// 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.CodeFixes;
using Microsoft.CodeAnalysis.Diagnostics;
using Microsoft.CodeAnalysis.Editing;
using Microsoft.CodeAnalysis.LanguageService;
using Microsoft.CodeAnalysis.Operations;
using Microsoft.CodeAnalysis.Shared.Extensions;
using Microsoft.CodeAnalysis.Simplification;

namespace Microsoft.CodeAnalysis.ForEachCast;

internal abstract class AbstractForEachCastCodeFixProvider<TForEachStatementSyntax> : SyntaxEditorBasedCodeFixProvider
    where TForEachStatementSyntax : SyntaxNode
{
    protected abstract ITypeSymbol GetForEachElementType(SemanticModel semanticModel, TForEachStatementSyntax forEachStatement);

    public sealed override ImmutableArray<string> FixableDiagnosticIds
        => [IDEDiagnosticIds.ForEachCastDiagnosticId];

    public override async Task RegisterCodeFixesAsync(CodeFixContext context)
    {
        if (context.Diagnostics.First().Properties.ContainsKey(ForEachCastHelpers.IsFixable))
        {
            RegisterCodeFix(context, AnalyzersResources.Add_explicit_cast, nameof(AbstractForEachCastCodeFixProvider<>));
        }
    }

    protected override bool IncludeDiagnosticDuringFixAll(Diagnostic diagnostic)
        => diagnostic.Properties.ContainsKey(ForEachCastHelpers.IsFixable);

    protected override async Task FixAllAsync(
        Document document, ImmutableArray<Diagnostic> diagnostics,
        SyntaxEditor editor, CancellationToken cancellationToken)
    {
        var syntaxFacts = document.GetRequiredLanguageService<ISyntaxFactsService>();
        var semanticModel = await document.GetRequiredSemanticModelAsync(cancellationToken).ConfigureAwait(false);
        foreach (var diagnostic in diagnostics)
        {
            var node = editor.OriginalRoot.FindNode(diagnostic.Location.SourceSpan, getInnermostNodeForTie: true);
            if (node is TForEachStatementSyntax foreachStatement)
                AddCast(syntaxFacts, semanticModel, editor, foreachStatement, cancellationToken);
        }
    }

    public void AddCast(
        ISyntaxFacts syntaxFacts,
        SemanticModel semanticModel,
        SyntaxEditor editor,
        TForEachStatementSyntax forEachStatement,
        CancellationToken cancellationToken)
    {
        var expression = syntaxFacts.GetExpressionOfForeachStatement(forEachStatement);
        var loopOperation = (IForEachLoopOperation)semanticModel.GetRequiredOperation(forEachStatement, cancellationToken);
        var variableDeclarator = (IVariableDeclaratorOperation)loopOperation.LoopControlVariable;
        var enumerableType = semanticModel.Compilation.GetBestTypeByMetadataName(typeof(Enumerable).FullName!);

        // These were already verified to be non-null in the analyzer.
        Contract.ThrowIfNull(variableDeclarator.Symbol.Type);
        Contract.ThrowIfNull(enumerableType);

        var elementType = GetForEachElementType(semanticModel, forEachStatement);
        var conversion = semanticModel.Compilation.ClassifyCommonConversion(elementType, variableDeclarator.Symbol.Type);

        var rewritten = GetRewrittenCollection(editor.Generator, expression, variableDeclarator.Symbol.Type, conversion);

        // Add an annotation for System.Linq.Enumerable so that we add a `using System.Linq;` if not present.
        rewritten = rewritten.WithAdditionalAnnotations(
            Simplifier.Annotation, Simplifier.AddImportsAnnotation, SymbolAnnotation.Create(enumerableType));

        editor.ReplaceNode(expression, rewritten);
    }

    private SyntaxNode GetRewrittenCollection(
        SyntaxGenerator generator,
        SyntaxNode collection,
        ITypeSymbol iterationVariableType,
        CommonConversion conversion)
    {
        if (conversion.Exists && conversion.IsReference)
        {
            // for a reference cast we can insert `.Cast<DestType>()`
            return generator.InvocationExpression(
                generator.MemberAccessExpression(
                    collection,
                    generator.GenericName(
                        nameof(Enumerable.Cast),
                        [iterationVariableType])));
        }
        else
        {
            // otherwise we need to ensure a language specific conversion by emitting the conversion into the code
            // like so: `.Select(v => (DestType)v)`
            return generator.InvocationExpression(
                generator.MemberAccessExpression(
                    collection,
                    generator.IdentifierName(nameof(Enumerable.Select))),
                generator.ValueReturningLambdaExpression(
                    "v",
                    generator.ConvertExpression(iterationVariableType, generator.IdentifierName("v"))));
        }
    }
}