// 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.Diagnostics;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.CodeActions;
using Microsoft.CodeAnalysis.CodeFixes;
using Microsoft.CodeAnalysis.Diagnostics;
using Microsoft.CodeAnalysis.Host.Mef;
using Microsoft.CodeAnalysis.PooledObjects;
using Microsoft.CodeAnalysis.Shared.Extensions;
using Microsoft.CodeAnalysis.Text;
 
namespace Microsoft.CodeAnalysis.CSharp.NewLines.ConsecutiveBracePlacement;
 
[ExportCodeFixProvider(LanguageNames.CSharp, Name = PredefinedCodeFixProviderNames.ConsecutiveBracePlacement), Shared]
[method: ImportingConstructor]
[method: Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
internal sealed class ConsecutiveBracePlacementCodeFixProvider() : CodeFixProvider
{
    public override ImmutableArray<string> FixableDiagnosticIds
        => [IDEDiagnosticIds.ConsecutiveBracePlacementDiagnosticId];
 
    public override Task RegisterCodeFixesAsync(CodeFixContext context)
    {
        var document = context.Document;
        var diagnostic = context.Diagnostics.First();
        context.RegisterCodeFix(
            CodeAction.Create(
                CSharpCodeFixesResources.Remove_blank_lines_between_braces,
                c => UpdateDocumentAsync(document, diagnostic, c),
                nameof(CSharpCodeFixesResources.Remove_blank_lines_between_braces)),
            context.Diagnostics);
        return Task.CompletedTask;
    }
 
    private static Task<Document> UpdateDocumentAsync(Document document, Diagnostic diagnostic, CancellationToken cancellationToken)
        => FixAllAsync(document, [diagnostic], cancellationToken);
 
    public static async Task<Document> FixAllAsync(Document document, ImmutableArray<Diagnostic> diagnostics, CancellationToken cancellationToken)
    {
        var text = await document.GetValueTextAsync(cancellationToken).ConfigureAwait(false);
        var root = await document.GetRequiredSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
        using var _ = PooledDictionary<SyntaxToken, SyntaxToken>.GetInstance(out var tokenToToken);
 
        foreach (var diagnostic in diagnostics)
            FixOne(root, text, tokenToToken, diagnostic, cancellationToken);
 
        var newRoot = root.ReplaceTokens(tokenToToken.Keys, (t1, _) => tokenToToken[t1]);
 
        return document.WithSyntaxRoot(newRoot);
    }
 
    private static void FixOne(
        SyntaxNode root, SourceText text,
        Dictionary<SyntaxToken, SyntaxToken> tokenToToken,
        Diagnostic diagnostic, CancellationToken cancellationToken)
    {
        cancellationToken.ThrowIfCancellationRequested();
 
        var token = root.FindToken(diagnostic.Location.SourceSpan.Start);
        if (!token.IsKind(SyntaxKind.CloseBraceToken))
        {
            Debug.Fail("Could not find close brace in fixer");
            return;
        }
 
        var firstBrace = token.GetPreviousToken();
        if (!firstBrace.IsKind(SyntaxKind.CloseBraceToken))
        {
            Debug.Fail("Could not find previous close brace in fixer");
            return;
        }
 
        if (!ConsecutiveBracePlacementDiagnosticAnalyzer.HasExcessBlankLinesAfter(
                text, firstBrace, out var secondBrace, out var lastEndOfLineTrivia))
        {
            Debug.Fail("Could not match analyzer pattern");
            return;
        }
 
        var updatedSecondBrace = secondBrace.WithLeadingTrivia(
            secondBrace.LeadingTrivia.SkipWhile(t => t != lastEndOfLineTrivia).Skip(1));
        tokenToToken[secondBrace] = updatedSecondBrace;
    }
 
    public override FixAllProvider GetFixAllProvider()
        => FixAllProvider.Create(async (context, document, diagnostics) => await FixAllAsync(document, diagnostics, context.CancellationToken).ConfigureAwait(false));
}