// 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.Composition;
using System.Diagnostics.CodeAnalysis;
using Microsoft.CodeAnalysis.CodeRefactorings;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Shared.Extensions;
using Microsoft.CodeAnalysis.SplitOrMergeIfStatements;
using Microsoft.CodeAnalysis.Text;

namespace Microsoft.CodeAnalysis.CSharp.SplitOrMergeIfStatements;

[ExportCodeRefactoringProvider(LanguageNames.CSharp, Name = PredefinedCodeRefactoringProviderNames.MergeConsecutiveIfStatements), Shared]
internal sealed class CSharpMergeConsecutiveIfStatementsCodeRefactoringProvider
    : AbstractMergeConsecutiveIfStatementsCodeRefactoringProvider
{
    [ImportingConstructor]
    [SuppressMessage("RoslynDiagnosticsReliability", "RS0033:Importing constructor should be [Obsolete]", Justification = "Used in test code: https://github.com/dotnet/roslyn/issues/42814")]
    public CSharpMergeConsecutiveIfStatementsCodeRefactoringProvider()
    {
    }

    protected override bool IsApplicableSpan(SyntaxNode node, TextSpan span, out SyntaxNode ifOrElseIf)
    {
        if (node is IfStatementSyntax ifStatement)
        {
            // Cases:
            // 1. Position is at a child token of an if statement with no selection (e.g. 'if' keyword, a parenthesis)
            // 2. Selection around the 'if' keyword
            // 3. Selection around the header - from 'if' keyword to the end of the condition
            // 4. Selection around the whole if statement *excluding* its else clause - from 'if' keyword to the end of its statement
            if (span.Length == 0 ||
                span.IsAround(ifStatement.IfKeyword) ||
                span.IsAround(ifStatement.IfKeyword, ifStatement.CloseParenToken) ||
                span.IsAround(ifStatement.IfKeyword, ifStatement.Statement))
            {
                ifOrElseIf = ifStatement;
                return true;
            }
        }

        if (node is ElseClauseSyntax elseClause && elseClause.Statement is IfStatementSyntax elseIfStatement)
        {
            // 5. Position is at a child token of an else clause with no selection ('else' keyword)
            // 6. Selection around the header including the 'else' keyword - from 'else' keyword to the end of the condition
            // 7. Selection from the 'else' keyword to the end of the if statement's statement
            if (span.Length == 0 ||
                span.IsAround(elseClause.ElseKeyword, elseIfStatement.CloseParenToken) ||
                span.IsAround(elseClause.ElseKeyword, elseIfStatement.Statement))
            {
                ifOrElseIf = elseIfStatement;
                return true;
            }
        }

        ifOrElseIf = null;
        return false;
    }
}