MapComplete/Logic/Web/LiveQueryHandler.ts

import { UIEventSource } from "../UIEventSource"
import { Utils } from "../../Utils"

/**
 * Fetches data from random data sources, used in the metatagging
 */
export default class LiveQueryHandler {
    private static neededShorthands = {} // url -> (shorthand:paths)[]

    public static FetchLiveData(
        url: string,
        shorthands: string[]
    ): UIEventSource<any /* string -> string */> {
        const shorthandsSet: string[] = LiveQueryHandler.neededShorthands[url] ?? []

        for (const shorthand of shorthands) {
            if (shorthandsSet.indexOf(shorthand) < 0) {
                shorthandsSet.push(shorthand)
            }
        }
        LiveQueryHandler.neededShorthands[url] = shorthandsSet

        if (LiveQueryHandler[url] === undefined) {
            const source = new UIEventSource({})
            LiveQueryHandler[url] = source

            console.log("Fetching live data from a third-party (unknown) API:", url)
            Utils.downloadJson(url).then((data) => {
                for (const shorthandDescription of shorthandsSet) {
                    const descr = shorthandDescription.trim().split(":")
                    const shorthand = descr[0]
                    const path = descr[1]
                    const parts = path.split(".")
                    let trail = data
                    for (const part of parts) {
                        if (trail !== undefined) {
                            trail = trail[part]
                        }
                    }
                    source.data[shorthand] = trail
                }
                source.ping()
            })
        }
        return LiveQueryHandler[url]
    }
}