// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

// ReSharper disable PartialTypeWithSinglePart
// ReSharper disable ConditionIsAlwaysTrueOrFalse

using System.Diagnostics;
using System.Globalization;
using System.Text;

namespace System.Net.WebSockets
{
    internal static partial class WebSocketValidate
    {
        internal const int MaxControlFramePayloadLength = 123;
        private const int CloseStatusCodeAbort = 1006;
        private const int CloseStatusCodeFailedTLSHandshake = 1015;
        private const int InvalidCloseStatusCodesFrom = 0;
        private const int InvalidCloseStatusCodesTo = 999;
        private const string Separators = "()<>@,;:\\\"/[]?={} ";

        internal static void ThrowIfInvalidState(WebSocketState currentState, bool isDisposed, WebSocketState[] validStates)
        {
            string validStatesText = string.Empty;

            if (validStates != null && validStates.Length > 0)
            {
                foreach (WebSocketState validState in validStates)
                {
                    if (currentState == validState)
                    {
                        // Ordering is important to maintain .NET 4.5 WebSocket implementation exception behavior.
                        if (isDisposed)
                        {
                            throw new ObjectDisposedException(nameof(WebSocket));
                        }

                        return;
                    }
                }

                validStatesText = string.Join(", ", validStates);
            }

            throw new WebSocketException(
                WebSocketError.InvalidState,
                SR.Format(SR.net_WebSockets_InvalidState, currentState, validStatesText));
        }

        internal static void ValidateSubprotocol(string subProtocol)
        {
            if (string.IsNullOrWhiteSpace(subProtocol))
            {
                throw new ArgumentException(SR.net_WebSockets_InvalidEmptySubProtocol, nameof(subProtocol));
            }

            string? invalidChar = null;
            int i = 0;
            while (i < subProtocol.Length)
            {
                char ch = subProtocol[i];
                if (ch < 0x21 || ch > 0x7e)
                {
                    invalidChar = string.Format(CultureInfo.InvariantCulture, "[{0}]", (int)ch);
                    break;
                }

                if (!char.IsLetterOrDigit(ch) &&
#pragma warning disable CA2249 // Consider using 'string.Contains' instead of 'string.IndexOf'.  This file is built into a project that doesn't have string.Contains(char).
                    Separators.IndexOf(ch) >= 0)
#pragma warning restore CA2249
                {
                    invalidChar = ch.ToString();
                    break;
                }

                i++;
            }

            if (invalidChar != null)
            {
                throw new ArgumentException(SR.Format(SR.net_WebSockets_InvalidCharInProtocolString, subProtocol, invalidChar), nameof(subProtocol));
            }
        }

        internal static void ValidateCloseStatus(WebSocketCloseStatus closeStatus, string? statusDescription)
        {
            if (closeStatus == WebSocketCloseStatus.Empty && !string.IsNullOrEmpty(statusDescription))
            {
                throw new ArgumentException(SR.Format(SR.net_WebSockets_ReasonNotNull,
                    statusDescription,
                    WebSocketCloseStatus.Empty),
                    nameof(statusDescription));
            }

            int closeStatusCode = (int)closeStatus;

            if ((closeStatusCode >= InvalidCloseStatusCodesFrom &&
                closeStatusCode <= InvalidCloseStatusCodesTo) ||
                closeStatusCode == CloseStatusCodeAbort ||
                closeStatusCode == CloseStatusCodeFailedTLSHandshake)
            {
                // CloseStatus 1006 means Aborted - this will never appear on the wire and is reflected by calling WebSocket.Abort
                throw new ArgumentException(SR.Format(SR.net_WebSockets_InvalidCloseStatusCode,
                    closeStatusCode),
                    nameof(closeStatus));
            }

            int length = 0;
            if (!string.IsNullOrEmpty(statusDescription))
            {
                length = Encoding.UTF8.GetByteCount(statusDescription);
            }

            if (length > MaxControlFramePayloadLength)
            {
                throw new ArgumentException(SR.Format(SR.net_WebSockets_InvalidCloseStatusDescription,
                    statusDescription,
                    MaxControlFramePayloadLength),
                    nameof(statusDescription));
            }
        }

        internal static void ValidateArraySegment(ArraySegment<byte> arraySegment, string parameterName)
        {
            Debug.Assert(!string.IsNullOrEmpty(parameterName), "'parameterName' MUST NOT be NULL or string.Empty");

            if (arraySegment.Array == null)
            {
                throw new ArgumentNullException(parameterName + "." + nameof(arraySegment.Array));
            }
            if (arraySegment.Offset < 0 || arraySegment.Offset > arraySegment.Array.Length)
            {
                throw new ArgumentOutOfRangeException(parameterName + "." + nameof(arraySegment.Offset));
            }
            if (arraySegment.Count < 0 || arraySegment.Count > (arraySegment.Array.Length - arraySegment.Offset))
            {
                throw new ArgumentOutOfRangeException(parameterName + "." + nameof(arraySegment.Count));
            }
        }

        internal static void ValidateBuffer(byte[] buffer, int offset, int count)
        {
            if (buffer == null)
            {
                throw new ArgumentNullException(nameof(buffer));
            }

            if (offset < 0 || offset > buffer.Length)
            {
                throw new ArgumentOutOfRangeException(nameof(offset));
            }

            if (count < 0 || count > (buffer.Length - offset))
            {
                throw new ArgumentOutOfRangeException(nameof(count));
            }
        }
    }
}