added base graph logic for cycle detection

utils/graph.js

@@ -0,0 +1,79 @@
+const logger = require("./logger")(module);
+
+const typedefs = require("../typedefs");
+
+/**
+ * Directed graph, may or may not be connected.
+ * 
+ * NOTE: Assumes that nodes and edges are valid.
+ */
+class myGraph {
+	/**
+	 * @param {string[]} nodes Graph nodes IDs
+	 * @param {{ from: string, to: string }[]} edges Graph edges b/w nodes
+	*/
+	constructor(nodes, edges) {
+		this.nodes = [...nodes];
+		this.edges = structuredClone(edges);
+	}
+
+	/**
+	 * @param {type} node
+	 * @returns {string[]}
+	 */
+	getNeighbors(node) {
+		return this.edges.filter(edge => edge.from == node).map(edge => edge.to);
+	}
+
+	/**
+	 * Kahn's topological sort
+	 * @returns {string[]}
+	 */
+	topoSort() {
+		let inDegree = {};
+		let zeroInDegreeQueue = [];
+		let topologicalOrder = [];
+
+		// Initialize inDegree of all nodes to 0
+		for (let node of this.nodes) {
+			inDegree[node] = 0;
+		}
+
+		// Calculate inDegree of each node
+		for (let edge of this.edges) {
+			inDegree[edge.to]++;
+		}
+
+		// Collect nodes with 0 inDegree
+		for (let node of this.nodes) {
+			if (inDegree[node] === 0) {
+				zeroInDegreeQueue.push(node);
+			}
+		}
+
+		// process nodes with 0 inDegree
+		while (zeroInDegreeQueue.length > 0) {
+			let node = zeroInDegreeQueue.shift();
+			topologicalOrder.push(node);
+
+			for (let neighbor of this.getNeighbors(node)) {
+				inDegree[neighbor]--;
+				if (inDegree[neighbor] === 0) {
+					zeroInDegreeQueue.push(neighbor);
+				}
+			}
+		}
+		return topologicalOrder;
+	}
+
+	/**
+	 * Check if the graph contains a cycle
+	 * @returns {boolean}
+	 */
+	detectCycle() {
+		// If topological order includes all nodes, no cycle exists
+		return this.topoSort().length < this.nodes.length;
+	}
+}
+
+module.exports = myGraph;