GoogleMapsGeoCoding

namespace MyNamespace
{
    [ServiceConfiguration(typeof(ISelectionQuery))]
    public class GoogleMapsGeocoding : ISelectionQuery
    {
        private readonly string _googleApiKey;
        public GoogleMapsGeocoding()
        {
            //get key from config
            _googleApiKey = ConfigurationManager.AppSettings["GoogleGeocodingApiKey"];
        }

        //Will be called when the editor types something in the selection editor.
        public IEnumerable<ISelectItem> GetItems(string query)
        {
            if (IsCoordinate(query))
            {
                //return value if it is coordinates
                var list = new List<ISelectItem> { new SelectItem() { Text = query, Value = query } };
                return list;
            }

            if (query.Length < 5) //don't waste API quota on short query
            {
                return null;
            }
            var items = GetResultFromGoogle(query);
            return EditorFriendlyItems(items, query);
        }

        //Will be called when initializing an editor with an existing value.
        public ISelectItem GetItemByValue(string value)
        {
            //just return the saved value
            return new SelectItem { Text = value, Value = value };
        }

        private IEnumerable<ISelectItem> GetResultFromGoogle(string query)
        {
            if (_googleApiKey.IsNullOrEmpty())
            {
                var list = new List<ISelectItem>();
                list.Add(new SelectItem() { Text = "Error: missing Google API key", Value = null });
                return list;
            }

            var apiUrl = $"https://maps.googleapis.com/maps/api/geocode/json?address={query}&key={_googleApiKey}";
            var webClient = new WebClient { Encoding = Encoding.UTF8 };
            var json = (JObject)JsonConvert.DeserializeObject(webClient.DownloadString(apiUrl));
            var results = json["results"].Select(r => new SelectItem()
            {
                Text = $"{r["formatted_address"].ToString()} ({r["geometry"]["location"]["lat"].ToString()} {r["geometry"]["location"]["lng"].ToString()})",
                Value = $"{r["geometry"]["location"]["lat"].ToString()} {r["geometry"]["location"]["lng"].ToString()}"
            });

            return results;
        }

        //If items returned by Google doesn't start with the query, add a dummy item to make a better experience for the editor.
        private IEnumerable<ISelectItem> EditorFriendlyItems(IEnumerable<ISelectItem> items, string query)
        {
            var itemsList = items.ToList();
            if (itemsList.Any())
            {
                if (!itemsList.Any(i => i.Text.StartsWith(query, StringComparison.OrdinalIgnoreCase)))
                {
                    itemsList.Insert(0, new SelectItem() { Text = query, Value = null });
                }
            }

            return itemsList;
        }

        //Check if query is coordinates
        private bool IsCoordinate(string query)
        {
            const string pattern = @"^[-+]?([1-8]?\d(\.\d+)?|90(\.0+)?)\s*[-+]?(180(\.0+)?|((1[0-7]\d)|([1-9]?\d))(\.\d+)?)$";
            var r = new Regex(pattern);
            return r.Match(query).Success;
        }

    }
}