// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System.Buffers;
 
namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http;
 
/// <summary>
/// Result of non-throwing HTTP parsing operations.
/// </summary>
internal readonly struct HttpParseResult
{
    private enum ParseStatus : byte { Incomplete, Complete, Error }
 
    private readonly ParseStatus _status;
    private readonly RequestRejectionReason _errorReason;
    private readonly int _errorOffset;
    private readonly int _errorLength;
 
    private HttpParseResult(ParseStatus status, RequestRejectionReason errorReason = default, int errorOffset = 0, int errorLength = 0)
    {
        _status = status;
        _errorReason = errorReason;
        _errorOffset = errorOffset;
        _errorLength = errorLength;
    }
 
    /// <summary>True if parsing completed successfully.</summary>
    public bool IsComplete => _status == ParseStatus.Complete;
 
    /// <summary>True if a parse error occurred.</summary>
    public bool HasError => _status == ParseStatus.Error;
 
    /// <summary>The reason for rejection, if HasError is true.</summary>
    public RequestRejectionReason ErrorReason => _errorReason;
 
    /// <summary>Offset into the buffer where the error was detected.</summary>
    public int ErrorOffset => _errorOffset;
 
    /// <summary>Length of the problematic data, for error reporting.</summary>
    public int ErrorLength => _errorLength;
 
    /// <summary>Parsing needs more data.</summary>
    public static HttpParseResult Incomplete => new(ParseStatus.Incomplete);
 
    /// <summary>Parsing completed successfully.</summary>
    public static HttpParseResult Complete => new(ParseStatus.Complete);
 
    /// <summary>Parsing failed with the specified error.</summary>
    public static HttpParseResult Error(RequestRejectionReason reason) => new(ParseStatus.Error, reason);
 
    /// <summary>Parsing failed with the specified error and location info for detailed error messages.</summary>
    public static HttpParseResult Error(RequestRejectionReason reason, int offset, int length) => new(ParseStatus.Error, reason, offset, length);
}
 
internal interface IHttpParser<TRequestHandler> where TRequestHandler : IHttpHeadersHandler, IHttpRequestLineHandler
{
    bool ParseRequestLine(TRequestHandler handler, ref SequenceReader<byte> reader);
 
    bool ParseHeaders(TRequestHandler handler, ref SequenceReader<byte> reader);
 
    HttpParseResult TryParseRequestLine(TRequestHandler handler, ref SequenceReader<byte> reader);
 
    HttpParseResult TryParseHeaders(TRequestHandler handler, ref SequenceReader<byte> reader);
}