fix: .

Author: aiAdrian

documentation/GTFS_IMPORT.md

@@ -112,7 +112,21 @@ After merge:
 
 Topology consolidation is executed only after this stage, i.e. on final trainruns/trainrun sections.
 
-## 7. Phase D: Topology Consolidation (Post-Creation)
+## 7. Phase D: Topology Consolidation (Post-Creation) 
+
+Once all trains have been created, meaning trainruns with their `n` trainrun sections, and once it is known whether a train is `ONE_WAY` or `ROUND_TRIP`, topology consolidation is executed as a follow-up step. This consolidation runs only when explicitly enabled. If enabled, the global detour limits are applied for alternative-path mapping: the alternative connection may be at most `(1 + xx%) * travelTime` of the replaced section, or at most `travelTime + yy` minutes. In addition, an edge is replaced only if the found alternative path contains more than one edge.
+
+The basis is an undirected graph built from already-created trainrun sections. For each trainrun section, `sourceNode` and `targetNode` are read; all appearing nodes form vertex set `V`, and all connections form edge set `E`. Each edge stores the list of attached trainrun sections, since `1:m` sections can belong to one edge. Edge weight is the minimum travel time over attached sections, constrained by lower bound `A`. This defines the basis graph `G(V,E)`.
+
+Consolidation starts by sorting all edges ascending by weight. Then edges are processed one by one. For an edge `e` between `n1` and `n2`, an alternative path from `n1` to `n2` is searched while temporarily excluding `e`. This is the shortest path without `e`. If no path is found, nothing happens. If path travel time exceeds the allowed threshold, nothing happens. If the path has only one edge, an error is logged, because that indicates an invalid parallel duplicate connection between the same node pair.
+
+If all criteria are met, all trainrun sections attached to edge `e` are replaced atomically: the direct connection between `n1` and `n2` is replaced by the alternative edge chain. One new trainrun section is created per path edge. Travel times of these new sections are interpolated proportionally based on cumulative minimum path travel time and the original section travel time. Each segment must be at least `A` minutes, with default `A = 1`, configurable via import options.
+
+After successful replacement, the old edge is removed from the basis graph, new sections are attached to affected edge lists, and minimum edge weights are recomputed. A change flag marks that the graph changed in this round. After one full pass over all edges, the next pass starts. This repeats until no further changes occur or maximum iterations are reached. The default starting value is `n = 10` full passes.
+
+Additional safety rules prevent invalid remappings: an alternative path may be used for a specific trainrun only if its newly inserted intermediate nodes do not already appear elsewhere in the same trainrun. This prevents loops and backtracking such as `A -> B -> C -> B -> D`. After replacement, the affected trainrun must still be a simple linear path without reusing already visited intermediate nodes. Optionally, replacements can also be forbidden when they reuse edges already used elsewhere in the same trainrun.
+
+For transition semantics, the target behavior is: GTFS-defined stops stay stop transitions, while consolidation-inserted intermediate nodes are non-stop passages. Note the boolean semantics: `isNonStopTransit = false` means stop, and `isNonStopTransit = true` means non-stop. Therefore, after 3rd-party transition materialization, GTFS stop nodes are explicitly enforced as stop per trainrun, and all other nodes on the route are marked non-stop.
 
 ### 7.1 Activation Condition
 
@@ -252,18 +266,3 @@ When validating a feed import, verify:
 
 The GTFS import pipeline first creates full trainruns/trainrun sections, then performs optional post-creation topology consolidation on an undirected basis graph with strict safety guards, iterative convergence, and stop/non-stop behavior enforcement aligned with original GTFS stop semantics.
 
-## 13. Consolidation as Prose (Merged Specification)
-
-Once all trains have been created, meaning trainruns with their `n` trainrun sections, and once it is known whether a train is `ONE_WAY` or `ROUND_TRIP`, topology consolidation is executed as a follow-up step. This consolidation runs only when explicitly enabled. If enabled, the global detour limits are applied for alternative-path mapping: the alternative connection may be at most `(1 + xx%) * travelTime` of the replaced section, or at most `travelTime + yy` minutes. In addition, an edge is replaced only if the found alternative path contains more than one edge.
-
-The basis is an undirected graph built from already-created trainrun sections. For each trainrun section, `sourceNode` and `targetNode` are read; all appearing nodes form vertex set `V`, and all connections form edge set `E`. Each edge stores the list of attached trainrun sections, since `1:m` sections can belong to one edge. Edge weight is the minimum travel time over attached sections, constrained by lower bound `A`. This defines the basis graph `G(V,E)`.
-
-Consolidation starts by sorting all edges ascending by weight. Then edges are processed one by one. For an edge `e` between `n1` and `n2`, an alternative path from `n1` to `n2` is searched while temporarily excluding `e`. This is the shortest path without `e`. If no path is found, nothing happens. If path travel time exceeds the allowed threshold, nothing happens. If the path has only one edge, an error is logged, because that indicates an invalid parallel duplicate connection between the same node pair.
-
-If all criteria are met, all trainrun sections attached to edge `e` are replaced atomically: the direct connection between `n1` and `n2` is replaced by the alternative edge chain. One new trainrun section is created per path edge. Travel times of these new sections are interpolated proportionally based on cumulative minimum path travel time and the original section travel time. Each segment must be at least `A` minutes, with default `A = 1`, configurable via import options.
-
-After successful replacement, the old edge is removed from the basis graph, new sections are attached to affected edge lists, and minimum edge weights are recomputed. A change flag marks that the graph changed in this round. After one full pass over all edges, the next pass starts. This repeats until no further changes occur or maximum iterations are reached. The default starting value is `n = 10` full passes.
-
-Additional safety rules prevent invalid remappings: an alternative path may be used for a specific trainrun only if its newly inserted intermediate nodes do not already appear elsewhere in the same trainrun. This prevents loops and backtracking such as `A -> B -> C -> B -> D`. After replacement, the affected trainrun must still be a simple linear path without reusing already visited intermediate nodes. Optionally, replacements can also be forbidden when they reuse edges already used elsewhere in the same trainrun.
-
-For transition semantics, the target behavior is: GTFS-defined stops stay stop transitions, while consolidation-inserted intermediate nodes are non-stop passages. Note the boolean semantics: `isNonStopTransit = false` means stop, and `isNonStopTransit = true` means non-stop. Therefore, after 3rd-party transition materialization, GTFS stop nodes are explicitly enforced as stop per trainrun, and all other nodes on the route are marked non-stop.