caesar.ts

Go to the documentation of this file.

 
import { BaseCipher } from "../base/baseCipher";
 
export class CaesarCipher extends BaseCipher {
    private shift: number;
 
    readonly CipherName = "Caesar";
 
    constructor(shift: number = 3) {
        super();
        this.shift = shift;
    }
 
    encode(plainText: string = ""): string {
        const output: string[] = [];
 
        for (const ch of plainText) {
            const index = BaseCipher.ALPHABET.indexOf(ch.toUpperCase());
            if (index === -1) {
                output.push(ch);
                continue;
            }
 
            const cipherIndex = this.mod(index + this.shift, 26);
            output.push(BaseCipher.ALPHABET[cipherIndex]);
        }
 
        return output.join("");
    }
 
    decode(cipherText: string = ""): string {
        const output: string[] = [];
 
        for (const ch of cipherText) {
            const index = BaseCipher.ALPHABET.indexOf(ch.toUpperCase());
            if (index === -1) {
                output.push(ch);
                continue;
            }
 
            const plainIndex = this.mod(index - this.shift, 26);
            output.push(BaseCipher.ALPHABET[plainIndex]);
        }
 
        return output.join("");
    }
}