// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System.Collections;
using System.Globalization;
using Microsoft.AspNetCore.Http;
 
namespace Microsoft.AspNetCore.Hosting;
 
internal sealed class HostingRequestStartingLog : IReadOnlyList<KeyValuePair<string, object?>>
{
    private const string OriginalFormat = "Request starting {Protocol} {Method} {Scheme}://{Host}{PathBase}{Path}{QueryString} - {ContentType} {ContentLength}";
    private const string EmptyEntry = "-";
 
    internal static readonly Func<object, Exception?, string> Callback = (state, exception) => ((HostingRequestStartingLog)state).ToString();
 
    private readonly HttpRequest _request;
 
    private string? _cachedToString;
 
    public int Count => 10;
 
    public KeyValuePair<string, object?> this[int index] => index switch
    {
        0 => new KeyValuePair<string, object?>(nameof(_request.Protocol), _request.Protocol),
        1 => new KeyValuePair<string, object?>(nameof(_request.Method), _request.Method),
        2 => new KeyValuePair<string, object?>(nameof(_request.ContentType), _request.ContentType),
        3 => new KeyValuePair<string, object?>(nameof(_request.ContentLength), _request.ContentLength),
        4 => new KeyValuePair<string, object?>(nameof(_request.Scheme), _request.Scheme),
        5 => new KeyValuePair<string, object?>(nameof(_request.Host), _request.Host.Value),
        6 => new KeyValuePair<string, object?>(nameof(_request.PathBase), _request.PathBase.Value),
        7 => new KeyValuePair<string, object?>(nameof(_request.Path), _request.Path.Value),
        8 => new KeyValuePair<string, object?>(nameof(_request.QueryString), _request.QueryString.Value),
        9 => new KeyValuePair<string, object?>("{OriginalFormat}", OriginalFormat),
        _ => throw new ArgumentOutOfRangeException(nameof(index)),
    };
 
    public HostingRequestStartingLog(HttpContext httpContext)
    {
        _request = httpContext.Request;
    }
 
    public override string ToString()
    {
        if (_cachedToString == null)
        {
            var request = _request;
            _cachedToString = $"Request starting {request.Protocol} {request.Method} {request.Scheme}://{request.Host.Value}{request.PathBase.Value}{request.Path.Value}{request.QueryString.Value} - {EscapedValueOrEmptyMarker(request.ContentType)} {ValueOrEmptyMarker(request.ContentLength)}";
        }
 
        return _cachedToString;
    }
 
    public IEnumerator<KeyValuePair<string, object?>> GetEnumerator()
    {
        for (var i = 0; i < Count; i++)
        {
            yield return this[i];
        }
    }
 
    IEnumerator IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }
 
    internal static string EscapedValueOrEmptyMarker(string? potentialValue)
        // Encode space as +
        => potentialValue?.Length > 0 ? potentialValue.Replace(' ', '+') : EmptyEntry;
 
    internal static string ValueOrEmptyMarker<T>(T? potentialValue) where T : struct, IFormattable
        => potentialValue?.ToString(null, CultureInfo.InvariantCulture) ?? EmptyEntry;
}