feat(operations): add ToFullwidth operation for ASCII to fullwidth conversion

src/core/config/Categories.json

@@ -49,6 +49,7 @@
             "Escape Unicode Characters",
             "Unescape Unicode Characters",
             "Normalise Unicode",
+            "To Fullwidth",
             "To Quoted Printable",
             "From Quoted Printable",
             "To Punycode",
@@ -591,4 +592,4 @@
             "Comment"
         ]
     }
-]
+]

src/core/operations/ToFullwidth.mjs

@@ -0,0 +1,57 @@
+/**
+ * @author jyeu [chen@jyeu.xyz]
+ * @copyright Crown Copyright 2026
+ * @license Apache-2.0
+ */
+
+import Operation from "../Operation.mjs";
+
+/**
+ * To Fullwidth operation
+ */
+class ToFullwidth extends Operation {
+    /**
+     * ToFullwidth constructor
+     */
+    constructor() {
+        super();
+
+        this.name = "To Fullwidth";
+        this.module = "Encodings";
+        this.description =
+            "Converts ASCII (halfwidth) characters to their fullwidth Unicode equivalents (U+FF01–U+FF5E). Commonly used in security testing to bypass WAF keyword filters, evade regex-based blocklists, and exploit Unicode normalization (NFKC/NFKD) vulnerabilities in web applications and path parsers. For example, <code>/ａdmin</code> may bypass a WAF rule matching <code>/admin</code> if the backend normalises Unicode before routing.";
+        this.infoURL =
+            "https://wikipedia.org/wiki/Halfwidth_and_fullwidth_forms_(Unicode_block)";
+        this.inputType = "string";
+        this.outputType = "string";
+        this.args = [];
+    }
+
+    /**
+     * @param {string} input
+     * @param {never} _args
+     * @returns {string}
+     */
+    run(input, _args) {
+        let output = "";
+
+        for (const char of input) {
+            const code = char.codePointAt(0);
+
+            if (code === 0x20) {
+                // Regular space -> Ideographic space (U+3000)
+                output += "\u3000";
+            } else if (code >= 0x21 && code <= 0x7e) {
+                // Visible ASCII characters -> Fullwidth equivalents (U+FF01–U+FF5E)
+                output += String.fromCodePoint(code + 0xfee0);
+            } else {
+                // Non-ASCII characters (CJK, newlines, etc.) are passed through unchanged
+                output += char;
+            }
+        }
+
+        return output;
+    }
+}
+
+export default ToFullwidth;