// 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;
using System.Collections.Generic;
using System.Collections.Immutable;
using System.Composition;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.Completion;
using Microsoft.CodeAnalysis.Completion.Providers;
using Microsoft.CodeAnalysis.CSharp.Extensions;
using Microsoft.CodeAnalysis.CSharp.Extensions.ContextQuery;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Host.Mef;
using Microsoft.CodeAnalysis.Text;
using Roslyn.Utilities;

namespace Microsoft.CodeAnalysis.CSharp.Completion.Providers;

[ExportCompletionProvider(nameof(PartialTypeCompletionProvider), LanguageNames.CSharp)]
[ExtensionOrder(After = nameof(PartialMethodCompletionProvider))]
[Shared]
internal sealed partial class PartialTypeCompletionProvider : AbstractPartialTypeCompletionProvider<CSharpSyntaxContext>
{
    private const string InsertionTextOnLessThan = nameof(InsertionTextOnLessThan);

    private static readonly SymbolDisplayFormat _symbolFormatWithGenerics =
        new(globalNamespaceStyle: SymbolDisplayGlobalNamespaceStyle.Omitted,
            typeQualificationStyle: SymbolDisplayTypeQualificationStyle.NameOnly,
            genericsOptions:
                SymbolDisplayGenericsOptions.IncludeTypeParameters |
                SymbolDisplayGenericsOptions.IncludeVariance,
            miscellaneousOptions:
                SymbolDisplayMiscellaneousOptions.EscapeKeywordIdentifiers |
                SymbolDisplayMiscellaneousOptions.UseSpecialTypes);

    [ImportingConstructor]
    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
    public PartialTypeCompletionProvider()
    {
    }

    internal override string Language => LanguageNames.CSharp;

    public override bool IsInsertionTrigger(SourceText text, int characterPosition, CompletionOptions options)
        => text[characterPosition] == ' ' ||
           options.TriggerOnTypingLetters && CompletionUtilities.IsStartingNewWord(text, characterPosition);

    public override ImmutableHashSet<char> TriggerCharacters { get; } = CompletionUtilities.SpaceTriggerCharacter;

    protected override SyntaxNode? GetPartialTypeSyntaxNode(SyntaxTree tree, int position, CancellationToken cancellationToken)
        => tree.IsPartialTypeDeclarationNameContext(position, cancellationToken, out var declaration) ? declaration : null;

    protected override (string displayText, string suffix, string insertionText) GetDisplayAndSuffixAndInsertionText(INamedTypeSymbol symbol, CSharpSyntaxContext context)
    {
        var displayAndInsertionText = symbol.ToMinimalDisplayString(context.SemanticModel, context.Position, _symbolFormatWithGenerics);
        return (displayAndInsertionText, "", displayAndInsertionText);
    }

    protected override IEnumerable<INamedTypeSymbol>? LookupCandidateSymbols(CSharpSyntaxContext context, INamedTypeSymbol declaredSymbol, CancellationToken cancellationToken)
    {
        var candidates = base.LookupCandidateSymbols(context, declaredSymbol, cancellationToken);

        // The base class applies a broad filter when finding candidates, but since C# requires
        // that all parts have the "partial" modifier, the results can be trimmed further here.
        return candidates?.Where(symbol => symbol.DeclaringSyntaxReferences.Any(static (reference, cancellationToken) => IsPartialTypeDeclaration(reference.GetSyntax(cancellationToken)), cancellationToken));
    }

    private static bool IsPartialTypeDeclaration(SyntaxNode syntax)
        => syntax is BaseTypeDeclarationSyntax declarationSyntax && declarationSyntax.Modifiers.Any(SyntaxKind.PartialKeyword);

    protected override ImmutableArray<KeyValuePair<string, string>> GetProperties(INamedTypeSymbol symbol, CSharpSyntaxContext context)
        => [KeyValuePair.Create(InsertionTextOnLessThan, symbol.Name.EscapeIdentifier())];

    public override async Task<TextChange?> GetTextChangeAsync(
        Document document, CompletionItem selectedItem, char? ch, CancellationToken cancellationToken)
    {
        if (ch == '<')
        {
            if (selectedItem.TryGetProperty(InsertionTextOnLessThan, out var insertionText))
            {
                return new TextChange(selectedItem.Span, insertionText);
            }
        }

        return await base.GetTextChangeAsync(document, selectedItem, ch, cancellationToken).ConfigureAwait(false);
    }
}