@graphty/layout/src/generators/basic.ts

graph layout algorithms based on networkx

/**
 * Basic graph generation functions
 */

import { Graph, Node, Edge } from '../types';

/**
 * Create a complete graph with n nodes
 * @param n - Number of nodes
 * @returns Graph object with all nodes connected to all other nodes
 */
export function completeGraph(n: number): Graph {
  const nodes: Node[] = Array.from({ length: n }, (_, i) => i);
  const edges: Edge[] = [];
  
  for (let i = 0; i < n; i++) {
    for (let j = i + 1; j < n; j++) {
      edges.push([i, j]);
    }
  }
  
  return {
    nodes: () => nodes,
    edges: () => edges
  };
}

/**
 * Create a cycle graph with n nodes
 * @param n - Number of nodes
 * @returns Graph object with nodes connected in a cycle
 */
export function cycleGraph(n: number): Graph {
  const nodes: Node[] = Array.from({ length: n }, (_, i) => i);
  const edges: Edge[] = [];
  
  for (let i = 0; i < n; i++) {
    edges.push([i, (i + 1) % n]);
  }
  
  return {
    nodes: () => nodes,
    edges: () => edges
  };
}

/**
 * Create a star graph with n nodes (1 center + n-1 leaves)
 * @param n - Total number of nodes
 * @returns Graph object with star topology
 */
export function starGraph(n: number): Graph {
  const nodes: Node[] = Array.from({ length: n }, (_, i) => i);
  const edges: Edge[] = [];
  
  // Connect all nodes to node 0 (center)
  for (let i = 1; i < n; i++) {
    edges.push([0, i]);
  }
  
  return {
    nodes: () => nodes,
    edges: () => edges
  };
}

/**
 * Create a wheel graph with n nodes (1 center + n-1 rim nodes)
 * @param n - Total number of nodes
 * @returns Graph object with wheel topology
 */
export function wheelGraph(n: number): Graph {
  const nodes: Node[] = Array.from({ length: n }, (_, i) => i);
  const edges: Edge[] = [];
  
  // Connect all rim nodes to center (node 0)
  for (let i = 1; i < n; i++) {
    edges.push([0, i]);
  }
  
  // Connect rim nodes in a cycle
  for (let i = 1; i < n - 1; i++) {
    edges.push([i, i + 1]);
  }
  if (n > 2) {
    edges.push([n - 1, 1]);
  }
  
  return {
    nodes: () => nodes,
    edges: () => edges
  };
}