isochrone-explorer/src/utils/osmUtils.js

A powerful isochrone and routing engine based on Dijkstra's algorithm for accurate travel time calculations.

const { calculateDistance } = require('./geoUtils');

function parseGraph(osmData) {
  const graph = {};
  const nodeCoords = {};

  for (const element of osmData.elements) {
    if (element.type === 'node') {
      nodeCoords[element.id] = { lat: element.lat, lon: element.lon };
    }
  }

  for (const element of osmData.elements) {
    if (element.type === 'way') {
      const nodes = element.nodes;
      for (let i = 0; i < nodes.length - 1; i++) {
        const node1 = nodes[i];
        const node2 = nodes[i + 1];

        if (!graph[node1]) graph[node1] = [];
        if (!graph[node2]) graph[node2] = [];

        const distance = calculateDistance(nodeCoords[node1], nodeCoords[node2]);

        graph[node1].push({ node: node2, distance });
        graph[node2].push({ node: node1, distance });
      }
    }
  }

  return { graph, nodeCoords };
}

function findClosestNode(nodeCoords, lat, lon) {
  let minDistance = Infinity;
  let closestNode = null;

  for (const nodeId in nodeCoords) {
    const node = nodeCoords[nodeId];
    const distance = calculateDistance({ lat, lon }, node);
    if (distance < minDistance) {
      minDistance = distance;
      closestNode = nodeId;
    }
  }

  return closestNode;
}

module.exports = { parseGraph, findClosestNode };