Added run method of Rail Fence Cipher encoding

src/core/config/Categories.json

@@ -95,6 +95,7 @@
             "Affine Cipher Decode",
             "A1Z26 Cipher Encode",
             "A1Z26 Cipher Decode",
+            "Rail Fence Cipher Decode",
             "Atbash Cipher",
             "Substitute",
             "Derive PBKDF2 key",

src/core/operations/RailFenceCypherDecode.mjs

@@ -0,0 +1,98 @@
+/**
+ * @author Flavio Diez [flaviofdiez+cyberchef@gmail.com]
+ * @copyright Crown Copyright 2020
+ * @license Apache-2.0
+ */
+
+import Operation from "../Operation.mjs";
+
+/**
+ * Rail Fence Cypher Decode operation
+ */
+class RailFenceCypherDecode extends Operation {
+
+    /**
+     * RailFenceCypherDecode constructor
+     */
+    constructor() {
+        super();
+
+        this.name = "Rail Fence Cypher Decode";
+        this.module = "Ciphers";
+        this.description = "Decodes Strings that were created using the Rail fence Cypher provided a key and an offset";
+        this.infoURL = "https://en.wikipedia.org/wiki/Rail_fence_cipher";
+        this.inputType = "string";
+        this.outputType = "string";
+        this.args = [
+            {
+                name: "Key",
+                type: "number",
+                value: 2
+            },
+            {
+                name: "Offset",
+                type: "number",
+                value: 0
+            }
+        ];
+    }
+
+    /**
+     * @param {string} input
+     * @param {Object[]} args
+     * @returns {string}
+     */
+    run(input, args) {
+        const [key] = args;
+        // const [key, offset] = args;
+
+        let cipher = input;
+
+        const rest = cipher.length % key;
+
+        if (rest !== 0) {
+            cipher = cipher + (" ".repeat(rest));
+        }
+
+        const blockLen = cipher.length / key;
+
+        let plaintext = "";
+
+        for (let i = 0; i < blockLen; i++) {
+            for (let j = 0; j < key; j++) {
+                plaintext += cipher[i + (j * blockLen)];
+            }
+        }
+
+        return plaintext;
+    }
+
+    /**
+     * Highlight Rail Fence Cypher Decode
+     *
+     * @param {Object[]} pos
+     * @param {number} pos[].start
+     * @param {number} pos[].end
+     * @param {Object[]} args
+     * @returns {Object[]} pos
+     */
+    highlight(pos, args) {
+        return pos;
+    }
+
+    /**
+     * Highlight Rail Fence Cypher Decode in reverse
+     *
+     * @param {Object[]} pos
+     * @param {number} pos[].start
+     * @param {number} pos[].end
+     * @param {Object[]} args
+     * @returns {Object[]} pos
+     */
+    highlightReverse(pos, args) {
+        return pos;
+    }
+}
+
+
+export default RailFenceCypherDecode;