squidex/backend/src/Squidex.Domain.Apps.Entities/Contents/Text/QueryParser.cs

// ==========================================================================
//  Squidex Headless CMS
// ==========================================================================
//  Copyright (c) Squidex UG (haftungsbeschraenkt)
//  All rights reserved. Licensed under the MIT license.
// ==========================================================================

using System;
using System.Text;

namespace Squidex.Domain.Apps.Entities.Contents.Text
{
    public sealed class QueryParser
    {
        private readonly Func<string, string> fieldProvider;

        public QueryParser(Func<string, string> fieldProvider)
        {
            this.fieldProvider = fieldProvider;
        }

        public Query? Parse(string text)
        {
            if (string.IsNullOrWhiteSpace(text))
            {
                return null;
            }

            text = text.Trim();
            text = ConvertFieldNames(text);

            return new Query
            {
                Text = text
            };
        }

        private string ConvertFieldNames(string query)
        {
            var indexOfColon = query.IndexOf(':', StringComparison.Ordinal);

            if (indexOfColon < 0)
            {
                return query;
            }

            var sb = new StringBuilder();

            int position = 0, lastIndexOfColon = 0;

            while (indexOfColon >= 0)
            {
                lastIndexOfColon = indexOfColon;

                var i = 0;

                for (i = indexOfColon - 1; i >= position; i--)
                {
                    var c = query[i];

                    if (!char.IsLetter(c) && c != '-' && c != '_')
                    {
                        break;
                    }
                }

                i++;

                sb.Append(query[position..i]);
                sb.Append(fieldProvider(query[i..indexOfColon]));

                position = indexOfColon + 1;

                indexOfColon = query.IndexOf(':', position);
            }

            sb.Append(query[lastIndexOfColon..]);

            return sb.ToString();
        }
    }
}