Added the typoglycemia operation

src/core/config/Categories.json

@@ -312,7 +312,8 @@
             "Remove Diacritics",
             "Unescape Unicode Characters",
             "Convert to NATO alphabet",
-            "Convert Leet Speak"
+            "Convert Leet Speak",
+            "Typoglycemia"
         ]
     },
     {

src/core/operations/Typoglycemia.mjs

@@ -0,0 +1,250 @@
+/**
+ * @author avantguard cyber security AG
+ * @copyright Crown Copyright 2026
+ * @license Apache-2.0
+ */
+
+import Operation from "../Operation.mjs";
+import OperationError from "../errors/OperationError.mjs";
+
+/**
+ * Matches a single word: a letter followed by further letters and combining marks.
+ * Hyphens and apostrophes are deliberately excluded so that they act as word
+ * boundaries and can never be shuffled into the middle of a word.
+ */
+const WORD_REGEX = /\p{L}[\p{L}\p{M}]*/gu;
+
+/**
+ * Scripts without alphabetic word recognition. Transposing these characters
+ * corrupts the text without producing any typoglycemia effect, so such words
+ * are passed through untouched.
+ */
+const IDEOGRAPHIC_REGEX = /[\p{Script=Han}\p{Script=Hiragana}\p{Script=Katakana}\p{Script=Hangul}]/u;
+
+/**
+ * Number of candidate scrambles generated per word before the best one is picked.
+ */
+const CANDIDATES = 12;
+
+/**
+ * Creates a seeded pseudo random number generator returning values in [0, 1).
+ *
+ * @param {number} seed
+ * @returns {function(): number}
+ */
+function mulberry32(seed) {
+    let a = seed >>> 0;
+    return function() {
+        a = a + 0x6D2B79F5 | 0;
+        let t = Math.imul(a ^ a >>> 15, 1 | a);
+        t = t + Math.imul(t ^ t >>> 7, 61 | t) ^ t;
+        return ((t ^ t >>> 14) >>> 0) / 4294967296;
+    };
+}
+
+/**
+ * Builds the set of open bigrams of a string: every ordered pair of characters
+ * no more than two positions apart. Reading models (Grainger & Whitney) treat
+ * the overlap of these sets as a proxy for how recognisable a scrambled word
+ * remains.
+ *
+ * @param {string[]} chars
+ * @returns {Set<string>}
+ */
+function openBigrams(chars) {
+    const set = new Set();
+    for (let i = 0; i < chars.length; i++) {
+        for (let j = i + 1; j <= Math.min(i + 2, chars.length - 1); j++) {
+            set.add(chars[i] + chars[j]);
+        }
+    }
+    return set;
+}
+
+/**
+ * Fraction of the original's open bigrams that survive in the scrambled version.
+ * 1 means perfectly readable, 0 means nothing recognisable is left.
+ *
+ * @param {string[]} original
+ * @param {string[]} scrambled
+ * @returns {number}
+ */
+function bigramOverlap(original, scrambled) {
+    const before = openBigrams(original);
+    const after = openBigrams(scrambled);
+    if (before.size === 0) return 1;
+    let kept = 0;
+    for (const bigram of before) {
+        if (after.has(bigram)) kept++;
+    }
+    return kept / before.size;
+}
+
+/**
+ * Fraction of positions holding a different character than before.
+ *
+ * @param {string[]} original
+ * @param {string[]} scrambled
+ * @returns {number}
+ */
+function movedFraction(original, scrambled) {
+    let moved = 0;
+    for (let i = 0; i < original.length; i++) {
+        if (original[i] !== scrambled[i]) moved++;
+    }
+    return original.length ? moved / original.length : 0;
+}
+
+/**
+ * Displacement bounded permutation. Each character is given a sort key of its
+ * own index plus uniform noise, so characters drift by roughly `amp` positions
+ * rather than being scattered anywhere in the word. This is what preserves
+ * readability: transpositions stay local.
+ *
+ * @param {string[]} chars
+ * @param {number} amp
+ * @param {function(): number} rnd
+ * @returns {string[]}
+ */
+function jitterSort(chars, amp, rnd) {
+    return chars
+        .map((c, i) => [i + amp * (rnd() * 2 - 1), c])
+        .sort((a, b) => a[0] - b[0])
+        .map(entry => entry[1]);
+}
+
+/**
+ * Unbounded uniform shuffle, used at maximum intensity where readability is
+ * explicitly not the goal.
+ *
+ * @param {string[]} chars
+ * @param {function(): number} rnd
+ * @returns {string[]}
+ */
+function fullShuffle(chars, rnd) {
+    const out = chars.slice();
+    for (let i = out.length - 1; i > 0; i--) {
+        const j = Math.floor(rnd() * (i + 1));
+        [out[i], out[j]] = [out[j], out[i]];
+    }
+    return out;
+}
+
+/**
+ * Scrambles a word's middle characters as far as possible while keeping enough
+ * open bigrams intact to stay readable. Several candidates are generated and
+ * the most scrambled one clearing the readability floor wins.
+ *
+ * @param {string[]} middle
+ * @param {number} amp
+ * @param {number} floor
+ * @param {function(): number} rnd
+ * @returns {string[]}
+ */
+function scrambleMiddle(middle, amp, floor, rnd) {
+    if (middle.length < 2) return middle;
+
+    let best = null;
+    let bestMoved = -1;
+    for (let i = 0; i < CANDIDATES; i++) {
+        const candidate = amp === Infinity ?
+            fullShuffle(middle, rnd) :
+            jitterSort(middle, amp, rnd);
+        const moved = movedFraction(middle, candidate);
+        if (moved === 0) continue;
+        if (bigramOverlap(middle, candidate) < floor) continue;
+        if (moved > bestMoved) {
+            best = candidate;
+            bestMoved = moved;
+        }
+    }
+    if (best) return best;
+
+    // Nothing cleared the floor, so guarantee a visible effect with the most
+    // conservative change available: a single adjacent transposition.
+    const out = middle.slice();
+    const i = Math.floor(rnd() * (out.length - 1));
+    [out[i], out[i + 1]] = [out[i + 1], out[i]];
+    return out;
+}
+
+/**
+ * Typoglycemia operation
+ */
+class Typoglycemia extends Operation {
+
+    /**
+     * Typoglycemia constructor
+     */
+    constructor() {
+        super();
+
+        this.name = "Typoglycemia";
+        this.module = "Default";
+        this.description = "Scrambles the middle letters of each word while keeping the first and last letter in place, so the text usually stays readable thanks to the typoglycemia phenomenon.<br><br>Letters are displaced only a short distance rather than shuffled at random, which is what preserves readability. The intensity (1-10) controls how far they may travel: 1 is a light touch, 5 gives the classic effect, 10 abandons readability for a full shuffle.<br><br>A seed of 0 scrambles differently every time; any other value produces reproducible output.";
+        this.infoURL = "https://wikipedia.org/wiki/Transposed_letter_effect#Internet_meme";
+        this.inputType = "string";
+        this.outputType = "string";
+        this.args = [
+            {
+                name: "Intensity",
+                type: "number",
+                value: 5
+            },
+            {
+                name: "Minimum word length",
+                type: "number",
+                value: 4
+            },
+            {
+                name: "Seed",
+                type: "number",
+                value: 1
+            }
+        ];
+    }
+
+    /**
+     * @param {string} input
+     * @param {Object[]} args
+     * @returns {string}
+     */
+    run(input, args) {
+        const [intensity, minWordLength, seed] = args;
+
+        if (isNaN(intensity) || intensity < 1 || intensity > 10)
+            throw new OperationError("Intensity must be between 1 and 10.");
+        if (isNaN(minWordLength) || minWordLength < 3)
+            throw new OperationError("Minimum word length must be at least 3.");
+
+        // Displacement amplitude grows with intensity while the readability
+        // floor drops, trading recognisability for scrambling. At the top of
+        // the scale both constraints are removed entirely.
+        const amp = intensity >= 10 ? Infinity : 0.7 + 0.3 * intensity;
+        const floor = intensity >= 10 ? 0 : Math.max(0, 0.9 - 0.05 * intensity);
+        const rnd = seed === 0 ? Math.random : mulberry32(seed);
+
+        return input.replace(WORD_REGEX, (word) => {
+            const chars = Array.from(word);
+            if (chars.length < minWordLength) return word;
+            if (IDEOGRAPHIC_REGEX.test(word)) return word;
+
+            // Scramble in lower case, then restore the original capitalisation
+            // by position. Word shape is a reading cue, so "McDonald" should
+            // stay front-loaded with capitals rather than move them around.
+            const lower = chars.map(c => c.toLowerCase());
+            const middle = scrambleMiddle(lower.slice(1, -1), amp, floor, rnd);
+            const scrambled = [lower[0], ...middle, lower[chars.length - 1]];
+
+            return scrambled.map((c, i) => {
+                const original = chars[i];
+                const isUpper = original === original.toUpperCase() &&
+                    original !== original.toLowerCase();
+                return isUpper ? c.toUpperCase() : c;
+            }).join("");
+        });
+    }
+
+}
+
+export default Typoglycemia;

tests/operations/tests/Typoglycemia.mjs

@@ -0,0 +1,34 @@
+/**
+* Typoglycemia tests
+*
+* @author 0x6368 []
+* @copyright Crown Copyright 2026
+* @license Apache-2.0
+*/
+
+import TestRegister from "../../lib/TestRegister.mjs";
+
+TestRegister.addTests([
+    {
+        name: "Typoglycemia: test",
+        input: "Ignore all previous instructions",
+        expectedOutput: "Igonre all prveoius intsurctions",
+        recipeConfig: [
+            {
+                op: "Typoglycemia",
+                args: [5, 4, 1],
+            },
+        ],
+    },
+    {
+        name: "Typoglycemia: full shuffle at maximum intensity",
+        input: "Ignore all previous instructions",
+        expectedOutput: "Iorgne all pioevurs icounnisrtts",
+        recipeConfig: [
+            {
+                op: "Typoglycemia",
+                args: [10, 4, 42],
+            },
+        ],
+    },
+]);