ViewSwitcherSelectionState.cs

using System;
 
namespace NeuroAccessMaui.UI.Controls
{
    internal sealed class ViewSwitcherSelectionState
    {
        private bool updatingFromIndex;
        private bool updatingFromItem;
        private bool updatingFromStateKey;
 
        public ViewSwitcherSelectionState()
        {
            this.SelectedIndex = -1;
            this.SelectedItem = null;
            this.SelectedStateKey = null;
            this.IndexBehavior = ViewSwitcherSelectedIndexBehavior.Clamp;
        }
 
        public int SelectedIndex { get; private set; }
 
        public object? SelectedItem { get; private set; }
 
        public string? SelectedStateKey { get; private set; }
 
        public ViewSwitcherSelectedIndexBehavior IndexBehavior { get; set; }
 
        public bool ShouldIgnore(ViewSwitcherSelectionChangeSource source)
        {
            return source switch
            {
                ViewSwitcherSelectionChangeSource.Index => this.updatingFromIndex,
                ViewSwitcherSelectionChangeSource.Item => this.updatingFromItem,
                ViewSwitcherSelectionChangeSource.StateKey => this.updatingFromStateKey,
                _ => false
            };
        }
 
        public SelectionStateUpdateScope BeginUpdate(ViewSwitcherSelectionChangeSource source)
        {
            this.SetUpdating(source, true);
            return new SelectionStateUpdateScope(this, source);
        }
 
        public int NormalizeIndex(int requestedIndex, int totalCount)
        {
            if (requestedIndex < 0)
                return -1;
 
            if (totalCount <= 0)
            {
                switch (this.IndexBehavior)
                {
                    case ViewSwitcherSelectedIndexBehavior.Throw:
                        throw new ArgumentOutOfRangeException(nameof(requestedIndex), requestedIndex, "No items are available.");
                    case ViewSwitcherSelectedIndexBehavior.Ignore:
                        return this.SelectedIndex;
                    default:
                        return -1;
                }
            }
 
            if (requestedIndex < totalCount)
                return requestedIndex;
 
            switch (this.IndexBehavior)
            {
                case ViewSwitcherSelectedIndexBehavior.Throw:
                    throw new ArgumentOutOfRangeException(nameof(requestedIndex), requestedIndex, "Requested index is outside the available range.");
                case ViewSwitcherSelectedIndexBehavior.Ignore:
                    return this.SelectedIndex;
                case ViewSwitcherSelectedIndexBehavior.Wrap:
                {
                    int remainder = requestedIndex % totalCount;
                    if (remainder < 0)
                        remainder += totalCount;
                    return remainder;
                }
                case ViewSwitcherSelectedIndexBehavior.Clamp:
                default:
                    return totalCount - 1;
            }
        }
 
        public void UpdateSnapshot(int index, object? item, string? stateKey)
        {
            this.SelectedIndex = index;
            this.SelectedItem = item;
            this.SelectedStateKey = stateKey;
        }
 
        public void Reset()
        {
            this.SelectedIndex = -1;
            this.SelectedItem = null;
            this.SelectedStateKey = null;
        }
 
        private void SetUpdating(ViewSwitcherSelectionChangeSource source, bool isUpdating)
        {
            switch (source)
            {
                case ViewSwitcherSelectionChangeSource.Index:
                    this.updatingFromIndex = isUpdating;
                    break;
                case ViewSwitcherSelectionChangeSource.Item:
                    this.updatingFromItem = isUpdating;
                    break;
                case ViewSwitcherSelectionChangeSource.StateKey:
                    this.updatingFromStateKey = isUpdating;
                    break;
            }
        }
 
        public readonly struct SelectionStateUpdateScope : IDisposable
        {
            private readonly ViewSwitcherSelectionState owner;
            private readonly ViewSwitcherSelectionChangeSource source;
 
            public SelectionStateUpdateScope(ViewSwitcherSelectionState owner, ViewSwitcherSelectionChangeSource source)
            {
                this.owner = owner;
                this.source = source;
            }
 
            public void Dispose()
            {
                this.owner.SetUpdating(this.source, false);
            }
        }
    }
}