// 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.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.CodeActions;
using Microsoft.CodeAnalysis.CodeFixes;
using Microsoft.CodeAnalysis.Diagnostics;
using Microsoft.CodeAnalysis.Editing;
using Microsoft.CodeAnalysis.LanguageService;
using Microsoft.CodeAnalysis.Shared.Extensions;
using Microsoft.CodeAnalysis.Simplification;
using Microsoft.CodeAnalysis.Text;

namespace Microsoft.CodeAnalysis.SimplifyTypeNames;

internal abstract partial class AbstractSimplifyTypeNamesCodeFixProvider<TSyntaxKind, TSimplifierOptions>(
    SimplifyTypeNamesDiagnosticAnalyzerBase<TSyntaxKind, TSimplifierOptions> analyzer)
    : SyntaxEditorBasedCodeFixProvider
    where TSyntaxKind : struct
    where TSimplifierOptions : SimplifierOptions
{
    private readonly SimplifyTypeNamesDiagnosticAnalyzerBase<TSyntaxKind, TSimplifierOptions> _analyzer = analyzer;

    protected abstract string GetTitle(string diagnosticId, string nodeText);
    protected abstract SyntaxNode AddSimplificationAnnotationTo(SyntaxNode node);

    public sealed override ImmutableArray<string> FixableDiagnosticIds { get; } =
        [
            IDEDiagnosticIds.SimplifyNamesDiagnosticId,
            IDEDiagnosticIds.SimplifyMemberAccessDiagnosticId,
            IDEDiagnosticIds.PreferBuiltInOrFrameworkTypeDiagnosticId,
        ];

    private (SyntaxNode, string diagnosticId) GetNodeToSimplify(
        SyntaxNode root, SemanticModel model, TextSpan span,
        TSimplifierOptions options, CancellationToken cancellationToken)
    {
        var token = root.FindToken(span.Start, findInsideTrivia: true);
        if (!token.Span.IntersectsWith(span))
        {
            return default;
        }

        SyntaxNode topmostSimplifiableNode = null;
        string topmostDiagnosticId = null;
        foreach (var node in token.GetAncestors<SyntaxNode>())
        {
            if (node.Span.IntersectsWith(span) && CanSimplifyTypeNameExpression(model, node, options, span, out var diagnosticId, cancellationToken))
            {
                // keep overwriting the best simplifiable node as long as we keep finding them.
                topmostSimplifiableNode = node;
                topmostDiagnosticId = diagnosticId;
            }
            else if (topmostSimplifiableNode != null)
            {
                // if we have found something simplifiable, but hit something that isn't, then
                // return the best thing we've found.
                break;
            }
        }

        return (topmostSimplifiableNode, topmostDiagnosticId);
    }

    public sealed override async Task RegisterCodeFixesAsync(CodeFixContext context)
    {
        var document = context.Document;
        var span = context.Span;
        var cancellationToken = context.CancellationToken;

        var root = await document.GetSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
        var model = await document.GetSemanticModelAsync(cancellationToken).ConfigureAwait(false);
        var options = (TSimplifierOptions)await document.GetSimplifierOptionsAsync(cancellationToken).ConfigureAwait(false);

        var (node, diagnosticId) = GetNodeToSimplify(
            root, model, span, options, cancellationToken);
        if (node == null)
            return;

        var syntaxFacts = document.GetLanguageService<ISyntaxFactsService>();
        var title = GetTitle(diagnosticId, syntaxFacts.ConvertToSingleLine(node).ToString());

        RegisterCodeFix(context, title, diagnosticId);
    }

    protected override async Task FixAllAsync(
        Document document, ImmutableArray<Diagnostic> diagnostics,
        SyntaxEditor editor, CancellationToken cancellationToken)
    {
        var root = await document.GetSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
        var model = await document.GetSemanticModelAsync(cancellationToken).ConfigureAwait(false);
        var simplifierOptions = (TSimplifierOptions)await document.GetSimplifierOptionsAsync(cancellationToken).ConfigureAwait(false);

        foreach (var diagnostic in diagnostics)
        {
            var (node, _) = GetNodeToSimplify(
                root, model, diagnostic.Location.SourceSpan,
                simplifierOptions, cancellationToken);

            if (node == null)
                return;

            editor.ReplaceNode(
                node,
                (current, _) => AddSimplificationAnnotationTo(current));
        }
    }

    private bool CanSimplifyTypeNameExpression(SemanticModel model, SyntaxNode node, TSimplifierOptions options, TextSpan span, out string diagnosticId, CancellationToken cancellationToken)
    {
        diagnosticId = null;
        if (!_analyzer.IsCandidate(node) ||
            !_analyzer.CanSimplifyTypeNameExpression(
                model, node, options, out var issueSpan, out diagnosticId, out _, cancellationToken))
        {
            return false;
        }

        return issueSpan.Equals(span);
    }
}