// 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 Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CodeStyle;
using Microsoft.CodeAnalysis.CSharp.CodeStyle;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Diagnostics;
using Microsoft.CodeAnalysis.Shared.Extensions;
 
namespace Microsoft.CodeAnalysis.CSharp.NewLines.EmbeddedStatementPlacement;
 
[DiagnosticAnalyzer(LanguageNames.CSharp)]
internal sealed class EmbeddedStatementPlacementDiagnosticAnalyzer : AbstractBuiltInCodeStyleDiagnosticAnalyzer
{
    public EmbeddedStatementPlacementDiagnosticAnalyzer()
        : base(IDEDiagnosticIds.EmbeddedStatementPlacementDiagnosticId,
               EnforceOnBuildValues.EmbeddedStatementPlacement,
               CSharpCodeStyleOptions.AllowEmbeddedStatementsOnSameLine,
               new LocalizableResourceString(
                   nameof(CSharpAnalyzersResources.Embedded_statements_must_be_on_their_own_line), CSharpAnalyzersResources.ResourceManager, typeof(CSharpAnalyzersResources)))
    {
    }
 
    public override DiagnosticAnalyzerCategory GetAnalyzerCategory()
        => DiagnosticAnalyzerCategory.SyntaxTreeWithoutSemanticsAnalysis;
 
    protected override void InitializeWorker(AnalysisContext context)
        => context.RegisterCompilationStartAction(context =>
            context.RegisterSyntaxTreeAction(treeContext => AnalyzeTree(treeContext, context.Compilation.Options)));
 
    private void AnalyzeTree(SyntaxTreeAnalysisContext context, CompilationOptions compilationOptions)
    {
        var option = context.GetCSharpAnalyzerOptions().AllowEmbeddedStatementsOnSameLine;
        if (option.Value || ShouldSkipAnalysis(context, compilationOptions, option.Notification))
            return;
 
        Recurse(context, option.Notification, context.GetAnalysisRoot(findInTrivia: false));
    }
 
    private void Recurse(SyntaxTreeAnalysisContext context, NotificationOption2 notificationOption, SyntaxNode node)
    {
        context.CancellationToken.ThrowIfCancellationRequested();
 
        // Don't bother analyzing nodes that have syntax errors in them.
        if (node.ContainsDiagnostics)
            return;
 
        // Report on the topmost statement that has an issue.  No need to recurse further at that point. Note: the
        // fixer will fix up all statements, but we don't want to clutter things with lots of diagnostics on the
        // same line.
        if (node is StatementSyntax statement &&
            CheckStatementSyntax(context, notificationOption, statement))
        {
            return;
        }
 
        foreach (var child in node.ChildNodesAndTokens())
        {
            if (!context.ShouldAnalyzeSpan(child.Span))
                continue;
 
            if (child.AsNode(out var childNode))
                Recurse(context, notificationOption, childNode);
        }
    }
 
    private bool CheckStatementSyntax(SyntaxTreeAnalysisContext context, NotificationOption2 notificationOption, StatementSyntax statement)
    {
        if (!StatementNeedsWrapping(statement))
            return false;
 
        var additionalLocations = ImmutableArray.Create(statement.GetLocation());
        context.ReportDiagnostic(DiagnosticHelper.Create(
            this.Descriptor,
            statement.GetFirstToken().GetLocation(),
            notificationOption,
            context.Options,
            additionalLocations,
            properties: null));
        return true;
    }
 
    public static bool StatementNeedsWrapping(StatementSyntax statement)
    {
        // Statement has to be parented by another statement (or an else-clause) to count.
        var parent = statement.Parent;
        var parentIsElseClause = parent.IsKind(SyntaxKind.ElseClause);
 
        if (!(parent is StatementSyntax || parentIsElseClause))
            return false;
 
        // `else if` is always allowed.
        if (statement.IsKind(SyntaxKind.IfStatement) && parentIsElseClause)
            return false;
 
        var statementStartToken = statement.GetFirstToken();
 
        // we have to have a newline between the start of this statement and the previous statement.
        if (ContainsEndOfLineBetween(statementStartToken.GetPreviousToken(), statementStartToken))
            return false;
 
        // Looks like a statement that might need wrapping.  However, we do suppress wrapping for a few well known
        // acceptable cases.
 
        if (parent.IsKind(SyntaxKind.Block))
        {
            // Blocks can be on a single line if parented by a member/accessor/lambda.
            // And if they only contain a single statement at most within them.
            var blockParent = parent.Parent;
            if (blockParent is MemberDeclarationSyntax or
                AccessorDeclarationSyntax or
                AnonymousFunctionExpressionSyntax)
            {
                if (parent.DescendantNodes().OfType<StatementSyntax>().Count() <= 1)
                    return false;
            }
        }
 
        return true;
    }
 
    public static bool ContainsEndOfLineBetween(SyntaxToken previous, SyntaxToken next)
        => ContainsEndOfLine(previous.TrailingTrivia) || ContainsEndOfLine(next.LeadingTrivia);
 
    private static bool ContainsEndOfLine(SyntaxTriviaList triviaList)
    {
        foreach (var trivia in triviaList)
        {
            if (trivia.IsKind(SyntaxKind.EndOfLineTrivia))
                return true;
        }
 
        return false;
    }
}