// 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.Composition;
using System.Diagnostics.CodeAnalysis;
using Microsoft.CodeAnalysis.CodeRefactorings;
using Microsoft.CodeAnalysis.CSharp.CodeGeneration;
using Microsoft.CodeAnalysis.CSharp.Extensions;
using Microsoft.CodeAnalysis.CSharp.LanguageService;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.InlineMethod;
 
namespace Microsoft.CodeAnalysis.CSharp.CodeRefactorings.InlineMethod;
 
[ExportCodeRefactoringProvider(LanguageNames.CSharp, Name = PredefinedCodeRefactoringProviderNames.InlineMethod), Shared]
[Export(typeof(CSharpInlineMethodRefactoringProvider))]
internal sealed class CSharpInlineMethodRefactoringProvider
    : AbstractInlineMethodRefactoringProvider<BaseMethodDeclarationSyntax, StatementSyntax, ExpressionSyntax, InvocationExpressionSyntax>
{
    [ImportingConstructor]
    [SuppressMessage("RoslynDiagnosticsReliability", "RS0033:Importing constructor should be [Obsolete]", Justification = "Used in test code: https://github.com/dotnet/roslyn/issues/42814")]
    public CSharpInlineMethodRefactoringProvider()
        : base(CSharpSyntaxFacts.Instance, CSharpSemanticFactsService.Instance)
    {
    }
 
    protected override ExpressionSyntax? GetRawInlineExpression(BaseMethodDeclarationSyntax methodDeclarationSyntax)
    {
        var blockSyntaxNode = methodDeclarationSyntax.Body;
        if (blockSyntaxNode != null)
        {
            // 1. If it is an ordinary method with block
            if (blockSyntaxNode.Statements is [var statementSyntax])
            {
                return statementSyntax switch
                {
                    // Note: For this case this will return null in Callee()
                    // void Caller() { Callee(); }
                    // void Callee() { return; }
                    // Refactoring won't be provided for this case.
                    ReturnStatementSyntax returnStatementSyntax => returnStatementSyntax.Expression,
                    ExpressionStatementSyntax expressionStatementSyntax => expressionStatementSyntax.Expression,
                    ThrowStatementSyntax throwStatementSyntax => throwStatementSyntax.Expression,
                    _ => null
                };
            }
        }
        else
        {
            // 2. If it is an Arrow Expression
            return methodDeclarationSyntax.ExpressionBody?.Expression;
        }
 
        return null;
    }
 
    protected override SyntaxNode GenerateTypeSyntax(ITypeSymbol symbol, bool allowVar)
        => symbol.GenerateTypeSyntax(allowVar);
 
    protected override ExpressionSyntax GenerateLiteralExpression(ITypeSymbol typeSymbol, object? value)
        => ExpressionGenerator.GenerateExpression(CSharpSyntaxGenerator.Instance, typeSymbol, value, canUseFieldReference: true);
 
    protected override bool IsFieldDeclarationSyntax(SyntaxNode node)
        => node.IsKind(SyntaxKind.FieldDeclaration);
 
    protected override bool IsValidExpressionUnderExpressionStatement(ExpressionSyntax expressionNode)
    {
        // C# Expression Statements defined in the language reference
        // expression_statement
        //     : statement_expression ';'
        //     ;
        //
        // statement_expression
        //     : invocation_expression
        //     | null_conditional_invocation_expression
        //     | object_creation_expression
        //     | assignment
        //     | post_increment_expression
        //     | post_decrement_expression
        //     | pre_increment_expression
        //     | pre_decrement_expression
        //     | await_expression
        //     ;
        var isNullConditionalInvocationExpression = IsNullConditionalInvocationExpression(expressionNode);
 
        return expressionNode.IsKind(SyntaxKind.InvocationExpression)
               || isNullConditionalInvocationExpression
               || expressionNode is AssignmentExpressionSyntax
               || expressionNode.Kind()
                    is SyntaxKind.InvocationExpression
                    or SyntaxKind.ObjectCreationExpression
                    or SyntaxKind.PreIncrementExpression
                    or SyntaxKind.PreDecrementExpression
                    or SyntaxKind.PostIncrementExpression
                    or SyntaxKind.PostDecrementExpression
                    or SyntaxKind.AwaitExpression;
    }
 
    protected override bool CanBeReplacedByThrowExpression(SyntaxNode syntaxNode)
    {
        // C# Throw Expression definition in language reference:
        // 'A throw expression is permitted in only the following syntactic contexts:
        // As the second or third operand of a ternary conditional operator ?:
        // As the second operand of a null coalescing operator ??
        // As the body of an expression-bodied lambda or method.'
        return syntaxNode.Parent switch
        {
            ConditionalExpressionSyntax conditionalExpressionSyntax
                => syntaxNode.Equals(conditionalExpressionSyntax.WhenTrue) ||
                   syntaxNode.Equals(conditionalExpressionSyntax.WhenFalse),
            BinaryExpressionSyntax(kind: SyntaxKind.CoalesceExpression) binaryExpressionSyntax
                => syntaxNode.Equals(binaryExpressionSyntax.Right),
            LambdaExpressionSyntax lambdaExpressionSyntax
                => lambdaExpressionSyntax.ExpressionBody != null,
            var parent => parent.IsKind(SyntaxKind.ArrowExpressionClause),
        };
    }
 
    private static bool IsNullConditionalInvocationExpression(ExpressionSyntax expressionSyntax)
    {
        // Check if the expression syntax is like an invocation expression nested inside ConditionalAccessExpressionSyntax.
        // For example: a?.b.c()
        //
        // If the expression is ended with an invocation
        // (if the expressions in the middle are not ConditionalAccessExpressionSyntax),
        // like a?.b.e.c(), the syntax tree would be
        // ConditionalAccessExpressionSyntax -> InvocationExpression.
        // And in case of example like a?.b?.d?.c();
        // This is case it would be
        // ConditionalAccessExpressionSyntax -> ConditionalAccessExpressionSyntax -> ... -> InvocationExpression.
        return expressionSyntax is ConditionalAccessExpressionSyntax { WhenNotNull: var whenNotNull } &&
            (whenNotNull.IsKind(SyntaxKind.InvocationExpression) || IsNullConditionalInvocationExpression(whenNotNull));
    }
}