#include <gtest/gtest.h>

#include "Viewport/SceneViewportCameraController.h"
#include "Viewport/SceneViewportHudOverlay.h"
#include "Viewport/SceneViewportMath.h"

#include <XCEngine/Components/GameObject.h>
#include <XCEngine/Core/Math/Vector4.h>
#include <XCEngine/Rendering/Passes/BuiltinInfiniteGridPass.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);
}

bool NearlyEqual(
    const XCEngine::Math::Matrix4x4& lhs,
    const XCEngine::Math::Matrix4x4& rhs,
    float epsilon = 1e-4f) {
    for (int row = 0; row < 4; ++row) {
        for (int column = 0; column < 4; ++column) {
            if (!NearlyEqual(lhs.m[row][column], rhs.m[row][column], epsilon)) {
                return false;
            }
        }
    }
    return true;
}

bool IsPowerOfTenSpacing(float value) {
    if (value <= 0.0f) {
        return false;
    }

    const float exponent = std::floor(std::log10(value));
    const float base = std::pow(10.0f, exponent);
    const float normalized = value / base;
    return NearlyEqual(normalized, 1.0f, 1e-4f);
}

} // namespace

XCEngine::Rendering::Passes::InfiniteGridPassData ToInfiniteGridPassData(
    const XCEngine::Editor::SceneViewportOverlayData& overlay) {
    XCEngine::Rendering::Passes::InfiniteGridPassData data = {};
    data.valid = overlay.valid;
    data.cameraPosition = overlay.cameraPosition;
    data.cameraForward = overlay.cameraForward;
    data.cameraRight = overlay.cameraRight;
    data.cameraUp = overlay.cameraUp;
    data.verticalFovDegrees = overlay.verticalFovDegrees;
    data.nearClipPlane = overlay.nearClipPlane;
    data.farClipPlane = overlay.farClipPlane;
    data.orbitDistance = overlay.orbitDistance;
    return data;
}

using XCEngine::Editor::BuildSceneViewportAxisDragPlaneNormal;
using XCEngine::Editor::SceneViewportCameraController;
using XCEngine::Editor::SceneViewportHudOverlayHitKind;
using XCEngine::Editor::SceneViewportHudOverlayHitResult;
using XCEngine::Editor::BuildSceneViewportProjectionMatrix;
using XCEngine::Editor::BuildSceneViewportHudOverlayData;
using XCEngine::Editor::BuildSceneViewportViewMatrix;
using XCEngine::Editor::HitTestSceneViewportHudOverlay;
using XCEngine::Editor::ProjectSceneViewportWorldPoint;
using XCEngine::Editor::SceneViewportOverlayFrameData;
using XCEngine::Editor::SceneViewportOverlaySpritePrimitive;
using XCEngine::Editor::SceneViewportOverlaySpriteTextureKind;
using XCEngine::Editor::SceneViewportOverlayData;
using XCEngine::Components::GameObject;
using XCEngine::Math::Vector3;
using XCEngine::Math::Vector4;
using XCEngine::Rendering::Passes::BuildInfiniteGridParameters;
using XCEngine::Rendering::Passes::InfiniteGridParameters;

TEST(SceneViewportOverlayRenderer_Test, BuildInfiniteGridParametersUsesPowerOfTenSpacingSeries) {
    SceneViewportOverlayData overlay = {};
    overlay.valid = true;
    overlay.cameraPosition = Vector3(0.0f, 6.0f, -6.0f);
    overlay.cameraForward = Vector3(0.0f, -0.5f, 0.8660254f);

    const InfiniteGridParameters parameters = BuildInfiniteGridParameters(ToInfiniteGridPassData(overlay));

    EXPECT_TRUE(parameters.valid);
    EXPECT_TRUE(IsPowerOfTenSpacing(parameters.baseScale));
    EXPECT_GE(parameters.transitionBlend, 0.0f);
    EXPECT_LE(parameters.transitionBlend, 1.0f);
    EXPECT_GT(parameters.fadeDistance, parameters.baseScale);
}

TEST(SceneViewportOverlayRenderer_Test, BuildInfiniteGridParametersIsStableAcrossHorizontalCameraMovement) {
    SceneViewportOverlayData left = {};
    left.valid = true;
    left.cameraPosition = Vector3(-120.0f, 12.0f, 40.0f);
    left.cameraForward = Vector3(0.0f, -0.5f, 0.8660254f);

    SceneViewportOverlayData right = left;
    right.cameraPosition = Vector3(380.0f, 12.0f, -260.0f);

    const InfiniteGridParameters leftParameters = BuildInfiniteGridParameters(ToInfiniteGridPassData(left));
    const InfiniteGridParameters rightParameters = BuildInfiniteGridParameters(ToInfiniteGridPassData(right));

    EXPECT_TRUE(leftParameters.valid);
    EXPECT_TRUE(rightParameters.valid);
    EXPECT_FLOAT_EQ(leftParameters.baseScale, rightParameters.baseScale);
    EXPECT_FLOAT_EQ(leftParameters.transitionBlend, rightParameters.transitionBlend);
    EXPECT_FLOAT_EQ(leftParameters.fadeDistance, rightParameters.fadeDistance);
}

TEST(SceneViewportOverlayRenderer_Test, BuildInfiniteGridParametersExpandsScaleAsCameraHeightGrows) {
    SceneViewportOverlayData nearOverlay = {};
    nearOverlay.valid = true;
    nearOverlay.cameraPosition = Vector3(0.0f, 3.0f, -4.0f);
    nearOverlay.cameraForward = Vector3(0.0f, -0.5f, 0.8660254f);

    SceneViewportOverlayData farOverlay = nearOverlay;
    farOverlay.cameraPosition = Vector3(0.0f, 120.0f, -150.0f);

    const InfiniteGridParameters nearParameters = BuildInfiniteGridParameters(ToInfiniteGridPassData(nearOverlay));
    const InfiniteGridParameters farParameters = BuildInfiniteGridParameters(ToInfiniteGridPassData(farOverlay));

    EXPECT_TRUE(nearParameters.valid);
    EXPECT_TRUE(farParameters.valid);
    EXPECT_GE(farParameters.baseScale, nearParameters.baseScale);
    EXPECT_GE(farParameters.fadeDistance, nearParameters.fadeDistance);
}

TEST(SceneViewportOverlayRenderer_Test, BuildInfiniteGridParametersPromotesMajorLinesByDecimalGrouping) {
    SceneViewportOverlayData overlay = {};
    overlay.valid = true;
    overlay.cameraPosition = Vector3(0.0f, 14.0f, -18.0f);
    overlay.cameraForward = Vector3(0.0f, -0.5f, 0.8660254f);

    const InfiniteGridParameters parameters = BuildInfiniteGridParameters(ToInfiniteGridPassData(overlay));

    EXPECT_TRUE(parameters.valid);
    EXPECT_TRUE(IsPowerOfTenSpacing(parameters.baseScale));
    EXPECT_TRUE(IsPowerOfTenSpacing(parameters.baseScale * 10.0f));
}

TEST(SceneViewportOverlayRenderer_Test, BuildInfiniteGridParametersFadesTowardNextScaleBeforeThreshold) {
    SceneViewportOverlayData earlyOverlay = {};
    earlyOverlay.valid = true;
    earlyOverlay.cameraPosition = Vector3(0.0f, 4.0f, -6.0f);

    SceneViewportOverlayData lateOverlay = earlyOverlay;
    lateOverlay.cameraPosition = Vector3(0.0f, 18.0f, -6.0f);

    const InfiniteGridParameters earlyParameters = BuildInfiniteGridParameters(ToInfiniteGridPassData(earlyOverlay));
    const InfiniteGridParameters lateParameters = BuildInfiniteGridParameters(ToInfiniteGridPassData(lateOverlay));

    EXPECT_FLOAT_EQ(earlyParameters.baseScale, 1.0f);
    EXPECT_FLOAT_EQ(lateParameters.baseScale, 1.0f);
    EXPECT_LT(earlyParameters.transitionBlend, 0.05f);
    EXPECT_GT(lateParameters.transitionBlend, 0.90f);
}

TEST(SceneViewportOverlayRenderer_Test, BuildInfiniteGridParametersSwitchesScaleAtHalfThePreviousDistanceThreshold) {
    SceneViewportOverlayData nearOverlay = {};
    nearOverlay.valid = true;
    nearOverlay.cameraPosition = Vector3(0.0f, 19.9f, -6.0f);

    SceneViewportOverlayData farOverlay = nearOverlay;
    farOverlay.cameraPosition = Vector3(0.0f, 20.0f, -6.0f);

    const InfiniteGridParameters nearParameters = BuildInfiniteGridParameters(ToInfiniteGridPassData(nearOverlay));
    const InfiniteGridParameters farParameters = BuildInfiniteGridParameters(ToInfiniteGridPassData(farOverlay));

    EXPECT_FLOAT_EQ(nearParameters.baseScale, 1.0f);
    EXPECT_FLOAT_EQ(farParameters.baseScale, 10.0f);
    EXPECT_GT(nearParameters.transitionBlend, 0.95f);
    EXPECT_LT(farParameters.transitionBlend, 0.05f);
}

TEST(SceneViewportOverlayRenderer_Test, BuildInfiniteGridParametersIgnoresStaleOrbitDistanceForSameView) {
    SceneViewportOverlayData nearOrbit = {};
    nearOrbit.valid = true;
    nearOrbit.cameraPosition = Vector3(0.0f, 12.0f, -24.0f);
    nearOrbit.cameraForward = Vector3(0.0f, -0.5f, 0.8660254f);
    nearOrbit.orbitDistance = 2.0f;

    SceneViewportOverlayData farOrbit = nearOrbit;
    farOrbit.orbitDistance = 200.0f;

    const InfiniteGridParameters nearOrbitParameters = BuildInfiniteGridParameters(ToInfiniteGridPassData(nearOrbit));
    const InfiniteGridParameters farOrbitParameters = BuildInfiniteGridParameters(ToInfiniteGridPassData(farOrbit));

    EXPECT_TRUE(nearOrbitParameters.valid);
    EXPECT_TRUE(farOrbitParameters.valid);
    EXPECT_FLOAT_EQ(nearOrbitParameters.baseScale, farOrbitParameters.baseScale);
    EXPECT_FLOAT_EQ(nearOrbitParameters.transitionBlend, farOrbitParameters.transitionBlend);
    EXPECT_FLOAT_EQ(nearOrbitParameters.fadeDistance, farOrbitParameters.fadeDistance);
}

TEST(SceneViewportOverlayRenderer_Test, ViewMatrixKeepsForwardWorldPointsInFrontOfCamera) {
    SceneViewportOverlayData overlay = {};
    overlay.valid = true;
    overlay.cameraPosition = Vector3(0.0f, 0.0f, 0.0f);
    overlay.cameraForward = Vector3::Forward();
    overlay.cameraRight = Vector3::Right();
    overlay.cameraUp = Vector3::Up();
    overlay.verticalFovDegrees = 60.0f;
    overlay.nearClipPlane = 0.03f;
    overlay.farClipPlane = 2000.0f;

    const auto view = BuildSceneViewportViewMatrix(overlay);
    const Vector3 pointInView = view.MultiplyPoint(Vector3(0.0f, 0.0f, 5.0f));
    EXPECT_TRUE(NearlyEqual(pointInView, Vector3(0.0f, 0.0f, 5.0f), 1e-4f));

    const auto projection = BuildSceneViewportProjectionMatrix(overlay, 1280.0f, 720.0f);
    const Vector4 clipPoint = projection * Vector4(Vector3(0.0f, 0.0f, 5.0f), 1.0f);
    EXPECT_GT(clipPoint.w, 0.0f);
}

TEST(SceneViewportOverlayRenderer_Test, ViewMatrixMatchesSceneCameraTransformConvention) {
    SceneViewportCameraController controller;
    controller.Reset();
    controller.Focus(Vector3(2.0f, 1.5f, -3.0f));

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

    SceneViewportOverlayData overlay = {};
    overlay.valid = true;
    overlay.cameraPosition = cameraObject.GetTransform()->GetPosition();
    overlay.cameraForward = cameraObject.GetTransform()->GetForward();
    overlay.cameraRight = cameraObject.GetTransform()->GetRight();
    overlay.cameraUp = cameraObject.GetTransform()->GetUp();
    overlay.verticalFovDegrees = 60.0f;
    overlay.nearClipPlane = 0.03f;
    overlay.farClipPlane = 2000.0f;

    EXPECT_TRUE(NearlyEqual(
        BuildSceneViewportViewMatrix(overlay),
        cameraObject.GetTransform()->GetWorldToLocalMatrix(),
        1e-3f));
}

TEST(SceneViewportOverlayRenderer_Test, ProjectSceneViewportWorldPointMapsOriginToViewportCenter) {
    SceneViewportOverlayData overlay = {};
    overlay.valid = true;
    overlay.cameraPosition = Vector3(0.0f, 0.0f, -5.0f);
    overlay.cameraForward = Vector3::Forward();
    overlay.cameraRight = Vector3::Right();
    overlay.cameraUp = Vector3::Up();
    overlay.verticalFovDegrees = 60.0f;
    overlay.nearClipPlane = 0.03f;
    overlay.farClipPlane = 2000.0f;

    const auto projected = ProjectSceneViewportWorldPoint(overlay, 800.0f, 600.0f, Vector3::Zero());

    EXPECT_TRUE(projected.visible);
    EXPECT_NEAR(projected.screenPosition.x, 400.0f, 1e-3f);
    EXPECT_NEAR(projected.screenPosition.y, 300.0f, 1e-3f);
}

TEST(SceneViewportOverlayRenderer_Test, BuildSceneViewportAxisDragPlaneNormalFallsBackWhenForwardAlignsWithAxis) {
    SceneViewportOverlayData overlay = {};
    overlay.valid = true;
    overlay.cameraForward = Vector3::Right();
    overlay.cameraRight = Vector3::Back();
    overlay.cameraUp = Vector3::Up();

    Vector3 planeNormal = Vector3::Zero();
    ASSERT_TRUE(BuildSceneViewportAxisDragPlaneNormal(overlay, Vector3::Right(), planeNormal));
    EXPECT_NEAR(Vector3::Dot(planeNormal, Vector3::Right()), 0.0f, 1e-4f);
    EXPECT_GT(planeNormal.SqrMagnitude(), 0.5f);
}

TEST(SceneViewportOverlayRenderer_Test, BuildSceneViewportHudOverlayDataTracksVisibilityIntent) {
    SceneViewportOverlayData overlay = {};
    overlay.valid = true;

    const auto visibleHud = BuildSceneViewportHudOverlayData(overlay);
    const auto hiddenHud = BuildSceneViewportHudOverlayData(overlay, false);

    EXPECT_TRUE(visibleHud.HasVisibleElements());
    EXPECT_FALSE(hiddenHud.HasVisibleElements());
}

TEST(SceneViewportOverlayRenderer_Test, BuildSceneViewportHudOverlayDataCanExposeSceneIconsWithoutOrientationGizmo) {
    SceneViewportOverlayData overlay = {};
    overlay.valid = true;

    SceneViewportOverlayFrameData frameData = {};
    frameData.overlay = overlay;
    SceneViewportOverlaySpritePrimitive& sprite = frameData.worldSprites.emplace_back();
    sprite.worldPosition = Vector3::Zero();
    sprite.sizePixels = XCEngine::Math::Vector2(32.0f, 32.0f);
    sprite.textureKind = SceneViewportOverlaySpriteTextureKind::Camera;

    const auto iconsOnlyHud = BuildSceneViewportHudOverlayData(
        overlay,
        false,
        &frameData,
        true);

    EXPECT_TRUE(iconsOnlyHud.HasVisibleElements());
}

TEST(SceneViewportOverlayRenderer_Test, HitTestSceneViewportHudOverlaySkipsInvalidOrHiddenOverlay) {
    const SceneViewportHudOverlayHitResult invalidHit =
        HitTestSceneViewportHudOverlay({}, ImVec2(0.0f, 0.0f), ImVec2(200.0f, 200.0f), ImVec2(100.0f, 100.0f));
    EXPECT_EQ(invalidHit.kind, SceneViewportHudOverlayHitKind::None);

    SceneViewportOverlayData overlay = {};
    overlay.valid = true;
    overlay.cameraPosition = Vector3(0.0f, 0.0f, -5.0f);
    overlay.cameraForward = Vector3::Forward();
    overlay.cameraRight = Vector3::Right();
    overlay.cameraUp = Vector3::Up();
    overlay.verticalFovDegrees = 60.0f;
    overlay.nearClipPlane = 0.03f;
    overlay.farClipPlane = 2000.0f;

    const SceneViewportHudOverlayHitResult hiddenHit =
        HitTestSceneViewportHudOverlay(
            BuildSceneViewportHudOverlayData(overlay, false),
            ImVec2(0.0f, 0.0f),
            ImVec2(200.0f, 200.0f),
            ImVec2(100.0f, 100.0f));
    EXPECT_EQ(hiddenHit.kind, SceneViewportHudOverlayHitKind::None);
}