obitools4/autodoc/docmd/pkg/obigraph/graph.md

obigraph Package: Semantic Overview

The obigraph package provides a generic, type-safe undirected/directed graph implementation in Go. Its core features include:

• Generic Graph Structure: Parametrized over vertex type V and edge data type T, enabling flexible use with arbitrary user-defined types.

• Bidirectional Edge Tracking: Maintains both forward (Edges) and reverse (ReverseEdges) adjacency maps for efficient neighbor/parent queries.

• Edge Management:

  • AddEdge: Adds an undirected edge (inserted in both directions).
  • AddDirectedEdge: Adds a directed edge (only one direction).
  • SetAsDirectedEdge: Converts an existing undirected edge into a directed one by removing the reverse link.

• Graph Queries:

  • Neighbors(v): Returns all adjacent vertices (outgoing in directed case).
  • Parents(v): Returns incoming neighbors via reverse adjacency.
  • Degree(v) / ParentDegree(v): Compute vertex degrees (total or incoming).

• Customizable Vertex/Edge Properties:

  • VertexWeight, EdgeWeight: Funcs to assign weights (default: constant weight = 1.0).
  • VertexId: Custom vertex label generator (default: "V%d").

• GML Export:

  • Gml(...) / WriteGml(...): Generates or writes a Graph Modelling Language (GML) representation.
  • Supports directed/undirected modes, degree-based filtering (min_degree), and visual styling:
    • Vertex shape: circle if weight ≥ threshold, else rectangle.
    • Size scaled by square root of vertex weight.
  • Uses Go’s text/template for rendering.

• File I/O: Directly writes GML to file via WriteGmlFile(...).

• Logging & Safety: Uses Logrus for bounds-checking errors; panics on template parsing/writing failures.

The package is designed for lightweight, high-performance graph modeling and visualization-ready export.