cipher-analytical-machine/src/main/java/cipher_analytical_machine/analyzers/caesar/FrequencyAnalyzer.java

package cipher_analytical_machine.analyzers.caesar;

import cipher_analytical_machine.analyzers.caesar.IsNonsense;
import cipher_analytical_machine.ciphers.caesar.Decrypted;

import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;

public class FrequencyAnalyzer {
    private String ciphertext;
    private String symbols;
    private String symbol_frequences;
    private Decrypted decryptor;
    private IsNonsense isNonsense;

    public FrequencyAnalyzer(String ciphertext, String symbols, String symbol_frequences, Decrypted decryptor, IsNonsense isNonsense) {
	    this.ciphertext = ciphertext;
        this.symbol_frequences = symbol_frequences;
        this.symbols = symbols;
	    this.decryptor = decryptor;
	    this.isNonsense = isNonsense;
    }

    public String crack() {
        // Знаходимо кількість літер
        Map<Character, Integer> encryptedLetterCounts = new HashMap<>();

        for (char c : ciphertext.toLowerCase().toCharArray()) {
            encryptedLetterCounts.put(c, encryptedLetterCounts.getOrDefault(c, 0) + 1);
        }

        // Знаходимо букву, яка зустрічається найчастіше
        char mostFrequentEncryptedLetter = ' ';
        int mostFrequentEncryptedLetterCount = 0;

        for (Entry<Character, Integer> entry : encryptedLetterCounts.entrySet()) {
            if (entry.getValue() > mostFrequentEncryptedLetterCount) {
                mostFrequentEncryptedLetter = entry.getKey();
                mostFrequentEncryptedLetterCount = entry.getValue();
            }
        }

        // Обчислимо зміщення
        int size = symbols.length();
        int indexOfMostFrequentEncryptedLetter = symbols.indexOf(mostFrequentEncryptedLetter);
        int indexOfMostFrequentLetter = symbols.indexOf(symbol_frequences.charAt(0));
        int shift = (indexOfMostFrequentEncryptedLetter - indexOfMostFrequentLetter) % size;

        return decryptor.decrypt(ciphertext, shift, symbols);
    }
}