [cipher-analytical-machine.cipher_analyzers :as ca])
+  (:gen-class))
+
+(defn get-all-texts
+  "Return a list of pairs which have a key and a second posible plaintext."
+  [ciphertext symbols]
+  (let [keys (range (count symbols))]
+    (reduce
+     (fn [acc key]
+       (conj acc [key (caesar/decrypt-message ciphertext key symbols)]))
+     '() keys)))
+
+(defn get-key
+  "To find the key with frequencies of letters."
+  [ciphertext symbols letter-frequences]
+  (->> (get-all-texts ciphertext symbols)
+       (map (fn [[key text]]
+              [key (ca/chi-squared-statistic text letter-frequences)]))
+       (reduce
+        (fn [[key value] [new-key new-value]]
+          (if (> value new-value) [new-key new-value]
+               [key value]))
+        [0 Double/MAX_VALUE])
+       (first)))
+
+(defn get-plaintext
+  "Return the plaintext from a ciphertext."
+  [ciphertext symbols letter-frequences]
+  (caesar/decrypt-message ciphertext
+                          (get-key ciphertext symbols letter-frequences)
+                          symbols))
+