aspnetcore/src/Microsoft.AspNetCore.Razor/Parser/TextReaderExtensions.cs

// 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.IO;
using System.Linq;
using System.Text;

namespace Microsoft.AspNetCore.Razor.Parser
{
    internal static class TextReaderExtensions
    {
        public static string ReadUntil(this TextReader reader, char terminator)
        {
            if (reader == null)
            {
                throw new ArgumentNullException(nameof(reader));
            }

            return ReadUntil(reader, terminator, inclusive: false);
        }

        public static string ReadUntil(this TextReader reader, char terminator, bool inclusive)
        {
            if (reader == null)
            {
                throw new ArgumentNullException(nameof(reader));
            }

            // Rather not allocate an array to use ReadUntil(TextReader, params char[]) so we'll just call the predicate version directly
            return ReadUntil(reader, c => c == terminator, inclusive);
        }

        public static string ReadUntil(this TextReader reader, params char[] terminators)
        {
            if (reader == null)
            {
                throw new ArgumentNullException(nameof(reader));
            }

            if (terminators == null)
            {
                throw new ArgumentNullException(nameof(terminators));
            }

            // NOTE: Using named parameters would be difficult here, hence the inline comment
            return ReadUntil(reader, inclusive: false, terminators: terminators);
        }

        public static string ReadUntil(
            this TextReader reader,
            bool inclusive,
            params char[] terminators)
        {
            if (reader == null)
            {
                throw new ArgumentNullException(nameof(reader));
            }

            if (terminators == null)
            {
                throw new ArgumentNullException(nameof(terminators));
            }

            return ReadUntil(reader, c => terminators.Any(tc => tc == c), inclusive: inclusive);
        }

        public static string ReadUntil(this TextReader reader, Predicate<char> condition)
        {
            if (reader == null)
            {
                throw new ArgumentNullException(nameof(reader));
            }

            if (condition == null)
            {
                throw new ArgumentNullException(nameof(condition));
            }

            return ReadUntil(reader, condition, inclusive: false);
        }

        public static string ReadUntil(
            this TextReader reader,
            Predicate<char> condition,
            bool inclusive)
        {
            if (reader == null)
            {
                throw new ArgumentNullException(nameof(reader));
            }

            if (condition == null)
            {
                throw new ArgumentNullException(nameof(condition));
            }

            var builder = new StringBuilder();
            var ch = -1;
            while ((ch = reader.Peek()) != -1 && !condition((char)ch))
            {
                reader.Read(); // Advance the reader
                builder.Append((char)ch);
            }

            if (inclusive && reader.Peek() != -1)
            {
                builder.Append((char)reader.Read());
            }

            return builder.ToString();
        }

        public static string ReadWhile(this TextReader reader, Predicate<char> condition)
        {
            if (reader == null)
            {
                throw new ArgumentNullException(nameof(reader));
            }

            if (condition == null)
            {
                throw new ArgumentNullException(nameof(condition));
            }

            return ReadWhile(reader, condition, inclusive: false);
        }

        public static string ReadWhile(
            this TextReader reader,
            Predicate<char> condition,
            bool inclusive)
        {
            if (reader == null)
            {
                throw new ArgumentNullException(nameof(reader));
            }

            if (condition == null)
            {
                throw new ArgumentNullException(nameof(condition));
            }

            return ReadUntil(reader, ch => !condition(ch), inclusive);
        }

        public static string ReadWhiteSpace(this TextReader reader)
        {
            if (reader == null)
            {
                throw new ArgumentNullException(nameof(reader));
            }

            return ReadWhile(reader, c => Char.IsWhiteSpace(c));
        }

        public static string ReadUntilWhiteSpace(this TextReader reader)
        {
            if (reader == null)
            {
                throw new ArgumentNullException(nameof(reader));
            }

            return ReadUntil(reader, c => Char.IsWhiteSpace(c));
        }
    }
}