// @flow

import {pick, extend} from '../util/util';

import {getJSON, ResourceType} from '../util/ajax';
import browser from '../util/browser';

import type {RequestManager} from '../util/mapbox';
import type {Callback} from '../types/callback';
import type {TileJSON} from '../types/tilejson';
import type {Cancelable} from '../types/cancelable';

export default function(options: any, requestManager: RequestManager, callback: Callback<TileJSON>): Cancelable {
    const loaded = function(err: ?Error, tileJSON: ?Object) {
        if (err) {
            return callback(err);
        } else if (tileJSON) {
            const result: any = pick(
                // explicit source options take precedence over TileJSON
                extend(tileJSON, options),
                ['tiles', 'minzoom', 'maxzoom', 'attribution', 'mapbox_logo', 'bounds', 'scheme', 'tileSize', 'encoding']
            );

            if (tileJSON.vector_layers) {
                result.vectorLayers = tileJSON.vector_layers;
                result.vectorLayerIds = result.vectorLayers.map((layer) => { return layer.id; });
            }

            result.tiles = requestManager.canonicalizeTileset(result, options.url);
            callback(null, result);
        }
    };

    if (options.url) {
        return getJSON(requestManager.transformRequest(requestManager.normalizeSourceURL(options.url), ResourceType.Source), loaded);
    } else {
        return browser.frame(() => loaded(null, options));
    }
}