use std::fmt::Debug;

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

macro_rules! dfs_tests {
    ($T:ty) => {
        dfs_tests!(@wrap $T,
            dfs_single_vertex,
            dfs_disconnected,
            dfs,
            dfs_visited_single_vertex,
            dfs_visited_disconnected,
            dfs_visited,
            dfs_find_source,
            dfs_find_disconnected,
            dfs_find,
            dfs_find_where_source_matches,
            dfs_find_where_disconnected,
            dfs_find_where_no_match,
            dfs_find_where_adjacent,
            dfs_find_where,
            dfs_find_path_source_equals_target,
            dfs_find_path_disconnected,
            dfs_find_path_adjacent,
            dfs_find_path,
            dfs_find_path_where_source_matches,
            dfs_find_path_where_disconnected,
            dfs_find_path_where_no_match,
            dfs_find_path_where,
        );
    };

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

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

    dfs_tests!(AppendGraph);
}

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

    dfs_tests!(Graph);
}

fn dfs_single_vertex<G: MakeTestGraph>()
where
    G::Vertex: Debug,
{
    let (graph, v) = G::single_vertex();
    let result = algorithms::dfs(&graph, v);
    assert!(result.visited[v], "source vertex should be visited");
    assert_eq!(
        result.predecessors[v], None,
        "unexpected predecessor of source vertex"
    );
}

fn dfs_disconnected<G: MakeTestGraph>()
where
    G::Vertex: Debug,
{
    let (graph, vertices) = G::disconnected();
    let result = algorithms::dfs(&graph, vertices[0]);
    assert!(
        result.visited[vertices[0]],
        "source vertex should be visited"
    );
    assert_eq!(
        result.predecessors[vertices[0]], None,
        "unexpected predecessor of source vertex"
    );
    for &v in &vertices[1..3] {
        assert!(
            !result.visited[v],
            "disconnected vertex {v:?} should not be visited"
        );
        assert_eq!(
            result.predecessors[v], None,
            "disconnected vertex {v:?} should have no predecessor"
        );
    }
}

fn dfs<G: MakeTestGraph>()
where
    G::Vertex: Debug,
{
    let (graph, vertices, _, _) = G::standard();
    let result = algorithms::dfs(&graph, vertices[0]);
    assert_dfs_visited::<G>(&result.visited, &vertices);
    assert_dfs_predecessors(&graph, &result.visited, &result.predecessors, &vertices);
}

fn dfs_visited_single_vertex<G: MakeTestGraph>() {
    let (graph, v) = G::single_vertex();
    let visited = algorithms::dfs_visited(&graph, v);
    assert!(visited[v], "source vertex should be visited");
}

fn dfs_visited_disconnected<G: MakeTestGraph>()
where
    G::Vertex: Debug,
{
    let (graph, vertices) = G::disconnected();
    let visited = algorithms::dfs_visited(&graph, vertices[0]);
    assert!(visited[vertices[0]], "source vertex should be visited");
    for &v in &vertices[1..3] {
        assert!(
            !visited[v],
            "disconnected vertex {v:?} should not be visited"
        );
    }
}

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

fn dfs_find_source<G: MakeTestGraph>() {
    let (graph, v) = G::single_vertex();
    assert!(
        algorithms::dfs_find(&graph, v, v),
        "source should find itself"
    );
}

fn dfs_find_disconnected<G: MakeTestGraph>() {
    let (graph, vertices) = G::disconnected();
    assert!(
        !algorithms::dfs_find(&graph, vertices[0], vertices[1]),
        "disconnected target should not be found"
    );
}

fn dfs_find<G: MakeTestGraph>()
where
    G::Vertex: Debug,
{
    let (graph, vertices, _, _) = G::standard();
    for i in 0..10 {
        assert!(
            algorithms::dfs_find(&graph, vertices[0], vertices[i]),
            "vertex {:?} should be reachable from {:?}",
            vertices[i],
            vertices[0]
        );
    }
}

fn dfs_find_where_source_matches<G: MakeTestGraph>()
where
    G::Vertex: Debug,
{
    let (graph, v) = G::single_vertex();
    assert_eq!(
        algorithms::dfs_find_where(&graph, v, |u| u == v),
        Some(v),
        "source should find itself"
    );
}

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

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

fn dfs_find_where_adjacent<G: MakeTestGraph>()
where
    G::Vertex: Debug,
{
    let (graph, vertices, _, _) = G::standard();
    assert_eq!(
        algorithms::dfs_find_where(&graph, vertices[0], |v| v == vertices[1]),
        Some(vertices[1]),
        "expected to find adjacent vertex"
    );
}

fn dfs_find_where<G: MakeTestGraph>()
where
    G::Vertex: Debug,
{
    let (graph, vertices, _, _) = G::standard();
    assert_eq!(
        algorithms::dfs_find_where(&graph, vertices[0], |v| v == vertices[9]),
        Some(vertices[9]),
        "expected to find connected vertex"
    );
}

fn dfs_find_path_source_equals_target<G: MakeTestGraph>()
where
    G::Edge: Debug,
{
    let (graph, v) = G::single_vertex();
    assert_eq!(
        algorithms::dfs_find_path(&graph, v, v),
        Some(vec![]),
        "path from source to itself should be empty"
    );
}

fn dfs_find_path_disconnected<G: MakeTestGraph>()
where
    G::Edge: Debug,
{
    let (graph, vertices) = G::disconnected();
    assert_eq!(
        algorithms::dfs_find_path(&graph, vertices[0], vertices[1]),
        None,
        "no path should exist to disconnected vertex"
    );
}

fn dfs_find_path_adjacent<G: MakeTestGraph>()
where
    G::Edge: Debug,
{
    let (graph, vertices, e) = G::single_edge();
    let path = algorithms::dfs_find_path(&graph, vertices[0], vertices[1])
        .expect("path should exist between adjacent vertices");
    assert_eq!(
        path.len(),
        1,
        "unexpected path length between adjacent vertices"
    );
    assert_eq!(path[0], e, "path should use the connecting edge");
}

fn dfs_find_path<G: MakeTestGraph>()
where
    G::Vertex: Debug,
    G::Edge: Debug,
{
    let (graph, vertices, _, _) = G::standard();
    let path = algorithms::dfs_find_path(&graph, vertices[0], vertices[9]).expect(&format!(
        "path should exist between connected vertices {:?} and {:?}",
        vertices[0], vertices[9]
    ));
    assert_valid_path(&graph, &path, vertices[0], vertices[9]);
}

fn dfs_find_path_where_source_matches<G: MakeTestGraph>()
where
    G::Edge: Debug,
{
    let (graph, v) = G::single_vertex();
    assert_eq!(
        algorithms::dfs_find_path_where(&graph, v, |u| u == v),
        Some(vec![]),
        "path from source to itself should be empty"
    );
}

fn dfs_find_path_where_disconnected<G: MakeTestGraph>()
where
    G::Edge: Debug,
{
    let (graph, vertices) = G::disconnected();
    assert_eq!(
        algorithms::dfs_find_path_where(&graph, vertices[0], |v| v == vertices[1]),
        None,
        "no path should exist to disconnected vertex"
    );
}

fn dfs_find_path_where_no_match<G: MakeTestGraph>()
where
    G::Edge: Debug,
{
    let (graph, vertices, _, _) = G::standard();
    assert_eq!(
        algorithms::dfs_find_path_where(&graph, vertices[0], |_| false),
        None,
        "no path should exist when predicate never matches"
    );
}

fn dfs_find_path_where<G: MakeTestGraph>()
where
    G::Vertex: Debug,
    G::Edge: Debug,
{
    let (graph, vertices, _, _) = G::standard();
    let path = algorithms::dfs_find_path_where(&graph, vertices[0], |v| v == vertices[9]).expect(
        &format!(
            "path should exist between connected vertices {:?} and {:?}",
            vertices[0], vertices[9]
        ),
    );
    assert_valid_path(&graph, &path, vertices[0], vertices[9]);
}

fn assert_dfs_visited<G: GraphTopology>(
    visited: &ElementMap<G::Vertex, bool>,
    vertices: &[G::Vertex],
) where
    G::Vertex: Debug,
{
    for i in 0..10 {
        assert!(
            visited[vertices[i]],
            "vertex {:?} should be visited",
            vertices[i]
        );
    }
}

fn assert_dfs_predecessors<G: GraphTopology>(
    graph: &G,
    visited: &ElementMap<G::Vertex, bool>,
    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"
    );
    for i in 1..10 {
        let v = vertices[i];
        let p = predecessors[v].expect(&format!("vertex {v:?} should have a predecessor"));
        assert!(
            visited[p],
            "predecessor {p:?} of vertex {v:?} should be visited"
        );
        assert!(
            graph.are_adjacent(v, p),
            "predecessor {p:?} of vertex {v:?} should be adjacent"
        );
    }
}

fn assert_valid_path<G: GraphTopology>(
    graph: &G,
    path: &[G::Edge],
    source: G::Vertex,
    target: G::Vertex,
) where
    G::Vertex: Debug,
    G::Edge: Debug,
{
    assert!(!path.is_empty(), "path should be non-empty");
    // Walks the path: tracks current vertex, confirm each edge is incident to it.
    let mut current = source;
    for (i, &e) in path.iter().enumerate() {
        let (v1, v2) = graph.incident_vertices(e);
        assert_ne!(v1, v2, "path should not contain loop edge {e:?}");
        assert!(
            v1 == current || v2 == current,
            "path edge {e:?} (idx {i}, {v1:?} to {v2:?}) not incident to vertex {current:?}"
        );
        current = if v1 == current { v2 } else { v1 };
    }
    assert_eq!(
        current, target,
        "path should end at target {target:?}, but ended at {current:?}"
    );
}