CyberChef/src/core/operations/LevenshteinDistance.mjs

99 lines
3.1 KiB
JavaScript

/**
* @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;