/**
 * @fileoverview
 *
 * Interface with the OpenStreetMap collaborative mapping database.
 */

import axios from "axios";
import { isObject } from "../../util.js";

/** Replace a value for use in an Overpass query. */
export const escape = value =>
    value.replace("'", "\\'").replace('"', '\\"').replace("\\", "\\\\");

/**
 * Transform a set of tag queries into an Overpass set of filters.
 *
 * @param {Object} tags A set of tag queries.
 * @return {string} Corresponding Overpass filter.
 */
export const buildFilter = tags => Object.entries(tags).filter(
    ([key, value]) => {
        return value !== undefined && value !== null;
    }
).map(
    ([key, value]) => {
        if (value === true) {
            return `[${key}]`;
        }

        if (value === false) {
            return `[!${key}]`;
        }

        if (value === "") {
            // See <https://github.com/drolbr/Overpass-API/issues/92>
            return `[${key}~"^$"]`;
        }

        return `[${key}="${escape(value)}"]`
    }
).join("");

/**
 * Get the appropriate tag query for matching ways that can be used by a given
 * public transport vehicle.
 * @param {string} type Type of public transport vehicle.
 * @return {Object} Set of tag queries.
 */
export const vehicleWayFilter = type => {
    switch (type) {
        case "bus":
            return {highway: true};

        case "train":
        case "subway":
        case "light_rail":
        case "tram":
            return {railway: type};

        default:
            throw new Error(`Unknown vehicle type: ${type}`);
    }
};

/**
 * Submit a query to an Overpass endpoint.
 *
 * @see <https://wiki.osm.org/Overpass_API/Overpass_QL> for more
 * information on the Overpass Query Language (Overpass QL).
 * @async
 * @param {string} query Query to send.
 * @param {string} [endpoint] Overpass endpoint to use.
 * @returns {string|Object} Results returned by the endpoint. If JSON output
 * is requested in the query, the result will automatically be parsed into
 * a JS object.
 */
export const runQuery = (
    query,
    endpoint = "https://lz4.overpass-api.de/api/interpreter"
) => {
    console.log("Running query:", query);
    return axios.post(endpoint, `data=${query}`)
        .then(res => res.data);
};

/**
 * Create a link to view a node.
 * @param {string|number} id Identifier for the node to view.
 * @returns {string} Link to view this node on the OSM website.
 */
export const viewNode = id => `https://www.osm.org/node/${id}`;

/**
 * Determine if an OSM way is one-way or not.
 *
 * @see <https://wiki.osm.org/Key:oneway>
 * @param {Object} obj OSM way object.
 * @returns {boolean} Whether the way is one-way.
 */
export const isOneWay = obj => (
    obj.type === "way" &&
    isObject(obj.tags) &&
    (obj.tags.oneway === "yes" || obj.tags.junction === "roundabout" ||
        obj.tags.highway === "motorway")
);

/**
 * Determine if a node is a railway crossing or not.
 *
 * @see <https://wiki.osm.org/Tag:railway=railway_crossing>
 * @param {Object} obj OSM node object.
 * @return {boolean} Whether the node is a railway crossing.
 */
export const isRailwayCrossing = obj => (
    obj.type === "node" &&
    isObject(obj.tags) &&
    (obj.tags.railway === "railway_crossing")
);

/**
 * Determine if an OSM object is a public transport line (route master).
 *
 * @see <https://wiki.osm.org/Relation:route_master>
 * @see <https://wiki.osm.org/Public_transport#Route_Master_relations>
 * @param {Object} obj OSM relation object.
 * @returns {boolean} Whether the relation is a public transport line.
 */
export const isTransportLine = obj => (
    obj.type === "relation" &&
    isObject(obj.tags) &&
    obj.tags.type === "route_master"
);

/**
 * Determine if a public transport route member has a valid role for
 * the initial segment of stops and platforms according to PTv2.
 *
 * @see <https://wiki.openstreetmap.org/wiki/Public_transport#Service_routes>
 * @param {string} role Role to check.
 * @returns {boolean} Whether the role is valid.
 */
export const isInitialRouteRole = role => (
    role === "stop" || role === "stop_entry_only" || role === "stop_exit_only"
    || role === "platform" || role === "platform_entry_only"
    || role === "platform_exit_only"
);