// 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.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.CSharp.Extensions;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Diagnostics;
using Microsoft.CodeAnalysis.Editing;
using Microsoft.CodeAnalysis.Formatting;
using Microsoft.CodeAnalysis.Host.Mef;
using Microsoft.CodeAnalysis.PooledObjects;
using Microsoft.CodeAnalysis.Shared.Extensions;
using Microsoft.CodeAnalysis.Text;
using Roslyn.Utilities;
 
namespace Microsoft.CodeAnalysis.CSharp.ConvertSwitchStatementToExpression
{
    using Constants = ConvertSwitchStatementToExpressionConstants;
 
    [ExportCodeFixProvider(LanguageNames.CSharp, Name = PredefinedCodeFixProviderNames.ConvertSwitchStatementToExpression), Shared]
    internal sealed partial class ConvertSwitchStatementToExpressionCodeFixProvider : SyntaxEditorBasedCodeFixProvider
    {
        [ImportingConstructor]
        [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
        public ConvertSwitchStatementToExpressionCodeFixProvider()
        {
        }
 
        public override ImmutableArray<string> FixableDiagnosticIds
            => ImmutableArray.Create(IDEDiagnosticIds.ConvertSwitchStatementToExpressionDiagnosticId);
 
        public override Task RegisterCodeFixesAsync(CodeFixContext context)
        {
            var switchLocation = context.Diagnostics.First().AdditionalLocations[0];
            var switchStatement = (SwitchStatementSyntax)switchLocation.FindNode(getInnermostNodeForTie: true, context.CancellationToken);
            if (switchStatement.ContainsDirectives)
            {
                // Avoid providing code fixes for switch statements containing directives
                return Task.CompletedTask;
            }
 
            RegisterCodeFix(context, CSharpAnalyzersResources.Convert_switch_statement_to_expression, nameof(CSharpAnalyzersResources.Convert_switch_statement_to_expression));
            return Task.CompletedTask;
        }
 
        protected override async Task FixAllAsync(
            Document document, ImmutableArray<Diagnostic> diagnostics,
            SyntaxEditor editor, CodeActionOptionsProvider fallbackOptions, CancellationToken cancellationToken)
        {
            using var _ = ArrayBuilder<TextSpan>.GetInstance(diagnostics.Length, out var spans);
            foreach (var diagnostic in diagnostics)
            {
                cancellationToken.ThrowIfCancellationRequested();
 
                var switchLocation = diagnostic.AdditionalLocations[0];
                if (spans.Any((s, nodeSpan) => s.Contains(nodeSpan), switchLocation.SourceSpan))
                {
                    // Skip nested switch expressions in case of a fix-all operation.
                    continue;
                }
 
                spans.Add(switchLocation.SourceSpan);
 
                var properties = diagnostic.Properties;
                var nodeToGenerate = (SyntaxKind)int.Parse(properties[Constants.NodeToGenerateKey]!);
                var shouldRemoveNextStatement = bool.Parse(properties[Constants.ShouldRemoveNextStatementKey]!);
 
                var declaratorToRemoveLocation = diagnostic.AdditionalLocations.ElementAtOrDefault(1);
                var semanticModel = await document.GetRequiredSemanticModelAsync(cancellationToken).ConfigureAwait(false);
 
                VariableDeclaratorSyntax? declaratorToRemoveNode = null;
                ITypeSymbol? declaratorToRemoveType = null;
 
                if (declaratorToRemoveLocation != null)
                {
                    declaratorToRemoveNode = (VariableDeclaratorSyntax)declaratorToRemoveLocation.FindNode(getInnermostNodeForTie: true, cancellationToken);
                    declaratorToRemoveType = semanticModel.GetDeclaredSymbol(declaratorToRemoveNode, cancellationToken).GetSymbolType();
                }
 
                var switchStatement = (SwitchStatementSyntax)switchLocation.FindNode(getInnermostNodeForTie: true, cancellationToken);
 
                var switchExpressionStatement = Rewriter.Rewrite(
                   switchStatement, semanticModel, declaratorToRemoveType, nodeToGenerate,
                   shouldMoveNextStatementToSwitchExpression: shouldRemoveNextStatement,
                   generateDeclaration: declaratorToRemoveLocation is not null,
                   cancellationToken);
 
                if (declaratorToRemoveNode is not null)
                {
                    editor.RemoveNode(declaratorToRemoveNode);
 
                    // If we are removing the declarator statement entirely, transfer its leading trivia to the
                    // expression-statement are converting to.
                    if (declaratorToRemoveNode.Parent is VariableDeclarationSyntax { Parent: LocalDeclarationStatementSyntax declStatement, Variables.Count: 1 })
                        switchExpressionStatement = switchExpressionStatement.WithPrependedLeadingTrivia(declStatement.GetLeadingTrivia());
                }
 
                editor.ReplaceNode(switchStatement, switchExpressionStatement.WithAdditionalAnnotations(Formatter.Annotation));
 
                if (shouldRemoveNextStatement)
                {
                    // Already morphed into the top-level switch expression.
                    var nextStatement = switchStatement.GetNextStatement();
                    Contract.ThrowIfNull(nextStatement);
                    Debug.Assert(nextStatement.Kind() is SyntaxKind.ThrowStatement or SyntaxKind.ReturnStatement);
                    editor.RemoveNode(nextStatement.IsParentKind(SyntaxKind.GlobalStatement) ? nextStatement.GetRequiredParent() : nextStatement);
                }
            }
        }
    }
}