#include <gtest/gtest.h>
#include "vde/brep/explode_view.h"
#include "vde/brep/modeling.h"
#include "vde/core/transform.h"
#include <cmath>

using namespace vde::brep;
using namespace vde::core;

// ═══════════════════════════════════════════════════════════
//  Basic explosion
// ═══════════════════════════════════════════════════════════

TEST(ExplodeViewTest, SinglePart_NoExplosion) {
    Assembly assy("single");
    assy.root.add_part("box", make_box(2, 2, 2));

    ExplodeConfig cfg;
    cfg.factor = 1.0;
    cfg.use_constraint_dirs = false;

    auto result = explode_view(assy, cfg);
    EXPECT_GE(result.steps.size(), 1u);
    EXPECT_GT(result.max_displacement(), 0.0);
}

TEST(ExplodeViewTest, TwoParts_DisplaceAway) {
    Assembly assy("two");
    assy.root.add_part("left", make_box(2, 2, 2), translate(-3, 0, 0));
    assy.root.add_part("right", make_box(2, 2, 2), translate(3, 0, 0));

    ExplodeConfig cfg;
    cfg.factor = 2.0;

    auto result = explode_view(assy, cfg);
    EXPECT_EQ(result.steps.size(), 2u);

    // Both parts should move further apart
    EXPECT_GT(result.max_displacement(), 3.0); // factor 2 × original offset 3
}

TEST(ExplodeViewTest, Explode_ExpandsBounds) {
    Assembly assy("expand");
    assy.root.add_part("a", make_box(2, 2, 2), translate(0, -3, 0));
    assy.root.add_part("b", make_box(2, 2, 2), translate(0, 3, 0));

    double orig_extent = assy.root.children[0]->model->bounds().extent().norm();

    ExplodeConfig cfg;
    cfg.factor = 2.0;

    auto result = explode_view(assy, cfg);
    Vector3D expl_ext = result.exploded_bounds.extent();

    // Exploded bounds should be larger than any single part
    EXPECT_GT(expl_ext.norm(), orig_extent);
}

TEST(ExplodeViewTest, UnExplode_RestoresTransforms) {
    Assembly assy("restore");
    assy.root.add_part("part", make_box(2, 2, 2), translate(5, 0, 0));

    // Save original transform
    Transform3D orig_tf = assy.root.children[0]->local_transform;

    ExplodeConfig cfg;
    cfg.factor = 3.0;

    auto result = explode_view(assy, cfg);

    // Transform should have changed
    bool changed = assy.root.children[0]->local_transform.matrix() != orig_tf.matrix();
    EXPECT_TRUE(changed);

    // Un-explode
    un_explode(assy, result);

    // Should be back to original
    bool restored = assy.root.children[0]->local_transform.matrix() == orig_tf.matrix();
    EXPECT_TRUE(restored);
}

TEST(ExplodeViewTest, AutoDirection_ChoosesLongestAxis) {
    Assembly assy("auto_dir");
    // Create a wide but flat assembly
    assy.root.add_part("wide", make_box(10, 1, 1));

    ExplodeConfig cfg;
    cfg.factor = 1.0;
    cfg.use_constraint_dirs = false;
    // direction is zero → auto

    auto result = explode_view(assy, cfg);
    // Should pick X axis (longest extent)
    // Verify by checking that displacement is primarily along X
    for (auto& step : result.steps) {
        Vector3D d = step.displacement;
        EXPECT_GE(std::abs(d.x()), std::abs(d.y()));
        EXPECT_GE(std::abs(d.x()), std::abs(d.z()));
    }
}

TEST(ExplodeViewTest, ExplicitDirection_Used) {
    Assembly assy("explicit_dir");
    assy.root.add_part("box", make_box(2, 2, 2), translate(0, 3, 0));

    ExplodeConfig cfg;
    cfg.factor = 2.0;
    cfg.direction = Vector3D(0, 0, 1); // explicit +Z direction
    cfg.use_constraint_dirs = false;

    auto result = explode_view(assy, cfg);
    for (auto& step : result.steps) {
        Vector3D d = step.displacement;
        // Displacement should be primarily along Z
        EXPECT_GE(std::abs(d.z()), std::abs(d.x()));
        EXPECT_GE(std::abs(d.z()), std::abs(d.y()));
    }
}

TEST(ExplodeViewTest, FactorScalesDisplacement) {
    Assembly assy("scale");
    assy.root.add_part("part", make_box(2, 2, 2), translate(0, 4, 0));

    ExplodeConfig cfg1;
    cfg1.factor = 1.0;
    auto r1 = explode_view(assy, cfg1);

    // Reset
    un_explode(assy, r1);

    ExplodeConfig cfg2;
    cfg2.factor = 3.0;
    auto r2 = explode_view(assy, cfg2);

    // Factor 3 should give roughly 3× the displacement
    EXPECT_NEAR(r2.max_displacement() / r1.max_displacement(), 3.0, 0.5);
}

TEST(ExplodeViewTest, Subassembly_NotExplodedInternally) {
    Assembly assy("parent");
    auto* sub = assy.root.add_subassembly("group", translate(0, 5, 0));
    sub->add_part("sub_a", make_box(1, 1, 1), translate(-1, 0, 0));
    sub->add_part("sub_b", make_box(1, 1, 1), translate(1, 0, 0));
    assy.root.add_part("main", make_box(3, 1, 3));

    ExplodeConfig cfg;
    cfg.factor = 2.0;
    cfg.preserve_subassemblies = true;

    auto result = explode_view(assy, cfg);
    // Should still work without crash
    EXPECT_GE(result.steps.size(), 1u);
}

TEST(ExplodeViewTest, MaxDisplacement_NonNegative) {
    Assembly assy("max_disp");
    assy.root.add_part("a", make_box(2, 2, 2));

    auto result = explode_view(assy);
    EXPECT_GE(result.max_displacement(), 0.0);
}

TEST(ExplodeViewTest, EmptyAssembly_NoSteps) {
    Assembly assy("empty");
    auto result = explode_view(assy);
    EXPECT_EQ(result.steps.size(), 0u);
    EXPECT_EQ(result.max_displacement(), 0.0);
}

TEST(ExplodeViewTest, ThreePartsChain_AllDisplaced) {
    Assembly assy("chain");
    assy.root.add_part("root", make_box(3, 1, 1));
    assy.root.add_part("middle", make_box(2, 1, 1), translate(4, 0, 0));
    assy.root.add_part("tip", make_box(1, 1, 1), translate(7, 0, 0));

    ExplodeConfig cfg;
    cfg.factor = 1.5;

    auto result = explode_view(assy, cfg);
    EXPECT_EQ(result.steps.size(), 3u);

    // Each part should have been displaced
    for (auto& step : result.steps) {
        EXPECT_GT(step.displacement.norm(), 0.0);
    }
}

TEST(ExplodeViewTest, ComputedDisplacement_DirectionConsistent) {
    Assembly assy("consistent");
    // Place parts in a line
    assy.root.add_part("p0", make_box(2, 2, 2), translate(0, 5, 0));
    assy.root.add_part("p1", make_box(2, 2, 2), translate(0, 10, 0));

    ExplodeConfig cfg;
    cfg.factor = 2.0;

    auto result = explode_view(assy, cfg);
    ASSERT_GE(result.steps.size(), 2u);

    // All displacements should be in roughly the same direction (away from origin)
    Vector3D d0 = result.steps[0].displacement.normalized();
    Vector3D d1 = result.steps[1].displacement.normalized();
    EXPECT_GT(d0.dot(d1), 0.5); // should point in similar direction
}