// 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.Generic;
using System.Linq;
using Microsoft.CodeAnalysis.CSharp.CodeGeneration;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.CSharp.Utilities;
using Microsoft.CodeAnalysis.OrganizeImports;
using Microsoft.CodeAnalysis.Text;
using Roslyn.Utilities;
 
namespace Microsoft.CodeAnalysis.CSharp.OrganizeImports
{
    internal partial class CSharpOrganizeImportsService
    {
        private sealed class Rewriter : CSharpSyntaxRewriter
        {
            private readonly bool _placeSystemNamespaceFirst;
            private readonly bool _separateGroups;
            private readonly SyntaxTrivia _newLineTrivia;
 
            public readonly IList<TextChange> TextChanges = new List<TextChange>();
 
            public Rewriter(OrganizeImportsOptions options)
            {
                _placeSystemNamespaceFirst = options.PlaceSystemNamespaceFirst;
                _separateGroups = options.SeparateImportDirectiveGroups;
                _newLineTrivia = CSharpSyntaxGeneratorInternal.Instance.EndOfLine(options.NewLine);
            }
 
            public override SyntaxNode VisitCompilationUnit(CompilationUnitSyntax node)
            {
                node = (CompilationUnitSyntax)base.VisitCompilationUnit(node)!;
                UsingsAndExternAliasesOrganizer.Organize(
                    node.Externs, node.Usings,
                    _placeSystemNamespaceFirst, _separateGroups,
                    _newLineTrivia,
                    out var organizedExternAliasList, out var organizedUsingList);
 
                var result = node.WithExterns(organizedExternAliasList).WithUsings(organizedUsingList);
                if (node != result)
                {
                    AddTextChange(node.Externs, organizedExternAliasList);
                    AddTextChange(node.Usings, organizedUsingList);
                }
 
                return result;
            }
 
            public override SyntaxNode VisitFileScopedNamespaceDeclaration(FileScopedNamespaceDeclarationSyntax node)
                => VisitBaseNamespaceDeclaration((BaseNamespaceDeclarationSyntax?)base.VisitFileScopedNamespaceDeclaration(node));
 
            public override SyntaxNode VisitNamespaceDeclaration(NamespaceDeclarationSyntax node)
                => VisitBaseNamespaceDeclaration((BaseNamespaceDeclarationSyntax?)base.VisitNamespaceDeclaration(node));
 
            private BaseNamespaceDeclarationSyntax VisitBaseNamespaceDeclaration(BaseNamespaceDeclarationSyntax? node)
            {
                Contract.ThrowIfNull(node);
                UsingsAndExternAliasesOrganizer.Organize(
                    node.Externs, node.Usings,
                    _placeSystemNamespaceFirst, _separateGroups,
                    _newLineTrivia,
                    out var organizedExternAliasList, out var organizedUsingList);
 
                var result = node.WithExterns(organizedExternAliasList).WithUsings(organizedUsingList);
                if (node != result)
                {
                    AddTextChange(node.Externs, organizedExternAliasList);
                    AddTextChange(node.Usings, organizedUsingList);
                }
 
                return result;
            }
 
            private void AddTextChange<TSyntax>(SyntaxList<TSyntax> list, SyntaxList<TSyntax> organizedList)
                where TSyntax : SyntaxNode
            {
                if (list.Count > 0)
                    this.TextChanges.Add(new TextChange(GetTextSpan(list), GetNewText(organizedList)));
            }
 
            private static string GetNewText<TSyntax>(SyntaxList<TSyntax> organizedList) where TSyntax : SyntaxNode
                => string.Join(string.Empty, organizedList.Select(t => t.ToFullString()));
 
            private static TextSpan GetTextSpan<TSyntax>(SyntaxList<TSyntax> list) where TSyntax : SyntaxNode
                => TextSpan.FromBounds(list.First().FullSpan.Start, list.Last().FullSpan.End);
        }
    }
}