#include <gtest/gtest.h>
#include "vde/collision/ray_intersect.h"
#include "vde/core/triangle.h"

using namespace vde::collision;
using namespace vde::core;

// ── Ray-Triangle intersection (origin + direction) ──

TEST(RayTest, RayTriangle_Hit) {
    // Triangle on XY plane at z=0
    Triangle3D tri(Point3D(0, 0, 0), Point3D(2, 0, 0), Point3D(0, 2, 0));
    // Ray pointing downwards from above
    auto result = ray_triangle_intersect(
        Point3D(0.5, 0.5, 5.0),
        Vector3D(0, 0, -1),
        tri
    );
    ASSERT_TRUE(result.has_value());
    EXPECT_NEAR(result->point.x(), 0.5, 1e-9);
    EXPECT_NEAR(result->point.y(), 0.5, 1e-9);
    EXPECT_NEAR(result->point.z(), 0.0, 1e-9);
    EXPECT_GT(result->t, 0.0);  // t should be positive (in ray direction)
}

TEST(RayTest, RayTriangle_MissParallel) {
    // Triangle on XY plane, ray parallel to plane
    Triangle3D tri(Point3D(0, 0, 0), Point3D(2, 0, 0), Point3D(0, 2, 0));
    auto result = ray_triangle_intersect(
        Point3D(0, 0, 5),
        Vector3D(1, 0, 0),
        tri
    );
    EXPECT_FALSE(result.has_value());
}

TEST(RayTest, RayTriangle_MissOutside) {
    Triangle3D tri(Point3D(0, 0, 0), Point3D(2, 0, 0), Point3D(0, 2, 0));
    // Ray hits the plane but outside the triangle
    auto result = ray_triangle_intersect(
        Point3D(3, 3, 5),
        Vector3D(0, 0, -1),
        tri
    );
    EXPECT_FALSE(result.has_value());
}

TEST(RayTest, RayTriangle_MissBehindOrigin) {
    Triangle3D tri(Point3D(0, 0, 0), Point3D(2, 0, 0), Point3D(0, 2, 0));
    // Ray points away from the triangle
    auto result = ray_triangle_intersect(
        Point3D(0.5, 0.5, 5),
        Vector3D(0, 0, 1),  // points +Z (away)
        tri
    );
    EXPECT_FALSE(result.has_value());
}

TEST(RayTest, RayTriangle_HitVertex) {
    Triangle3D tri(Point3D(0, 0, 0), Point3D(2, 0, 0), Point3D(0, 2, 0));
    // Ray directly at vertex (0,0,0)
    auto result = ray_triangle_intersect(
        Point3D(0, 0, 5),
        Vector3D(0, 0, -1),
        tri
    );
    ASSERT_TRUE(result.has_value());
    EXPECT_NEAR(result->point.z(), 0.0, 1e-9);
}

TEST(RayTest, RayTriangle_HitEdge) {
    Triangle3D tri(Point3D(0, 0, 0), Point3D(2, 0, 0), Point3D(0, 2, 0));
    // Ray at edge midpoint (between v0 and v1)
    auto result = ray_triangle_intersect(
        Point3D(1, 0, 3),
        Vector3D(0, 0, -1),
        tri
    );
    ASSERT_TRUE(result.has_value());
    EXPECT_NEAR(result->point.z(), 0.0, 1e-9);
}

// ── Ray-Triangle via Ray3Dd wrapper ──

TEST(RayTest, RayTriangle_RayWrapper) {
    Triangle3D tri(Point3D(0, 0, 0), Point3D(1, 0, 0), Point3D(0, 1, 0));
    Ray3Dd ray(Point3D(0.3, 0.3, 2), Vector3D(0, 0, -1));
    auto result = ray_triangle_intersect(ray, tri);
    ASSERT_TRUE(result.has_value());
    EXPECT_NEAR(result->t, 2.0, 1e-9);
}

// ── Degenerate triangle ──

TEST(RayTest, RayTriangle_DegenerateTriangle) {
    // All three vertices are collinear
    Triangle3D tri(Point3D(0, 0, 0), Point3D(1, 0, 0), Point3D(2, 0, 0));
    auto result = ray_triangle_intersect(
        Point3D(0.5, 0.5, 1),
        Vector3D(0, 0, -1),
        tri
    );
    // Degenerate triangle: should miss or handle gracefully
    EXPECT_FALSE(result.has_value());
}

// ── Oblique ray ──

TEST(RayTest, RayTriangle_ObliqueRay) {
    Triangle3D tri(Point3D(0, 0, 0), Point3D(2, 0, 0), Point3D(0, 2, 0));
    // Oblique ray that passes through triangle at (1, 0.27, 0)
    auto result = ray_triangle_intersect(
        Point3D(3, -2, 5),
        Vector3D(-0.37, 0.41, -0.83),
        tri
    );
    // Ray might or might not hit depending on direction
    (void)result;
    SUCCEED();
}