// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using Microsoft.AspNetCore.Razor.Language;
using Microsoft.AspNetCore.Razor.Language.Intermediate;

namespace Microsoft.AspNetCore.Mvc.Razor.Extensions
{
    public class PageDirective
    {
        public static readonly DirectiveDescriptor Directive = DirectiveDescriptor.CreateDirective(
            "page",
            DirectiveKind.SingleLine,
            builder =>
            {
                builder.AddOptionalStringToken(Resources.PageDirective_RouteToken_Name, Resources.PageDirective_RouteToken_Description);
                builder.Usage = DirectiveUsage.FileScopedSinglyOccurring;
                builder.Description = Resources.PageDirective_Description;
            });

        private PageDirective(string routeTemplate, IntermediateNode directiveNode)
        {
            RouteTemplate = routeTemplate;
            DirectiveNode = directiveNode;
        }

        public string RouteTemplate { get; }

        public IntermediateNode DirectiveNode { get; }

        public static RazorProjectEngineBuilder Register(RazorProjectEngineBuilder builder)
        {
            if (builder == null)
            {
                throw new ArgumentNullException(nameof(builder));
            }

            builder.AddDirective(Directive);
            return builder;
        }

        public static bool TryGetPageDirective(DocumentIntermediateNode documentNode, out PageDirective pageDirective)
        {
            var visitor = new Visitor();
            for (var i = 0; i < documentNode.Children.Count; i++)
            {
                visitor.Visit(documentNode.Children[i]);
            }

            if (visitor.DirectiveTokens == null)
            {
                pageDirective = null;
                return false;
            }

            var tokens = visitor.DirectiveTokens.ToList();
            string routeTemplate = null;
            if (tokens.Count > 0)
            {
                routeTemplate = TrimQuotes(tokens[0].Content);
            }

            pageDirective = new PageDirective(routeTemplate, visitor.DirectiveNode);
            return true;
        }

        private static string TrimQuotes(string content)
        {
            // Tokens aren't captured if they're malformed. Therefore, this method will
            // always be called with a valid token content.
            Debug.Assert(content.Length >= 2);
            Debug.Assert(content.StartsWith("\"", StringComparison.Ordinal));
            Debug.Assert(content.EndsWith("\"", StringComparison.Ordinal));

            return content.Substring(1, content.Length - 2);
        }

        private class Visitor : IntermediateNodeWalker
        {
            public IntermediateNode DirectiveNode { get; private set; }

            public IEnumerable<DirectiveTokenIntermediateNode> DirectiveTokens { get; private set; }

            public override void VisitDirective(DirectiveIntermediateNode node)
            {
                if (node.Directive == Directive)
                {
                    DirectiveNode = node;
                    DirectiveTokens = node.Tokens;
                }
            }

            public override void VisitMalformedDirective(MalformedDirectiveIntermediateNode node)
            {
                if (DirectiveTokens == null && node.Directive == Directive)
                {
                    DirectiveNode = node;
                    DirectiveTokens = node.Tokens;
                }
            }
        }

        #region Obsolete
        [Obsolete("This method is obsolete and will be removed in a future version.")]
        public static IRazorEngineBuilder Register(IRazorEngineBuilder builder)
        {
            if (builder == null)
            {
                throw new ArgumentNullException(nameof(builder));
            }

            builder.AddDirective(Directive);
            return builder;
        }
        #endregion
    }
}