From 5d79e0ac2fb76de764b109550decadf4af4259d4 Mon Sep 17 00:00:00 2001
From: Moritz Kobitzsch <moritz@mapbox.com>
Date: Mon, 5 Sep 2016 10:06:50 +0200
Subject: [PATCH] catch infinite loops

---
 features/guidance/bugs.feature                | 35 +++++++++++++++++++
 src/engine/guidance/post_processing.cpp       |  1 -
 .../guidance/intersection_generator.cpp       |  7 ++++
 3 files changed, 42 insertions(+), 1 deletion(-)
 create mode 100644 features/guidance/bugs.feature

diff --git a/features/guidance/bugs.feature b/features/guidance/bugs.feature
new file mode 100644
index 000000000..489262c68
--- /dev/null
+++ b/features/guidance/bugs.feature
@@ -0,0 +1,35 @@
+@routing @guidance
+Feature: Features related to bugs
+
+    Background:
+        Given the profile "car"
+        Given a grid size of 5 meters
+
+    @2852
+    Scenario: Loop
+        Given the node map
+            | a | 1 |   | g |   |   | b |
+            |   |   |   |   |   |   |   |
+            |   |   |   |   |   |   |   |
+            | e |   |   |   |   |   | f |
+            |   |   |   |   |   |   |   |
+            |   |   |   |   |   |   | 2 |
+            | d |   |   | h |   |   | c |
+
+        And the ways
+            | nodes | name   | oneway |
+            | agb   | top    | yes    |
+            | bfc   | right  | yes    |
+            | chd   | bottom | yes    |
+            | dea   | left   | yes    |
+
+        And the nodes
+            | node | highway         |
+            | g    | traffic_signals |
+            | f    | traffic_signals |
+            | h    | traffic_signals |
+            | e    | traffic_signals |
+
+        When I route I should get
+            | waypoints | route           | turns                        |
+            | 1,2       | top,right,right | depart,new name right,arrive |
diff --git a/src/engine/guidance/post_processing.cpp b/src/engine/guidance/post_processing.cpp
index 5c678711b..3c847fd05 100644
--- a/src/engine/guidance/post_processing.cpp
+++ b/src/engine/guidance/post_processing.cpp
@@ -1158,7 +1158,6 @@ std::vector<RouteStep> buildIntersections(std::vector<RouteStep> steps)
     std::size_t last_valid_instruction = 0;
     for (std::size_t step_index = 0; step_index < steps.size(); ++step_index)
     {
-        const auto next_step_index = step_index + 1;
         auto &step = steps[step_index];
         const auto instruction = step.maneuver.instruction;
         if (instruction.type == TurnType::Suppressed)
diff --git a/src/extractor/guidance/intersection_generator.cpp b/src/extractor/guidance/intersection_generator.cpp
index 049cea59e..e09fa7b48 100644
--- a/src/extractor/guidance/intersection_generator.cpp
+++ b/src/extractor/guidance/intersection_generator.cpp
@@ -574,6 +574,9 @@ IntersectionGenerator::GetActualNextIntersection(const NodeID starting_node,
     NodeID node_at_intersection = starting_node;
     EdgeID incoming_edge = via_edge;
 
+    // to prevent endless loops
+    const auto termination_node = node_based_graph.GetTarget(via_edge);
+
     while (result.size() == 2 &&
            node_based_graph.GetEdgeData(via_edge).IsCompatibleTo(
                node_based_graph.GetEdgeData(result[1].turn.eid)))
@@ -581,6 +584,10 @@ IntersectionGenerator::GetActualNextIntersection(const NodeID starting_node,
         node_at_intersection = node_based_graph.GetTarget(incoming_edge);
         incoming_edge = result[1].turn.eid;
         result = GetConnectedRoads(node_at_intersection, incoming_edge);
+
+        // When looping back to the original node, we obviously are in a loop. Stop there.
+        if (termination_node == node_based_graph.GetTarget(incoming_edge))
+            break;
     }
 
     // return output if requested