// Copyright 2025 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "third_party/blink/renderer/platform/geometry/path_builder.h"

#include "third_party/blink/renderer/platform/geometry/contoured_rect.h"
#include "third_party/blink/renderer/platform/geometry/infinite_int_rect.h"
#include "third_party/blink/renderer/platform/geometry/path.h"
#include "third_party/blink/renderer/platform/geometry/path_types.h"
#include "third_party/blink/renderer/platform/geometry/skia_geometry_utils.h"
#include "third_party/blink/renderer/platform/transforms/affine_transform.h"
#include "third_party/skia/include/pathops/SkPathOps.h"
#include "ui/gfx/geometry/point_f.h"
#include "ui/gfx/geometry/rect_f.h"
#include "ui/gfx/geometry/skia_conversions.h"
#include "ui/gfx/geometry/vector2d_f.h"

namespace blink {

namespace {

using Corner = ContouredRect::Corner;

// Given a superellipse with the supplied curvature in the coordinate space
// -1,-1,1,1, returns 3 vectors (2 control points and the end point)
// of a bezier curve, going from t=0 (0, 1) clockwise to t=0.5 (45 degrees),
// and following the path of the superellipse with a small margin of error.
// TODO(fserb) document how this works.
std::array<gfx::Vector2dF, 3> ApproximateSuperellipseHalfCornerAsBezierCurve(
    float curvature) {
  static constexpr std::array<double, 7> p = {
      1.2430920942724248, 2.010479023614843,  0.32922901179443753,
      0.2823023142212073, 1.3473704261055421, 2.9149468637949814,
      0.9106507102917086};

  // This formula only works with convex superellipses. To apply to a concave
  // superellipse, flip the center and the outer point and apply the
  // equivalent convex formula (1/curvature).
  DCHECK_GE(curvature, 1);
  const float s = std::log2(curvature);
  const float slope =
      p[0] + (p[6] - p[0]) * 0.5 * (1 + std::tanh(p[5] * (s - p[1])));
  const float base = 1 / (1 + std::exp(-slope * (0 - p[1])));
  const float logistic = 1 / (1 + std::exp(-slope * (s - p[1])));

  const float a = (logistic - base) / (1 - base);
  const float b = p[2] * std::exp(-p[3] * std::pow(s, p[4]));

  // This is the superellipse formula at t=0.5 (45 degrees),
  // the middle of the corner.
  const float half_corner = Corner::HalfCornerForCurvature(curvature);

  const gfx::Vector2dF P1(a, 1);
  const gfx::Vector2dF P2(half_corner - b, half_corner + b);
  const gfx::Vector2dF P3(half_corner, half_corner);
  return {P1, P2, P3};
}

// Adds a curved corner to a path. The vertex argument is the 4 points
// of the corner rectangle, starting from the beginning of the corner
// and continuing clockwise.
void AddCurvedCorner(SkPath& path, const Corner& corner) {
  if (corner.IsConcave()) {
    AddCurvedCorner(path, corner.Inverse());
    return;
  }

  CHECK_GE(corner.Curvature(), 1);
  // Start the path from the beginning of the curve.
  path.lineTo(gfx::PointFToSkPoint(corner.Start()));

  if (corner.IsStraight()) {
    // Straight or very close to it, draw two lines.
    path.lineTo(gfx::PointFToSkPoint(corner.Outer()));
    path.lineTo(gfx::PointFToSkPoint(corner.End()));
  } else if (corner.IsBevel()) {
    path.lineTo(gfx::PointFToSkPoint(corner.End()));
  } else if (corner.IsRound()) {
    path.conicTo(gfx::PointFToSkPoint(corner.Outer()),
                 gfx::PointFToSkPoint(corner.End()), SK_ScalarRoot2Over2);
  } else {
    // Approximate 1/2 corner (45 degrees) of the superellipse as a
    // cubic bezier curve, and draw it twice, transposed, meeting at the t=0.5
    // (45 degrees) point.
    std::array<gfx::Vector2dF, 3> control_points =
        ApproximateSuperellipseHalfCornerAsBezierCurve(corner.Curvature());

    path.cubicTo(gfx::PointFToSkPoint(corner.MapPoint(control_points.at(0))),
                 gfx::PointFToSkPoint(corner.MapPoint(control_points.at(1))),
                 gfx::PointFToSkPoint(corner.MapPoint(control_points.at(2))));

    path.cubicTo(gfx::PointFToSkPoint(
                     corner.MapPoint(TransposeVector2d(control_points.at(1)))),
                 gfx::PointFToSkPoint(
                     corner.MapPoint(TransposeVector2d(control_points.at(0)))),
                 gfx::PointFToSkPoint(corner.End()));
  }
}

}  // anonymous namespace

PathBuilder::PathBuilder() = default;
PathBuilder::~PathBuilder() = default;

PathBuilder::PathBuilder(const Path& path) : builder_(path.GetSkPath()) {}

void PathBuilder::Reset() {
  builder_.reset();
  current_path_.reset();
}

Path PathBuilder::Finalize() {
  Path path(std::move(builder_));

  Reset();

  return path;
}

gfx::RectF PathBuilder::BoundingRect() const {
  return gfx::SkRectToRectF(builder_.getBounds());
}

const Path& PathBuilder::CurrentPath() const {
  if (!current_path_) {
    current_path_.emplace(builder_);
  }

  return current_path_.value();
}

std::optional<gfx::PointF> PathBuilder::CurrentPoint() const {
  SkPoint point;
  if (builder_.getLastPt(&point)) {
    return gfx::SkPointToPointF(point);
  }
  return std::nullopt;
}

PathBuilder& PathBuilder::Close() {
  builder_.close();

  current_path_.reset();
  return *this;
}

PathBuilder& PathBuilder::MoveTo(const gfx::PointF& pt) {
  builder_.moveTo(gfx::PointFToSkPoint(pt));

  current_path_.reset();
  return *this;
}

PathBuilder& PathBuilder::LineTo(const gfx::PointF& pt) {
  builder_.lineTo(gfx::PointFToSkPoint(pt));

  current_path_.reset();
  return *this;
}

PathBuilder& PathBuilder::QuadTo(const gfx::PointF& ctrl,
                                 const gfx::PointF& pt) {
  builder_.quadTo(gfx::PointFToSkPoint(ctrl), gfx::PointFToSkPoint(pt));

  current_path_.reset();
  return *this;
}

PathBuilder& PathBuilder::CubicTo(const gfx::PointF& ctrl1,
                                  const gfx::PointF& ctrl2,
                                  const gfx::PointF& pt) {
  builder_.cubicTo(gfx::PointFToSkPoint(ctrl1), gfx::PointFToSkPoint(ctrl2),
                   gfx::PointFToSkPoint(pt));

  current_path_.reset();
  return *this;
}

PathBuilder& PathBuilder::ArcTo(const gfx::PointF& p,
                                float radius_x,
                                float radius_y,
                                float x_rotate,
                                bool large_arc,
                                bool sweep) {
  builder_.arcTo(radius_x, radius_y, x_rotate,
                 large_arc ? SkPath::kLarge_ArcSize : SkPath::kSmall_ArcSize,
                 sweep ? SkPathDirection::kCW : SkPathDirection::kCCW, p.x(),
                 p.y());

  current_path_.reset();
  return *this;
}

PathBuilder& PathBuilder::ArcTo(const gfx::PointF& p1,
                                const gfx::PointF& p2,
                                float radius) {
  builder_.arcTo(gfx::PointFToSkPoint(p1), gfx::PointFToSkPoint(p2), radius);

  current_path_.reset();
  return *this;
}

PathBuilder& PathBuilder::AddRect(const gfx::PointF& origin,
                                  const gfx::PointF& opposite_point) {
  builder_.addRect(SkRect::MakeLTRB(origin.x(), origin.y(), opposite_point.x(),
                                    opposite_point.y()),
                   SkPathDirection::kCW, 0);

  current_path_.reset();
  return *this;
}

PathBuilder& PathBuilder::AddPath(const Path& src,
                                  const AffineTransform& transform) {
  builder_.addPath(src.GetSkPath(), transform.ToSkMatrix());

  current_path_.reset();
  return *this;
}

PathBuilder& PathBuilder::AddRoundedRect(const FloatRoundedRect& rect,
                                         bool clockwise) {
  if (rect.IsEmpty()) {
    return *this;
  }

  builder_.addRRect(SkRRect(rect),
                    clockwise ? SkPathDirection::kCW : SkPathDirection::kCCW,
                    /* start at upper-left after corner radius */ 0);

  current_path_.reset();
  return *this;
}

PathBuilder& PathBuilder::AddCorner(const ContouredRect::Corner& corner) {
  AddCurvedCorner(builder_, corner);
  current_path_.reset();
  return *this;
}

PathBuilder& PathBuilder::AddContouredRect(
    const ContouredRect& contoured_rect) {
  const FloatRoundedRect& target_rect = contoured_rect.AsRoundedRect();

  if (contoured_rect.HasRoundCurvature()) {
    AddRoundedRect(target_rect);
    return *this;
  }
  const FloatRoundedRect& origin_rect = contoured_rect.GetOriginRect();

  // This would include the outer border of the rect, as well as shadow and
  // margin.
  if (origin_rect == target_rect ||
      target_rect.Rect().Contains(origin_rect.Rect())) {
    // A rect with no insets/outsets, we can draw all the corners and not worry
    // about intersections.
    const Corner top_right_corner = contoured_rect.TopRightCorner();
    MoveTo(top_right_corner.Start());
    AddCurvedCorner(builder_, top_right_corner);
    AddCurvedCorner(builder_, contoured_rect.BottomRightCorner());
    AddCurvedCorner(builder_, contoured_rect.BottomLeftCorner());
    AddCurvedCorner(builder_, contoured_rect.TopLeftCorner());
    current_path_.reset();
    return *this;
  }

  // To generate curves that have constant thickness, we compute the
  // superellipse based on the same center and an increased radius. Since the
  // resulting path segments don't start/end at the target rect, we use
  // path-intersection logic, and intersect 3 paths: (1) the target rect (2) the
  // top-left & bottom-right corners together with the bottom-left and top-right
  // of the infinite rect (3) the top-right & bottom-left corners together with
  // the top-left and bottom-right corners of the infinite rect.
  // This generates a path that corresponds to the inset/outset rect but has the
  // corners carved out.
  SkOpBuilder op_builder;

  const SkRect infinite_rect =
      gfx::RectFToSkRect(gfx::RectF(InfiniteIntRect()));

  // Start with the target rect
  op_builder.add(SkPath::Rect(gfx::RectFToSkRect(target_rect.Rect())),
                 kUnion_SkPathOp);

  ContouredRect origin_contoured_rect(origin_rect,
                                      contoured_rect.GetCornerCurvature());

  if (!contoured_rect.GetRadii().TopRight().IsZero()) {
    SkPath path;
    path.moveTo(infinite_rect.left(), infinite_rect.top());
    AddCurvedCorner(path, contoured_rect.TopRightCorner());
    path.lineTo(infinite_rect.right(), infinite_rect.bottom());
    path.lineTo(infinite_rect.left(), infinite_rect.bottom());
    path.close();
    op_builder.add(path, kIntersect_SkPathOp);
  }

  if (!contoured_rect.GetRadii().BottomRight().IsZero()) {
    SkPath path;
    path.moveTo(infinite_rect.right(), infinite_rect.top());
    AddCurvedCorner(path, contoured_rect.BottomRightCorner());
    path.lineTo(infinite_rect.left(), infinite_rect.bottom());
    path.lineTo(infinite_rect.left(), infinite_rect.top());
    path.close();
    op_builder.add(path, kIntersect_SkPathOp);
  }

  if (!contoured_rect.GetRadii().BottomLeft().IsZero()) {
    SkPath path;
    path.moveTo(infinite_rect.right(), infinite_rect.bottom());
    AddCurvedCorner(path, contoured_rect.BottomLeftCorner());
    path.lineTo(infinite_rect.left(), infinite_rect.top());
    path.lineTo(infinite_rect.right(), infinite_rect.top());
    path.close();
    op_builder.add(path, kIntersect_SkPathOp);
  }

  if (!contoured_rect.GetRadii().TopLeft().IsZero()) {
    SkPath path;
    path.moveTo(infinite_rect.left(), infinite_rect.bottom());
    AddCurvedCorner(path, contoured_rect.TopLeftCorner());
    path.lineTo(infinite_rect.right(), infinite_rect.top());
    path.lineTo(infinite_rect.right(), infinite_rect.bottom());
    path.close();
    op_builder.add(path, kIntersect_SkPathOp);
  }

  SkPath result;
  CHECK(op_builder.resolve(&result));
  builder_.addPath(result);
  current_path_.reset();
  return *this;
}

PathBuilder& PathBuilder::AddEllipse(const gfx::PointF& p,
                                     float radius_x,
                                     float radius_y,
                                     float start_angle,
                                     float end_angle) {
  DCHECK(EllipseIsRenderable(start_angle, end_angle));
  DCHECK_GE(start_angle, 0);
  DCHECK_LT(start_angle, kTwoPiFloat);

  const SkRect oval = SkRect::MakeLTRB(p.x() - radius_x, p.y() - radius_y,
                                       p.x() + radius_x, p.y() + radius_y);

  const float start_degrees = Rad2deg(start_angle);
  const float sweep_degrees = Rad2deg(end_angle - start_angle);

  // We can't use SkPath::addOval(), because addOval() makes a new sub-path.
  // addOval() calls moveTo() and close() internally.

  // Use 180, not 360, because SkPath::arcTo(oval, angle, 360, false) draws
  // nothing.
  // TODO(fmalita): we should fix that in Skia.
  if (WebCoreFloatNearlyEqual(std::abs(sweep_degrees), 360)) {
    // incReserve() results in a single allocation instead of multiple as is
    // done by multiple calls to arcTo().
    builder_.incReserve(10, 5, 4);
    // // SkPath::arcTo can't handle the sweepAngle that is equal to or greater
    // // than 2Pi.
    const float sweep180 = std::copysign(180, sweep_degrees);
    builder_.arcTo(oval, start_degrees, sweep180, false);
    builder_.arcTo(oval, start_degrees + sweep180, sweep180, false);
  } else {
    builder_.arcTo(oval, start_degrees, sweep_degrees, false);
  }
  current_path_.reset();
  return *this;
}

PathBuilder& PathBuilder::AddEllipse(const gfx::PointF& p,
                                     float radius_x,
                                     float radius_y,
                                     float rotation,
                                     float start_angle,
                                     float end_angle) {
  DCHECK(EllipseIsRenderable(start_angle, end_angle));
  DCHECK_GE(start_angle, 0);
  DCHECK_LT(start_angle, kTwoPiFloat);

  if (!rotation) {
    return AddEllipse(p, radius_x, radius_y, start_angle, end_angle);
  }

  // Add an arc after the relevant transform.
  AffineTransform ellipse_transform =
      AffineTransform::Translation(p.x(), p.y()).RotateRadians(rotation);
  DCHECK(ellipse_transform.IsInvertible());
  AffineTransform inverse_ellipse_transform = ellipse_transform.Inverse();
  Transform(inverse_ellipse_transform);
  AddEllipse(gfx::PointF(), radius_x, radius_y, start_angle, end_angle);
  return Transform(ellipse_transform);
}

PathBuilder& PathBuilder::AddRect(const gfx::RectF& rect) {
  // Start at upper-left, add clock-wise.
  builder_.addRect(gfx::RectFToSkRect(rect), SkPathDirection::kCW, 0);

  current_path_.reset();
  return *this;
}

PathBuilder& PathBuilder::AddEllipse(const gfx::PointF& center,
                                     float radius_x,
                                     float radius_y) {
  // Start at 3 o'clock, add clock-wise.
  builder_.addOval(
      SkRect::MakeLTRB(center.x() - radius_x, center.y() - radius_y,
                       center.x() + radius_x, center.y() + radius_y),
      SkPathDirection::kCW, 1);

  current_path_.reset();
  return *this;
}

PathBuilder& PathBuilder::SetWindRule(WindRule rule) {
  const SkPathFillType fill_type = WebCoreWindRuleToSkFillType(rule);

  if (fill_type == builder_.getFillType()) {
    return *this;
  }

  builder_.setFillType(fill_type);

  current_path_.reset();
  return *this;
}

PathBuilder& PathBuilder::Translate(const gfx::Vector2dF& offset) {
  builder_.offset(offset.x(), offset.y());

  current_path_.reset();
  return *this;
}

PathBuilder& PathBuilder::Transform(const AffineTransform& xform) {
  builder_.transform(xform.ToSkMatrix());

  current_path_.reset();
  return *this;
}

}  // namespace blink