add new operation: Levenshtein Distance

src/core/config/Categories.json

@@ -269,6 +269,7 @@
             "Fuzzy Match",
             "Offset checker",
             "Hamming Distance",
+            "Levenshtein Distance",
             "Convert distance",
             "Convert area",
             "Convert mass",

src/core/operations/LevenshteinDistance.mjs

@@ -0,0 +1,98 @@
+/**
+ * @author mikecat
+ * @copyright Crown Copyright 2023
+ * @license Apache-2.0
+ */
+
+import Operation from "../Operation.mjs";
+import OperationError from "../errors/OperationError.mjs";
+
+/**
+ * Levenshtein Distance operation
+ */
+class LevenshteinDistance extends Operation {
+
+    /**
+     * LevenshteinDistance constructor
+     */
+    constructor() {
+        super();
+
+        this.name = "Levenshtein Distance";
+        this.module = "Default";
+        this.description = "Levenshtein Distance (also known as Edit Distance) is a string metric to measure a difference between two strings that counts operations (insertions, deletions, and substitutions) on single character that are required to change one string to another.";
+        this.infoURL = "https://wikipedia.org/wiki/Levenshtein_distance";
+        this.inputType = "string";
+        this.outputType = "number";
+        this.args = [
+            {
+                name: "Sample delimiter",
+                type: "binaryString",
+                value: "\\n"
+            },
+            {
+                name: "Insertion cost",
+                type: "number",
+                value: 1
+            },
+            {
+                name: "Deletion cost",
+                type: "number",
+                value: 1
+            },
+            {
+                name: "Substitution cost",
+                type: "number",
+                value: 1
+            },
+        ];
+    }
+
+    /**
+     * @param {string} input
+     * @param {Object[]} args
+     * @returns {number}
+     */
+    run(input, args) {
+        const [delim, insCost, delCost, subCost] = args;
+        const samples = input.split(delim);
+        if (samples.length !== 2) {
+            throw new OperationError("Incorrect number of samples. Check your input and/or delimiter.");
+        }
+        if (insCost < 0 || delCost < 0 || subCost < 0) {
+            throw new OperationError("Negative costs are not allowed.");
+        }
+        const src = samples[0], dest = samples[1];
+        let currentCost = new Array(src.length + 1);
+        let nextCost = new Array(src.length + 1);
+        for (let i = 0; i < currentCost.length; i++) {
+            currentCost[i] = delCost * i;
+        }
+        for (let i = 0; i < dest.length; i++) {
+            const destc = dest.charAt(i);
+            nextCost[0] = currentCost[0] + insCost;
+            for (let j = 0; j < src.length; j++) {
+                let candidate;
+                // insertion
+                let optCost = currentCost[j + 1] + insCost;
+                // deletion
+                candidate = nextCost[j] + delCost;
+                if (candidate < optCost) optCost = candidate;
+                // substitution or matched character
+                candidate = currentCost[j];
+                if (src.charAt(j) !== destc) candidate += subCost;
+                if (candidate < optCost) optCost = candidate;
+                // store calculated cost
+                nextCost[j + 1] = optCost;
+            }
+            const tempCost = nextCost;
+            nextCost = currentCost;
+            currentCost = tempCost;
+        }
+
+        return currentCost[currentCost.length - 1];
+    }
+
+}
+
+export default LevenshteinDistance;

tests/operations/index.mjs

@@ -130,6 +130,7 @@ import "./tests/FletcherChecksum.mjs";
 import "./tests/CMAC.mjs";
 import "./tests/AESKeyWrap.mjs";
 import "./tests/Rabbit.mjs";
+import "./tests/LevenshteinDistance.mjs";
 
 // Cannot test operations that use the File type yet
 // import "./tests/SplitColourChannels.mjs";

tests/operations/tests/LevenshteinDistance.mjs

@@ -0,0 +1,165 @@
+/**
+ * @author mikecat
+ * @copyright Crown Copyright 2023
+ * @license Apache-2.0
+ */
+import TestRegister from "../../lib/TestRegister.mjs";
+
+TestRegister.addTests([
+    {
+        "name": "Levenshtein Distance: Wikipedia example 1",
+        "input": "kitten\nsitting",
+        "expectedOutput": "3",
+        "recipeConfig": [
+            {
+                "op": "Levenshtein Distance",
+                "args": [
+                    "\\n", 1, 1, 1,
+                ],
+            },
+        ],
+    },
+    {
+        "name": "Levenshtein Distance: Wikipedia example 2",
+        "input": "saturday\nsunday",
+        "expectedOutput": "3",
+        "recipeConfig": [
+            {
+                "op": "Levenshtein Distance",
+                "args": [
+                    "\\n", 1, 1, 1,
+                ],
+            },
+        ],
+    },
+    {
+        "name": "Levenshtein Distance: Wikipedia example 1 with substitution cost 2",
+        "input": "kitten\nsitting",
+        "expectedOutput": "5",
+        "recipeConfig": [
+            {
+                "op": "Levenshtein Distance",
+                "args": [
+                    "\\n", 1, 1, 2,
+                ],
+            },
+        ],
+    },
+    {
+        "name": "Levenshtein Distance: varied costs 1",
+        "input": "kitten\nsitting",
+        "expectedOutput": "230",
+        "recipeConfig": [
+            {
+                "op": "Levenshtein Distance",
+                "args": [
+                    "\\n", 10, 100, 1000,
+                ],
+            },
+        ],
+    },
+    {
+        "name": "Levenshtein Distance: varied costs 2",
+        "input": "kitten\nsitting",
+        "expectedOutput": "1020",
+        "recipeConfig": [
+            {
+                "op": "Levenshtein Distance",
+                "args": [
+                    "\\n", 1000, 100, 10,
+                ],
+            },
+        ],
+    },
+    {
+        "name": "Levenshtein Distance: another delimiter",
+        "input": "kitten sitting",
+        "expectedOutput": "3",
+        "recipeConfig": [
+            {
+                "op": "Levenshtein Distance",
+                "args": [
+                    " ", 1, 1, 1,
+                ],
+            },
+        ],
+    },
+    {
+        "name": "Levenshtein Distance: too few samples",
+        "input": "kitten",
+        "expectedOutput": "Incorrect number of samples. Check your input and/or delimiter.",
+        "recipeConfig": [
+            {
+                "op": "Levenshtein Distance",
+                "args": [
+                    "\\n", 1, 1, 1,
+                ],
+            },
+        ],
+    },
+    {
+        "name": "Levenshtein Distance: too many samples",
+        "input": "kitten\nsitting\nkitchen",
+        "expectedOutput": "Incorrect number of samples. Check your input and/or delimiter.",
+        "recipeConfig": [
+            {
+                "op": "Levenshtein Distance",
+                "args": [
+                    "\\n", 1, 1, 1,
+                ],
+            },
+        ],
+    },
+    {
+        "name": "Levenshtein Distance: negative insertion cost",
+        "input": "kitten\nsitting",
+        "expectedOutput": "Negative costs are not allowed.",
+        "recipeConfig": [
+            {
+                "op": "Levenshtein Distance",
+                "args": [
+                    "\\n", -1, 1, 1,
+                ],
+            },
+        ],
+    },
+    {
+        "name": "Levenshtein Distance: negative deletion cost",
+        "input": "kitten\nsitting",
+        "expectedOutput": "Negative costs are not allowed.",
+        "recipeConfig": [
+            {
+                "op": "Levenshtein Distance",
+                "args": [
+                    "\\n", 1, -1, 1,
+                ],
+            },
+        ],
+    },
+    {
+        "name": "Levenshtein Distance: negative substitution cost",
+        "input": "kitten\nsitting",
+        "expectedOutput": "Negative costs are not allowed.",
+        "recipeConfig": [
+            {
+                "op": "Levenshtein Distance",
+                "args": [
+                    "\\n", 1, 1, -1,
+                ],
+            },
+        ],
+    },
+    {
+        "name": "Levenshtein Distance: cost zero",
+        "input": "kitten\nsitting",
+        "expectedOutput": "0",
+        "recipeConfig": [
+            {
+                "op": "Levenshtein Distance",
+                "args": [
+                    "\\n", 0, 0, 0,
+                ],
+            },
+        ],
+    },
+]);