#include <gtest/gtest.h>

#include <XCEngine/UI/Runtime/UIScreenDocumentHost.h>
#include <XCEngine/UI/Runtime/UIScreenPlayer.h>

#include <chrono>
#include <filesystem>
#include <fstream>
#include <limits>
#include <string>

namespace {

using XCEngine::UI::UIDrawCommand;
using XCEngine::UI::UIDrawCommandType;
using XCEngine::UI::UIDrawData;
using XCEngine::UI::UIDrawList;
using XCEngine::UI::UIInputEvent;
using XCEngine::UI::UIInputEventType;
using XCEngine::UI::UIPoint;
using XCEngine::UI::UIRect;
using XCEngine::UI::Runtime::UIScreenAsset;
using XCEngine::UI::Runtime::UIScreenFrameInput;
using XCEngine::UI::Runtime::UIScreenPlayer;
using XCEngine::UI::Runtime::UIDocumentScreenHost;

namespace fs = std::filesystem;

class TempFileScope {
public:
    TempFileScope(std::string stem, std::string extension, std::string contents) {
        const auto uniqueId = std::to_string(
            std::chrono::steady_clock::now().time_since_epoch().count());
        m_path = fs::temp_directory_path() / (std::move(stem) + "_" + uniqueId + std::move(extension));
        std::ofstream output(m_path, std::ios::binary | std::ios::trunc);
        output << contents;
    }

    ~TempFileScope() {
        std::error_code errorCode = {};
        fs::remove(m_path, errorCode);
    }

    const fs::path& Path() const {
        return m_path;
    }

private:
    fs::path m_path = {};
};

UIScreenAsset BuildScreenAsset(const fs::path& viewPath, const char* screenId) {
    UIScreenAsset screen = {};
    screen.screenId = screenId;
    screen.documentPath = viewPath.string();
    return screen;
}

UIScreenFrameInput BuildInputState(std::uint64_t frameIndex = 1u) {
    UIScreenFrameInput input = {};
    input.viewportRect = UIRect(0.0f, 0.0f, 520.0f, 340.0f);
    input.frameIndex = frameIndex;
    input.focused = true;
    return input;
}

const UIDrawCommand* FindTextCommand(
    const UIDrawData& drawData,
    const std::string& text) {
    for (const UIDrawList& drawList : drawData.GetDrawLists()) {
        for (const UIDrawCommand& command : drawList.GetCommands()) {
            if (command.type == UIDrawCommandType::Text &&
                command.text == text) {
                return &command;
            }
        }
    }

    return nullptr;
}

std::size_t CountCommandsOfType(
    const UIDrawData& drawData,
    UIDrawCommandType type) {
    std::size_t count = 0u;
    for (const UIDrawList& drawList : drawData.GetDrawLists()) {
        for (const UIDrawCommand& command : drawList.GetCommands()) {
            if (command.type == type) {
                ++count;
            }
        }
    }
    return count;
}

bool RectContainsPoint(const UIRect& rect, const UIPoint& point) {
    return point.x >= rect.x &&
        point.x <= rect.x + rect.width &&
        point.y >= rect.y &&
        point.y <= rect.y + rect.height;
}

bool TryFindSmallestFilledRectContainingPoint(
    const UIDrawData& drawData,
    const UIPoint& point,
    UIRect& outRect) {
    bool found = false;
    float bestArea = (std::numeric_limits<float>::max)();

    for (const UIDrawList& drawList : drawData.GetDrawLists()) {
        for (const UIDrawCommand& command : drawList.GetCommands()) {
            if (command.type != UIDrawCommandType::FilledRect ||
                !RectContainsPoint(command.rect, point)) {
                continue;
            }

            const float area = command.rect.width * command.rect.height;
            if (!found || area < bestArea) {
                outRect = command.rect;
                bestArea = area;
                found = true;
            }
        }
    }

    return found;
}

bool TryFindFilledRectForText(
    const UIDrawData& drawData,
    const std::string& text,
    UIRect& outRect) {
    const UIDrawCommand* textCommand = FindTextCommand(drawData, text);
    return textCommand != nullptr &&
        TryFindSmallestFilledRectContainingPoint(drawData, textCommand->position, outRect);
}

UIPoint GetRectCenter(const UIRect& rect) {
    return UIPoint(rect.x + rect.width * 0.5f, rect.y + rect.height * 0.5f);
}

} // namespace

TEST(UIRuntimeScrollViewTest, ScrollViewClipsOverflowingChildrenAndPersistsWheelOffset) {
    TempFileScope viewFile(
        "xcui_runtime_scroll_view",
        ".xcui",
        "<View name=\"Scroll View Test\">\n"
        "  <Column padding=\"18\" gap=\"10\">\n"
        "    <Card title=\"Console\" subtitle=\"Scroll smoke\" height=\"200\">\n"
        "      <ScrollView id=\"log-scroll\" height=\"fill\">\n"
        "        <Column gap=\"8\">\n"
        "          <Text text=\"Line 01\" />\n"
        "          <Text text=\"Line 02\" />\n"
        "          <Text text=\"Line 03\" />\n"
        "          <Text text=\"Line 04\" />\n"
        "          <Text text=\"Line 05\" />\n"
        "          <Text text=\"Line 06\" />\n"
        "          <Text text=\"Line 07\" />\n"
        "          <Text text=\"Line 08\" />\n"
        "          <Text text=\"Line 09\" />\n"
        "          <Text text=\"Line 10\" />\n"
        "          <Text text=\"Line 11\" />\n"
        "          <Text text=\"Line 12\" />\n"
        "        </Column>\n"
        "      </ScrollView>\n"
        "    </Card>\n"
        "  </Column>\n"
        "</View>\n");
    UIDocumentScreenHost host = {};
    UIScreenPlayer player(host);

    ASSERT_TRUE(player.Load(BuildScreenAsset(viewFile.Path(), "runtime.scroll.view")));

    UIScreenFrameInput firstInput = BuildInputState(1u);
    const auto& firstFrame = player.Update(firstInput);
    const auto* line01Before = FindTextCommand(firstFrame.drawData, "Line 01");
    ASSERT_NE(line01Before, nullptr);
    EXPECT_GT(CountCommandsOfType(firstFrame.drawData, UIDrawCommandType::PushClipRect), 0u);
    EXPECT_GT(CountCommandsOfType(firstFrame.drawData, UIDrawCommandType::PopClipRect), 0u);

    UIScreenFrameInput secondInput = BuildInputState(2u);
    UIInputEvent wheelEvent = {};
    wheelEvent.type = UIInputEventType::PointerWheel;
    wheelEvent.position = UIPoint(90.0f, 130.0f);
    wheelEvent.wheelDelta = -120.0f;
    secondInput.events.push_back(wheelEvent);

    const auto& secondFrame = player.Update(secondInput);
    const auto* line01After = FindTextCommand(secondFrame.drawData, "Line 01");
    ASSERT_NE(line01After, nullptr);
    EXPECT_LT(line01After->position.y, line01Before->position.y);

    const auto& scrollDebug = host.GetScrollDebugSnapshot();
    EXPECT_NE(scrollDebug.lastTargetStateKey.find("/log-scroll"), std::string::npos);
    EXPECT_EQ(scrollDebug.lastResult, "Handled");
    EXPECT_EQ(scrollDebug.handledWheelEventCount, 1u);
    EXPECT_LT(scrollDebug.lastOffsetBefore, scrollDebug.lastOffsetAfter);

    UIScreenFrameInput thirdInput = BuildInputState(3u);
    const auto& thirdFrame = player.Update(thirdInput);
    const auto* line01Persisted = FindTextCommand(thirdFrame.drawData, "Line 01");
    ASSERT_NE(line01Persisted, nullptr);
    EXPECT_FLOAT_EQ(line01Persisted->position.y, line01After->position.y);
}

TEST(UIRuntimeScrollViewTest, WheelOutsideScrollViewportDoesNotChangeContentOffset) {
    TempFileScope viewFile(
        "xcui_runtime_scroll_view_outside",
        ".xcui",
        "<View name=\"Scroll Outside Test\">\n"
        "  <Column padding=\"18\" gap=\"10\">\n"
        "    <Card title=\"Console\" subtitle=\"Outside wheel should do nothing\" height=\"200\">\n"
        "      <ScrollView id=\"log-scroll\" height=\"fill\">\n"
        "        <Column gap=\"8\">\n"
        "          <Text text=\"Line 01\" />\n"
        "          <Text text=\"Line 02\" />\n"
        "          <Text text=\"Line 03\" />\n"
        "          <Text text=\"Line 04\" />\n"
        "          <Text text=\"Line 05\" />\n"
        "          <Text text=\"Line 06\" />\n"
        "          <Text text=\"Line 07\" />\n"
        "          <Text text=\"Line 08\" />\n"
        "          <Text text=\"Line 09\" />\n"
        "          <Text text=\"Line 10\" />\n"
        "          <Text text=\"Line 11\" />\n"
        "          <Text text=\"Line 12\" />\n"
        "        </Column>\n"
        "      </ScrollView>\n"
        "    </Card>\n"
        "    <Card title=\"Outside Area\" subtitle=\"not scrollable\" height=\"72\" />\n"
        "  </Column>\n"
        "</View>\n");
    UIDocumentScreenHost host = {};
    UIScreenPlayer player(host);

    ASSERT_TRUE(player.Load(BuildScreenAsset(viewFile.Path(), "runtime.scroll.outside")));

    UIScreenFrameInput firstInput = BuildInputState(1u);
    const auto& firstFrame = player.Update(firstInput);
    const auto* line01Before = FindTextCommand(firstFrame.drawData, "Line 01");
    ASSERT_NE(line01Before, nullptr);

    UIScreenFrameInput secondInput = BuildInputState(2u);
    UIInputEvent wheelEvent = {};
    wheelEvent.type = UIInputEventType::PointerWheel;
    wheelEvent.position = UIPoint(110.0f, 300.0f);
    wheelEvent.wheelDelta = -120.0f;
    secondInput.events.push_back(wheelEvent);

    const auto& secondFrame = player.Update(secondInput);
    const auto* line01After = FindTextCommand(secondFrame.drawData, "Line 01");
    ASSERT_NE(line01After, nullptr);
    EXPECT_FLOAT_EQ(line01After->position.y, line01Before->position.y);

    const auto& scrollDebug = host.GetScrollDebugSnapshot();
    EXPECT_EQ(scrollDebug.lastResult, "No hovered ScrollView");
    EXPECT_EQ(scrollDebug.handledWheelEventCount, 0u);
}

TEST(UIRuntimeScrollViewTest, NestedScrollViewRoutesWheelToDeepestHoveredTarget) {
    TempFileScope viewFile(
        "xcui_runtime_nested_scroll_view",
        ".xcui",
        "<View name=\"Nested Scroll View Test\">\n"
        "  <Column padding=\"18\" gap=\"10\">\n"
        "    <ScrollView id=\"outer-scroll\" height=\"260\">\n"
        "      <Column gap=\"8\">\n"
        "        <Text text=\"Outer 01\" />\n"
        "        <Text text=\"Outer 02\" />\n"
        "        <Text text=\"Outer 03\" />\n"
        "        <Card title=\"Nested Panel\" subtitle=\"inner scroll host\" height=\"180\">\n"
        "          <ScrollView id=\"inner-scroll\" height=\"fill\">\n"
        "            <Column gap=\"8\">\n"
        "              <Text text=\"Inner 01\" />\n"
        "              <Text text=\"Inner 02\" />\n"
        "              <Text text=\"Inner 03\" />\n"
        "              <Text text=\"Inner 04\" />\n"
        "              <Text text=\"Inner 05\" />\n"
        "              <Text text=\"Inner 06\" />\n"
        "              <Text text=\"Inner 07\" />\n"
        "              <Text text=\"Inner 08\" />\n"
        "              <Text text=\"Inner 09\" />\n"
        "              <Text text=\"Inner 10\" />\n"
        "              <Text text=\"Inner 11\" />\n"
        "              <Text text=\"Inner 12\" />\n"
        "            </Column>\n"
        "          </ScrollView>\n"
        "        </Card>\n"
        "        <Text text=\"Outer 04\" />\n"
        "        <Text text=\"Outer 05\" />\n"
        "        <Text text=\"Outer 06\" />\n"
        "        <Text text=\"Outer 07\" />\n"
        "        <Text text=\"Outer 08\" />\n"
        "        <Text text=\"Outer 09\" />\n"
        "      </Column>\n"
        "    </ScrollView>\n"
        "  </Column>\n"
        "</View>\n");
    UIDocumentScreenHost host = {};
    UIScreenPlayer player(host);

    ASSERT_TRUE(player.Load(BuildScreenAsset(viewFile.Path(), "runtime.scroll.nested")));

    UIScreenFrameInput firstInput = BuildInputState(1u);
    const auto& firstFrame = player.Update(firstInput);
    const auto* innerBefore = FindTextCommand(firstFrame.drawData, "Inner 01");
    ASSERT_NE(innerBefore, nullptr);

    UIRect innerRect = {};
    ASSERT_TRUE(TryFindFilledRectForText(firstFrame.drawData, "Inner 01", innerRect));
    const UIPoint wheelPoint = GetRectCenter(innerRect);

    UIScreenFrameInput secondInput = BuildInputState(2u);
    UIInputEvent wheelEvent = {};
    wheelEvent.type = UIInputEventType::PointerWheel;
    wheelEvent.position = wheelPoint;
    wheelEvent.wheelDelta = -120.0f;
    secondInput.events.push_back(wheelEvent);

    const auto& secondFrame = player.Update(secondInput);
    const auto* innerAfter = FindTextCommand(secondFrame.drawData, "Inner 01");
    ASSERT_NE(innerAfter, nullptr);
    EXPECT_LT(innerAfter->position.y, innerBefore->position.y);

    const auto& scrollDebug = host.GetScrollDebugSnapshot();
    EXPECT_NE(scrollDebug.lastTargetStateKey.find("/inner-scroll"), std::string::npos);
    EXPECT_NE(scrollDebug.primaryTargetStateKey.find("/outer-scroll"), std::string::npos);
    EXPECT_EQ(scrollDebug.lastResult, "Handled");
    EXPECT_GT(scrollDebug.lastOverflow, 0.0f);
}