Repo created

libs/geometry/line2d.cpp

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+#include "geometry/line2d.hpp"
+
+#include <cmath>
+#include <sstream>
+
+namespace m2
+{
+namespace
+{
+bool Collinear(PointD const & a, PointD const & b, double eps)
+{
+  return std::fabs(CrossProduct(a, b)) < eps;
+}
+}  // namespace
+
+std::string DebugPrint(Line2D const & line)
+{
+  std::ostringstream os;
+  os << "Line2D [ ";
+  os << "point: " << DebugPrint(line.m_point) << ", ";
+  os << "direction: " << DebugPrint(line.m_direction);
+  os << " ]";
+  return os.str();
+}
+
+IntersectionResult Intersect(Line2D const & lhs, Line2D const & rhs, double eps)
+{
+  auto const & a = lhs.m_point;
+  auto const & ab = lhs.m_direction;
+
+  auto const & c = rhs.m_point;
+  auto const & cd = rhs.m_direction;
+
+  if (Collinear(ab, cd, eps))
+  {
+    if (Collinear(c - a, cd, eps))
+      return IntersectionResult(IntersectionResult::Type::Infinity);
+    return IntersectionResult(IntersectionResult::Type::Zero);
+  }
+
+  auto const ac = c - a;
+
+  auto const n = CrossProduct(ac, cd);
+  auto const d = CrossProduct(ab, cd);
+  auto const scale = n / d;
+
+  return IntersectionResult(a + ab * scale);
+}
+}  // namespace m2