#include "Scene/RuntimeLoop.h"

#include <algorithm>

namespace XCEngine {
namespace Components {

namespace {

RuntimeLoop::Settings SanitizeSettings(RuntimeLoop::Settings settings) {
    if (settings.fixedDeltaTime <= 0.0f) {
        settings.fixedDeltaTime = 1.0f / 50.0f;
    }
    if (settings.maxFrameDeltaTime < 0.0f) {
        settings.maxFrameDeltaTime = 0.0f;
    }
    if (settings.maxFixedStepsPerFrame == 0) {
        settings.maxFixedStepsPerFrame = 1;
    }
    return settings;
}

} // namespace

RuntimeLoop::RuntimeLoop(Settings settings)
    : m_settings(SanitizeSettings(settings)) {
}

void RuntimeLoop::SetSettings(const Settings& settings) {
    m_settings = SanitizeSettings(settings);
}

void RuntimeLoop::Start(Scene* scene) {
    m_fixedAccumulator = 0.0f;
    m_paused = false;
    m_stepRequested = false;
    m_sceneRuntime.Start(scene);
}

void RuntimeLoop::Stop() {
    m_sceneRuntime.Stop();
    m_fixedAccumulator = 0.0f;
    m_paused = false;
    m_stepRequested = false;
}

void RuntimeLoop::ReplaceScene(Scene* scene) {
    m_sceneRuntime.ReplaceScene(scene);
    m_fixedAccumulator = 0.0f;
    m_stepRequested = false;
}

void RuntimeLoop::Tick(float deltaTime) {
    if (!IsRunning()) {
        return;
    }

    if (m_paused && !m_stepRequested) {
        return;
    }

    const float clampedDeltaTime = std::clamp(deltaTime, 0.0f, m_settings.maxFrameDeltaTime);
    m_fixedAccumulator += clampedDeltaTime;

    uint32_t fixedStepsExecuted = 0;
    while (m_fixedAccumulator >= m_settings.fixedDeltaTime &&
           fixedStepsExecuted < m_settings.maxFixedStepsPerFrame) {
        m_sceneRuntime.FixedUpdate(m_settings.fixedDeltaTime);
        m_fixedAccumulator -= m_settings.fixedDeltaTime;
        ++fixedStepsExecuted;
    }

    m_sceneRuntime.Update(clampedDeltaTime);
    m_sceneRuntime.LateUpdate(clampedDeltaTime);
    m_stepRequested = false;
}

void RuntimeLoop::Pause() {
    if (!IsRunning()) {
        return;
    }

    m_paused = true;
    m_stepRequested = false;
}

void RuntimeLoop::Resume() {
    if (!IsRunning()) {
        return;
    }

    m_paused = false;
    m_stepRequested = false;
}

void RuntimeLoop::StepFrame() {
    if (!IsRunning()) {
        return;
    }

    m_paused = true;
    m_stepRequested = true;
}

} // namespace Components
} // namespace XCEngine