#include "PlotView.hpp"

#include <algorithm>
#include <cmath>
#include <limits>

#include "Utf8Util.hpp"

namespace jdi
{

	namespace
	{
		const int kTimeTickTarget = 8;			/**< 时间轴期望刻度数。 */
		const int kYTickTarget = 4;				/**< 幅值轴期望刻度数。 */
		const float kScrollBarThickness = 9.0f;	/**< 滚动条宽度（逻辑像素）。 */
		const float kLanePadding = 8.0f;		/**< 网格内边距。 */
		const float kAxisLabelGap = 10.0f;		/**< 轴上文字与轴线的间距。 */
		const size_t kMaxPolylinePoints = 20000;/**< 单条折线最大顶点数。 */
		const size_t kMaxScatterPoints = 2500;	/**< 单条散点最大绘制点数。 */
		const float kMinScatterRadius = 1.6f;	/**< 散点最小半径（逻辑像素）。 */
		const float kMaxScatterRadius = 4.0f;	/**< 散点最大半径（逻辑像素）。 */
		const double kMinTimeSpan = 1.0e-12;	/**< 允许的最小时间跨度。 */

		/**
		 * @brief 将数值限制到合法区间。
		 * @param [IN] value 输入值。
		 * @param [IN] low 下限。
		 * @param [IN] high 上限。
		 * @return 限制后的数值。
		 */
		double ClampDouble(double value, double low, double high)
		{
			if (value < low)
			{
				return low;
			}
			if (value > high)
			{
				return high;
			}
			return value;
		}
	}

	PlotView::PlotView() = default;

	void PlotView::Setup(const UiFonts* fonts, const Theme* theme)
	{
		m_fonts = fonts;
		m_theme = theme;
	}

	void PlotView::SetDocument(SignalSet* document)
	{
		m_document = document;
		m_laneScroll = 0.0f;
		m_cursorVisible = false;
		m_cursorPinned = false;
		m_hoverLane = -1;
		if (m_document != nullptr && m_document->IsLoaded())
		{
			FitTime();
		}
	}

	void PlotView::SetScale(float scale)
	{
		m_scale = (scale > 0.1f) ? scale : 1.0f;
	}

	void PlotView::Layout(const gd::RectF& area)
	{
		m_area = area;

		m_yAxisWidth = 74.0f * m_scale;
		m_timeAxisHeight = 32.0f * m_scale;
		m_laneGap = 6.0f * m_scale;
		m_minLaneHeight = 46.0f * m_scale;

		const float topPadding = 6.0f * m_scale;
		const float availHeight = std::max(0.0f, area.Height - m_timeAxisHeight - topPadding);

		// 预估是否需要纵向滚动条：仅取决于网格数量与最小网格高度。
		std::size_t laneCount = 0;
		if (m_document != nullptr && m_document->IsLoaded())
		{
			laneCount = m_document->Lanes().size();
		}
		if (laneCount > 0)
		{
			const float needed = static_cast<float>(laneCount) * m_minLaneHeight +
			                     m_laneGap * static_cast<float>(laneCount - 1);
			m_scrollBarVisible = (needed > availHeight);
		}
		else
		{
			m_scrollBarVisible = false;
		}

		const float rightReserve = m_scrollBarVisible ? (kScrollBarThickness * m_scale + 6.0f * m_scale)
		                                              : (6.0f * m_scale);
		const float plotWidth = std::max(0.0f, area.Width - m_yAxisWidth - rightReserve);

		m_plotRect = gd::RectF(area.X + m_yAxisWidth, area.Y + topPadding, plotWidth, availHeight);
		m_timeAxisRect = gd::RectF(m_plotRect.X, m_plotRect.Y + m_plotRect.Height, m_plotRect.Width,
		                           m_timeAxisHeight);
		m_scrollBarRect = gd::RectF(area.X + area.Width - kScrollBarThickness * m_scale - 3.0f * m_scale,
		                            m_plotRect.Y, kScrollBarThickness * m_scale, m_plotRect.Height);

		BuildLaneVisuals();
	}

	float PlotView::LaneContentHeight() const
	{
		return m_laneContentHeight;
	}

	void PlotView::ClampLaneScroll()
	{
		const float maxOffset = std::max(0.0f, m_laneContentHeight - m_plotRect.Height);
		m_laneScroll = ClampDouble(m_laneScroll, 0.0, maxOffset);
	}

	void PlotView::BuildLaneVisuals()
	{
		m_lanes.clear();
		if (m_document == nullptr || !m_document->IsLoaded())
		{
			m_laneContentHeight = 0.0f;
			return;
		}

		const std::vector<Lane>& lanes = m_document->Lanes();
		const std::size_t count = lanes.size();
		if (count == 0)
		{
			m_laneContentHeight = 0.0f;
			return;
		}

		const float gap = m_laneGap * m_scale;
		float laneHeight = (m_plotRect.Height - gap * static_cast<float>(count - 1)) /
		                   static_cast<float>(count);
		if (laneHeight < m_minLaneHeight * m_scale)
		{
			laneHeight = m_minLaneHeight * m_scale;
		}
		m_laneContentHeight = laneHeight * static_cast<float>(count) + gap * static_cast<float>(count - 1);
		ClampLaneScroll();

		m_lanes.resize(count);
		for (std::size_t index = 0; index < count; ++index)
		{
			LaneVisual& visual = m_lanes[index];
			visual.rect = gd::RectF(m_plotRect.X,
			                        m_plotRect.Y + static_cast<float>(index) * (laneHeight + gap) - m_laneScroll,
			                        m_plotRect.Width, laneHeight);
			m_document->ComputeLaneRange(static_cast<int>(index), visual.yMin, visual.yMax);
			if (!(visual.yMax > visual.yMin))
			{
				visual.yMin = 0.0;
				visual.yMax = 1.0;
			}

			visual.empty = true;
			for (const int signalIndex : lanes[index].signalIndices)
			{
				if (signalIndex >= 0 && signalIndex < static_cast<int>(m_document->Signals().size()) &&
				    m_document->Signals()[static_cast<std::size_t>(signalIndex)].visible)
				{
					visual.empty = false;
					break;
				}
			}
		}
	}

	float PlotView::TimeToX(double time) const
	{
		const double span = m_viewMax - m_viewMin;
		if (!(span > 0.0) || m_plotRect.Width <= 0.0f)
		{
			return m_plotRect.X;
		}
		return m_plotRect.X + static_cast<float>((time - m_viewMin) / span * m_plotRect.Width);
	}

	double PlotView::XToTime(float x) const
	{
		if (m_plotRect.Width <= 0.0f)
		{
			return m_viewMin;
		}
		const double ratio = static_cast<double>(x - m_plotRect.X) / static_cast<double>(m_plotRect.Width);
		return m_viewMin + ratio * (m_viewMax - m_viewMin);
	}

	float PlotView::ValueToY(double value, const LaneVisual& lane) const
	{
		const double span = lane.yMax - lane.yMin;
		if (!(span > 0.0))
		{
			return lane.rect.Y + lane.rect.Height * 0.5f;
		}

		double ratio = (value - lane.yMin) / span;
		ratio = ClampDouble(ratio, -50.0, 50.0);
		return lane.rect.Y + lane.rect.Height * static_cast<float>(1.0 - ratio);
	}

	double PlotView::YToValue(float y, const LaneVisual& lane) const
	{
		if (lane.rect.Height <= 0.0f)
		{
			return lane.yMin;
		}
		const double ratio = 1.0 - static_cast<double>(y - lane.rect.Y) / static_cast<double>(lane.rect.Height);
		return lane.yMin + ratio * (lane.yMax - lane.yMin);
	}

	int PlotView::LaneAtY(int y) const
	{
		const float fy = static_cast<float>(y);
		for (std::size_t index = 0; index < m_lanes.size(); ++index)
		{
			const gd::RectF& rect = m_lanes[index].rect;
			if (fy >= rect.Y && fy <= rect.Y + rect.Height)
			{
				return static_cast<int>(index);
			}
		}
		return -1;
	}

	void PlotView::ClampTimeView()
	{
		if (m_document == nullptr || !m_document->IsLoaded())
		{
			return;
		}

		double span = m_viewMax - m_viewMin;
		if (!(span > 0.0))
		{
			span = kMinTimeSpan;
		}

		const double dataSpan = std::max(m_document->MaxTime() - m_document->MinTime(), kMinTimeSpan);
		const double pad = span * 2.0;
		const double minAllowed = m_document->MinTime() - pad;
		const double maxAllowed = m_document->MaxTime() + pad;

		if (m_viewMin < minAllowed)
		{
			m_viewMin = minAllowed;
			m_viewMax = m_viewMin + span;
		}
		if (m_viewMax > maxAllowed)
		{
			m_viewMax = maxAllowed;
			m_viewMin = m_viewMax - span;
		}
		(void)dataSpan;
	}

	void PlotView::ZoomTimeAt(double factor, double anchorTime)
	{
		if (m_document == nullptr || !m_document->IsLoaded() || !(factor > 0.0))
		{
			return;
		}

		const double dataSpan = std::max(m_document->MaxTime() - m_document->MinTime(), kMinTimeSpan);
		const double minSpan = dataSpan * 1.0e-9;
		const double maxSpan = dataSpan * 100.0;

		const double span = m_viewMax - m_viewMin;
		double newSpan = span / factor;
		newSpan = ClampDouble(newSpan, minSpan, maxSpan);

		const double ratio = (span > 0.0) ? (anchorTime - m_viewMin) / span : 0.5;
		m_viewMin = anchorTime - ratio * newSpan;
		m_viewMax = m_viewMin + newSpan;
		ClampTimeView();
	}

	void PlotView::ZoomTimeStep(double factor)
	{
		const double anchor = (m_viewMin + m_viewMax) * 0.5;
		ZoomTimeAt(factor, anchor);
	}

	void PlotView::PanTimeByFraction(double fraction)
	{
		const double span = m_viewMax - m_viewMin;
		const double delta = span * fraction;
		m_viewMin += delta;
		m_viewMax += delta;
		ClampTimeView();
	}

	void PlotView::ScrollLanesByFraction(double fraction)
	{
		m_laneScroll += static_cast<float>(fraction * static_cast<double>(m_laneContentHeight));
		ClampLaneScroll();
	}

	void PlotView::FitTime()
	{
		if (m_document == nullptr || !m_document->IsLoaded())
		{
			m_viewMin = 0.0;
			m_viewMax = 1.0;
			return;
		}

		m_viewMin = m_document->MinTime();
		m_viewMax = m_document->MaxTime();
		if (!(m_viewMax - m_viewMin > 0.0))
		{
			const double center = m_viewMin;
			const double padding = std::max(1.0e-6, std::fabs(center) * 0.01);
			m_viewMin = center - padding;
			m_viewMax = center + padding;
		}
	}

	void PlotView::FitAll()
	{
		FitTime();
		m_laneScroll = 0.0f;
		if (m_document != nullptr)
		{
			for (Lane& lane : m_document->Lanes())
			{
				lane.autoRange = true;
			}
		}
	}

	void PlotView::ClearCursor()
	{
		m_cursorVisible = false;
		m_cursorPinned = false;
	}

	bool PlotView::HitTest(int x, int y) const
	{
		return UiPointInRect(m_area, static_cast<float>(x), static_cast<float>(y));
	}

	HCURSOR PlotView::QueryCursor(int x, int y) const
	{
		switch (m_dragMode)
		{
		case PlotDragMode::PAN_TIME:
		case PlotDragMode::BOX_ZOOM:
			return LoadCursorW(nullptr, IDC_SIZEALL);
		case PlotDragMode::ZOOM_Y:
		case PlotDragMode::SCROLL_LANES:
			return LoadCursorW(nullptr, IDC_SIZENS);
		default:
			break;
		}

		if (m_scrollBarVisible && UiPointInRect(m_scrollBarRect, static_cast<float>(x), static_cast<float>(y)))
		{
			return LoadCursorW(nullptr, IDC_SIZENS);
		}
		if (static_cast<float>(x) < m_plotRect.X && UiPointInRect(m_area, static_cast<float>(x), static_cast<float>(y)))
		{
			if (LaneAtY(y) >= 0)
			{
				return LoadCursorW(nullptr, IDC_SIZENS);
			}
		}
		if (UiPointInRect(m_plotRect, static_cast<float>(x), static_cast<float>(y)))
		{
			return LoadCursorW(nullptr, IDC_CROSS);
		}
		return nullptr;
	}

	bool PlotView::OnMouseMove(int x, int y)
	{
		if (m_document == nullptr || !m_document->IsLoaded())
		{
			return false;
		}

		const float fx = static_cast<float>(x);
		const float fy = static_cast<float>(y);

		switch (m_dragMode)
		{
		case PlotDragMode::PAN_TIME:
		{
			if (m_plotRect.Width <= 0.0f)
			{
				return false;
			}
			const double span = m_viewMax - m_viewMin;
			const double delta = -static_cast<double>(x - m_dragLastX) / static_cast<double>(m_plotRect.Width) * span;
			m_viewMin += delta;
			m_viewMax += delta;
			ClampTimeView();
			m_dragLastX = x;
			m_dragLastY = y;
			if (std::abs(x - m_dragStartX) > 3 || std::abs(y - m_dragStartY) > 3)
			{
				m_dragMoved = true;
			}
			return true;
		}
		case PlotDragMode::ZOOM_Y:
		{
			if (m_dragLane < 0 || m_dragLane >= static_cast<int>(m_lanes.size()))
			{
				return false;
			}
			const gd::RectF& rect = m_lanes[static_cast<std::size_t>(m_dragLane)].rect;
			if (rect.Height <= 0.0f)
			{
				return false;
			}

			// 上拖放大、下拖缩小，并保持按下点处的幅值不动。
			const double travel = static_cast<double>(m_dragStartY - y) / static_cast<double>(rect.Height);
			const double factor = std::exp(travel * 2.0);
			const double span = m_dragStartYMax - m_dragStartYMin;
			if (!(span > 0.0))
			{
				return false;
			}

			double newSpan = span / factor;
			const double dataSpan = std::max(std::fabs(m_dragStartYMax), std::fabs(m_dragStartYMin));
			const double minSpan = std::max(dataSpan * 1.0e-9, 1.0e-12);
			newSpan = ClampDouble(newSpan, minSpan, dataSpan * 100.0 + 1.0);

			Lane& lane = m_document->Lanes()[static_cast<std::size_t>(m_dragLane)];
			lane.autoRange = false;
			lane.yMin = m_dragAnchorValue - m_dragAnchorRatio * newSpan;
			lane.yMax = lane.yMin + newSpan;
			if (std::abs(y - m_dragStartY) > 2)
			{
				m_dragMoved = true;
			}
			return true;
		}
		case PlotDragMode::BOX_ZOOM:
		{
			const float left = static_cast<float>(std::min(x, m_dragStartX));
			const float top = static_cast<float>(std::min(y, m_dragStartY));
			m_boxRect = gd::RectF(left, top, static_cast<float>(std::abs(x - m_dragStartX)),
			                      static_cast<float>(std::abs(y - m_dragStartY)));
			m_dragMoved = true;
			return true;
		}
		case PlotDragMode::SCROLL_LANES:
		{
			if (m_plotRect.Height <= 0.0f || m_laneContentHeight <= m_plotRect.Height)
			{
				return false;
			}
			const double travel = static_cast<double>(y - m_dragLastY) / static_cast<double>(m_plotRect.Height);
			m_laneScroll += static_cast<float>(travel * m_laneContentHeight);
			ClampLaneScroll();
			m_dragLastY = y;
			m_dragMoved = true;
			return true;
		}
		case PlotDragMode::NONE:
		default:
			break;
		}

		bool changed = false;

		const int lane = LaneAtY(y);
		if (lane != m_hoverLane)
		{
			m_hoverLane = lane;
			changed = true;
		}

		const bool insidePlot = UiPointInRect(m_plotRect, fx, fy);
		if (insidePlot && !m_cursorPinned)
		{
			const double time = XToTime(fx);
			if (!m_cursorVisible || std::fabs(time - m_cursorTime) > 0.0)
			{
				m_cursorTime = time;
				m_cursorVisible = true;
				changed = true;
			}
		}
		return changed;
	}

	bool PlotView::OnLButtonDown(int x, int y)
	{
		if (m_document == nullptr || !m_document->IsLoaded())
		{
			return false;
		}

		m_dragStartX = x;
		m_dragStartY = y;
		m_dragLastX = x;
		m_dragLastY = y;
		m_dragMoved = false;
		m_dragStartViewMin = m_viewMin;
		m_dragStartViewMax = m_viewMax;

		if (m_scrollBarVisible && UiPointInRect(m_scrollBarRect, static_cast<float>(x), static_cast<float>(y)))
		{
			m_dragMode = PlotDragMode::SCROLL_LANES;
			return true;
		}

		const int laneIndex = LaneAtY(y);
		if (laneIndex < 0)
		{
			m_dragMode = PlotDragMode::NONE;
			return false;
		}

		if (static_cast<float>(x) < m_plotRect.X)
		{
			m_dragMode = PlotDragMode::ZOOM_Y;
			m_dragLane = laneIndex;

			const LaneVisual& visual = m_lanes[static_cast<std::size_t>(laneIndex)];
			Lane& lane = m_document->Lanes()[static_cast<std::size_t>(laneIndex)];
			lane.autoRange = false;
			lane.yMin = visual.yMin;
			lane.yMax = visual.yMax;

			m_dragStartYMin = visual.yMin;
			m_dragStartYMax = visual.yMax;
			m_dragAnchorValue = YToValue(static_cast<float>(y), visual);
			const double span = visual.yMax - visual.yMin;
			m_dragAnchorRatio = (span > 0.0) ? (visual.yMax - m_dragAnchorValue) / span : 0.5;
			return true;
		}

		if (UiPointInRect(m_plotRect, static_cast<float>(x), static_cast<float>(y)))
		{
			m_dragMode = PlotDragMode::PAN_TIME;
			return true;
		}

		m_dragMode = PlotDragMode::NONE;
		return false;
	}

	bool PlotView::OnLButtonUp(int x, int y)
	{
		bool changed = (m_dragMode != PlotDragMode::NONE);

		if (m_dragMode == PlotDragMode::PAN_TIME && !m_dragMoved &&
		    UiPointInRect(m_plotRect, static_cast<float>(x), static_cast<float>(y)))
		{
			const double time = XToTime(static_cast<float>(x));
			if (m_cursorPinned && std::fabs(time - m_cursorTime) < 1.0e-12)
			{
				m_cursorPinned = false;
				m_cursorVisible = false;
			}
			else
			{
				m_cursorTime = time;
				m_cursorVisible = true;
				m_cursorPinned = true;
			}
			changed = true;
		}

		m_dragMode = PlotDragMode::NONE;
		m_dragLane = -1;
		m_dragMoved = false;
		return changed;
	}

	bool PlotView::OnRButtonDown(int x, int y)
	{
		if (m_document == nullptr || !m_document->IsLoaded())
		{
			return false;
		}
		if (!UiPointInRect(m_plotRect, static_cast<float>(x), static_cast<float>(y)))
		{
			return false;
		}

		m_dragMode = PlotDragMode::BOX_ZOOM;
		m_dragStartX = x;
		m_dragStartY = y;
		m_dragLastX = x;
		m_dragLastY = y;
		m_dragMoved = false;
		m_dragLane = LaneAtY(y);
		m_boxRect = gd::RectF(static_cast<float>(x), static_cast<float>(y), 0.0f, 0.0f);
		return true;
	}

	bool PlotView::OnRButtonUp(int x, int y)
	{
		if (m_dragMode != PlotDragMode::BOX_ZOOM)
		{
			return false;
		}

		const bool moved = m_dragMoved;
		const int laneIndex = m_dragLane;
		const gd::RectF box = m_boxRect;

		m_dragMode = PlotDragMode::NONE;
		m_dragMoved = false;
		m_dragLane = -1;

		if (!moved || box.Width < 6.0f * m_scale)
		{
			// 未形成有效框：清除已固定光标。
			if (!m_cursorPinned)
			{
				m_cursorVisible = false;
			}
			return true;
		}

		double timeA = XToTime(box.X);
		double timeB = XToTime(box.X + box.Width);
		if (timeB < timeA)
		{
			std::swap(timeA, timeB);
		}
		if (timeB - timeA > 0.0)
		{
			m_viewMin = timeA;
			m_viewMax = timeB;
			ClampTimeView();
		}

		if (laneIndex >= 0 && laneIndex < static_cast<int>(m_lanes.size()) &&
		    box.Height > 12.0f * m_scale)
		{
			const LaneVisual& visual = m_lanes[static_cast<std::size_t>(laneIndex)];
			const double valueTop = YToValue(box.Y, visual);
			const double valueBottom = YToValue(box.Y + box.Height, visual);
			if (std::fabs(valueTop - valueBottom) > 0.0)
			{
				Lane& lane = m_document->Lanes()[static_cast<std::size_t>(laneIndex)];
				lane.autoRange = false;
				lane.yMin = std::min(valueTop, valueBottom);
				lane.yMax = std::max(valueTop, valueBottom);
			}
		}
		(void)y;
		return true;
	}

	bool PlotView::OnMouseWheel(int x, int y, int delta, bool ctrl, bool shift, bool alt)
	{
		if (m_document == nullptr || !m_document->IsLoaded() || delta == 0)
		{
			return false;
		}

		const double notches = static_cast<double>(delta) / 120.0;

		if (alt)
		{
			m_laneScroll -= static_cast<float>(notches * 48.0 * m_scale);
			ClampLaneScroll();
			return true;
		}

		if (shift)
		{
			const double span = m_viewMax - m_viewMin;
			const double sweep = -notches * span * 0.15;
			m_viewMin += sweep;
			m_viewMax += sweep;
			ClampTimeView();
			return true;
		}

		if (ctrl)
		{
			int laneIndex = LaneAtY(y);
			if (laneIndex < 0)
			{
				laneIndex = m_hoverLane;
			}
			if (laneIndex < 0 || laneIndex >= static_cast<int>(m_lanes.size()))
			{
				return false;
			}

			const LaneVisual& visual = m_lanes[static_cast<std::size_t>(laneIndex)];
			Lane& lane = m_document->Lanes()[static_cast<std::size_t>(laneIndex)];
			LaneVisual mutableVisual = visual;
			if (lane.autoRange)
			{
				lane.autoRange = false;
			}
			lane.yMin = visual.yMin;
			lane.yMax = visual.yMax;

			const double anchorValue = YToValue(static_cast<float>(y), mutableVisual);
			const double span = visual.yMax - visual.yMin;
			if (!(span > 0.0))
			{
				return false;
			}

			const double factor = std::pow(1.25, notches);
			double newSpan = span / factor;
			const double scaleRef = std::max(std::fabs(visual.yMax), std::fabs(visual.yMin));
			const double minSpan = std::max(scaleRef * 1.0e-9, 1.0e-12);
			newSpan = ClampDouble(newSpan, minSpan, scaleRef * 100.0 + 1.0);

			const double ratio = (visual.yMax - anchorValue) / span;
			lane.yMin = anchorValue - ratio * newSpan;
			lane.yMax = lane.yMin + newSpan;
			return true;
		}

		const double anchorTime = XToTime(static_cast<float>(x));
		ZoomTimeAt(std::pow(1.25, notches), anchorTime);
		return true;
	}

	bool PlotView::OnDoubleClick(int x, int y)
	{
		if (!UiPointInRect(m_area, static_cast<float>(x), static_cast<float>(y)))
		{
			return false;
		}
		FitAll();
		return true;
	}

	bool PlotView::OnMouseLeave()
	{
		bool changed = false;
		if (m_hoverLane != -1)
		{
			m_hoverLane = -1;
			changed = true;
		}
		if (!m_cursorPinned && m_cursorVisible)
		{
			m_cursorVisible = false;
			changed = true;
		}
		return changed;
	}

	void PlotView::BuildPolyline(const Signal& signal, const LaneVisual& lane, bool stepMode,
	                             std::vector<gd::PointF>& points, std::vector<std::size_t>& breaks) const
	{
		points.clear();
		breaks.clear();

		if (m_document == nullptr)
		{
			return;
		}

		const std::vector<double>& time = m_document->Time();
		const std::vector<double>& values = signal.values;
		const std::size_t count = std::min(time.size(), values.size());
		if (count == 0 || m_plotRect.Width <= 1.0f)
		{
			return;
		}

		std::size_t begin = 0;
		std::size_t end = count;

		if (m_document->TimeMonotonic())
		{
			const std::vector<double>::const_iterator first =
			    std::lower_bound(time.begin(), time.end(), m_viewMin);
			begin = static_cast<std::size_t>(first - time.begin());
			if (begin > 0)
			{
				--begin;
			}
			const std::vector<double>::const_iterator last = std::lower_bound(time.begin(), time.end(), m_viewMax);
			end = static_cast<std::size_t>(last - time.begin());
			if (end < count)
			{
				++end;
			}
		}

		if (end <= begin)
		{
			return;
		}

		std::size_t stride = 1;
		const std::size_t visibleCount = end - begin;
		if (visibleCount > kMaxPolylinePoints)
		{
			stride = (visibleCount + kMaxPolylinePoints - 1) / kMaxPolylinePoints;
		}

		const float limitTop = lane.rect.Y - lane.rect.Height * 4.0f;
		const float limitBottom = lane.rect.Y + lane.rect.Height * 5.0f;

		bool inSegment = false;
		double previousY = 0.0;

		for (std::size_t index = begin; index < end; index += stride)
		{
			const double t = time[index];
			const double value = values[index];
			if (!std::isfinite(t) || !std::isfinite(value))
			{
				inSegment = false;
				continue;
			}

			const float x = TimeToX(t);
			float y = ValueToY(value, lane);
			y = ClampDouble(y, limitTop, limitBottom);

			if (!inSegment)
			{
				breaks.push_back(points.size());
				points.push_back(gd::PointF(x, y));
				inSegment = true;
			}
			else if (stepMode)
			{
				points.push_back(gd::PointF(x, static_cast<float>(previousY)));
				points.push_back(gd::PointF(x, y));
			}
			else
			{
				points.push_back(gd::PointF(x, y));
			}

			previousY = y;
		}
	}

	void PlotView::Paint(gd::Graphics& g)
	{
		if (m_theme == nullptr || m_fonts == nullptr)
		{
			return;
		}

		UiFillRect(g, m_area, m_theme->plotBg);

		if (m_document == nullptr || !m_document->IsLoaded())
		{
			UiText(g, L"打开 CSV 文件以查看仿真数据波形", m_fonts->ui, m_area, m_theme->textMuted,
			       TextAlign::CENTER);
			return;
		}

		BuildLaneVisuals();

		const double span = m_viewMax - m_viewMin;
		const double timeStep = NiceStep((span > 0.0) ? span : 1.0, kTimeTickTarget);
		std::vector<double> timeTicks;
		BuildTicks(m_viewMin, m_viewMax, timeStep, timeTicks);

		// 波形区域边框。
		UiFillRect(g, m_plotRect, m_theme->cardBg);

		for (std::size_t index = 0; index < m_lanes.size(); ++index)
		{
			PaintLane(g, static_cast<int>(index), m_lanes[index], timeTicks, timeStep);
		}

		PaintTimeAxis(g, timeTicks, timeStep);
		PaintCursor(g, m_lanes);

		if (m_dragMode == PlotDragMode::BOX_ZOOM && m_dragMoved)
		{
			UiFillRect(g, m_boxRect, WithAlpha(m_theme->accent, 0x2A));
			UiDrawRoundRect(g, m_boxRect, 2.0f * m_scale, m_theme->accent, 1.0f);
		}

		PaintScrollBar(g);

		// 绘图区外框。
		gd::Pen borderPen(ToGdiColor(m_theme->border), 1.0f);
		g.DrawRectangle(&borderPen, m_plotRect.X, m_plotRect.Y, m_plotRect.Width, m_plotRect.Height);
	}

	void PlotView::PaintLane(gd::Graphics& g, int laneIndex, const LaneVisual& lane,
	                         const std::vector<double>& timeTicks, double timeStep)
	{
		const int saveState = g.Save();
		g.SetClip(gd::RectF(m_area.X, lane.rect.Y, m_area.Width, lane.rect.Height));

		// 悬停高亮。
		if (laneIndex == m_hoverLane && m_dragMode == PlotDragMode::NONE)
		{
			UiFillRect(g, lane.rect, MixColor(m_theme->cardBg, m_theme->accent, 0.035));
		}

		// 幅值网格线与标签。
		const double yStep = NiceStep(lane.yMax - lane.yMin, kYTickTarget);
		std::vector<double> yTicks;
		BuildTicks(lane.yMin, lane.yMax, yStep, yTicks);

		const bool showLabels = (lane.rect.Height >= 34.0f * m_scale);
		float lastLabelY = -1.0e9f;

		for (const double tick : yTicks)
		{
			const float y = ValueToY(tick, lane);
			if (y < lane.rect.Y - 1.0f || y > lane.rect.Y + lane.rect.Height + 1.0f)
			{
				continue;
			}

			const bool zeroLine = (tick == 0.0);
			UiDrawLine(g, lane.rect.X, y, lane.rect.X + lane.rect.Width, y,
			           zeroLine ? m_theme->gridStrong : m_theme->gridWeak, 1.0f);

			if (!showLabels || std::fabs(y - lastLabelY) < 15.0f * m_scale)
			{
				continue;
			}
			lastLabelY = y;

			const gd::RectF labelRect(m_area.X, y - 9.0f * m_scale, m_yAxisWidth - kAxisLabelGap * m_scale,
			                          18.0f * m_scale);
			UiText(g, FormatTick(tick, yStep), m_fonts->monoSmall, labelRect,
			       zeroLine ? m_theme->text : m_theme->textMuted, TextAlign::RIGHT);
		}

		// 时间网格线。
		for (const double tick : timeTicks)
		{
			const float x = TimeToX(tick);
			if (x < lane.rect.X || x > lane.rect.X + lane.rect.Width)
			{
				continue;
			}
			UiDrawLine(g, x, lane.rect.Y, x, lane.rect.Y + lane.rect.Height, m_theme->gridWeak, 1.0f);
		}

		// 波形绘制。
		if (m_document->Lanes()[static_cast<std::size_t>(laneIndex)].signalIndices.empty())
		{
			UiText(g, L"（空网格）", m_fonts->uiSmall, lane.rect, m_theme->textMuted, TextAlign::CENTER);
		}
		else
		{
			const int waveSave = g.Save();
			g.SetClip(lane.rect, gd::CombineModeIntersect);

			std::vector<gd::PointF> points;
			std::vector<std::size_t> breaks;

			for (const int signalIndex : m_document->Lanes()[static_cast<std::size_t>(laneIndex)].signalIndices)
			{
				if (signalIndex < 0 || signalIndex >= static_cast<int>(m_document->Signals().size()))
				{
					continue;
				}
				const Signal& signal = m_document->Signals()[static_cast<std::size_t>(signalIndex)];
				if (!signal.visible)
				{
					continue;
				}

				const bool stepMode = (signal.mode == DrawMode::STEP);
				BuildPolyline(signal, lane, stepMode, points, breaks);

				const bool drawLine = (signal.mode != DrawMode::SCATTER);
				const bool drawScatter = (signal.mode == DrawMode::SCATTER || signal.mode == DrawMode::LINE_SCATTER);

				if (drawLine && !breaks.empty())
				{
					gd::Pen pen(ToGdiColor(signal.color), signal.lineWidth * m_scale);
					pen.SetLineJoin(stepMode ? gd::LineJoinMiter : gd::LineJoinRound);
					pen.SetStartCap(gd::LineCapRound);
					pen.SetEndCap(gd::LineCapRound);

					for (std::size_t k = 0; k < breaks.size(); ++k)
					{
						const std::size_t start = breaks[k];
						const std::size_t stop = (k + 1 < breaks.size()) ? breaks[k + 1] : points.size();
						if (stop <= start + 1)
						{
							continue;
						}
						g.DrawLines(&pen, points.data() + start, static_cast<INT>(stop - start));
					}
				}

				if (drawScatter && !points.empty())
				{
					const float radius = static_cast<float>(
					    ClampDouble(std::max(1.0f, signal.lineWidth) * (kMinScatterRadius + 0.6f),
					                kMinScatterRadius, kMaxScatterRadius) *
					    m_scale);
					const std::size_t scatterStride = std::max<std::size_t>(1, points.size() / kMaxScatterPoints);
					gd::SolidBrush brush(ToGdiColor(signal.color));
					for (std::size_t k = 0; k < points.size(); k += scatterStride)
					{
						g.FillEllipse(&brush, points[k].X - radius, points[k].Y - radius, radius * 2.0f,
						              radius * 2.0f);
					}
				}
			}

			g.Restore(waveSave);
		}

		// 波形区边框与网格标题。
		UiDrawLine(g, lane.rect.X, lane.rect.Y + lane.rect.Height, lane.rect.X + lane.rect.Width,
		           lane.rect.Y + lane.rect.Height, m_theme->gridStrong, 1.0f);
		UiDrawLine(g, m_area.X, lane.rect.Y, m_area.X + m_area.Width, lane.rect.Y, m_theme->border, 1.0f);

		if (lane.rect.Height >= 24.0f * m_scale)
		{
			PaintLaneLegend(g, laneIndex, lane);
			if (m_cursorVisible && !lane.empty && lane.rect.Height >= 40.0f * m_scale)
			{
				PaintLaneReadout(g, laneIndex, lane);
			}
		}

		g.Restore(saveState);
		(void)timeStep;
	}

	void PlotView::PaintLaneLegend(gd::Graphics& g, int laneIndex, const LaneVisual& lane)
	{
		const std::vector<Lane>& lanes = m_document->Lanes();
		if (laneIndex < 0 || laneIndex >= static_cast<int>(lanes.size()))
		{
			return;
		}

		const float top = lane.rect.Y + 4.0f * m_scale;
		const float height = 18.0f * m_scale;
		float cursorX = lane.rect.X + kLanePadding * m_scale;
		const float maxX = lane.rect.X + lane.rect.Width - kLanePadding * m_scale;

		bool anyVisible = false;
		int visibleCount = 0;
		int drawnCount = 0;

		// 先测量图例总宽度，再用半透明底板掠开底下的网格线，提升可读性。
		float legendWidth = 0.0f;
		for (const int signalIndex : lanes[static_cast<std::size_t>(laneIndex)].signalIndices)
		{
			if (signalIndex < 0 || signalIndex >= static_cast<int>(m_document->Signals().size()))
			{
				continue;
			}
			const Signal& signal = m_document->Signals()[static_cast<std::size_t>(signalIndex)];
			if (!signal.visible)
			{
				continue;
			}

			std::wstring label = signal.name;
			if (!signal.unit.empty())
			{
				label += L" [" + signal.unit + L"]";
			}
			const float itemWidth = 8.0f * m_scale + 5.0f * m_scale +
			                        UiTextWidth(g, label, m_fonts->uiSmall) + 14.0f * m_scale;
			if (cursorX + legendWidth + itemWidth > maxX)
			{
				break;
			}
			legendWidth += itemWidth;
		}
		if (legendWidth > 0.0f)
		{
			UiFillRoundRect(g, gd::RectF(cursorX - 5.0f * m_scale, top - 1.0f * m_scale,
			                              legendWidth + 6.0f * m_scale, height + 2.0f * m_scale),
			                3.0f * m_scale, WithAlpha(m_theme->cardBg, 0xD8));
		}

		// 绘制图例条目（与测量阶段保持一致的裁剪条件）。
		float drawnWidth = 0.0f;
		for (const int signalIndex : lanes[static_cast<std::size_t>(laneIndex)].signalIndices)
		{
			if (signalIndex < 0 || signalIndex >= static_cast<int>(m_document->Signals().size()))
			{
				continue;
			}
			const Signal& signal = m_document->Signals()[static_cast<std::size_t>(signalIndex)];
			if (!signal.visible)
			{
				continue;
			}
			anyVisible = true;
			++visibleCount;

			std::wstring label = signal.name;
			if (!signal.unit.empty())
			{
				label += L" [" + signal.unit + L"]";
			}

			const float textWidth = UiTextWidth(g, label, m_fonts->uiSmall);
			const float itemWidth = 8.0f * m_scale + 5.0f * m_scale + textWidth + 14.0f * m_scale;
			if (drawnWidth + itemWidth > legendWidth + 0.5f)
			{
				break;
			}
			drawnWidth += itemWidth;

			const float swatchSize = 8.0f * m_scale;
			UiFillRoundRect(g, gd::RectF(cursorX, top + (height - swatchSize) * 0.5f, swatchSize, swatchSize),
			                1.5f * m_scale, signal.color);
			cursorX += swatchSize + 5.0f * m_scale;

			UiText(g, label, m_fonts->uiSmall, gd::RectF(cursorX, top, textWidth + 2.0f, height), m_theme->text,
			       TextAlign::LEFT);
			cursorX += textWidth + 14.0f * m_scale;
			++drawnCount;
		}

		if (!anyVisible)
		{
			UiText(g, L"（无可见信号）", m_fonts->uiSmall,
			       gd::RectF(lane.rect.X + kLanePadding * m_scale, top, lane.rect.Width, height),
			       m_theme->textMuted, TextAlign::LEFT);
		}
		else if (drawnCount < visibleCount)
		{
			// 图例空间不足时提示剩余信号数量，避免误认为信号丢失。
			const std::wstring moreText = L"+" + std::to_wstring(visibleCount - drawnCount);
			if (cursorX + 20.0f * m_scale <= maxX)
			{
				UiText(g, moreText, m_fonts->uiSmall, gd::RectF(cursorX, top, 24.0f * m_scale, height),
				       m_theme->textMuted, TextAlign::LEFT);
			}
		}
	}

	void PlotView::PaintLaneReadout(gd::Graphics& g, int laneIndex, const LaneVisual& lane)
	{
		const std::vector<Lane>& lanes = m_document->Lanes();
		if (laneIndex < 0 || laneIndex >= static_cast<int>(lanes.size()))
		{
			return;
		}

		if (m_cursorTime < m_viewMin || m_cursorTime > m_viewMax)
		{
			return;
		}

		struct ReadoutLine
		{
			std::wstring text;
			std::uint32_t color;
			float value;
		};

		std::vector<ReadoutLine> lines;
		for (const int signalIndex : lanes[static_cast<std::size_t>(laneIndex)].signalIndices)
		{
			if (signalIndex < 0 || signalIndex >= static_cast<int>(m_document->Signals().size()))
			{
				continue;
			}
			const Signal& signal = m_document->Signals()[static_cast<std::size_t>(signalIndex)];
			if (!signal.visible)
			{
				continue;
			}

			const bool interpolate = (signal.mode != DrawMode::SCATTER);
			double value = 0.0;
			if (!m_document->SampleAt(signalIndex, m_cursorTime, interpolate, value))
			{
				continue;
			}

			ReadoutLine line;
			line.text = signal.name + L" = " + FormatValue(value);
			line.color = signal.color;
			line.value = ValueToY(value, lane);
			lines.push_back(std::move(line));
		}

		if (lines.empty())
		{
			return;
		}

		const float lineHeight = 17.0f * m_scale;
		const float maxLines = std::max(1.0f, std::floor((lane.rect.Height - 12.0f * m_scale) / lineHeight));
		const std::size_t shown = std::min(lines.size(), static_cast<std::size_t>(maxLines));

		float boxWidth = 0.0f;
		for (std::size_t index = 0; index < shown; ++index)
		{
			boxWidth = std::max(boxWidth, UiTextWidth(g, lines[index].text, m_fonts->monoSmall));
		}
		boxWidth += 20.0f * m_scale;

		const float boxHeight = static_cast<float>(shown) * lineHeight + 8.0f * m_scale;
		const gd::RectF box(lane.rect.X + lane.rect.Width - kLanePadding * m_scale - boxWidth,
		                    lane.rect.Y + 4.0f * m_scale, boxWidth, boxHeight);

		UiFillRoundRect(g, box, 4.0f * m_scale, WithAlpha(m_theme->readoutBg, 0xEE));
		UiDrawRoundRect(g, box, 4.0f * m_scale, m_theme->border, 1.0f);

		float textY = box.Y + 4.0f * m_scale;
		for (std::size_t index = 0; index < shown; ++index)
		{
			const gd::RectF lineRect(box.X + 10.0f * m_scale, textY, boxWidth - 14.0f * m_scale, lineHeight);
			UiText(g, lines[index].text, m_fonts->monoSmall, lineRect, m_theme->textStrong, TextAlign::LEFT);
			textY += lineHeight;
		}
	}

	void PlotView::PaintTimeAxis(gd::Graphics& g, const std::vector<double>& timeTicks, double timeStep)
	{
		const float axisY = m_plotRect.Y + m_plotRect.Height;
		UiDrawLine(g, m_plotRect.X, axisY, m_plotRect.X + m_plotRect.Width, axisY, m_theme->axisLine, 1.0f);

		for (const double tick : timeTicks)
		{
			const float x = TimeToX(tick);
			if (x < m_plotRect.X - 1.0f || x > m_plotRect.X + m_plotRect.Width + 1.0f)
			{
				continue;
			}

			UiDrawLine(g, x, axisY, x, axisY + 4.0f * m_scale, m_theme->axisLine, 1.0f);

			const gd::RectF labelRect(x - 48.0f * m_scale, axisY + 4.0f * m_scale, 96.0f * m_scale,
			                          m_timeAxisRect.Height - 6.0f * m_scale);
			UiText(g, FormatTick(tick, timeStep), m_fonts->monoSmall, labelRect, m_theme->textMuted,
			       TextAlign::CENTER);
		}

		// 时间轴列名（过长时自动省略）。
		const std::wstring axisName =
		    m_document->TimeColumnName().empty() ? std::wstring(L"时间") : m_document->TimeColumnName();
		UiText(g, axisName, m_fonts->monoSmall,
		       gd::RectF(m_area.X, axisY, m_yAxisWidth - kAxisLabelGap * m_scale, m_timeAxisRect.Height),
		       m_theme->textMuted, TextAlign::RIGHT);
	}

	void PlotView::PaintCursor(gd::Graphics& g, const std::vector<LaneVisual>& lanes)
	{
		if (!m_cursorVisible)
		{
			return;
		}

		const float x = TimeToX(m_cursorTime);
		if (x < m_plotRect.X - 2.0f || x > m_plotRect.X + m_plotRect.Width + 2.0f)
		{
			return;
		}

		UiDrawDashedLine(g, x, m_plotRect.Y, x, m_plotRect.Y + m_plotRect.Height, m_theme->cursor,
		                 1.0f, m_cursorPinned ? gd::DashStyleSolid : gd::DashStyleDash);

		// 波形上的取值标记。
		for (std::size_t laneIndex = 0; laneIndex < lanes.size(); ++laneIndex)
		{
			const LaneVisual& lane = lanes[laneIndex];
			if (lane.empty)
			{
				continue;
			}
			const std::vector<int>& indices = m_document->Lanes()[laneIndex].signalIndices;
			for (const int signalIndex : indices)
			{
				if (signalIndex < 0 || signalIndex >= static_cast<int>(m_document->Signals().size()))
				{
					continue;
				}
				const Signal& signal = m_document->Signals()[static_cast<std::size_t>(signalIndex)];
				if (!signal.visible)
				{
					continue;
				}

				double value = 0.0;
				if (!m_document->SampleAt(signalIndex, m_cursorTime, signal.mode != DrawMode::SCATTER, value))
				{
					continue;
				}

				const float y = ValueToY(value, lane);
				if (y < lane.rect.Y - 2.0f || y > lane.rect.Y + lane.rect.Height + 2.0f)
				{
					continue;
				}

				const float radius = 3.4f * m_scale;
				gd::SolidBrush ring(ToGdiColor(m_theme->cardBg));
				gd::SolidBrush fill(ToGdiColor(signal.color));
				g.FillEllipse(&ring, x - radius - 1.2f * m_scale, y - radius - 1.2f * m_scale,
				              (radius + 1.2f * m_scale) * 2.0f, (radius + 1.2f * m_scale) * 2.0f);
				g.FillEllipse(&fill, x - radius, y - radius, radius * 2.0f, radius * 2.0f);
			}
		}

		// 时间轴上的光标标签。
		const std::wstring label = FormatValue(m_cursorTime);
		const float textWidth = UiTextWidth(g, label, m_fonts->monoSmall);
		const float pillWidth = textWidth + 14.0f * m_scale;
		const float pillHeight = 19.0f * m_scale;
		float pillX = x - pillWidth * 0.5f;
		pillX = std::max(m_plotRect.X, std::min(pillX, m_plotRect.X + m_plotRect.Width - pillWidth));

		const gd::RectF pill(pillX, m_plotRect.Y + m_plotRect.Height + 2.0f * m_scale, pillWidth, pillHeight);
		UiFillRoundRect(g, pill, 3.0f * m_scale, m_theme->cursor);
		UiText(g, label, m_fonts->monoSmall, pill, m_theme->textOnAccent, TextAlign::CENTER);
	}

	void PlotView::PaintScrollBar(gd::Graphics& g)
	{
		if (!m_scrollBarVisible || m_laneContentHeight <= m_plotRect.Height)
		{
			return;
		}

		UiFillRoundRect(g, m_scrollBarRect, kScrollBarThickness * m_scale * 0.5f, m_theme->gridWeak);

		const float ratio = std::min(1.0f, m_plotRect.Height / m_laneContentHeight);
		const float thumbHeight = std::max(24.0f * m_scale, m_scrollBarRect.Height * ratio);
		const float maxScroll = m_laneContentHeight - m_plotRect.Height;
		const float progress = (maxScroll > 0.0f) ? (m_laneScroll / maxScroll) : 0.0f;
		const float thumbY = m_scrollBarRect.Y + progress * (m_scrollBarRect.Height - thumbHeight);

		const gd::RectF thumb(m_scrollBarRect.X, thumbY, m_scrollBarRect.Width, thumbHeight);
		UiFillRoundRect(g, thumb, kScrollBarThickness * m_scale * 0.5f, m_theme->borderStrong);
	}

} // namespace jdi