From 4562557d599fd70d32b15313ffebd976c3ddfa7d Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Sun, 14 Feb 2021 16:44:00 +0000
Subject: Maintain a history of links traversed

---
 game/vehicles/railloco.cpp | 18 ++++++++----------
 game/vehicles/vehicle.cpp  | 30 +++++++++++++++++++++++++++++-
 game/vehicles/vehicle.h    | 17 +++++++++++++++--
 3 files changed, 52 insertions(+), 13 deletions(-)

(limited to 'game/vehicles')

diff --git a/game/vehicles/railloco.cpp b/game/vehicles/railloco.cpp
index d06474c..146d2e0 100644
--- a/game/vehicles/railloco.cpp
+++ b/game/vehicles/railloco.cpp
@@ -12,25 +12,23 @@ void
 RailLoco::tick(TickDuration dur)
 {
 	linkDist += dur.count() * speed;
-	auto curLink {link.lock()};
-	while (linkDist > curLink->length) {
-		location = curLink->positionAt(curLink->length, linkDir);
-		const auto & nexts {curLink->nexts[1 - linkDir]};
+	auto curLink {linkHist.getAt(0.F)};
+	while (linkDist > curLink.first->length) {
+		location = curLink.first->positionAt(curLink.first->length, curLink.second);
+		const auto & nexts {curLink.first->nexts[1 - curLink.second]};
 		const auto next = std::find_if(nexts.begin(), nexts.end(), [ang = location.GetRot().y](const Link::Next & n) {
 			return std::abs(normalize(n.first.lock()->ends[n.second].second - ang)) < 0.1F;
 		});
 		if (next != nexts.end()) {
-			linkDist -= curLink->length;
-			link = next->first;
-			curLink = link.lock();
-			linkDir = next->second;
+			linkDist -= curLink.first->length;
+			curLink = linkHist.add(next->first, next->second);
 		}
 		else {
-			linkDist = curLink->length;
+			linkDist = curLink.first->length;
 			speed = 0;
 		}
 	}
-	location = curLink->positionAt(linkDist, linkDir);
+	location = curLink.first->positionAt(linkDist, curLink.second);
 }
 
 Brush47::Brush47(const LinkPtr & l) : RailLoco(l, "brush47.obj", "brush47.png") { }
diff --git a/game/vehicles/vehicle.cpp b/game/vehicles/vehicle.cpp
index c12181f..569063d 100644
--- a/game/vehicles/vehicle.cpp
+++ b/game/vehicles/vehicle.cpp
@@ -5,6 +5,34 @@
 #include <utility>
 
 Vehicle::Vehicle(const LinkPtr & l, const std::string & obj, const std::string & tex) :
-	Physical(l->ends.front().first->pos, obj, tex), link(l)
+	Physical(l->ends.front().first->pos, obj, tex)
 {
+	linkHist.add(l, 0);
+}
+
+LinkHistory::Return
+LinkHistory::add(const LinkWPtr & l, unsigned char d)
+{
+	links.insert(links.begin(), {l, d});
+	const auto lp = l.lock();
+	totalLen += lp->length;
+	while (totalLen >= 1000.F && !links.empty()) {
+		totalLen -= links.back().first.lock()->length;
+		links.pop_back();
+	}
+	return {lp, d};
+}
+
+LinkHistory::Return
+LinkHistory::getAt(float len) const
+{
+	auto litr = links.begin();
+	while (len > 0.F && litr != links.end()) {
+		len -= litr->first.lock()->length;
+		litr++;
+	}
+	if (litr == links.end()) {
+		litr--;
+	}
+	return {litr->first.lock(), litr->second};
 }
diff --git a/game/vehicles/vehicle.h b/game/vehicles/vehicle.h
index d59588c..f7defb3 100644
--- a/game/vehicles/vehicle.h
+++ b/game/vehicles/vehicle.h
@@ -6,13 +6,26 @@
 #include <game/worldobject.h>
 #include <string>
 
+class LinkHistory {
+public:
+	using Entry = std::pair<LinkWPtr, unsigned char /*dir*/>;
+	using Return = std::pair<LinkCPtr, unsigned char /*dir*/>;
+	Return add(const LinkWPtr &, unsigned char);
+	Return getAt(float) const;
+
+private:
+	std::vector<Entry> links;
+	float totalLen;
+};
+
 class Vehicle : public WorldObject, public Physical {
 public:
 	Vehicle(const LinkPtr & link, const std::string & obj, const std::string & tex);
-	LinkWPtr link; // Which link are we travelling along
-	unsigned char linkDir {0}; // Starting end e0->e1 or e1->e0
 	float linkDist {0}; // distance long current link
 	float speed {50}; // speed in m/s (~75 km/h)
+
+protected:
+	LinkHistory linkHist;
 };
 
 #endif
-- 
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