Handle edge casesbetter-network

...where extending a network results in something that can be a straight
or collapsed into a single arc from a bi-arc.

4 files changed, 165 insertions, 45 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/lib/maths.cpp b/lib/maths.cpp
index 000cea7..7dd313e 100644
--- a/lib/maths.cpp
+++ b/lib/maths.cpp
@@ -1,5 +1,6 @@
 #include "maths.h"
 #include <cmath>
+#include <functional>
 #include <glm/glm.hpp>
 #include <glm/gtx/rotate_vector.hpp>
 #include <glm/gtx/transform.hpp>
@@ -32,6 +33,7 @@ static_assert(pow(3, 1) == 3);
 static_assert(pow(3, 2) == 9);
 static_assert(pow(pi, 3) == 31.006278991699219F);
 
+#ifndef __clang__
 static_assert(!linesIntersectAt<int>({0, 10}, {10, 10}, {10, 0}, {0, 0}).has_value());
 static_assert(*linesIntersectAt<int>({0, 0}, {10, 10}, {10, 0}, {0, 10}) == GlobalPosition2D {5, 5});
 static_assert(*linesIntersectAt<int>({300'000'000, 400'000'00}, {300'010'000, 400'010'00}, {310'010'000, 410'000'00},
@@ -43,6 +45,13 @@ constexpr auto EAST2D = RelativePosition2D(east);
 static_assert(!linesIntersectAtDirs<int>({0, 0}, NORTH2D, {10, 10}, NORTH2D).has_value());
 static_assert(linesIntersectAtDirs<int>({0, 0}, NORTH2D, {10, 10}, EAST2D) == GlobalPosition2D {0, 10});
 static_assert(linesIntersectAtDirs<int>({0, 0}, EAST2D, {10, 10}, NORTH2D) == GlobalPosition2D {10, 0});
+
+static_assert(find_arc_centre<int>({0, 0}, -NORTH2D, {10, 10}) == std::make_pair<GlobalPosition2D>({10, 0}, 10.F));
+static_assert(find_arc_centre<int>({20, 0}, -NORTH2D, {10, 10}) == std::make_pair<GlobalPosition2D>({10, 0}, -10.F));
+static_assert(find_arc_centre<int>({10, 0}, -NORTH2D, {10, 10}).second == 0.F);
+static_assert(isWithinLimit(find_arc_centre<int>({0, 0}, pi + quarter_pi, {1000, 1000}).second, 0.F, 0.1F));
+#endif
+
 // NOLINTEND(readability-magic-numbers)
 
 float
diff --git a/lib/maths.h b/lib/maths.h
index 93a4322..09af048 100644
--- a/lib/maths.h
+++ b/lib/maths.h
@@ -427,38 +427,36 @@ linesIntersectAt(const glm::vec<2, T, Q> Aabs, const glm::vec<2, T, Q> Babs, con
 template<std::floating_point T> constexpr auto EPSILON = 0.0001F;
 
 template<std::floating_point T>
-auto
+[[nodiscard]] constexpr auto
 isWithinLimit(T lhs, T rhs, T limit = EPSILON<T>)
 {
 	return std::abs(lhs - rhs) <= limit;
 }
 
-template<Arithmetic T, glm::qualifier Q = glm::defaultp>
-std::pair<glm::vec<2, T, Q>, bool>
-find_arc_centre(glm::vec<2, T, Q> start, Angle entrys, glm::vec<2, T, Q> end, Angle entrye)
+template<Arithmetic T, std::floating_point D, glm::qualifier Q = glm::defaultp>
+constexpr std::pair<glm::vec<2, T, Q>, D>
+find_arc_centre(glm::vec<2, T, Q> start, glm::vec<2, D, Q> entrys, glm::vec<2, T, Q> end)
 {
 	if (start == end) {
-		return {start, false};
+		return {start, 0};
 	}
-	return find_arc_centre(start, sincos(entrys + half_pi), end, sincos(entrye - half_pi));
+	const auto diffEnds = difference(end, start);
+	const auto offset = entrys.x * diffEnds.y - entrys.y * diffEnds.x;
+	if (offset == 0.F) {
+		return {start, offset};
+	}
+	const auto midEnds = start + ((end - start) / 2);
+	const auto centre = linesIntersectAtDirs(start, vector_normal(entrys), midEnds, vector_normal(diffEnds));
+	return {*centre, offset};
 }
 
 template<Arithmetic T, glm::qualifier Q = glm::defaultp>
-std::pair<glm::vec<2, T, Q>, bool>
+constexpr std::pair<glm::vec<2, T, Q>, float>
 find_arc_centre(glm::vec<2, T, Q> start, Angle entrys, glm::vec<2, T, Q> end)
 {
-	if (start == end) {
-		return {start, false};
-	}
-	const auto startNormal = vector_normal(sincos(entrys) * 10'000.F);
-	const auto diffEnds = difference(end, start);
-	const auto midEnds = start + ((end - start) / 2);
-	const auto diffNormal = vector_normal(diffEnds);
-	const auto centre = linesIntersectAt(start, start + startNormal, midEnds, midEnds + diffNormal);
-	return {*centre, normalize(vector_yaw(diffEnds) - entrys) < 0};
+	return find_arc_centre(start, sincos(entrys), end);
 }
 
-
 template<Arithmetic T>
 auto
 midpoint(const std::pair<T, T> & v)
diff --git a/test/test-network.cpp b/test/test-network.cpp
index 0739073..9a9ceb3 100644
--- a/test/test-network.cpp
+++ b/test/test-network.cpp
@@ -102,21 +102,25 @@ namespace {
 	struct TestNetwork : public EmptyNetwork {
 		TestNetwork()
 		{
-			/*       0        1        2
-			 /   -> p000 <-> p100 <-> p200 <-> p300
-			 / /            /              \.
-			 / 3            5              4
-			 /  \           /             /
-			 /    --> p110 <-------------   */
+			/*
+			 *   4--> p110 <---------6-------
+			 * /            8                 \.
+			 * 3            7                  5
+			 *  \           \                 /
+			 *   -> p000 <-0-> p100 <-1-> p200 <-2-> p300  */
+			// 0, 1 and 2 - 3 straight links between 4 nodes
 			add(nullptr, createChain(nullptr, std::array {P000, P100, P200, P300}));
+			// 3 and 4 - RH biarc from p000 to p110
 			add(nullptr,
 					create(nullptr,
 							{.fromEnd = {.position = P000, .direction = -half_pi},
 									.toEnd = {.position = P110, .direction = -half_pi}}));
+			// 5 and 6 - LH biarc from p200 to p110
 			add(nullptr,
 					create(nullptr,
 							{.fromEnd = {.position = P200, .direction = half_pi},
 									.toEnd = {.position = P110, .direction = half_pi}}));
+			// 7 and 8 - RL S biarc from p100 to p110
 			add(nullptr,
 					create(nullptr,
 							{.fromEnd = {.position = P100, .direction = -half_pi},
@@ -182,21 +186,25 @@ BOOST_AUTO_TEST_CASE(NetworkJoins)
 	// Join 0 <-> 1
 	BOOST_REQUIRE_EQUAL(links[0]->ends[1].nexts.size(), 2);
 	BOOST_CHECK_EQUAL(links[0]->ends[1].nexts[0].first.lock().get(), links[1].get());
-	BOOST_CHECK_EQUAL(links[0]->ends[1].nexts[0].second, 1);
+	BOOST_CHECK_EQUAL(links[0]->ends[1].nexts[0].second, 0);
 	BOOST_CHECK_EQUAL(links[0]->ends[1].nexts[1].first.lock().get(), links[7].get());
 	BOOST_CHECK_EQUAL(links[0]->ends[1].nexts[1].second, 1);
 	BOOST_REQUIRE_EQUAL(links[1]->ends[0].nexts.size(), 2);
-	BOOST_CHECK_EQUAL(links[1]->ends[0].nexts[0].first.lock().get(), links[2].get());
-	BOOST_CHECK_EQUAL(links[1]->ends[0].nexts[0].second, 0);
-	BOOST_CHECK_EQUAL(links[1]->ends[0].nexts[1].first.lock().get(), links[5].get());
-	BOOST_CHECK_EQUAL(links[1]->ends[0].nexts[1].second, 0);
+	BOOST_CHECK_EQUAL(links[1]->ends[0].nexts[0].first.lock().get(), links[0].get());
+	BOOST_CHECK_EQUAL(links[1]->ends[0].nexts[0].second, 1);
+	BOOST_CHECK_EQUAL(links[1]->ends[0].nexts[1].first.lock().get(), links[7].get());
+	BOOST_CHECK_EQUAL(links[1]->ends[0].nexts[1].second, 1);
 	// Join 1 <-> 2
 	BOOST_REQUIRE_EQUAL(links[1]->ends[1].nexts.size(), 2);
-	BOOST_CHECK_EQUAL(links[1]->ends[1].nexts[0].first.lock().get(), links[0].get());
-	BOOST_CHECK_EQUAL(links[1]->ends[1].nexts[0].second, 1);
+	BOOST_CHECK_EQUAL(links[1]->ends[1].nexts[0].first.lock().get(), links[2].get());
+	BOOST_CHECK_EQUAL(links[1]->ends[1].nexts[0].second, 0);
+	BOOST_CHECK_EQUAL(links[1]->ends[1].nexts[1].first.lock().get(), links[5].get());
+	BOOST_CHECK_EQUAL(links[1]->ends[1].nexts[1].second, 0);
 	BOOST_REQUIRE_EQUAL(links[2]->ends[0].nexts.size(), 2);
 	BOOST_CHECK_EQUAL(links[2]->ends[0].nexts[0].first.lock().get(), links[1].get());
-	BOOST_CHECK_EQUAL(links[2]->ends[0].nexts[0].second, 0);
+	BOOST_CHECK_EQUAL(links[2]->ends[0].nexts[0].second, 1);
+	BOOST_CHECK_EQUAL(links[2]->ends[0].nexts[1].first.lock().get(), links[5].get());
+	BOOST_CHECK_EQUAL(links[2]->ends[0].nexts[1].second, 0);
 }
 
 BOOST_DATA_TEST_CASE(RouteToNodeNotInNetwork, INVALID_NODES, dest)
@@ -302,6 +310,54 @@ BOOST_AUTO_TEST_CASE(NetworkCreateStraight)
 	BOOST_CHECK_EQUAL(nodes.size(), 2);
 }
 
+BOOST_AUTO_TEST_CASE(NetworkCreateExtendingStraight)
+{
+	const auto link = create(nullptr,
+			CreationDefinition {
+					.fromEnd = {.position = {0, 0, 0}, .direction = pi + quarter_pi},
+					.toEnd = {.position = {1000, 1000, 0}, .direction = {}},
+			});
+	BOOST_REQUIRE_EQUAL(link.size(), 1);
+	BOOST_CHECK(links.empty());
+	BOOST_CHECK(nodes.empty());
+
+	BOOST_CHECK_IF(straight, std::dynamic_pointer_cast<TestLinkS>(link.front())) {
+		BOOST_CHECK_CLOSE(straight->length, 1414, 1);
+		BOOST_CHECK_CLOSE_VECI(straight->ends.front().node->pos, GlobalPosition3D(0, 0, 0));
+		BOOST_CHECK_CLOSE(straight->ends.front().dir, quarter_pi - pi, 1);
+		BOOST_CHECK_CLOSE_VECI(straight->ends.back().node->pos, GlobalPosition3D(1000, 1000, 0));
+		BOOST_CHECK_CLOSE(straight->ends.back().dir, quarter_pi, 1);
+	}
+
+	add(nullptr, link.front());
+	BOOST_CHECK_EQUAL(links.size(), 1);
+	BOOST_CHECK_EQUAL(nodes.size(), 2);
+}
+
+BOOST_AUTO_TEST_CASE(NetworkCreateExtendeeStraight)
+{
+	const auto link = create(nullptr,
+			CreationDefinition {
+					.fromEnd = {.position = {0, 0, 0}, .direction = {}},
+					.toEnd = {.position = {1000, 1000, 0}, .direction = quarter_pi},
+			});
+	BOOST_REQUIRE_EQUAL(link.size(), 1);
+	BOOST_CHECK(links.empty());
+	BOOST_CHECK(nodes.empty());
+
+	BOOST_CHECK_IF(straight, std::dynamic_pointer_cast<TestLinkS>(link.front())) {
+		BOOST_CHECK_CLOSE(straight->length, 1414, 1);
+		BOOST_CHECK_CLOSE_VECI(straight->ends.front().node->pos, GlobalPosition3D(1000, 1000, 0));
+		BOOST_CHECK_CLOSE(straight->ends.front().dir, quarter_pi, 1);
+		BOOST_CHECK_CLOSE_VECI(straight->ends.back().node->pos, GlobalPosition3D(0, 0, 0));
+		BOOST_CHECK_CLOSE(straight->ends.back().dir, quarter_pi - pi, 1);
+	}
+
+	add(nullptr, link.front());
+	BOOST_CHECK_EQUAL(links.size(), 1);
+	BOOST_CHECK_EQUAL(nodes.size(), 2);
+}
+
 BOOST_AUTO_TEST_CASE(NetworkCreateExtendingCurve)
 {
 	const auto link = create(nullptr,
@@ -396,24 +452,41 @@ BOOST_AUTO_TEST_CASE(NetworkCreateBiarcPair)
 	BOOST_CHECK_EQUAL(link.back()->ends.back().nexts.front().first.lock(), link.front());
 }
 
-BOOST_AUTO_TEST_CASE(NetworkCreateBiarcPairEqTan)
+BOOST_AUTO_TEST_CASE(NetworkCreateBiarcPairEqTanLH)
 {
-	// This could be achieved with a single curve, but not there yet
+	// Creates a biarc pair and then merges them into a single curve
 	const auto link = create(nullptr,
 			CreationDefinition {
-					.fromEnd = {.position = {0, 0, 0}, .direction = 0},
-					.toEnd = {.position = {1000, 0, 0}, .direction = 0},
+					.fromEnd = {.position = {1000, 0, 0}, .direction = 0},
+					.toEnd = {.position = {0, 0, 0}, .direction = 0},
 			});
-	BOOST_REQUIRE_EQUAL(link.size(), 2);
+	BOOST_REQUIRE_EQUAL(link.size(), 1);
 	BOOST_CHECK(links.empty());
 	BOOST_CHECK(nodes.empty());
 
 	BOOST_CHECK_IF(firstCurve, std::dynamic_pointer_cast<TestLinkC>(link.front())) {
+		BOOST_CHECK_CLOSE_VECI(firstCurve->ends.front().node->pos, GlobalPosition3D(1000, 0, 0));
+		BOOST_CHECK_CLOSE_VECI(firstCurve->ends.back().node->pos, GlobalPosition3D(0, 0, 0));
 		BOOST_CHECK_CLOSE_VECI(firstCurve->centreBase, GlobalPosition3D(500, 0, 0));
 	}
+}
 
-	BOOST_CHECK_IF(secondCurve, std::dynamic_pointer_cast<TestLinkC>(link.back())) {
-		BOOST_CHECK_CLOSE_VECI(secondCurve->centreBase, GlobalPosition3D(500, 0, 0));
+BOOST_AUTO_TEST_CASE(NetworkCreateBiarcPairEqTanRH)
+{
+	// Creates a biarc pair and then merges them into a single curve
+	const auto link = create(nullptr,
+			CreationDefinition {
+					.fromEnd = {.position = {0, 0, 0}, .direction = 0},
+					.toEnd = {.position = {1000, 0, 0}, .direction = 0},
+			});
+	BOOST_REQUIRE_EQUAL(link.size(), 1);
+	BOOST_CHECK(links.empty());
+	BOOST_CHECK(nodes.empty());
+
+	BOOST_CHECK_IF(firstCurve, std::dynamic_pointer_cast<TestLinkC>(link.front())) {
+		BOOST_CHECK_CLOSE_VECI(firstCurve->ends.front().node->pos, GlobalPosition3D(1000, 0, 0));
+		BOOST_CHECK_CLOSE_VECI(firstCurve->ends.back().node->pos, GlobalPosition3D(0, 0, 0));
+		BOOST_CHECK_CLOSE_VECI(firstCurve->centreBase, GlobalPosition3D(500, 0, 0));
 	}
 }