Statistical query group and sort

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// Copyright 2022 Esri.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License.
// You may obtain a copy of the License at: http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific
// language governing permissions and limitations under the License.

using Esri.ArcGISRuntime.Data;
using System.Collections.ObjectModel;

namespace ArcGIS.Samples.StatsQueryGroupAndSort
{
    [ArcGIS.Samples.Shared.Attributes.Sample(
        name: "Statistical query group and sort",
        category: "Data",
        description: "Query a feature table for statistics, grouping and sorting by different fields.",
        instructions: "The sample will start with some default options selected. You can immediately tap the \"Get Statistics\" button to see the results for these options. There are several ways to customize your queries:",
        tags: new[] { "correlation", "data", "fields", "filter", "group", "sort", "statistics", "table" })]
    public partial class StatsQueryGroupAndSort : ContentPage
    {
        // URI for the US states map service.
        private Uri _usStatesServiceUri = new Uri("https://services.arcgis.com/jIL9msH9OI208GCb/arcgis/rest/services/Counties_Obesity_Inactivity_Diabetes_2013/FeatureServer/0");

        // US states feature table.
        private FeatureTable _usStatesTable;

        // Collection of (user-defined) statistics to use in the query.
        private ObservableCollection<StatisticDefinition> _statDefinitions = new ObservableCollection<StatisticDefinition>();

        // Selected fields for grouping results.
        private List<string> _groupByFields = new List<string>();

        // Collection to hold fields to order results by.
        private ObservableCollection<OrderFieldOption> _orderByFields = new ObservableCollection<OrderFieldOption>();

        public StatsQueryGroupAndSort()
        {
            InitializeComponent();

            // Initialize the US states feature table and populate UI controls.
            _ = Initialize();
        }

        private async Task Initialize()
        {
            // Create the US states feature table.
            _usStatesTable = new ServiceFeatureTable(_usStatesServiceUri);

            try
            {
                // Load the table.
                await _usStatesTable.LoadAsync();

                // Fill the fields combo and "group by" list with field names from the table.
                List<string> fieldNames = _usStatesTable.Fields.Select(field => field.Name).ToList();
                FieldsComboBox.ItemsSource = fieldNames;
                GroupFieldsListBox.ItemsSource = _usStatesTable.Fields;

                // Set the (initially empty) collection of fields as the "order by" fields list data source.
                OrderByFieldsListBox.ItemsSource = _orderByFields;

                // Fill the statistics type combo with values from the StatisticType enum.
                StatTypeComboBox.ItemsSource = Enum.GetValues(typeof(StatisticType));

                // Set the (initially empty) collection of statistic definitions as the statistics list box data source.
                StatFieldsListBox.ItemsSource = _statDefinitions;
            }
            catch (Exception e)
            {
                await Application.Current.MainPage.DisplayAlert("Error", e.ToString(), "OK");
            }
        }

        // Execute a statistical query using the parameters defined by the user and display the results.
        private async void GetStatisticsButton_Clicked(object sender, EventArgs e)
        {
            // Verify that there is at least one statistic definition.
            if (!_statDefinitions.Any())
            {
                _ = Application.Current.MainPage.DisplayAlert("Please define at least one statistic for the query.", "Statistical Query", "OK");
                return;
            }

            // Create the statistics query parameters, pass in the list of statistic definitions.
            var statQueryParams = new StatisticsQueryParameters(_statDefinitions);

            // Specify the group fields (if any).
            foreach (string groupField in _groupByFields)
            {
                statQueryParams.GroupByFieldNames.Add(groupField);
            }

            // Specify the fields to order by (if any).
            foreach (OrderFieldOption orderBy in _orderByFields)
            {
                statQueryParams.OrderByFields.Add(orderBy.OrderInfo);
            }

            // Ignore counties with missing data.
            statQueryParams.WhereClause = "\"State\" IS NOT NULL";

            try
            {
                // Execute the statistical query with these parameters and await the results.
                StatisticsQueryResult statQueryResult = await _usStatesTable.QueryStatisticsAsync(statQueryParams);

                // Get results formatted as a lookup (list of group names and their associated dictionary of results).
                ILookup<string, IReadOnlyDictionary<string, object>> resultsLookup = statQueryResult.ToLookup(result => string.Join(", ", result.Group.Values), result => result.Statistics);

                // Loop through the formatted results and build a list of classes to display as grouped results in the list view.
                var resultsGroupCollection = new List<ResultGroup>();
                foreach (IGrouping<string, IReadOnlyDictionary<string, object>> group in resultsLookup)
                {
                    // Create a new group.
                    var resultGroup = new ResultGroup() { GroupName = group.Key };

                    // Loop through all the results for this group and add them to the collection.
                    foreach (IReadOnlyDictionary<string, object> resultSet in group)
                    {
                        foreach (KeyValuePair<string, object> result in resultSet)
                        {
                            resultGroup.Add(new StatisticResult { FieldName = result.Key, StatValue = result.Value });
                        }
                    }

                    // Add the group of results to the collection.
                    resultsGroupCollection.Add(resultGroup);
                }

                // Apply the results to the collection view items source.
                StatResultsList.ItemsSource = resultsGroupCollection;

                // Hide the query configuration layout and show the results layout.
                QueryConfigurationLayout.IsVisible = false;
                ResultsLayout.IsVisible = true;
            }
            catch (Exception ex)
            {
                await Application.Current.MainPage.DisplayAlert("Error", ex.ToString(), "OK");
            }
        }

        // Handle when the switch for a "group by" field is toggled on or off by adding or removing the field from the collection.
        private void GroupField_Toggled(object sender, ToggledEventArgs e)
        {
            // Get the switch that raised the event (group field).
            var groupFieldSwitch = (Switch)sender;

            // Get the field name.
            string fieldName = groupFieldSwitch.BindingContext.ToString();

            // See if the field is being added or removed from the "group by" list.
            bool fieldAdded = groupFieldSwitch.IsToggled;

            // See if the field already exists in the "group by" list.
            bool fieldIsInList = _groupByFields.Contains(fieldName);

            // If the field is being added, and is not in the list, add it.
            if (fieldAdded && !fieldIsInList)
            {
                _groupByFields.Add(fieldName);

                // Also add it to the "order by" list.
                var orderBy = new OrderBy(fieldName, SortOrder.Ascending);
                var orderOption = new OrderFieldOption(false, orderBy);
                _orderByFields.Add(orderOption);
            }
            // If the field is being removed and it is in the list, remove it.
            else if (!fieldAdded && fieldIsInList)
            {
                _groupByFields.Remove(fieldName);

                // Also check for this field in the "order by" list and remove if necessary (only group fields can be used to order results).
                OrderFieldOption orderBy = _orderByFields.FirstOrDefault(field => field.OrderInfo.FieldName == fieldName);
                if (orderBy != null)
                {
                    // Remove the field from the "order by" list.
                    _orderByFields.Remove(orderBy);
                }
            }
        }

        // Create a statistic definition and add it to the collection based on the user selection in the combo boxes.
        private void AddStatistic_Clicked(object sender, EventArgs e)
        {
            // Verify that a field name and statistic type has been selected.
            if (FieldsComboBox.SelectedItem == null || StatTypeComboBox.SelectedItem == null) { return; }

            // Get the chosen field name and statistic type from the combo boxes.
            string fieldName = FieldsComboBox.SelectedItem.ToString();
            var statType = (StatisticType)StatTypeComboBox.SelectedItem;

            // Check if this statistic definition has already be created (same field name and statistic type).
            StatisticDefinition existingStatDefinition = _statDefinitions.FirstOrDefault(def => def.OnFieldName == fieldName && def.StatisticType == statType);

            // If it doesn't exist, create it and add it to the collection (use the field name and statistic type to build the output alias).
            if (existingStatDefinition == null)
            {
                StatisticDefinition statDefinition = new StatisticDefinition(fieldName, statType, fieldName + "_" + statType.ToString());
                _statDefinitions.Add(statDefinition);
            }
        }

        // Toggle the sort order (ascending/descending) for the field selected in the sort fields list.
        private void SortOrderButton_Clicked(object sender, EventArgs e)
        {
            // Verify that there is a selected sort field in the list.
            var selectedSortField = OrderByFieldsListBox.SelectedItem as OrderFieldOption;
            if (selectedSortField == null) { return; }

            // Create a new order field info to define the sort for the selected field.
            var newOrderBy = new OrderBy(selectedSortField.OrderInfo.FieldName, selectedSortField.OrderInfo.SortOrder);
            var newSortDefinition = new OrderFieldOption(true, newOrderBy);

            // Toggle the sort order from the current value.
            if (newSortDefinition.OrderInfo.SortOrder == SortOrder.Ascending)
            {
                newSortDefinition.OrderInfo.SortOrder = SortOrder.Descending;
            }
            else
            {
                newSortDefinition.OrderInfo.SortOrder = SortOrder.Ascending;
            }

            // Add the new OrderBy at the same location in the collection and remove the old one.
            _orderByFields.Insert(_orderByFields.IndexOf(selectedSortField), newSortDefinition);
            _orderByFields.Remove(selectedSortField);
        }

        // Remove the selected statistic definition from the list.
        private void RemoveStatistic_Clicked(object sender, EventArgs e)
        {
            // Verify that there is a selected statistic definition.
            if (StatFieldsListBox.SelectedItem == null) { return; }

            // Get the selected statistic definition and remove it from the collection.
            var selectedStat = StatFieldsListBox.SelectedItem as StatisticDefinition;
            _statDefinitions.Remove(selectedStat);
        }

        private void DismissResults_Clicked(object sender, EventArgs e)
        {
            // Hide the results layout and show the query configuration layout.
            ResultsLayout.IsVisible = false;
            QueryConfigurationLayout.IsVisible = true;

            // Clear the results.
            StatResultsList.ItemsSource = null;
        }
    }

    // Simple class to describe an "order by" option.
    public class OrderFieldOption
    {
        // Whether or not to use this field to order results.
        public bool OrderWith { get; set; }

        // The order by info: field name and sort order.
        public OrderBy OrderInfo { get; set; }

        public OrderFieldOption(bool orderWith, OrderBy orderInfo)
        {
            OrderWith = orderWith;
            OrderInfo = orderInfo;
        }
    }

    // A simple class to hold a single statistic result.
    public class StatisticResult
    {
        public string FieldName { get; set; }
        public object StatValue { get; set; }
    }

    // A class to represent a group of statistics results
    public class ResultGroup : ObservableCollection<StatisticResult>
    {
        public string GroupName { get; set; }
    }
}