Extract helper method; add tests.

Author: bgrainger

src/MySqlConnector/Core/ServerSession.cs

@@ -477,37 +477,21 @@ public async Task ConnectAsync(ConnectionSettings cs, int startTickCount, ILoadB
 					{
 						Log.Info("Session{0} is already redirected; ignoring it.", m_logArguments);
 					}
-					else
+					else if (Utility.TryParseRedirectionHeader(ok.StatusInfo, out var host, out var port, out var user))
 					{
-						var hostIndex = 18;
-						var colonIndex = ok.StatusInfo.IndexOf(':', hostIndex);
-						if (colonIndex != -1)
-						{
-							var host = ok.StatusInfo.Substring(hostIndex, colonIndex - hostIndex);
-							var portIndex = colonIndex + 1;
-							var userIndex = ok.StatusInfo.IndexOf("/user=", StringComparison.Ordinal);
-							if (userIndex != -1)
-							{
-								if (int.TryParse(ok.StatusInfo.Substring(portIndex, userIndex - portIndex), out var port))
-								{
-									var ampersandIndex = ok.StatusInfo.IndexOf('&', userIndex);
-									var userId = ampersandIndex == -1 ? ok.StatusInfo.Substring(userIndex + 6) : ok.StatusInfo.Substring(userIndex + 6, ampersandIndex - userIndex - 6);
-									Log.Info("Session{0} found server redirection Host={1}; Port={2}; User={3}", m_logArguments[0], host, port, userId);
+						Log.Info("Session{0} found server redirection Host={1}; Port={2}; User={3}", m_logArguments[0], host, port, user);
 
-									if (host != cs.HostNames![0] || port != cs.Port || userId != cs.UserID)
-									{
-										Log.Info("Session{0} closing existing connection", m_logArguments);
-										await SendAsync(QuitPayload.Instance, ioBehavior, cancellationToken).ConfigureAwait(false);
-										Log.Info("Session{0} opening new connection to Host={1}; Port={2}; User={3}", m_logArguments[0], host, port, userId);
-										cs = cs.CloneWith(host, port, userId, isRedirected: true);
-										goto serverRedirection;
-									}
-									else
-									{
-										Log.Info("Session{0} is already connected to this server; ignoring redirection", m_logArguments);
-									}
-								}
-							}
+						if (host != cs.HostNames![0] || port != cs.Port || user != cs.UserID)
+						{
+							Log.Info("Session{0} closing existing connection", m_logArguments);
+							await SendAsync(QuitPayload.Instance, ioBehavior, cancellationToken).ConfigureAwait(false);
+							Log.Info("Session{0} opening new connection to Host={1}; Port={2}; User={3}", m_logArguments[0], host, port, user);
+							cs = cs.CloneWith(host, port, user, isRedirected: true);
+							goto serverRedirection;
+						}
+						else
+						{
+							Log.Info("Session{0} is already connected to this server; ignoring redirection", m_logArguments);
 						}
 					}
 				}

src/MySqlConnector/Utilities/Utility.cs

@@ -318,6 +318,34 @@ public static void Resize<T>([NotNull] ref ResizableArray<T>? resizableArray, in
 			resizableArray.DoResize(newLength);
 		}
 
+		public static bool TryParseRedirectionHeader(string header, out string host, out int port, out string user)
+		{
+			host = "";
+			port = 0;
+			user = "";
+
+			if (!header.StartsWith("Location: mysql://", StringComparison.Ordinal))
+				return false;
+
+			var hostIndex = 18;
+			var colonIndex = header.IndexOf(':', hostIndex);
+			if (colonIndex == -1)
+				return false;
+
+			host = header.Substring(hostIndex, colonIndex - hostIndex);
+			var portIndex = colonIndex + 1;
+			var userIndex = header.IndexOf("/user=", StringComparison.Ordinal);
+			if (userIndex == -1)
+				return false;
+
+			if (!int.TryParse(header.Substring(portIndex, userIndex - portIndex), out port) || port <= 0)
+				return false;
+
+			var ampersandIndex = header.IndexOf('&', userIndex);
+			user = ampersandIndex == -1 ? header.Substring(userIndex + 6) : header.Substring(userIndex + 6, ampersandIndex - userIndex - 6);
+			return true;
+		}
+
 		public static TimeSpan ParseTimeSpan(ReadOnlySpan<byte> value)
 		{
 			var originalValue = value;

tests/MySqlConnector.Tests/UtilityTests.cs

@@ -8,6 +8,32 @@ namespace MySqlConnector.Tests
 {
 	public class UtilityTests
 	{
+		[Theory]
+		[InlineData("Location: mysql://host.example.com:1234/user=user@host", "host.example.com", 1234, "user@host")]
+		[InlineData("Location: mysql://host.example.com:1234/user=user@host&ttl=60", "host.example.com", 1234, "user@host")]
+		public void ParseRedirectionHeader(string input, string expectedHost, int expectedPort, string expectedUser)
+		{
+			Assert.True(Utility.TryParseRedirectionHeader(input, out var host, out var port, out var user));
+			Assert.Equal(expectedHost, host);
+			Assert.Equal(expectedPort, port);
+			Assert.Equal(expectedUser, user);
+		}
+
+		[Theory]
+		[InlineData("")]
+		[InlineData("Location: mysql")]
+		[InlineData("Location: mysql://host.example.com")]
+		[InlineData("Location: mysql://host.example.com:123")]
+		[InlineData("Location: mysql://host.example.com:123/")]
+		[InlineData("Location: mysql://host.example.com:/user=")]
+		[InlineData("Location: mysql://host.example.com:/user=user@host")]
+		[InlineData("Location: mysql://host.example.com:-1/user=user@host")]
+		[InlineData("Location: mysql://host.example.com:0/user=user@host")]
+		public void ParseRedirectionHeaderFails(string input)
+		{
+			Assert.False(Utility.TryParseRedirectionHeader(input, out _, out _, out _));
+		}
+
 		[Theory]
 		[InlineData("00:00:00", "00:00:00")]
 		[InlineData("00:00:01", "00:00:01")]