[transit][world_feed] New helper functions for subway rendering.

transit/world_feed/feed_helpers.cpp

@@ -283,4 +283,104 @@ gtfs::StopTimes GetStopTimesForTrip(gtfs::StopTimes const & allStopTimes,
   });
   return res;
 }
+
+void UpdateLinePart(LineParts & lineParts, LineSegment const & segment,
+                    m2::PointD const & startPoint, TransitId commonLineId,
+                    m2::PointD const & startPointParallel)
+{
+  if (auto it = FindLinePart(lineParts, segment); it == lineParts.end())
+  {
+    LinePart lp;
+    lp.m_segment = segment;
+    lp.m_commonLines[commonLineId] = startPointParallel;
+    lp.m_firstPoint = startPoint;
+    lineParts.push_back(lp);
+  }
+  else
+  {
+    it->m_commonLines[commonLineId] = startPointParallel;
+  }
+}
+
+std::pair<LineSegments, LineSegments> FindIntersections(std::vector<m2::PointD> const & line1,
+                                                        std::vector<m2::PointD> const & line2)
+{
+  double const eps = 1e-5;
+  size_t constexpr minIntersection = 2;
+
+  CHECK_GREATER_OR_EQUAL(line1.size(), minIntersection, ());
+  CHECK_GREATER_OR_EQUAL(line2.size(), minIntersection, ());
+
+  std::pair<LineSegments, LineSegments> intersections;
+
+  // Find start indexes of line1 and line2 intersections.
+  size_t i = 0;
+
+  while (i < line1.size() - minIntersection + 1)
+  {
+    size_t j = 0;
+    size_t delta = 1;
+
+    while (j < line2.size() - minIntersection + 1)
+    {
+      size_t intersection = 0;
+      size_t const len = std::min(line1.size() - i, line2.size() - j);
+
+      for (size_t k = 0; k < len; ++k)
+      {
+        if (!base::AlmostEqualAbs(line1[i + k], line2[j + k], eps))
+          break;
+        ++intersection;
+      }
+
+      if (intersection >= minIntersection)
+      {
+        intersections.first.emplace_back(i, i + intersection - 1);
+        intersections.second.emplace_back(j, j + intersection - 1);
+        delta = intersection;
+        break;
+      }
+
+      ++j;
+    }
+
+    i += delta;
+  }
+
+  CHECK_EQUAL(intersections.first.size(), intersections.second.size(), ());
+
+  return intersections;
+}
+
+LineParts::iterator FindLinePart(LineParts & lineParts, LineSegment const & segment)
+{
+  return std::find_if(lineParts.begin(), lineParts.end(), [&segment](LinePart const & linePart) {
+    return linePart.m_segment == segment;
+  });
+}
+
+std::optional<LineSegment> GetIntersection(size_t start1, size_t finish1, size_t start2,
+                                           size_t finish2)
+{
+  int const maxStart = static_cast<int>(std::max(start1, start2));
+  int const minFinish = static_cast<int>(std::min(finish1, finish2));
+
+  size_t const intersectionLen = std::max(minFinish - maxStart, 0);
+
+  if (intersectionLen == 0)
+    return std::nullopt;
+
+  return LineSegment(maxStart, maxStart + intersectionLen);
+}
+
+int CalcSegmentOrder(size_t segIndex, size_t totalSegCount)
+{
+  int constexpr shapeOffsetIncrement = 2;
+
+  int const shapeOffset =
+      -static_cast<int>(totalSegCount / 2) * 2 - static_cast<int>(totalSegCount % 2) + 1;
+  int const curSegOffset = shapeOffset + shapeOffsetIncrement * static_cast<int>(segIndex);
+
+  return curSegOffset;
+}
 }  // namespace transit

transit/world_feed/feed_helpers.hpp

@@ -1,8 +1,10 @@
 #pragma once
+#include "transit/transit_entities.hpp"
 
 #include "geometry/point2d.hpp"
 
 #include <algorithm>
+#include <optional>
 #include <string>
 #include <utility>
 #include <vector>
@@ -71,4 +73,53 @@ void DeleteAllEntriesByIds(C & container, S const & keysForDel)
 
 inline double KmphToMps(double kmph) { return kmph * 1'000.0 / (60.0 * 60.0); }
 inline double MpsToKmph(double mps) { return mps / 1'000.0 * 60.0 * 60.0; }
+
+// We have routes with multiple lines. Each line corresponds to the geometric polyline. Lines may
+// be parallel in some segments. |LinePart| represents these operlapping segments for each line.
+struct LinePart
+{
+  // Start and end indexes on polyline.
+  LineSegment m_segment;
+  // Parallel line ids to its start points on the segment.
+  std::map<TransitId, m2::PointD> m_commonLines;
+  // First coordinate of current line on the segment. It is used for determining if the line is
+  // co-directional or reversed regarding the main line on the segment.
+  m2::PointD m_firstPoint;
+};
+
+using LineParts = std::vector<LinePart>;
+
+// Returns iterator to the line part with equivalent segment.
+LineParts::iterator FindLinePart(LineParts & lineParts, LineSegment const & segment);
+
+// Data required for finding parallel polyline segments and calculating offsets for each line on the
+// segment.
+struct LineSchemeData
+{
+  TransitId m_lineId = 0;
+  TransitId m_routeId = 0;
+  ShapeLink m_shapeLink;
+
+  LineParts m_lineParts;
+};
+
+// Returns overlapping segments between two polylines.
+std::pair<LineSegments, LineSegments> FindIntersections(std::vector<m2::PointD> const & line1,
+                                                        std::vector<m2::PointD> const & line2);
+
+// Finds item in |lineParts| equal to |segment| and updates it. If it doesn't exist it is added to
+// the |lineParts|.
+void UpdateLinePart(LineParts & lineParts, LineSegment const & segment,
+                    m2::PointD const & startPoint, TransitId commonLineId,
+                    m2::PointD const & startPointParallel);
+
+// Calculates start and end indexes of intersection of two segments: [start1, finish1] and [start2,
+// finish2].
+std::optional<LineSegment> GetIntersection(size_t start1, size_t finish1, size_t start2,
+                                           size_t finish2);
+
+// Calculates line order on segment based on two parameters: line index between all parallel lines,
+// total parallel lines count. Line order must be symmetrical with respect to the сentral axis of
+// the polyline.
+int CalcSegmentOrder(size_t segIndex, size_t totalSegCount);
 }  // namespace transit