using System.Collections.Generic;
using System.Collections.Immutable;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Diagnostics;

namespace Ariadne.Generator
{
    /// <summary>
    /// Silences CS0164 ("label not referenced") on step labels in passages, and nowhere else.
    /// </summary>
    [DiagnosticAnalyzer(LanguageNames.CSharp)]
    public class StepLabelSuppressor : DiagnosticSuppressor
    {
        public static readonly SuppressionDescriptor UnreferencedStepLabel = new SuppressionDescriptor(
            "ARIS0001", "CS0164", "In a passage, a label names a step for saves; nothing jumps to it.");

        public override ImmutableArray<SuppressionDescriptor> SupportedSuppressions
        {
            get
            {
                return ImmutableArray.Create(UnreferencedStepLabel);
            }
        }

        public override void ReportSuppressions(SuppressionAnalysisContext context)
        {
            var scripts = new Dictionary<INamedTypeSymbol, ScriptClass>(SymbolEqualityComparer.Default);
            foreach (Diagnostic diagnostic in context.ReportedDiagnostics)
            {
                SyntaxTree tree = diagnostic.Location.SourceTree;
                if (tree == null)
                {
                    continue;
                }

                SyntaxNode node = tree.GetRoot(context.CancellationToken).FindNode(diagnostic.Location.SourceSpan);
                MethodDeclarationSyntax methodSyntax = node.FirstAncestorOrSelf<MethodDeclarationSyntax>();
                if (methodSyntax == null)
                {
                    continue;
                }

                var method = context.GetSemanticModel(tree).GetDeclaredSymbol(methodSyntax) as IMethodSymbol;
                if (method == null)
                {
                    continue;
                }

                ScriptClass script;
                if (!scripts.TryGetValue(method.ContainingType, out script))
                {
                    script = ScriptClass.Create(method.ContainingType, context.Compilation);
                    scripts[method.ContainingType] = script;
                }

                if (script != null && script.Passages.Contains(method))
                {
                    context.ReportSuppression(Suppression.Create(UnreferencedStepLabel, diagnostic));
                }
            }
        }
    }
}