// 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.
 
#nullable disable
 
using System.Collections.Generic;
using Microsoft.CodeAnalysis.SignatureHelp;
using Microsoft.CodeAnalysis.Text;
using Microsoft.CodeAnalysis.Text.Shared.Extensions;
using Microsoft.VisualStudio.Text;
 
namespace Microsoft.CodeAnalysis.Editor.Implementation.IntelliSense.SignatureHelp;
 
internal sealed class Model
{
    private readonly DisconnectedBufferGraph _disconnectedBufferGraph;
 
    public TextSpan TextSpan { get; }
    public IList<SignatureHelpItem> Items { get; }
    public SignatureHelpItem SelectedItem { get; }
 
    /// <summary>UserSelected is true if the SelectedItem is the result of a user selection (up/down arrows).</summary>
    public bool UserSelected { get; }
 
    /// <inheritdoc cref="SignatureHelpItems.SemanticParameterIndex"/>
    public int SemanticParameterIndex { get; }
 
    /// <inheritdoc cref="SignatureHelpItems.SyntacticArgumentCount"/>
    public int SyntacticArgumentCount { get; }
    public string ArgumentName { get; }
    public int? SelectedParameter { get; }
    public ISignatureHelpProvider Provider { get; }
 
    public Model(
        DisconnectedBufferGraph disconnectedBufferGraph,
        TextSpan textSpan,
        ISignatureHelpProvider provider,
        IList<SignatureHelpItem> items,
        SignatureHelpItem selectedItem,
        int semanticParameterIndex,
        int syntacticArgumentCount,
        string argumentName,
        int? selectedParameter,
        bool userSelected)
    {
        Contract.ThrowIfNull(selectedItem);
        Contract.ThrowIfFalse(items.Count != 0, "Must have at least one item.");
        Contract.ThrowIfFalse(items.Contains(selectedItem), "Selected item must be in list of items.");
 
        _disconnectedBufferGraph = disconnectedBufferGraph;
        this.TextSpan = textSpan;
        this.Items = items;
        this.Provider = provider;
        this.SelectedItem = selectedItem;
        this.UserSelected = userSelected;
        this.SemanticParameterIndex = semanticParameterIndex;
        this.SyntacticArgumentCount = syntacticArgumentCount;
        this.ArgumentName = argumentName;
        this.SelectedParameter = selectedParameter;
    }
 
    public Model WithSelectedItem(SignatureHelpItem selectedItem, bool userSelected)
    {
        return selectedItem == this.SelectedItem && userSelected == this.UserSelected
            ? this
            : new Model(_disconnectedBufferGraph, TextSpan, Provider, Items, selectedItem, SemanticParameterIndex, SyntacticArgumentCount, ArgumentName, SelectedParameter, userSelected);
    }
 
    public Model WithSelectedParameter(int? selectedParameter)
    {
        return selectedParameter == this.SelectedParameter
            ? this
            : new Model(_disconnectedBufferGraph, TextSpan, Provider, Items, SelectedItem, SemanticParameterIndex, SyntacticArgumentCount, ArgumentName, selectedParameter, UserSelected);
    }
 
    public SnapshotSpan GetCurrentSpanInSubjectBuffer(ITextSnapshot bufferSnapshot)
    {
        return _disconnectedBufferGraph.SubjectBufferSnapshot
            .CreateTrackingSpan(this.TextSpan.ToSpan(), SpanTrackingMode.EdgeInclusive)
            .GetSpan(bufferSnapshot);
    }
 
    public SnapshotSpan GetCurrentSpanInView(ITextSnapshot textSnapshot)
    {
        var originalSpan = _disconnectedBufferGraph.GetSubjectBufferTextSpanInViewBuffer(this.TextSpan);
        var trackingSpan = _disconnectedBufferGraph.ViewSnapshot.CreateTrackingSpan(originalSpan.TextSpan.ToSpan(), SpanTrackingMode.EdgeInclusive);
        return trackingSpan.GetSpan(textSnapshot);
    }
}