//resource used: https://dev.to/shoupn/javascript-fetch-api-and-using-asyncawait-47mp

//MDN await: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/await

export default async function fetchData(){

//puts the endpoint in a variable

const url ="https://api.data.netwerkdigitaalerfgoed.nl/datasets/ivo/NMVW/services/NMVW-36/sparql"

const query = `

PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>

PREFIX dc: <http://purl.org/dc/elements/1.1/>

PREFIX dct: <http://purl.org/dc/terms/>

PREFIX skos: <http://www.w3.org/2004/02/skos/core#>

PREFIX edm: <http://www.europeana.eu/schemas/edm/>

PREFIX foaf: <http://xmlns.com/foaf/0.1/>

SELECT ?herkomstSuper ?herkomstSuperLabel ?typeLabel (COUNT(?cho) AS ?amount)

WHERE {

# geef ruilmiddelen

<https://hdl.handle.net/20.500.11840/termmaster14607> skos:narrower* ?type .

?type skos:prefLabel ?typeLabel .

# geef de continenten

<https://hdl.handle.net/20.500.11840/termmaster2> skos:narrower ?herkomstSuper .

?herkomstSuper skos:prefLabel ?herkomstSuperLabel .

# geef per continent de onderliggende geografische termen

?herkomstSuper skos:narrower* ?herkomstSub .

?herkomstSub skos:prefLabel ?herkomstSubLabel .

# geef objecten bij de onderliggende geografische termen

?cho dct:spatial ?herkomstSub .

?cho edm:object ?type .

} #GROUP BY ?herkomstSuper ?herkomstSuperLabel

`

//await pauses async function to pause untill promis is settled => when function resumes value of await becomes that of fulfilled promise

let response = await fetch(url + "?query=" + encodeURIComponent(query) + "&format=json");

let json = await response.json();

const data = json.results.bindings;

return data

}