// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
 
using System.Collections.Immutable;
using Microsoft.CodeAnalysis.Shared.Collections;
using Microsoft.VisualStudio.Text;
 
namespace Microsoft.VisualStudio.LanguageServices.DocumentOutline;
 
internal sealed partial class DocumentOutlineViewModel
{
    /// <summary>
    /// Snapshot of all state used to compute and present our models. Used when we produce new models to both
    /// transfer state over from the old ones, and to efficiently tell what is different between the last results
    /// and the new ones.
    /// </summary>
    private sealed class DocumentOutlineViewState
    {
        /// <summary>
        /// The snapshot of the document used to compute this state.
        /// </summary>
        public readonly ITextSnapshot TextSnapshot;
 
        /// <summary>
        /// The text string that was used to filter the original LSP results down to the set of <see
        /// cref="DocumentSymbolData"/> we have.
        /// </summary>
        public readonly string SearchText;
 
        /// <summary>
        /// The view items we created from <see cref="DocumentSymbolData"/>.  Note: these values are a bit odd in
        /// that they represent mutable UI state.  Docs on DocumentSymbolDataViewModel indicate that it likely
        /// should be as the only mutable state is <see cref="DocumentSymbolDataViewModel.IsExpanded"/>/<see
        /// cref="DocumentSymbolDataViewModel.IsSelected"/>, both of which are threadsafe.
        /// </summary>
        public readonly ImmutableArray<DocumentSymbolDataViewModel> ViewModelItems;
 
        /// <summary>
        /// Interval-tree view over <see cref="ViewModelItems"/> so that we can quickly determine which of them
        /// intersect with a particular position in the document.
        /// </summary>
        public readonly ImmutableIntervalTree<DocumentSymbolDataViewModel> ViewModelItemsTree;
 
        public DocumentOutlineViewState(
            ITextSnapshot textSnapshot,
            string searchText,
            ImmutableArray<DocumentSymbolDataViewModel> viewModelItems,
            ImmutableIntervalTree<DocumentSymbolDataViewModel> viewModelItemsTree)
        {
            TextSnapshot = textSnapshot;
            SearchText = searchText;
            ViewModelItems = viewModelItems;
            ViewModelItemsTree = viewModelItemsTree;
        }
    }
}