using Microsoft.Dnx.Compilation.CSharp;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.CSharp;

namespace Microsoft.StandardsPolice
{
    // This project can output the Class library as a NuGet Package.
    // To enable this option, right-click on the project and select the Properties menu item. In the Build tab select "Produce outputs on build".
    public class StandardsPoliceCompileModule : ICompileModule
    {
        public void BeforeCompile(BeforeCompileContext context)
        {
            ScanCompilation(context.Diagnostics, context.Compilation);
        }

        internal static void ScanCompilation(IList<Diagnostic> diagnostics, CSharpCompilation compilation)
        {
            ScanNamespace(diagnostics, compilation.GlobalNamespace);

            foreach (var st in compilation.SyntaxTrees)
            {
                if (!st.FilePath.EndsWith(".Generated.cs"))
                {
                    ScanSyntaxTree(diagnostics, st);
                }
            }
        }

        internal static void ScanSyntaxTree(IList<Diagnostic> diagnostics, SyntaxTree syntaxTree)
        {
            var root = syntaxTree.GetRoot();

            var typeDeclarations = root.DescendantNodes(descendIntoChildren: node => !(node is TypeDeclarationSyntax))
                .OfType<TypeDeclarationSyntax>()
                .ToArray();

            if (typeDeclarations.Length > 1)
            {
                foreach (var typeDeclaration in typeDeclarations)
                {
                    diagnostics.Add(Diagnostic.Create(
                        "SP1002", "StandardsPolice", "more than one type per file",
                        DiagnosticSeverity.Warning,
                        DiagnosticSeverity.Warning,
                        false,
                        3,
                        location: typeDeclaration.GetLocation()));
                }
            }
        }

        private static void ScanNamespace(IList<Diagnostic> diagnostics, INamespaceSymbol namespaceSymbol)
        {
            foreach (var member in namespaceSymbol.GetNamespaceMembers())
            {
                ScanNamespace(diagnostics, member);
            }
            foreach (var member in namespaceSymbol.GetTypeMembers())
            {
                ScanType(diagnostics, member);
            }
        }

        private static void ScanType(IList<Diagnostic> diagnostics, INamedTypeSymbol typeSymbol)
        {
            if (typeSymbol.Locations.Any(location => location.IsInSource))
            {
                RuleFieldPrivateKeyword(diagnostics, typeSymbol);
                RuleNestedTypesAreLast(diagnostics, typeSymbol);
            }

            foreach (var member in typeSymbol.GetTypeMembers())
            {
                ScanType(diagnostics, member);
            }
        }

        private static void RuleFieldPrivateKeyword(IList<Diagnostic> diagnostics, INamedTypeSymbol typeSymbol)
        {
            foreach (var member in typeSymbol.GetMembers().OfType<IFieldSymbol>())
            {
                if (member.DeclaredAccessibility != Accessibility.Private)
                {
                    continue;
                }

                foreach (var syntaxReference in member.DeclaringSyntaxReferences)
                {
                    var fieldHasPrivateKeyword = false;
                    var syntax = syntaxReference.GetSyntax();
                    var fds = syntax?.Parent?.Parent as FieldDeclarationSyntax;
                    if (fds == null)
                    {
                        continue;
                    }
                    foreach (var mod in fds.Modifiers)
                    {
                        if (mod.IsKind(CodeAnalysis.CSharp.SyntaxKind.PrivateKeyword))
                        {
                            fieldHasPrivateKeyword = true;
                        }
                    }
                    if (!fieldHasPrivateKeyword)
                    {
                        diagnostics.Add(Diagnostic.Create(
                            "SP1001", "StandardsPolice", "private keyword missing",
                            DiagnosticSeverity.Warning,
                            DiagnosticSeverity.Warning,
                            false,
                            3,
                            location: member.Locations.SingleOrDefault()));
                    }
                }
            }
        }

        private static void RuleNestedTypesAreLast(IList<Diagnostic> diagnostics, INamedTypeSymbol typeSymbol)
        {
            var otherThingsWereLower = false;
            var members = typeSymbol.GetMembers().Reverse().ToArray();
            foreach (var member in members)
            {
                var namedType = member as INamedTypeSymbol;
                if (namedType == null || (namedType.TypeKind != TypeKind.Class && namedType.TypeKind != TypeKind.Enum && namedType.TypeKind != TypeKind.Struct))
                {
                    if (member.IsImplicitlyDeclared == false)
                    {
                        otherThingsWereLower = true;
                    }
                    continue;
                }
                if (otherThingsWereLower)
                {
                    if (member.Locations.Count() == 1)
                    {
                        diagnostics.Add(Diagnostic.Create(
                            "SP1003", "StandardsPolice", $"nested types must be last {typeSymbol.Name}:{member.Name}",
                            DiagnosticSeverity.Warning,
                            DiagnosticSeverity.Warning,
                            false,
                            3,
                            location: member.Locations.Single()));
                    }
                }
            }
        }

        public void AfterCompile(AfterCompileContext context)
        {
        }
    }
}