#include "omath/collision/epa_algorithm.hpp" // Epa<Collider> + GjkAlgorithmWithSimplex<Collider>
#include "omath/collision/gjk_algorithm.hpp"
#include "omath/collision/simplex.hpp"
#include "omath/engines/source_engine/collider.hpp"
#include "omath/engines/source_engine/mesh.hpp"
#include "omath/linear_algebra/vector3.hpp"
#include <gtest/gtest.h>

using Mesh = omath::source_engine::Mesh;
using Collider = omath::source_engine::MeshCollider;
using GJK      = omath::collision::GjkAlgorithm<Collider>;
using EPA      = omath::collision::Epa<Collider>;

TEST(UnitTestEpa, TestCollisionTrue)
{
    // Unit cube [-1,1]^3
    std::vector<omath::Vector3<float>> vbo = {
        {-1,-1,-1}, {-1,-1, 1}, {-1, 1,-1}, {-1, 1, 1},
        { 1, 1, 1}, { 1, 1,-1}, { 1,-1, 1}, { 1,-1,-1}
    };
    std::vector<omath::Vector3<std::size_t>> vao; // not needed

    Mesh a(vbo, vao, {1,1,1});
    Mesh b(vbo, vao, {1,1,1});

    // Overlap along +X by 0.5
    a.set_origin({0,0,0});
    b.set_origin({0.5f,0,0});

    Collider A(a), B(b);

    // GJK
    auto gjk = GJK::is_collide_with_simplex_info(A, B);
    ASSERT_TRUE(gjk.hit) << "GJK should report collision";

    // EPA
    EPA::Params params; params.max_iterations = 64; params.tolerance = 1e-4f;
    auto epa = EPA::solve(A, B, gjk.simplex, params);
    ASSERT_TRUE(epa.success) << "EPA should converge";

    // Normal is unit
    EXPECT_NEAR(epa.normal.dot(epa.normal), 1.0f, 1e-5f);

    // For this setup, depth ≈ 1.5 (2 - 0.5)
    EXPECT_NEAR(epa.depth, 1.5f, 1e-3f);

    // Normal axis sanity: near X axis
    EXPECT_NEAR(std::abs(epa.normal.x), 1.0f, 1e-3f);
    EXPECT_NEAR(epa.normal.y, 0.0f, 1e-3f);
    EXPECT_NEAR(epa.normal.z, 0.0f, 1e-3f);

    // Try both signs with a tiny margin (avoid grazing contacts)
    const float margin = 1.0f + 1e-3f;
    const auto   pen    = epa.normal * epa.depth;

    Mesh b_plus = b;  b_plus.set_origin(b_plus.get_origin() + pen * margin);
    Mesh b_minus= b;  b_minus.set_origin(b_minus.get_origin() - pen * margin);

    Collider B_plus(b_plus), B_minus(b_minus);

    const bool sep_plus  = !GJK::is_collide_with_simplex_info(A, B_plus).hit;
    const bool sep_minus = !GJK::is_collide_with_simplex_info(A, B_minus).hit;

    // Exactly one direction should separate
    EXPECT_NE(sep_plus, sep_minus) << "Exactly one of ±penetration must separate";

    // Optional: pick the resolving direction and assert round-trip
    const auto resolve = sep_plus ? ( pen * margin) : (-pen * margin);

    Mesh b_resolved = b; b_resolved.set_origin(b_resolved.get_origin() + resolve);
    EXPECT_FALSE(GJK::is_collide(A, Collider(b_resolved))) << "Resolved position should be non-colliding";

    // Moving the other way should still collide
    Mesh b_wrong = b; b_wrong.set_origin(b_wrong.get_origin() - resolve);
    EXPECT_TRUE(GJK::is_collide(A, Collider(b_wrong)));
}