feat(country-data): Add country data service

src/app/app.module.ts

@@ -3,14 +3,16 @@ import { NgModule } from '@angular/core';
 
 import { AppRoutingModule } from './app-routing.module';
 import { AppComponent } from './app.component';
+import { CountryDataServiceModule } from './services/country-data/country-data.module';
 
 @NgModule({
   declarations: [
     AppComponent
   ],
   imports: [
     BrowserModule,
-    AppRoutingModule
+    AppRoutingModule,
+    CountryDataServiceModule
   ],
   providers: [],
   bootstrap: [

src/app/services/country-data/country-data.model.ts

@@ -0,0 +1,26 @@
+export const COUNTRY_DATA_ENDPOINT = 'http://api.geonames.org/countryInfoJSON?formatted=true&username=hydrane';
+
+export interface CountryDataResponseModel {
+  geonames: CountryDataModel[];
+}
+
+export interface CountryDataModel {
+  continent: string;
+  capital: string;
+  languages: string;
+  geonameId: number;
+  isoAlpha3: string;
+  fipsCode: string;
+  population: string;
+  north: number;
+  south: number;
+  east: number;
+  west: number;
+  isoNumeric: string;
+  areaInSqKm: string;
+  countryCode: string;
+  countryName: string;
+  continentName: string;
+  currencyCode: string;
+}
+

src/app/services/country-data/country-data.module.ts

@@ -0,0 +1,13 @@
+import { NgModule } from '@angular/core';
+import { CountryDataService } from './country-data.service';
+import { HttpClientModule } from '@angular/common/http';
+
+@NgModule({
+  imports: [
+    HttpClientModule,
+  ],
+  providers: [
+    CountryDataService,
+  ],
+})
+export class CountryDataServiceModule { }

src/app/services/country-data/country-data.service.ts

@@ -0,0 +1,32 @@
+import { Injectable } from '@angular/core';
+import { HttpClient } from '@angular/common/http';
+import { CountryDataResponseModel, COUNTRY_DATA_ENDPOINT, CountryDataModel } from './country-data.model';
+
+@Injectable()
+export class CountryDataService {
+
+  constructor(
+    public http: HttpClient,
+  ) {}
+
+  private static getUniqueAttributeValues(countriesData: CountryDataModel[], attributeName: string): string[] {
+    return [ ...new Set(countriesData.map((country: CountryDataModel) => country[attributeName])) ];
+  }
+
+  private static sortAlphabeticallyIgnoreCase(list: string[]): string[] {
+    return list.sort((a: string, b: string) => a.toLowerCase().localeCompare(b.toLowerCase()));
+  }
+
+  async fetchData(): Promise<{ countriesData: CountryDataModel[], uniqueContinents: string[] }> {
+    const responseData = await this.fetchCountriesData();
+    const uniqueContinents = CountryDataService.getUniqueAttributeValues(responseData.geonames, 'continentName');
+    return {
+      countriesData: responseData.geonames,
+      uniqueContinents: CountryDataService.sortAlphabeticallyIgnoreCase(uniqueContinents),
+    };
+  }
+
+  private fetchCountriesData(): Promise<CountryDataResponseModel> {
+    return this.http.get<CountryDataResponseModel>(COUNTRY_DATA_ENDPOINT).toPromise();
+  }
+}