// 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.Collections.Immutable;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.CodeActions;
using Microsoft.CodeAnalysis.CodeGeneration;
using Microsoft.CodeAnalysis.Editing;
using Microsoft.CodeAnalysis.GenerateFromMembers;
using Microsoft.CodeAnalysis.Shared.Extensions;
 
namespace Microsoft.CodeAnalysis.GenerateConstructors;
 
using static GenerateFromMembersHelpers;
 
internal abstract partial class AbstractGenerateConstructorsCodeRefactoringProvider
{
    private sealed class FieldDelegatingCodeAction(
        AbstractGenerateConstructorsCodeRefactoringProvider service,
        Document document,
        State state,
        bool addNullChecks) : CodeAction
    {
        private readonly AbstractGenerateConstructorsCodeRefactoringProvider _service = service;
        private readonly Document _document = document;
        private readonly State _state = state;
        private readonly bool _addNullChecks = addNullChecks;
 
        protected override async Task<Document> GetChangedDocumentAsync(CancellationToken cancellationToken)
        {
            // First, see if there are any constructors that would take the first 'n' arguments
            // we've provided.  If so, delegate to those, and then create a field for any
            // remaining arguments.  Try to match from largest to smallest.
            //
            // Otherwise, just generate a normal constructor that assigns any provided
            // parameters into fields.
            var parameterToExistingFieldMap = ImmutableDictionary.CreateBuilder<string, ISymbol>();
            for (var i = 0; i < _state.Parameters.Length; i++)
                parameterToExistingFieldMap[_state.Parameters[i].Name] = _state.SelectedMembers[i];
 
            var factory = _document.GetRequiredLanguageService<SyntaxGenerator>();
 
            var semanticModel = await _document.GetRequiredSemanticModelAsync(cancellationToken).ConfigureAwait(false);
            var syntaxTree = semanticModel.SyntaxTree;
            var preferThrowExpression = await _service.PrefersThrowExpressionAsync(_document, cancellationToken).ConfigureAwait(false);
 
            var members = factory.CreateMemberDelegatingConstructor(
                factory.SyntaxGeneratorInternal,
                semanticModel,
                _state.ContainingType.Name,
                _state.ContainingType,
                _state.Parameters,
                _state.Accessibility,
                parameterToExistingFieldMap.ToImmutable(),
                parameterToNewMemberMap: null,
                addNullChecks: _addNullChecks,
                preferThrowExpression: preferThrowExpression,
                generateProperties: false,
                _state.IsContainedInUnsafeType);
 
            // If the user has selected a set of members (i.e. TextSpan is not empty), then we will
            // choose the right location (i.e. null) to insert the constructor.  However, if they're 
            // just invoking the feature manually at a specific location, then we'll insert the 
            // members at that specific place in the class/struct.
            var afterThisLocation = _state.TextSpan.IsEmpty
                ? syntaxTree.GetLocation(_state.TextSpan)
                : null;
 
            var result = await CodeGenerator.AddMemberDeclarationsAsync(
                new CodeGenerationSolutionContext(
                    _document.Project.Solution,
                    new CodeGenerationContext(
                        contextLocation: syntaxTree.GetLocation(_state.TextSpan),
                        afterThisLocation: afterThisLocation)),
                _state.ContainingType,
                members,
                cancellationToken).ConfigureAwait(false);
 
            return await AddNavigationAnnotationAsync(result, cancellationToken).ConfigureAwait(false);
        }
 
        public override string Title
        {
            get
            {
                var parameters = _state.Parameters.Select(p => _service.ToDisplayString(p, SimpleFormat));
                var parameterString = string.Join(", ", parameters);
 
                if (_state.DelegatedConstructor == null)
                {
                    return string.Format(CodeFixesResources.Generate_constructor_0_1,
                        _state.ContainingType.Name, parameterString);
                }
                else
                {
                    return string.Format(CodeFixesResources.Generate_field_assigning_constructor_0_1,
                        _state.ContainingType.Name, parameterString);
                }
            }
        }
    }
}