// 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.Immutable;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.CSharp.Extensions;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.ExtractMethod;
using Microsoft.CodeAnalysis.Shared.Extensions;

namespace Microsoft.CodeAnalysis.CSharp.ExtractMethod;

internal sealed partial class CSharpExtractMethodService
{
    internal sealed partial class CSharpMethodExtractor
    {
        private abstract partial class CSharpCodeGenerator
        {
            private sealed class ExpressionCodeGenerator(
                SelectionResult selectionResult,
                AnalyzerResult analyzerResult,
                ExtractMethodGenerationOptions options,
                bool localFunction) : CSharpCodeGenerator(selectionResult, analyzerResult, options, localFunction)
            {
                protected override SyntaxToken CreateMethodName()
                {
                    var methodName = GenerateMethodNameFromUserPreference();

                    var containingScope = this.SelectionResult.GetContainingScope();

                    methodName = GetMethodNameBasedOnExpression(methodName, containingScope);

                    var semanticModel = SemanticDocument.SemanticModel;
                    var nameGenerator = new UniqueNameGenerator(semanticModel);
                    return SyntaxFactory.Identifier(nameGenerator.CreateUniqueMethodName(containingScope, methodName));
                }

                private static string GetMethodNameBasedOnExpression(string methodName, SyntaxNode expression)
                {
                    if (expression.Parent != null &&
                        expression.Parent.Kind() == SyntaxKind.EqualsValueClause &&
                        expression.Parent.Parent != null &&
                        expression.Parent.Parent.Kind() == SyntaxKind.VariableDeclarator)
                    {
                        var name = ((VariableDeclaratorSyntax)expression.Parent.Parent).Identifier.ValueText;
                        return (name != null && name.Length > 0) ? MakeMethodName("Get", name, methodName.Equals(NewMethodCamelCaseStr)) : methodName;
                    }

                    if (expression is MemberAccessExpressionSyntax memberAccess)
                    {
                        expression = memberAccess.Name;
                    }

                    if (expression is NameSyntax)
                    {
                        SimpleNameSyntax unqualifiedName;

                        switch (expression.Kind())
                        {
                            case SyntaxKind.IdentifierName:
                            case SyntaxKind.GenericName:
                                unqualifiedName = (SimpleNameSyntax)expression;
                                break;
                            case SyntaxKind.QualifiedName:
                                unqualifiedName = ((QualifiedNameSyntax)expression).Right;
                                break;
                            case SyntaxKind.AliasQualifiedName:
                                unqualifiedName = ((AliasQualifiedNameSyntax)expression).Name;
                                break;
                            default:
                                throw new System.NotSupportedException("Unexpected name kind: " + expression.Kind().ToString());
                        }

                        var unqualifiedNameIdentifierValueText = unqualifiedName.Identifier.ValueText;
                        return (unqualifiedNameIdentifierValueText != null && unqualifiedNameIdentifierValueText.Length > 0) ?
                            MakeMethodName("Get", unqualifiedNameIdentifierValueText, methodName.Equals(NewMethodCamelCaseStr)) : methodName;
                    }

                    return methodName;
                }

                protected override ImmutableArray<StatementSyntax> GetInitialStatementsForMethodDefinitions()
                {
                    Contract.ThrowIfFalse(this.SelectionResult.IsExtractMethodOnExpression);

                    // special case for array initializer
                    var returnType = AnalyzerResult.CoreReturnType;
                    var containingScope = (ExpressionSyntax)this.SelectionResult.GetContainingScope();

                    var expression = returnType.TypeKind == TypeKind.Array && containingScope is InitializerExpressionSyntax initializerExpression
                        ? SyntaxFactory.ArrayCreationExpression((ArrayTypeSyntax)returnType.GenerateTypeSyntax(), initializerExpression)
                        : containingScope;

                    return AnalyzerResult.CoreReturnType.SpecialType != SpecialType.System_Void
                        ? [SyntaxFactory.ReturnStatement(WrapInCheckedExpressionIfNeeded(expression))]
                        : [SyntaxFactory.ExpressionStatement(WrapInCheckedExpressionIfNeeded(expression))];
                }

                private ExpressionSyntax WrapInCheckedExpressionIfNeeded(ExpressionSyntax expression)
                {
                    var kind = UnderCheckedExpressionContext();
                    if (kind == SyntaxKind.None)
                    {
                        return expression;
                    }

                    return SyntaxFactory.CheckedExpression(kind, expression);
                }

                protected override SyntaxNode GetFirstStatementOrInitializerSelectedAtCallSite()
                {
                    var scope = (SyntaxNode)this.SelectionResult.GetContainingScopeOf<StatementSyntax>();
                    scope ??= this.SelectionResult.GetContainingScopeOf<FieldDeclarationSyntax>();

                    scope ??= this.SelectionResult.GetContainingScopeOf<ConstructorInitializerSyntax>();

                    // This is similar to FieldDeclaration case but we only want to do this 
                    // if the member has an expression body.
                    scope ??= this.SelectionResult.GetContainingScopeOf<ArrowExpressionClauseSyntax>()?.Parent;

                    scope ??= this.SelectionResult.GetContainingScopeOf<PrimaryConstructorBaseTypeSyntax>();

                    return scope;
                }

                protected override SyntaxNode GetLastStatementOrInitializerSelectedAtCallSite()
                    => GetFirstStatementOrInitializerSelectedAtCallSite();

                protected override async Task<SyntaxNode> GetStatementOrInitializerContainingInvocationToExtractedMethodAsync(CancellationToken cancellationToken)
                {
                    var enclosingStatement = GetFirstStatementOrInitializerSelectedAtCallSite();

                    var callSignature = CreateCallSignature().WithAdditionalAnnotations(CallSiteAnnotation);

                    var sourceNode = this.SelectionResult.GetContainingScope();
                    Contract.ThrowIfTrue(
                        sourceNode.Parent is MemberAccessExpressionSyntax memberAccessExpression && memberAccessExpression.Name == sourceNode,
                        "invalid scope. given scope is not an expression");

                    // To lower the chances that replacing sourceNode with callSignature will break the user's
                    // code, we make the enclosing statement semantically explicit. This ends up being a little
                    // bit more work because we need to annotate the sourceNode so that we can get back to it
                    // after rewriting the enclosing statement.
                    var updatedDocument = SemanticDocument.Document;
                    var sourceNodeAnnotation = new SyntaxAnnotation();
                    var enclosingStatementAnnotation = new SyntaxAnnotation();
                    var newEnclosingStatement = enclosingStatement
                        .ReplaceNode(sourceNode, sourceNode.WithAdditionalAnnotations(sourceNodeAnnotation))
                        .WithAdditionalAnnotations(enclosingStatementAnnotation);

                    updatedDocument = await updatedDocument.ReplaceNodeAsync(enclosingStatement, newEnclosingStatement, cancellationToken).ConfigureAwait(false);

                    var updatedRoot = await updatedDocument.GetSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
                    newEnclosingStatement = updatedRoot.GetAnnotatedNodesAndTokens(enclosingStatementAnnotation).Single().AsNode();

                    // because of the complexification we cannot guarantee that there is only one annotation.
                    // however complexification of names is prepended, so the last annotation should be the original one.
                    sourceNode = updatedRoot.GetAnnotatedNodesAndTokens(sourceNodeAnnotation).Last().AsNode();

                    return newEnclosingStatement.ReplaceNode(sourceNode, callSignature);
                }
            }
        }
    }
}