use std::fmt::Debug;

use grapherity::algorithms;
use grapherity::maps::ElementMap;
use grapherity::testing::fixtures::MakeTestGraph;
use grapherity::traits::GraphTopology;

macro_rules! bfs_tests {
    ($T:ty) => {
        bfs_tests!(@wrap $T,
            bfs_single_vertex,
            bfs_disconnected,
            bfs,
            bfs_distances_single_vertex,
            bfs_distances_disconnected,
            bfs_distances,
            bfs_find_source,
            bfs_find_disconnected,
            bfs_find,
            bfs_find_where_source_matches,
            bfs_find_where_disconnected,
            bfs_find_where_no_match,
            bfs_find_where_nearest,
        );
    };

    (@wrap $T:ty, $($name:ident),* $(,)?) => {
        $(
            #[test]
            fn $name() {
                super::$name::<$T>();
            }
        )*
    };
}

mod append_graph {
    use grapherity::models::AppendGraph;

    bfs_tests!(AppendGraph);
}

mod graph {
    use grapherity::models::Graph;

    bfs_tests!(Graph);
}

fn bfs_single_vertex<G: MakeTestGraph>()
where
    G::Vertex: Debug,
{
    let (graph, v) = G::single_vertex();
    let result = algorithms::bfs(&graph, v);
    assert_eq!(
        result.distances[v],
        Some(0),
        "unexpected distance of source vertex"
    );
    assert_eq!(
        result.predecessors[v], None,
        "unexpected predecessor of source vertex"
    );
}

fn bfs_disconnected<G: MakeTestGraph>()
where
    G::Vertex: Debug,
{
    let (graph, vertices) = G::disconnected();
    let result = algorithms::bfs(&graph, vertices[0]);
    assert_eq!(
        result.distances[vertices[0]],
        Some(0),
        "unexpected distance of source vertex"
    );
    assert_eq!(
        result.predecessors[vertices[0]], None,
        "unexpected predecessor of source vertex"
    );
    for &v in &vertices[1..3] {
        assert_eq!(
            result.distances[v], None,
            "disconnected vertex {v:?} should have no distance"
        );
        assert_eq!(
            result.predecessors[v], None,
            "disconnected vertex {v:?} should have no predecessor"
        );
    }
}

fn bfs<G: MakeTestGraph>()
where
    G::Vertex: Debug,
{
    let (graph, vertices, _, _) = G::standard();
    let result = algorithms::bfs(&graph, vertices[0]);
    assert_bfs_distances::<G>(&result.distances, &vertices);
    assert_bfs_predecessors::<G>(&result.predecessors, &vertices);
}

fn bfs_distances_single_vertex<G: MakeTestGraph>() {
    let (graph, v) = G::single_vertex();
    let distances = algorithms::bfs_distances(&graph, v);
    assert_eq!(
        distances[v],
        Some(0),
        "unexpected distance of source vertex"
    );
}

fn bfs_distances_disconnected<G: MakeTestGraph>()
where
    G::Vertex: Debug,
{
    let (graph, vertices) = G::disconnected();
    let distances = algorithms::bfs_distances(&graph, vertices[0]);
    assert_eq!(
        distances[vertices[0]],
        Some(0),
        "unexpected distance of source vertex"
    );
    for &v in &vertices[1..3] {
        assert_eq!(
            distances[v], None,
            "disconnected vertex {v:?} should have no distance"
        );
    }
}

fn bfs_distances<G: MakeTestGraph>()
where
    G::Vertex: Debug,
{
    let (graph, vertices, _, _) = G::standard();
    let distances = algorithms::bfs_distances(&graph, vertices[0]);
    assert_bfs_distances::<G>(&distances, &vertices);
}

fn bfs_find_source<G: MakeTestGraph>() {
    let (graph, v) = G::single_vertex();
    assert_eq!(
        algorithms::bfs_find(&graph, v, v),
        Some(0),
        "source should be found at distance 0"
    );
}

fn bfs_find_disconnected<G: MakeTestGraph>() {
    let (graph, vertices) = G::disconnected();
    assert_eq!(
        algorithms::bfs_find(&graph, vertices[0], vertices[1]),
        None,
        "disconnected target should not be found"
    );
}

fn bfs_find<G: MakeTestGraph>()
where
    G::Vertex: Debug,
{
    let (graph, vertices, _, _) = G::standard();
    let expected_distances = [
        Some(0),
        Some(1),
        Some(2),
        Some(2),
        Some(2),
        Some(3),
        Some(3),
        Some(3),
        Some(3),
        Some(4),
    ];
    for i in 0..10 {
        assert_eq!(
            algorithms::bfs_find(&graph, vertices[0], vertices[i]),
            expected_distances[i],
            "unexpected distance from {:?} to {:?}",
            vertices[0],
            vertices[i]
        );
    }
}

fn bfs_find_where_source_matches<G: MakeTestGraph>()
where
    G::Vertex: Debug,
{
    let (graph, v) = G::single_vertex();
    assert_eq!(
        algorithms::bfs_find_where(&graph, v, |u| u == v),
        Some((v, 0)),
        "source should match with distance 0"
    );
}

fn bfs_find_where_disconnected<G: MakeTestGraph>()
where
    G::Vertex: Debug,
{
    let (graph, vertices) = G::disconnected();
    assert_eq!(
        algorithms::bfs_find_where(&graph, vertices[0], |v| v == vertices[1]),
        None,
        "disconnected vertex {:?} should not be found",
        vertices[1]
    );
}

fn bfs_find_where_no_match<G: MakeTestGraph>()
where
    G::Vertex: Debug,
{
    let (graph, vertices, _, _) = G::standard();
    assert_eq!(
        algorithms::bfs_find_where(&graph, vertices[0], |_| false),
        None,
        "no vertex should match an always-false predicate"
    );
}

fn bfs_find_where_nearest<G: MakeTestGraph>()
where
    G::Vertex: Debug,
{
    let (graph, vertices, _, _) = G::standard();
    // vertices[5], vertices[6], vertices[7], vertices[8] are all at distance 3 from vertices[0].
    // vertices[9] is at distance 4. Predicate matches vertices[7], vertices[8], vertices[9].
    // BFS must return one of the distance-3 ones, not vertices[9].
    let result = algorithms::bfs_find_where(&graph, vertices[0], |v| {
        v == vertices[7] || v == vertices[8] || v == vertices[9]
    });
    assert!(result.is_some(), "expected a match");
    let (found, distance) = result.unwrap();
    assert_eq!(
        distance, 3,
        "unexpected distance to nearest matching vertex {found:?}",
    );
    assert!(
        found == vertices[7] || found == vertices[8],
        "unexpected nearest match vertex {found:?}, should be {:?} or {:?}",
        vertices[7],
        vertices[8]
    );
}

fn assert_bfs_distances<G: GraphTopology>(
    distances: &ElementMap<G::Vertex, Option<u32>>,
    vertices: &[G::Vertex],
) where
    G::Vertex: Debug,
{
    let expected = [
        Some(0),
        Some(1),
        Some(2),
        Some(2),
        Some(2),
        Some(3),
        Some(3),
        Some(3),
        Some(3),
        Some(4),
    ];
    for i in 0..10 {
        assert_eq!(
            distances[vertices[i]], expected[i],
            "unexpected distance from {:?} to {:?}",
            vertices[0], vertices[i]
        );
    }
}

fn assert_bfs_predecessors<G: GraphTopology>(
    predecessors: &ElementMap<G::Vertex, Option<G::Vertex>>,
    vertices: &[G::Vertex],
) where
    G::Vertex: Debug,
{
    assert_eq!(
        predecessors[vertices[0]], None,
        "source should have no predecessor"
    );
    // Each non-source vertex's predecessor must be adjacent and at distance one less.
    let expected_predecessors = [
        vec![None],
        vec![Some(vertices[0])],
        vec![Some(vertices[1])],
        vec![Some(vertices[1])],
        vec![Some(vertices[1])],
        vec![Some(vertices[2])],
        vec![Some(vertices[2]), Some(vertices[3])],
        vec![Some(vertices[4])],
        vec![Some(vertices[4])],
        vec![Some(vertices[5]), Some(vertices[6]), Some(vertices[7])],
    ];
    for i in 1..10 {
        assert!(
            expected_predecessors[i].contains(&predecessors[vertices[i]]),
            "unexpected predecessor {:?} of {:?}",
            predecessors[vertices[i]],
            vertices[i]
        );
    }
}