import graphlib.edges.DirectedEdge;
import graphlib.graphs.DirectedGraph;
import graphlib.nodes.Node;
import graphlib.util.Graphs;

import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;

import java.util.Arrays;
import java.util.Collections;


public class SimpleTest {

    private static ShortestPaths sp;

    @BeforeAll 
    public static void initClass() {
        sp = new BellmanFordShortestPaths();
    }

    private DirectedGraph<String> graph;

    @BeforeEach
    public void init() {
        graph = new DirectedGraph<>();
        for(int i = 0; i < 4; i++) {
            graph.addNode(new Node<>("n" + i));
        }

        DirectedEdge<String> e01 = new DirectedEdge<>(graph.getNode("n0"), graph.getNode("n1"), 50);
        DirectedEdge<String> e03 = new DirectedEdge<>(graph.getNode("n0"), graph.getNode("n3"), -34);
        DirectedEdge<String> e02 = new DirectedEdge<>(graph.getNode("n0"), graph.getNode("n2"), 20);
        DirectedEdge<String> e13 = new DirectedEdge<>(graph.getNode("n1"), graph.getNode("n3"), 10);
        DirectedEdge<String> e23 = new DirectedEdge<>(graph.getNode("n2"), graph.getNode("n3"), 15);

        graph.addEdge(e01);
        graph.addEdge(e02);
        graph.addEdge(e03);
        graph.addEdge(e13);
        graph.addEdge(e23);
    }

    @Test
    public void testSameNode() {
        Assertions.assertEquals(Collections.singletonList(graph.getNode("n0")), sp.shortestPath(Graphs.unmodifiableDirectedGraph(graph), graph.getNode("n0"), graph.getNode("n0")));
    }

    @Test
    public void testPath01() {
        Assertions.assertEquals(Arrays.asList(graph.getNode("n0"), graph.getNode("n1")), sp.shortestPath(Graphs.unmodifiableDirectedGraph(graph), graph.getNode("n0"), graph.getNode("n1")));
    }

    @Test
    public void testPath02() {
        Assertions.assertEquals(Arrays.asList(graph.getNode("n0"), graph.getNode("n2")), sp.shortestPath(Graphs.unmodifiableDirectedGraph(graph), graph.getNode("n0"), graph.getNode("n2")));
    }

    @Test
    public void testPath03() {
        Assertions.assertEquals(Arrays.asList(graph.getNode("n0"), graph.getNode("n3")), sp.shortestPath(Graphs.unmodifiableDirectedGraph(graph), graph.getNode("n0"), graph.getNode("n3")));
    }

    @Test
    public void testPath13() {
        graph.addEdge(new DirectedEdge<>(graph.getNode("n1"), graph.getNode("n0"), 40));
        Assertions.assertEquals(Arrays.asList(graph.getNode("n1"), graph.getNode("n0"), graph.getNode("n3")), sp.shortestPath(Graphs.unmodifiableDirectedGraph(graph), graph.getNode("n1"), graph.getNode("n3")));
    }

    @Test
    public void testUnreachableNode() {
        Assertions.assertThrows(ShortestPaths.UnreachableDestinationException.class, () ->
                sp.shortestPath(Graphs.unmodifiableDirectedGraph(graph), graph.getNode("n1"), graph.getNode("n2")));
    }

    @Test
    public void testNegativeCycle() {
        graph.addEdge(new DirectedEdge<>(graph.getNode("n3"), graph.getNode("n0"), -34));
        Assertions.assertThrows(ShortestPaths.NegativeCycleException.class, () ->
                sp.shortestPath(Graphs.unmodifiableDirectedGraph(graph), graph.getNode("n0"), graph.getNode("n1")));
    }
    
}