#include "TouchWindowBase.h"
#include <vector>
#include <cmath>

#ifndef TOUCH_COORD_TO_PIXEL
// TOUCH 输入单位是 1/100 英寸，通常使用这个宏转换为像素
#define TOUCH_COORD_TO_PIXEL(l) ((l) / 100)
#endif

TouchWindowBase::TouchWindowBase()
{
}

TouchWindowBase::~TouchWindowBase()
{
	StopInertia();
}

std::int64_t TouchWindowBase::NowMs() const
{
	using namespace std::chrono;
	return duration_cast<milliseconds>(steady_clock::now().time_since_epoch()).count();
}

void TouchWindowBase::AddTouchSample(LONG y)
{
	std::int64_t t = NowMs();
	m_samples.push_back({ t, y });

	// 保留时间窗口或最大条目数
	while (!m_samples.empty() && (t - m_samples.front().tms) > SAMPLE_WINDOW_MS)
		m_samples.pop_front();

	while ((int)m_samples.size() > MAX_SAMPLE_COUNT)
		m_samples.pop_front();
}

void TouchWindowBase::StartInertia(float velocityPxPerMs)
{
	if (m_inertiaActive)
		StopInertia();

	m_inertiaVelocityPxPerMs = velocityPxPerMs;
	if (std::abs(m_inertiaVelocityPxPerMs) < MIN_INERTIA_VELOCITY)
	{
		// 速度太小，不启动惯性
		m_inertiaActive = false;
		return;
	}

	m_lastInertiaTms = NowMs();
	m_inertiaTimerId = ::SetTimer(m_hWnd, INERTIA_TIMER_ID, INERTIA_TIMER_INTERVAL_MS, NULL);
	m_inertiaActive = (m_inertiaTimerId != 0);
}

void TouchWindowBase::StopInertia()
{
	if (m_inertiaActive && m_inertiaTimerId)
	{
		::KillTimer(m_hWnd, m_inertiaTimerId);
		m_inertiaTimerId = 0;
	}
	m_inertiaActive = false;
	m_inertiaVelocityPxPerMs = 0.0f;
}

LRESULT TouchWindowBase::HandleMessage(UINT uMsg, WPARAM wParam, LPARAM lParam)
{
	switch (uMsg)
	{
		case WM_CREATE:
			// 注册接收触摸（移除：由外部窗口统一注册，避免重复注册）
			// ::RegisterTouchWindow(m_hWnd, 0);
			break;

		case WM_TOUCH:
		{
			UINT cInputs = LOWORD(wParam);
			std::vector<TOUCHINPUT> inputs(cInputs);
			if (GetTouchInputInfo((HTOUCHINPUT)lParam, cInputs, inputs.data(), sizeof(TOUCHINPUT)))
			{
				for (UINT i = 0; i < cInputs; ++i)
				{
					TOUCHINPUT& ti = inputs[i];
					POINT pt;
					pt.x = TOUCH_COORD_TO_PIXEL(ti.x);
					pt.y = TOUCH_COORD_TO_PIXEL(ti.y);

					// 把屏幕坐标转换为目标 paint 窗口客户区坐标
					HWND target = m_hWndPaint ? m_hWndPaint : m_hWnd;
					ScreenToClient(target, &pt);

					// 触摸按下
					if (ti.dwFlags & TOUCHEVENTF_DOWN)
					{
						// 停止可能正在进行的惯性
						StopInertia();

						m_touchDown = true;
						m_lastY = pt.y;
						m_accumWheel = 0;
						m_samples.clear();
						AddTouchSample(pt.y);

						// 保存最后触摸点（用于惯性期间发送位置）
						m_lastTouchPt = pt;

						::PostMessage(target, WM_LBUTTONDOWN, MK_LBUTTON, MAKELPARAM(pt.x, pt.y));
						::SetCapture(target);
					}
					// 触摸移动
					else if (ti.dwFlags & TOUCHEVENTF_MOVE)
					{
						if (m_touchDown)
						{
							LONG dy = pt.y - m_lastY; // 按手机习惯：手指上滑(坐标减小) -> 负增量
							m_lastY = pt.y;

							AddTouchSample(pt.y);

							int wheelUnits = static_cast<int>(dy * PIXEL_TO_WHEEL);
							m_accumWheel += wheelUnits;

							// 更新最后触摸点（用于惯性期间发送位置）
							m_lastTouchPt = pt;

							// 每当累积达到 WHEEL_DELTA 就发送一次 WM_MOUSEWHEEL
							while (abs(m_accumWheel) >= WHEEL_DELTA)
							{
								int sendDelta = (m_accumWheel > 0) ? WHEEL_DELTA : -WHEEL_DELTA;
								m_accumWheel -= sendDelta;

								WPARAM wParamWheel = (WPARAM)(((DWORD)sendDelta) << 16);
								LPARAM lParamPos = MAKELPARAM(pt.x, pt.y);
								::PostMessage(target, WM_MOUSEWHEEL, wParamWheel, lParamPos);
							}

							// 仍然发送鼠标移动，兼容需要拖拽的控件
							::PostMessage(target, WM_MOUSEMOVE, MK_LBUTTON, MAKELPARAM(pt.x, pt.y));
						}
					}
					// 触摸抬起
					else if (ti.dwFlags & TOUCHEVENTF_UP)
					{
						if (m_touchDown)
						{
							// 计算速度（px/ms）
							float velocityPxPerMs = 0.0f;
							if (m_samples.size() >= 2)
							{
								TouchSample first = m_samples.front();
								TouchSample last = m_samples.back();
								std::int64_t dt = last.tms - first.tms;
								if (dt > 0)
								{
									// 与 MOVE 中 dy 方向保持一致：last - first
									velocityPxPerMs = static_cast<float>(last.y - first.y) / static_cast<float>(dt);
								}
							}

							m_touchDown = false;
							// 保存最后触摸点（确保惯性期间有位置可用）
							m_lastTouchPt = pt;
							m_lastY = 0;
							m_accumWheel = 0;
							m_samples.clear();

							::PostMessage(target, WM_LBUTTONUP, 0, MAKELPARAM(pt.x, pt.y));
							::ReleaseCapture();

							// 启动惯性滚动（如果速度足够大）
							StartInertia(velocityPxPerMs);
						}
					}
				}
				CloseTouchInputHandle((HTOUCHINPUT)lParam);
			}
			else
			{
				// 可添加日志：GetTouchInputInfo 失败
			}
			return 0; // 已处理
		}

		case WM_TIMER:
		{
			if (wParam == INERTIA_TIMER_ID && m_inertiaActive)
			{
				HWND target = m_hWndPaint ? m_hWndPaint : m_hWnd;
				std::int64_t now = NowMs();
				std::int64_t dt = now - m_lastInertiaTms;
				if (dt <= 0) dt = INERTIA_TIMER_INTERVAL_MS;
				m_lastInertiaTms = now;

				// 计算本帧移动的像素
				float pixels = m_inertiaVelocityPxPerMs * static_cast<float>(dt);

				// 将像素转换为 wheel units 累积并发送
				int wheelUnits = static_cast<int>(pixels * PIXEL_TO_WHEEL);
				m_accumWheel += wheelUnits;

				// 使用保存的最后触摸点（target 的客户区坐标）
				POINT pt = m_lastTouchPt;
				LPARAM lParamPos = MAKELPARAM(pt.x, pt.y);

				while (abs(m_accumWheel) >= WHEEL_DELTA)
				{
					int sendDelta = (m_accumWheel > 0) ? WHEEL_DELTA : -WHEEL_DELTA;
					m_accumWheel -= sendDelta;
					WPARAM wParamWheel = (WPARAM)(((DWORD)sendDelta) << 16);
					::PostMessage(target, WM_MOUSEWHEEL, wParamWheel, lParamPos);
				}

				// 衰减速度（指数衰减）
				// velocity *= pow(INERTIA_DECAY_PER_MS, dt)
				m_inertiaVelocityPxPerMs *= std::pow(INERTIA_DECAY_PER_MS, static_cast<float>(dt));

				// 停止条件
				if (std::abs(m_inertiaVelocityPxPerMs) < MIN_INERTIA_VELOCITY)
				{
					StopInertia();
				}

				return 0;
			}
			break;
		}

		case WM_DESTROY:
			StopInertia();
			break;
	}

	// 若未处理，交给基类
	return CWindowWnd::HandleMessage(uMsg, wParam, lParam);
}