From 3bb238d41ca4f3e4a40f4ee3700b27ca7bf03b56 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Fri, 28 Oct 2022 01:08:28 +0100
Subject: Implement extending a network to join link ends

---
 game/network/network.cpp    | 28 ++++++++++++++++++++++++++++
 game/network/network.h      |  2 ++
 game/network/network.impl.h | 21 +++++++++++++++++----
 3 files changed, 47 insertions(+), 4 deletions(-)

diff --git a/game/network/network.cpp b/game/network/network.cpp
index 7724c20..dd61f9b 100644
--- a/game/network/network.cpp
+++ b/game/network/network.cpp
@@ -109,3 +109,31 @@ Network::genCurveDef(const glm::vec3 & start, const glm::vec3 & end, float start
 	}
 	return {start, end, centre.first};
 }
+
+std::pair<GenCurveDef, GenCurveDef>
+Network::genCurveDef(const glm::vec3 & start, const glm::vec3 & end, float startDir, float endDir)
+{
+	startDir += pi;
+	endDir += pi;
+	const glm::vec2 flatStart {!start}, flatEnd {!end};
+	auto midheight = [&](auto mid) {
+		const auto sm = glm::distance(flatStart, mid), em = glm::distance(flatEnd, mid);
+		return start.z + ((end.z - start.z) * (sm / (sm + em)));
+	};
+	if (const auto radii = find_arcs_radius(flatStart, startDir, flatEnd, endDir); radii.first < radii.second) {
+		const auto radius {radii.first};
+		const auto c1 = flatStart + sincosf(startDir + half_pi) * radius;
+		const auto c2 = flatEnd + sincosf(endDir + half_pi) * radius;
+		const auto mid = (c1 + c2) / 2.F;
+		const auto midh = mid ^ midheight(mid);
+		return {{start, midh, c1}, {end, midh, c2}};
+	}
+	else {
+		const auto radius {radii.second};
+		const auto c1 = flatStart + sincosf(startDir - half_pi) * radius;
+		const auto c2 = flatEnd + sincosf(endDir - half_pi) * radius;
+		const auto mid = (c1 + c2) / 2.F;
+		const auto midh = mid ^ midheight(mid);
+		return {{midh, start, c1}, {midh, end, c2}};
+	}
+}
diff --git a/game/network/network.h b/game/network/network.h
index f37f335..4a2f56a 100644
--- a/game/network/network.h
+++ b/game/network/network.h
@@ -48,6 +48,8 @@ public:
 protected:
 	static void joinLinks(const Link::Ptr & l, const Link::Ptr & ol);
 	static GenCurveDef genCurveDef(const glm::vec3 & start, const glm::vec3 & end, float startDir);
+	static std::pair<GenCurveDef, GenCurveDef> genCurveDef(
+			const glm::vec3 & start, const glm::vec3 & end, float startDir, float endDir);
 
 	using Nodes = std::set<Node::Ptr, PtrMemberSorter<Node::Ptr, &Node::pos>>;
 	Nodes nodes;
diff --git a/game/network/network.impl.h b/game/network/network.impl.h
index 859d1ac..5b1649d 100644
--- a/game/network/network.impl.h
+++ b/game/network/network.impl.h
@@ -61,9 +61,16 @@ NetworkOf<T>::candidateStraight(glm::vec3 n1, glm::vec3 n2)
 
 template<typename T>
 Link::CCollection
-NetworkOf<T>::candidateJoins(glm::vec3 n1, glm::vec3 n2)
+NetworkOf<T>::candidateJoins(glm::vec3 start, glm::vec3 end)
 {
-	return {candidateLink<typename T::StraightLink>(n1, n2)};
+	if (glm::distance(start, end) < 2.F) {
+		return {};
+	}
+	const auto defs = genCurveDef(
+			start, end, findNodeDirection(candidateNodeAt(start).first), findNodeDirection(candidateNodeAt(end).first));
+	const auto & [c1s, c1e, c1c] = defs.first;
+	const auto & [c2s, c2e, c2c] = defs.second;
+	return {candidateLink<typename T::CurveLink>(c1s, c1e, c1c), candidateLink<typename T::CurveLink>(c2s, c2e, c2c)};
 }
 
 template<typename T>
@@ -83,9 +90,15 @@ NetworkOf<T>::addStraight(glm::vec3 n1, glm::vec3 n2)
 
 template<typename T>
 Link::CCollection
-NetworkOf<T>::addJoins(glm::vec3 n1, glm::vec3 n2)
+NetworkOf<T>::addJoins(glm::vec3 start, glm::vec3 end)
 {
-	return {addLink<typename T::StraightLink>(n1, n2)};
+	if (glm::distance(start, end) < 2.F) {
+		return {};
+	}
+	const auto defs = genCurveDef(start, end, findNodeDirection(nodeAt(start)), findNodeDirection(nodeAt(end)));
+	const auto & [c1s, c1e, c1c] = defs.first;
+	const auto & [c2s, c2e, c2c] = defs.second;
+	return {addLink<typename T::CurveLink>(c1s, c1e, c1c), addLink<typename T::CurveLink>(c2s, c2e, c2c)};
 }
 
 template<typename T>
-- 
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