4 files changed, 78 insertions, 7 deletions

diff --git a/game/network/network.cpp b/game/network/network.cpp
index 70c4e21..ae4865a 100644
--- a/game/network/network.cpp
+++ b/game/network/network.cpp
@@ -179,10 +179,13 @@ Network::genDef(const GlobalPosition3D & start, const GlobalPosition3D & end, An
 	const auto flatStart = start.xy(), flatEnd = end.xy();
 	const auto centre = find_arc_centre(flatStart, dir, flatEnd);
 
-	if (centre.second) { // right hand arc
+	if (centre.second > 0.1F) {
 		return {GenCurveDef {end, start, centre.first}};
 	}
-	return {GenCurveDef {start, end, centre.first}};
+	if (centre.second < -0.1F) {
+		return {GenCurveDef {start, end, centre.first}};
+	}
+	return {GenStraightDef {start, end}};
 }
 
 GenLinksDef
@@ -219,13 +222,38 @@ Network::genDef(const GlobalPosition3D & start, const GlobalPosition3D & end, An
 	return genDef(start, joint, startDir) + genDef(end, joint, endDir);
 }
 
+namespace {
+	struct MergeEq {
+		bool
+		operator()(GenCurveDef & lhs, const GenCurveDef & rhs) const
+		{
+			if (distance(std::get<2>(lhs), std::get<2>(rhs)) < 100.F) { // LHS.centre near RHS.centre
+				if (std::get<1>(lhs) == std::get<0>(rhs)) { // LHS.end == RHS.start
+					std::get<1>(lhs) = std::get<1>(rhs);
+				}
+				else if (std::get<0>(lhs) == std::get<1>(rhs)) { // LHS.start == RHS.end
+					std::get<0>(lhs) = std::get<0>(rhs);
+				}
+				else {
+					return false;
+				}
+				std::get<2>(lhs) = midpoint(std::get<2>(lhs), std::get<2>(rhs));
+				return true;
+			}
+			return false;
+		}
+
+		bool
+		operator()(const auto &, const auto &) const
+		{
+			return false;
+		}
+	};
+}
+
 Link::Collection
 Network::create(const GeoData * geoData, const CreationDefinition & def)
 {
-	// TODO
-	// Where to make a straight to join because angles align?
-	// Where to drop part of S curve pair if a single curve works?
-
 	const auto linkDefs = [&def]() -> GenLinksDef {
 		if (!def.fromEnd.direction && !def.toEnd.direction) {
 			// No specific directions at either end, straight link
@@ -251,8 +279,20 @@ Network::create(const GeoData * geoData, const CreationDefinition & def)
 						   def);
 		});
 	};
+	// Merge adjacent pairs where possible
+	auto linkDefsGen = geoData ? splitDefs() : linkDefs();
+	if (!linkDefsGen.empty()) {
+		for (auto lhsIter = linkDefsGen.begin(), rhsIter = lhsIter + 1; rhsIter != linkDefsGen.end();) {
+			if (std::visit(MergeEq {}, *lhsIter, *rhsIter)) {
+				rhsIter = linkDefsGen.erase(rhsIter);
+			}
+			else {
+				lhsIter = rhsIter++;
+			}
+		}
+	}
 	Link::Collection links;
-	std::ranges::transform(geoData ? splitDefs() : linkDefs(), std::back_inserter(links), [this](const auto & def) {
+	std::ranges::transform(linkDefsGen, std::back_inserter(links), [this](const auto & def) {
 		return std::visit(
 				[this](const auto & typedDef) {
 					return this->create(typedDef);
diff --git a/game/network/network.h b/game/network/network.h
index d3370b3..7bfd2ce 100644
--- a/game/network/network.h
+++ b/game/network/network.h
@@ -35,6 +35,19 @@ struct CreationDefinition {
 	CreationDefinitionEnd toEnd;
 };
 
+struct SnapPoint : CreationDefinitionEnd {
+	template<typename... CDE>
+		requires std::is_constructible_v<CreationDefinitionEnd, CDE...>
+	explicit SnapPoint(GlobalPosition3D snapPosition, CDE &&... cde) :
+		CreationDefinitionEnd {std::forward<CDE>(cde)...}, snapPosition(snapPosition)
+	{
+	}
+
+	GlobalPosition3D snapPosition;
+};
+
+using SnapPoints = std::vector<SnapPoint>;
+
 class Network {
 public:
 	using LinkEnd = std::pair<Link::Ptr, unsigned char>;
@@ -55,6 +68,7 @@ public:
 	[[nodiscard]] static Link::Nexts routeFromTo(const Link::End &, const Node::Ptr &);
 
 	[[nodiscard]] virtual float findNodeDirection(Node::AnyCPtr) const = 0;
+	[[nodiscard]] virtual SnapPoints getSnapPoints() const = 0;
 
 	[[nodiscard]] Link::Collection create(const GeoData *, const CreationDefinition &);
 	[[nodiscard]] Link::Collection createChain(const GeoData *, std::span<const GlobalPosition3D>);
diff --git a/game/network/rail.cpp b/game/network/rail.cpp
index 342a2ad..45d55d6 100644
--- a/game/network/rail.cpp
+++ b/game/network/rail.cpp
@@ -137,3 +137,19 @@ RailLinks::getBaseWidth() const
 	static constexpr auto BASE_WIDTH = 5'700;
 	return BASE_WIDTH;
 }
+
+SnapPoints
+RailLinks::getSnapPoints() const
+{
+	static constexpr auto EXTENSION_SNAP_DIST = 1'200.F;
+	SnapPoints out;
+	for (const auto & link : links) {
+		for (const auto & end : link->ends) {
+			// Link end node; directionless, suitable crossings
+			out.emplace_back(end.node->pos, end.node->pos, std::nullopt);
+			// Link end; with direction, suitable for continuing/joining
+			out.emplace_back(end.node->pos - ((sincos(end.dir) * EXTENSION_SNAP_DIST) || 0.F), end.node->pos, end.dir);
+		}
+	}
+	return out;
+}
diff --git a/game/network/rail.h b/game/network/rail.h
index 15b9ae4..48b1410 100644
--- a/game/network/rail.h
+++ b/game/network/rail.h
@@ -78,6 +78,7 @@ public:
 
 	[[nodiscard]] const Surface * getBaseSurface() const override;
 	[[nodiscard]] RelativeDistance getBaseWidth() const override;
+	[[nodiscard]] SnapPoints getSnapPoints() const override;
 
 private:
 	void tick(TickDuration elapsed) override;