var viewer;

function launchViewer(urn) {
    var options = {
        env: 'AutodeskProduction',
        getAccessToken: getForgeToken
    };

    Autodesk.Viewing.Initializer(options, () => {
        viewer = new Autodesk.Viewing.GuiViewer3D(document.getElementById('forgeViewer'));
        viewer.start();
        var documentId = 'urn:' + urn;
        Autodesk.Viewing.Document.load(documentId, onDocumentLoadSuccess, onDocumentLoadFailure);
    });
}

function onDocumentLoadSuccess(doc) {
    var viewables = doc.getRoot().getDefaultGeometry();
    viewer.loadDocumentNode(doc, viewables).then(i => {
        // documented loaded, any action?
    });
}

function onDocumentLoadFailure(viewerErrorCode) {
    console.error('onDocumentLoadFailure() - errorCode:' + viewerErrorCode);
}

function getForgeToken(callback) {
    fetch('/api/forge/oauth/token').then(res => {
        res.json().then(data => {
            callback(data.dictionary.access_token, data.dictionary.expires_in);
        });
    });
}