#include <gtest/gtest.h>

#include "Viewport/SceneViewportCameraController.h"

#include <XCEngine/Components/GameObject.h>

#include <cmath>

namespace {

bool NearlyEqual(float lhs, float rhs, float epsilon = 1e-4f) {
    return std::abs(lhs - rhs) <= epsilon;
}

bool NearlyEqual(const XCEngine::Math::Vector3& lhs, const XCEngine::Math::Vector3& rhs, float epsilon = 1e-4f) {
    return NearlyEqual(lhs.x, rhs.x, epsilon) &&
           NearlyEqual(lhs.y, rhs.y, epsilon) &&
           NearlyEqual(lhs.z, rhs.z, epsilon);
}

} // namespace

using XCEngine::Components::GameObject;
using XCEngine::Editor::SceneViewportCameraController;
using XCEngine::Editor::SceneViewportCameraInputState;
using XCEngine::Math::Vector3;

TEST(SceneViewportCameraController_Test, ApplyToMatchesComputedPositionAndForward) {
    SceneViewportCameraController controller;
    controller.Reset();
    controller.Focus(Vector3(2.0f, 1.0f, -3.0f));

    GameObject cameraObject("EditorCamera");
    controller.ApplyTo(*cameraObject.GetTransform());

    EXPECT_TRUE(NearlyEqual(cameraObject.GetTransform()->GetPosition(), controller.GetPosition()));
    EXPECT_TRUE(NearlyEqual(
        cameraObject.GetTransform()->GetForward().Normalized(),
        controller.GetForward(),
        1e-3f));
    EXPECT_GT(Vector3::Dot(cameraObject.GetTransform()->GetUp().Normalized(), Vector3::Up()), 0.0f);
}

TEST(SceneViewportCameraController_Test, LookInputRotatesCameraInPlaceAndKeepsDistance) {
    SceneViewportCameraController controller;
    controller.Reset();

    const Vector3 initialPosition = controller.GetPosition();
    const Vector3 initialFocus = controller.GetFocalPoint();
    const float initialPitch = controller.GetPitchDegrees();

    SceneViewportCameraInputState input = {};
    input.viewportHeight = 720.0f;
    input.lookDeltaX = 20.0f;
    input.lookDeltaY = -15.0f;
    controller.ApplyInput(input);

    EXPECT_TRUE(NearlyEqual(controller.GetPosition(), initialPosition));
    EXPECT_FALSE(NearlyEqual(controller.GetFocalPoint(), initialFocus));
    EXPECT_LT(controller.GetPitchDegrees(), initialPitch);
    EXPECT_TRUE(NearlyEqual(
        controller.GetFocalPoint(),
        controller.GetPosition() + controller.GetForward() * controller.GetDistance(),
        1e-3f));
}

TEST(SceneViewportCameraController_Test, OrbitInputRotatesAroundFocalPointAndKeepsDistance) {
    SceneViewportCameraController controller;
    controller.Reset();

    const Vector3 initialPosition = controller.GetPosition();
    const Vector3 initialFocus = controller.GetFocalPoint();
    const float initialDistance = controller.GetDistance();
    const float initialPitch = controller.GetPitchDegrees();

    SceneViewportCameraInputState input = {};
    input.viewportHeight = 720.0f;
    input.orbitDeltaX = 20.0f;
    input.orbitDeltaY = -15.0f;
    controller.ApplyInput(input);

    EXPECT_FALSE(NearlyEqual(controller.GetPosition(), initialPosition));
    EXPECT_TRUE(NearlyEqual(controller.GetFocalPoint(), initialFocus));
    EXPECT_LT(controller.GetPitchDegrees(), initialPitch);
    EXPECT_NEAR((controller.GetFocalPoint() - controller.GetPosition()).Magnitude(), initialDistance, 1e-3f);
}

TEST(SceneViewportCameraController_Test, PanAndZoomUpdateCameraStateConsistently) {
    SceneViewportCameraController controller;
    controller.Reset();

    const Vector3 initialPosition = controller.GetPosition();
    const Vector3 initialFocus = controller.GetFocalPoint();
    const float initialDistance = controller.GetDistance();
    const Vector3 right = Vector3::Normalize(Vector3::Cross(Vector3::Up(), controller.GetForward()));
    const Vector3 up = Vector3::Normalize(Vector3::Cross(controller.GetForward(), right));

    SceneViewportCameraInputState input = {};
    input.viewportHeight = 720.0f;
    input.panDeltaX = 16.0f;
    input.panDeltaY = -10.0f;
    input.zoomDelta = 1.0f;
    controller.ApplyInput(input);

    EXPECT_FALSE(NearlyEqual(controller.GetPosition(), initialPosition));
    EXPECT_FALSE(NearlyEqual(controller.GetFocalPoint(), initialFocus));
    EXPECT_LT(controller.GetDistance(), initialDistance);
    const Vector3 panDelta = controller.GetFocalPoint() - initialFocus;
    EXPECT_NEAR(Vector3::Dot(panDelta, controller.GetForward()), 0.0f, 1e-3f);
    EXPECT_GT(std::abs(Vector3::Dot(panDelta, right)), 0.0f);
    EXPECT_GT(std::abs(Vector3::Dot(panDelta, up)), 0.0f);
    EXPECT_TRUE(NearlyEqual(
        controller.GetFocalPoint(),
        controller.GetPosition() + controller.GetForward() * controller.GetDistance(),
        1e-3f));
}

TEST(SceneViewportCameraController_Test, FlyInputMovesCameraAndFocalPointTogether) {
    SceneViewportCameraController controller;
    controller.Reset();

    const Vector3 initialPosition = controller.GetPosition();
    const Vector3 initialFocus = controller.GetFocalPoint();
    const Vector3 initialOffset = initialFocus - initialPosition;
    const Vector3 forward = controller.GetForward();
    const Vector3 right = Vector3::Normalize(Vector3::Cross(Vector3::Up(), forward));

    SceneViewportCameraInputState input = {};
    input.viewportHeight = 720.0f;
    input.deltaTime = 0.5f;
    input.moveForward = 1.0f;
    input.moveRight = 1.0f;
    controller.ApplyInput(input);

    EXPECT_FALSE(NearlyEqual(controller.GetPosition(), initialPosition));
    EXPECT_FALSE(NearlyEqual(controller.GetFocalPoint(), initialFocus));
    const Vector3 positionDelta = controller.GetPosition() - initialPosition;
    EXPECT_GT(std::abs(Vector3::Dot(positionDelta, forward)), 0.0f);
    EXPECT_GT(std::abs(Vector3::Dot(positionDelta, right)), 0.0f);
    EXPECT_TRUE(NearlyEqual(controller.GetFocalPoint() - controller.GetPosition(), initialOffset, 1e-3f));
}

TEST(SceneViewportCameraController_Test, FocusMovesPivotWithoutChangingDistance) {
    SceneViewportCameraController controller;
    controller.Reset();

    const float initialDistance = controller.GetDistance();
    const Vector3 target(5.0f, -2.0f, 7.5f);
    controller.Focus(target);

    EXPECT_TRUE(NearlyEqual(controller.GetFocalPoint(), target));
    EXPECT_FLOAT_EQ(controller.GetDistance(), initialDistance);
}