Fetch taginfo: add code to get all countries, imrove docs

src/Logic/Web/TagInfo.ts

@@ -1,35 +1,48 @@
 import { Utils } from "../../Utils"
+import type { FeatureCollection } from "geojson"
 
 export interface TagInfoStats {
     /**
      * The total number of entries in the data array, **not** the total number of objects known in OSM!
      *
      * Use `data.find(item => item.type==="all").count` for this
+     * @deprecated: you probably want to use data.find(item => item.type==="all").count
      */
     total: number
     data: {
         type: "all" | "nodes" | "ways" | "relations"
+        // Absolute number
         count: number
+        // Relative, percentage
         count_fraction: number
     }[]
 }
 
+interface GeofabrikCountryProperties {
+    id: string,
+    parent: string | "europe" | "asia",
+    urls: string[],
+    name: string,
+    "iso3166-1:alpha2": string[]
+}
+
 export default class TagInfo {
     public static readonly global = new TagInfo()
     private readonly _backend: string
+    private static _geofabrikCountries = undefined
 
     constructor(backend = "https://taginfo.openstreetmap.org/") {
         this._backend = backend
     }
 
-    public getStats(key: string, value?: string): Promise<TagInfoStats> {
+    public async getStats(key: string, value?: string): Promise<TagInfoStats> {
         let url: string
         if (value) {
             url = `${this._backend}api/4/tag/stats?key=${key}&value=${value}`
         } else {
             url = `${this._backend}api/4/key/stats?key=${key}`
         }
-        return Utils.downloadJsonCached(url, 1000 * 60 * 60)
+        return await Utils.downloadJsonCached<TagInfoStats>(url, 1000 * 60 * 60)
     }
 
     /**
@@ -44,4 +57,65 @@ export default class TagInfo {
             return `${this._backend}/keys/${k}#overview`
         }
     }
+
+    /**
+     * Does not work in the browser due to some resources not being CORS-accessible
+     */
+    public static async geofabrikCountries(): Promise<GeofabrikCountryProperties[]> {
+        if (TagInfo._geofabrikCountries) {
+            return TagInfo._geofabrikCountries
+        }
+        const countriesFC: FeatureCollection = await Utils.downloadJsonCached<FeatureCollection>("https://download.geofabrik.de/index-v1-nogeom.json", 24 * 1000 * 60 * 60)
+        TagInfo._geofabrikCountries = countriesFC.features.map(f => <GeofabrikCountryProperties>f.properties)
+        return TagInfo._geofabrikCountries
+    }
+
+    /**
+     * Creates a TagInfo-api-object for geofabrik for the given country.
+     * Returns undefined if geofabrik does not have such a country
+     *
+     * Does not work in the browser due to some resources not being CORS-accessible
+     * @param countryCode: an iso3166-1:alpha2 code
+     */
+    public static async getInstanceFor(countryCode: string) {
+        const countries = await this.geofabrikCountries()
+        countryCode = countryCode.toUpperCase()
+        const country = countries.find(c => c["iso3166-1:alpha2"]?.indexOf(countryCode) >= 0)
+        if (!country || !country?.parent || !country?.id) {
+            return undefined
+        }
+        const url = `https://taginfo.geofabrik.de/${country.parent}:${country.id}/`
+        return new TagInfo(url)
+    }
+
+    private static async getDistributionsFor(countryCode: string, key: string, value?: string): Promise<TagInfoStats>{
+        if (!countryCode) {
+            return undefined
+        }
+        const ti = await TagInfo.getInstanceFor(countryCode)
+        if (!ti) {
+            return undefined
+        }
+        try {
+           return await ti.getStats(key, value)
+        } catch (e) {
+            console.warn("Could not fetch info for", countryCode,key,value, "due to", e)
+            return undefined
+        }
+    }
+
+    public static async getGlobalDistributionsFor(key: string, value?: string): Promise<Record<string, TagInfoStats>> {
+        const countries = await this.geofabrikCountries()
+        const perCountry: Record<string, TagInfoStats> = {}
+        const results = await Promise.all(countries.map(country => TagInfo.getDistributionsFor(country?.["iso3166-1:alpha2"]?.[0], key, value)))
+        for (let i = 0; i < countries.length; i++){
+            const country = countries[i]
+            const countryCode = country["iso3166-1:alpha2"]?.[0]
+            if(results[i]){
+             perCountry[countryCode] = results[i]
+            }
+        }
+        return perCountry
+    }
+
 }