import network from "./network.json";

/**
 * Find a route linking two nodes or stops.
 * @param {string} from ID of the starting stop or node.
 * @param {string} to ID of the ending stop or node.
 * @return {lineString?} If it exists, a segment linking the two nodes that has
 * the least number of nodes possible.
 */
export const findRoute = (from, to) => {
    const queue = [from];
    const parent = {from: from};

    while (queue.length > 0 && !(to in parent)) {
        const current = queue.shift();

        for (const successor of network.navigation[current].successors) {
            if (!(successor in parent)) {
                queue.push(successor);
                parent[successor] = current;
            }
        }
    }

    if (!(to in parent)) {
        return null;
    }

    const path = [];
    let current = to;

    while (current !== from) {
        path.push(current);
        current = parent[current];
    }

    path.push(from);
    path.reverse();
    return path;
};