test(graph): add tests for cycle detection

libs/common/src/app/graph/algorithms/graph.has-cycle.spec.ts

@@ -0,0 +1,87 @@
+import { graphHasCycle } from "./graph.has-cycle";
+import { AdjacencyListTransformationParams, getAdjacencyList } from "../transformations";
+
+describe("graphHasCycle", () => {
+	it("should not have a cycle", () => {
+		const graphs: AdjacencyListTransformationParams[] = [
+			// "Empty" graphs
+			{ arcs: [], nodes: [] },
+			{
+				arcs: [],
+				nodes: [
+					{ inputs: [], outputs: [] },
+					{ inputs: [], outputs: [] }
+				]
+			},
+			{
+				arcs: [],
+				nodes: [
+					{ inputs: [{ _id: 1 }], outputs: [{ _id: 2 }] },
+					{ inputs: [{ _id: 3 }], outputs: [{ _id: 4 }] }
+				]
+			},
+
+			{
+				arcs: [{ __from: 1, __to: 2 }],
+				nodes: [
+					{ inputs: [], outputs: [{ _id: 1 }] },
+					{ inputs: [{ _id: 2 }], outputs: [] }
+				]
+			},
+			{
+				arcs: [
+					{ __from: 11, __to: 20 },
+					{ __from: 11, __to: 21 },
+					{ __from: 11, __to: 30 },
+					{ __from: 22, __to: 31 }
+				],
+				nodes: [
+					{ inputs: [{ _id: 10 }], outputs: [{ _id: 11 }] },
+					{ inputs: [{ _id: 20 }, { _id: 21 }], outputs: [{ _id: 22 }] },
+					{ inputs: [{ _id: 30 }, { _id: 31 }], outputs: [] }
+				]
+			}
+		];
+
+		for (const graph of graphs) {
+			expect(graphHasCycle(getAdjacencyList(graph))).toBeFalse();
+		}
+	});
+
+	it("should have a cycle", () => {
+		const graphs: AdjacencyListTransformationParams[] = [
+			{
+				arcs: [{ __from: 2, __to: 1 }],
+				nodes: [{ inputs: [{ _id: 1 }], outputs: [{ _id: 2 }] }]
+			},
+			{
+				arcs: [
+					{ __from: 11, __to: 20 },
+					{ __from: 21, __to: 10 }
+				],
+				nodes: [
+					{ inputs: [{ _id: 10 }], outputs: [{ _id: 11 }] },
+					{ inputs: [{ _id: 20 }], outputs: [{ _id: 21 }] }
+				]
+			},
+			{
+				arcs: [
+					{ __from: 11, __to: 20 },
+					{ __from: 11, __to: 30 },
+					{ __from: 22, __to: 30 },
+					{ __from: 22, __to: 31 },
+					{ __from: 32, __to: 10 }
+				],
+				nodes: [
+					{ inputs: [{ _id: 10 }], outputs: [{ _id: 11 }] },
+					{ inputs: [{ _id: 20 }], outputs: [{ _id: 22 }] },
+					{ inputs: [{ _id: 30 }, { _id: 31 }], outputs: [{ _id: 32 }] }
+				]
+			}
+		];
+
+		for (const graph of graphs) {
+			expect(graphHasCycle(getAdjacencyList(graph))).toBeTrue();
+		}
+	});
+});

libs/common/src/app/graph/algorithms/graph.has-cycle.ts

@@ -0,0 +1,13 @@
+import { AdjacencyList } from "../transformations";
+
+/**
+ * Detects if the given graph has a cycle.
+ *
+ * The cycle is determined by the explored nodes.
+ *
+ * @param graph the graph by its adjacency list
+ * @returns true if the graphs contains at least one cycle
+ */
+export function graphHasCycle(graph: AdjacencyList): boolean {
+	throw new Error("TODO");
+}

libs/common/src/app/graph/algorithms/index.ts

@@ -0,0 +1 @@
+export * from "./graph.has-cycle";

libs/common/src/app/graph/transformations/get-adjacency.list.ts

@@ -74,6 +74,16 @@ export interface AdjacencyListItem<Arc extends AdjacencyListArc, Node extends Ad
 	node: Node;
 }
 
+/**
+ * The final adjacency list.
+ *
+ * On a Map to access more simply the nodes.
+ */
+export type AdjacencyList<
+	Arc extends AdjacencyListArc = AdjacencyListArc,
+	Node extends AdjacencyListNode = AdjacencyListNode
+> = ReadonlyMap<Node, AdjacencyListItem<Arc, Node>>;
+
 /**
  * Gets the adjacency list from the arcs and the nodes of a graph
  *
@@ -83,7 +93,7 @@ export interface AdjacencyListItem<Arc extends AdjacencyListArc, Node extends Ad
  */
 export function getAdjacencyList<Arc extends AdjacencyListArc, Node extends AdjacencyListNode>(
 	params: AdjacencyListTransformationParams<Arc, Node>
-): ReadonlyMap<Node, AdjacencyListItem<Arc, Node>> {
+): AdjacencyList<Arc, Node> {
 	const { arcs, nodes } = params;
 
 	// TODO: If the data becomes too big, transform to a non-functional approach