import * as turfHelpers from "@turf/helpers";
import dijkstra from "dijkstrajs";
import network from "./network.json";

// Transform the navigation graph to be in the format expected by dijkstrajs
const graph = {};

for (const [beginId, begin] of Object.entries(network.navigation)) {
    const neighbors = {};

    for (const [endId, end] of Object.entries(begin)) {
        neighbors[endId] = end.properties.length;
    }

    graph[beginId] = neighbors;
}

/**
 * Get the OSM ID of a stop.
 * @param {string} stopId Network ID of the stop.
 * @return {string} OSM ID of the stop.
 */
export const stopToOSM = stopId => network.stops[stopId].properties.node;

/**
 * Find the shortest path of nodes linking two stops.
 * @param {string} fromStop Network ID of the starting stop.
 * @param {string} toStop Network ID of the ending stop.
 * @return {Array.<string>} If it exists, a path of nodes joining the two stops.
 */
export const findPath = (fromStop, toStop) => {
    try {
        return dijkstra.find_path(
            graph, stopToOSM(fromStop), stopToOSM(toStop)
        );
    } catch (err) {
        return null;
    }
};

/**
 * Find the shortest segment linking two nodes or stops.
 * @param {string} fromStop Network ID of the starting stop.
 * @param {string} toStop Network ID of the ending stop.
 * @return {LineString?} If it exists, a segment joining the two stops.
 */
export const findSegment = (fromStop, toStop) => {
    const path = findPath(fromStop, toStop);

    if (path === null) {
        return null;
    }

    const initial = network.navigation[path[0]][path[1]];
    let points = [...initial.geometry.coordinates];
    let length = initial.properties.length;

    for (let i = 1; i + 1 < path.length; ++i) {
        const current = network.navigation[path[i]][path[i + 1]];
        points = points.concat(current.geometry.coordinates.slice(1));
        length += current.properties.length;
    }

    const route = turfHelpers.lineString(points);
    route.properties.length = length;
    return route;
};