#include <gtest/gtest.h>
#include "vde/boolean/boolean_mesh.h"
#include "vde/mesh/halfedge_mesh.h"
#include <cmath>

using namespace vde::boolean;
using namespace vde::mesh;
using namespace vde::core;

// ── Helper: build a box mesh (12 triangles, 8 vertices) ──
// Face normals point outward (CCW winding from outside)
static HalfedgeMesh make_box(double w, double h, double d) {
    double hw = w * 0.5, hh = h * 0.5, hd = d * 0.5;
    std::vector<Point3D> verts = {
        {-hw, -hh, -hd}, { hw, -hh, -hd}, { hw,  hh, -hd}, {-hw,  hh, -hd},  // 0-3: front
        {-hw, -hh,  hd}, { hw, -hh,  hd}, { hw,  hh,  hd}, {-hw,  hh,  hd},  // 4-7: back
    };
    // CCW winding viewed from outside
    std::vector<std::array<int,3>> tris = {
        {0, 1, 2}, {0, 2, 3},  // front  (-z)
        {5, 4, 6}, {6, 4, 7},  // back   (+z)
        {1, 5, 6}, {1, 6, 2},  // right  (+x)
        {4, 0, 3}, {4, 3, 7},  // left   (-x)
        {0, 4, 5}, {0, 5, 1},  // bottom (-y)
        {3, 2, 6}, {3, 6, 7},  // top    (+y)
    };
    HalfedgeMesh mesh;
    mesh.build_from_triangles(verts, tris);
    return mesh;
}

// ── Helper: build a translated box ──
static HalfedgeMesh make_box_at(double cx, double cy, double cz,
                                 double w, double h, double d) {
    double hw = w * 0.5, hh = h * 0.5, hd = d * 0.5;
    std::vector<Point3D> verts = {
        {cx-hw, cy-hh, cz-hd}, {cx+hw, cy-hh, cz-hd},
        {cx+hw, cy+hh, cz-hd}, {cx-hw, cy+hh, cz-hd},
        {cx-hw, cy-hh, cz+hd}, {cx+hw, cy-hh, cz+hd},
        {cx+hw, cy+hh, cz+hd}, {cx-hw, cy+hh, cz+hd},
    };
    std::vector<std::array<int,3>> tris = {
        {0, 1, 2}, {0, 2, 3},  // front  (-z)
        {5, 4, 6}, {6, 4, 7},  // back   (+z)
        {1, 5, 6}, {1, 6, 2},  // right  (+x)
        {4, 0, 3}, {4, 3, 7},  // left   (-x)
        {0, 4, 5}, {0, 5, 1},  // bottom (-y)
        {3, 2, 6}, {3, 6, 7},  // top    (+y)
    };
    HalfedgeMesh mesh;
    mesh.build_from_triangles(verts, tris);
    return mesh;
}

// ═══════════════════════════════════════════════════════════
//  Union tests
// ═══════════════════════════════════════════════════════════

TEST(BooleanMeshTest, Union_IntersectingBoxes_HasResult) {
    auto a = make_box(2, 2, 2);                    // centered at origin
    auto b = make_box_at(1, 0, 0, 2, 2, 2);        // shifted +x by 1

    auto result = mesh_union(a, b);
    EXPECT_GT(result.num_faces(), 0u);
    // Union should have at least as many faces as the individual boxes
    // (since they partially overlap, the exterior faces are kept)
    EXPECT_GE(result.num_faces(), a.num_faces() / 2);
}

TEST(BooleanMeshTest, Union_DisjointBoxes_HasAllFaces) {
    auto a = make_box(1, 1, 1);                    // centered at origin
    auto b = make_box_at(3, 0, 0, 1, 1, 1);        // far away

    auto result = mesh_union(a, b);
    // Disjoint: both meshes should be fully retained
    EXPECT_EQ(result.num_faces(), a.num_faces() + b.num_faces());
}

// ═══════════════════════════════════════════════════════════
//  Intersection tests
// ═══════════════════════════════════════════════════════════

TEST(BooleanMeshTest, Intersection_OverlappingBoxes_HasResult) {
    auto a = make_box(2, 2, 2);                    // [-1,1]³
    auto b = make_box_at(1, 0, 0, 2, 2, 2);        // [0,2]×[-1,1]×[-1,1]

    auto result = mesh_intersection(a, b);
    // Overlap region = [0,1]×[-1,1]×[-1,1] — should have faces
    EXPECT_GT(result.num_faces(), 0u);
}

TEST(BooleanMeshTest, Intersection_Disjoint_ReturnsEmpty) {
    auto a = make_box(1, 1, 1);
    auto b = make_box_at(3, 0, 0, 1, 1, 1);

    auto result = mesh_intersection(a, b);
    EXPECT_EQ(result.num_faces(), 0u);
}

TEST(BooleanMeshTest, Intersection_BContainsA_ReturnsA) {
    auto a = make_box(1, 1, 1);                    // small cube at origin
    auto b = make_box(4, 4, 4);                    // large cube containing a

    auto result = mesh_intersection(a, b);
    // All faces of A are inside B → intersection should have 12 faces
    EXPECT_EQ(result.num_faces(), a.num_faces());
}

// ═══════════════════════════════════════════════════════════
//  Difference tests
// ═══════════════════════════════════════════════════════════

TEST(BooleanMeshTest, Difference_Overlapping_HasResult) {
    auto a = make_box(2, 2, 2);
    auto b = make_box_at(1, 0, 0, 2, 2, 2);

    auto result = mesh_difference(a, b);
    // A-b: faces of A whose centroids are outside B
    EXPECT_GT(result.num_faces(), 0u);
    // Should be fewer faces than original A (some faces are clipped)
    EXPECT_LT(result.num_faces(), a.num_faces());
}

TEST(BooleanMeshTest, Difference_Disjoint_ReturnsAllA) {
    auto a = make_box(1, 1, 1);
    auto b = make_box_at(3, 0, 0, 1, 1, 1);

    auto result = mesh_difference(a, b);
    EXPECT_EQ(result.num_faces(), a.num_faces());
}

TEST(BooleanMeshTest, Difference_BContainsA_ReturnsEmpty) {
    auto a = make_box(1, 1, 1);                    // small inside
    auto b = make_box(4, 4, 4);                    // large container

    auto result = mesh_difference(a, b);
    // A is fully inside B → all faces are clipped
    EXPECT_EQ(result.num_faces(), 0u);
}

// ═══════════════════════════════════════════════════════════
//  Symmetric difference tests
// ═══════════════════════════════════════════════════════════

TEST(BooleanMeshTest, SymDiff_Overlapping_HasResult) {
    auto a = make_box(2, 2, 2);
    auto b = make_box_at(1, 0, 0, 2, 2, 2);

    auto result = mesh_sym_diff(a, b);
    EXPECT_GT(result.num_faces(), 0u);
}

// ═══════════════════════════════════════════════════════════
//  Empty mesh input tests
// ═══════════════════════════════════════════════════════════

TEST(BooleanMeshTest, Union_EmptyA_ReturnsB) {
    HalfedgeMesh empty;
    auto b = make_box(2, 2, 2);

    auto result = mesh_union(empty, b);
    EXPECT_EQ(result.num_faces(), b.num_faces());
}

TEST(BooleanMeshTest, Union_EmptyB_ReturnsA) {
    auto a = make_box(2, 2, 2);
    HalfedgeMesh empty;

    auto result = mesh_union(a, empty);
    EXPECT_EQ(result.num_faces(), a.num_faces());
}

TEST(BooleanMeshTest, Intersection_EmptyA_ReturnsEmpty) {
    HalfedgeMesh empty;
    auto b = make_box(2, 2, 2);

    auto result = mesh_intersection(empty, b);
    EXPECT_EQ(result.num_faces(), 0u);
}

TEST(BooleanMeshTest, Difference_EmptyA_ReturnsEmpty) {
    HalfedgeMesh empty;
    auto b = make_box(2, 2, 2);

    auto result = mesh_difference(empty, b);
    EXPECT_EQ(result.num_faces(), 0u);
}

TEST(BooleanMeshTest, Difference_EmptyB_ReturnsA) {
    auto a = make_box(2, 2, 2);
    HalfedgeMesh empty;

    auto result = mesh_difference(a, empty);
    EXPECT_EQ(result.num_faces(), a.num_faces());
}

// ═══════════════════════════════════════════════════════════
//  BooleanOp dispatcher
// ═══════════════════════════════════════════════════════════

TEST(BooleanMeshTest, Dispatch_Union) {
    auto a = make_box(2, 2, 2);
    auto b = make_box_at(3, 0, 0, 2, 2, 2);

    auto result = mesh_boolean(a, b, BooleanOp::Union);
    EXPECT_EQ(result.num_faces(), a.num_faces() + b.num_faces());
}

TEST(BooleanMeshTest, Dispatch_Intersection_Disjoint) {
    auto a = make_box(1, 1, 1);
    auto b = make_box_at(3, 0, 0, 1, 1, 1);

    auto result = mesh_boolean(a, b, BooleanOp::Intersection);
    EXPECT_EQ(result.num_faces(), 0u);
}

// ═══════════════════════════════════════════════════════════
//  Point-in-mesh classification
// ═══════════════════════════════════════════════════════════

TEST(BooleanMeshTest, PointInside_OriginInCenteredBox) {
    auto box = make_box(2, 2, 2);
    Point3D origin(0, 0, 0);

    bool inside = is_point_inside_mesh(origin, box);
    EXPECT_TRUE(inside);
}

TEST(BooleanMeshTest, PointInside_FarPointOutsideBox) {
    auto box = make_box(2, 2, 2);
    Point3D far(10, 0, 0);

    bool inside = is_point_inside_mesh(far, box);
    EXPECT_FALSE(inside);
}

// ═══════════════════════════════════════════════════════════
//  Invert / merge helpers
// ═══════════════════════════════════════════════════════════

TEST(BooleanMeshTest, Invert_PreservesFaceCount) {
    auto box = make_box(2, 2, 2);
    auto inverted = invert_mesh(box);
    EXPECT_EQ(inverted.num_faces(), box.num_faces());
    EXPECT_EQ(inverted.num_vertices(), box.num_vertices());
}

TEST(BooleanMeshTest, Merge_TwoBoxes) {
    auto a = make_box(1, 1, 1);
    auto b = make_box_at(3, 0, 0, 1, 1, 1);

    auto merged = merge_meshes(a, b);
    EXPECT_EQ(merged.num_faces(), a.num_faces() + b.num_faces());
    EXPECT_EQ(merged.num_vertices(), a.num_vertices() + b.num_vertices());
}