Function build_topology_graph 

pub fn build_topology_graph(
    netelements: &[Netelement],
    netrelations: &[NetRelation],
) -> Result<(DiGraph<NetelementSide, f64>, HashMap<NetelementSide, NodeIndex>), ProjectionError>

Build a directed graph representing the railway network topology

Creates a petgraph DiGraph where:

• Nodes are NetelementSide (each netelement has 2 nodes: start and end)
• Edges represent navigability:
  • Internal edges: start→end and end→start within each netelement
  • External edges: connections between netelements via netrelations

Graph Structure Example

For netelement “NE_A”:

• Node: NE_A position 0 (start)
• Node: NE_A position 1 (end)
• Internal edges: start→end (forward), end→start (backward)

For netrelation connecting NE_A(end) to NE_B(start) with forward navigability:

• External edge: NE_A position 1 → NE_B position 0

Parameters

• netelements: All track segments in the network
• netrelations: Navigability connections between segments

Returns

A DiGraph where edges represent valid navigation paths, and a mapping from NetelementSide to NodeIndex for efficient lookups.

Examples

use tp_lib_core::path::build_topology_graph;
use tp_lib_core::models::{Netelement, NetRelation};

let netelements = vec![/* ... */];
let netrelations = vec![/* ... */];

let (graph, node_map) = build_topology_graph(&netelements, &netrelations)?;

// Use graph for path finding algorithms