isochrone-explorer/src/utils/dijkstra.js

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

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

function dijkstra(graph, startNode, maxDistance, maxTime, nodeCoords, mode, modeType) {
  const visited = new Set();
  const distances = {};
  const queue = [];

  distances[startNode] = 0;
  queue.push({ node: startNode, cost: 0 });

  while (queue.length > 0) {
    queue.sort((a, b) => a.cost - b.cost);
    const { node: currentNode } = queue.shift();

    if (visited.has(currentNode)) continue;
    visited.add(currentNode);

    const neighbors = graph[currentNode] || [];
    for (const neighbor of neighbors) {
      const distance = neighbor.distance;
      const time = distance / (MODE_SPEEDS[mode] * 1000 / 3600);
      const cost = modeType === 'distance' ? distance : time;

      const newCost = distances[currentNode] + cost;

      const limit = modeType === 'distance' ? maxDistance : maxTime;
      if (limit && newCost > limit) continue;

      if (distances[neighbor.node] === undefined || newCost < distances[neighbor.node]) {
        distances[neighbor.node] = newCost;
        queue.push({ node: neighbor.node, cost: newCost });
      }
    }
  }

  return Object.keys(distances);
}

module.exports = { dijkstra };