using NUnit.Framework;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Threading;
using static Vanara.PInvoke.DnsApi;

namespace Vanara.PInvoke.Tests;

[TestFixture]
public class DnsApiTests
{
	private const string dnsSvr = "c1dns.cableone.net";
	private const string dnsSvrIp = "24.116.0.53";

	[Test]
	public void DnsAcquireContextHandleTest()
	{
		Assert.That(DnsAcquireContextHandle(true, default, out var ctx), ResultIs.Successful);
		Assert.That(ctx, ResultIs.ValidHandle);
		Assert.That(ctx.Dispose, Throws.Nothing);
	}

	[Test]
	public void DnsExtractRecordsFromMessageTest()
	{
		using var mem = new SafeHGlobalHandle(64);
		Assert.That(DnsExtractRecordsFromMessage(mem, (ushort)(uint)mem.Size, out SafeDnsRecordList? results), ResultIs.Value((Win32Error)Win32Error.DNS_ERROR_BAD_PACKET));
	}

	[Test]
	public void DnsGetCacheDataTableTest()
	{
		Assert.That(DnsGetCacheDataTable(out var table), ResultIs.Successful);
		foreach (var d in table)
			TestContext.WriteLine($"{d.pszName} => {d.wType}");
		Assert.That(table.Dispose, Throws.Nothing);
	}

	[Test]
	public void DnsGetProxyInformationTest()
	{
		var pi = new DNS_PROXY_INFORMATION { version = 1 };
		var rpi = new DNS_PROXY_INFORMATION { version = 1 };
		Assert.That(DnsGetProxyInformation(dnsSvr, ref pi, ref rpi), ResultIs.Successful);
		if (pi.proxyName != default)
			DnsFreeProxyName(pi.proxyName);
		if (rpi.proxyName != default)
			DnsFreeProxyName(rpi.proxyName);
	}

	[Test]
	public void DnsModifyRecordsInSetTest()
	{
		Assert.That(DnsQuery(dnsSvr, DNS_TYPE.DNS_TYPE_ALL, 0, default, out var results), ResultIs.Successful);
		Assert.That(results, ResultIs.ValidHandle);
		Assert.That(DnsModifyRecordsInSet(results, results, DNS_UPDATE.DNS_UPDATE_SECURITY_USE_DEFAULT), ResultIs.Value((Win32Error)Win32Error.DNS_ERROR_RCODE_BADKEY));
	}

	[Test]
	public void DnsNameCompareTest()
	{
		Assert.That(DnsNameCompare(dnsSvr, dnsSvr), Is.True);
	}

	[Test]
	public void DnsQueryConfigTest([Values] DNS_CONFIG_TYPE ctype)
	{
		var type = CorrespondingTypeAttribute.GetCorrespondingTypes(ctype, CorrespondingAction.GetSet).FirstOrDefault();
		if (type is null || type == typeof(StrPtrAnsi)) Assert.Pass($"{ctype} Ignored");
		var sz = 0U;
		var err = DnsQueryConfig(ctype, 0, null, default, default, ref sz);
		if (ctype == DNS_CONFIG_TYPE.DnsConfigPrimaryDomainName_W) return;
		Assert.That(sz, Is.GreaterThan(0U));
		using var mem = new SafeCoTaskMemHandle(sz);
		Assert.That(DnsQueryConfig(ctype, 0, null, default, mem, ref sz), ResultIs.Successful);
		mem.DangerousGetHandle().Convert(sz, type, CharSet.Unicode)?.WriteValues();
	}

	[Test]
	public void DnsQueryExTest()
	{
		using var evt = new System.Threading.AutoResetEvent(false);
		var cancel = new DNS_QUERY_CANCEL();
		var req = new DNS_QUERY_REQUEST
		{
			Version = DNS_QUERY_REQUEST_VERSION1,
			QueryName = dnsSvr,
			QueryOptions = DNS_QUERY_OPTIONS.DNS_QUERY_WIRE_ONLY | DNS_QUERY_OPTIONS.DNS_QUERY_BYPASS_CACHE,
			QueryType = DNS_TYPE.DNS_TYPE_ALL,
			pQueryCompletionCallback = Callback
		};
		var res = new DNS_QUERY_RESULT { Version = DNS_QUERY_REQUEST_VERSION1 };
		var err = DnsQueryEx(req, ref res, ref cancel);
		if (err == Win32Error.DNS_REQUEST_PENDING && !evt.WaitOne(20000))
		{
			Assert.That(DnsCancelQuery(ref cancel), ResultIs.Successful);
			Assert.Fail("Completion callback not called.");
		}
		else if (err.Failed)
			Assert.Fail(err.ToString());
		if (res.pQueryRecords != default)
		{
			using var rlist = new SafeDnsRecordList(res.pQueryRecords);
			foreach (var r in rlist)
				r.WriteValues();
		}

		void Callback(IntPtr pQueryContext, ref DNS_QUERY_RESULT pQueryResults)
		{
			evt.Set();
		}
	}

	[Test]
	public void DnsQueryTest()
	{
		Assert.That(DnsQuery(dnsSvr, DNS_TYPE.DNS_TYPE_ALL, 0, default, out var results), ResultIs.Successful);
		Assert.That(results, ResultIs.ValidHandle);
		results.ToArray().WriteValues();
	}

	[Test]
	public void DnsRecordCompareTest()
	{
		var r1 = new DNS_RECORD { pName = dnsSvr, wType = DNS_TYPE.DNS_TYPE_A, Data = new DNS_A_DATA { IpAddress = 0xFFFFFF0U } };
		Assert.That(DnsRecordCompare(r1, r1), Is.True);
	}

	[Test]
	public void DnsRecordSetCompareTest()
	{
		Assert.That(DnsQuery(dnsSvr, DNS_TYPE.DNS_TYPE_ALL, 0, default, out var results), ResultIs.Successful);
		Assert.That(DnsRecordSetCompare(results, results, out var p1, out var p2), ResultIs.Successful);
	}

	[Test]
	public void DnsServiceBrowseTest()
	{
		const int timeout = 20000;
		const string query = "_http._tcp.local";

		using var evt = Kernel32.CreateEvent(null, false, false);

		var br = new DNS_SERVICE_BROWSE_REQUEST
		{
			Version = DNS_QUERY_REQUEST_VERSION1,
			QueryName = query,
			pQueryContext = (IntPtr)evt,
			Callback = new() { pBrowseCallback = (DNS_SERVICE_BROWSE_CALLBACK)Callback }
		};
		Assert.That(DnsServiceBrowse(br, out var cancel), ResultIs.Value(Win32Error.DNS_REQUEST_PENDING));
		if (Kernel32.WaitForSingleObject(evt, timeout) != Kernel32.WAIT_STATUS.WAIT_OBJECT_0)
		{
			Assert.That(DnsServiceBrowseCancel(cancel), ResultIs.Successful);
			Assert.Fail("Browse callback not called.");
		}

		var queryRequest = new MDNS_QUERY_REQUEST
		{
			Version = DNS_QUERY_REQUEST_VERSION1,
			Query = query,
			QueryType = DNS_TYPE.DNS_TYPE_PTR,
			QueryOptions = (ulong)DNS_QUERY_OPTIONS.DNS_QUERY_STANDARD,
			pQueryCallback = QueryCallback,
			pQueryContext = (IntPtr)evt
		};
		Assert.That(DnsStartMulticastQuery(queryRequest, out var queryHandle), ResultIs.Successful);
		if (Kernel32.WaitForSingleObject(evt, timeout) != Kernel32.WAIT_STATUS.WAIT_OBJECT_0)
		{
			Assert.That(DnsStopMulticastQuery(queryHandle), ResultIs.Successful);
			Assert.Fail("Multicast callback not called.");
		}

		void Callback(Win32Error Status, IntPtr pQueryContext, IntPtr pDnsRecord)
		{
			using var recs = new SafeDnsRecordList(pDnsRecord);
			System.Diagnostics.Debug.WriteLine($"Stat:{(Win32Error)Status}; Name:{recs.FirstOrDefault().pName}");
			Kernel32.SetEvent(pQueryContext);
		}

		void QueryCallback(IntPtr pQueryContext, IntPtr pQueryHandle, IntPtr pQueryResults)
		{
			ref DNS_QUERY_RESULT pQR = ref pQueryResults.AsRef<DNS_QUERY_RESULT>();
			System.Diagnostics.Debug.WriteLine($"Stat:{pQR.QueryStatus}; Opt:{pQR.QueryOptions}");
			using var recs = new SafeDnsRecordList(pQR.pQueryRecords);
			using var qevt = Kernel32.CreateEvent(null, false, true);
			var rec = recs.FirstOrDefault();
			if (rec.wDataLength == 0)
				return;
			var resolveRequest = new DNS_SERVICE_RESOLVE_REQUEST
			{
				Version = DNS_QUERY_REQUEST_VERSION1,
				QueryName = rec.Data is DNS_PTR_DATA d ? d.pNameHost : null,
				pResolveCompletionCallback = (DNS_SERVICE_RESOLVE_COMPLETE)ResolveCallback,
				pQueryContext = (IntPtr)qevt
			};
			Assert.That(DnsServiceResolve(resolveRequest, out var cancel), ResultIs.Value(Win32Error.DNS_REQUEST_PENDING));
			if (Kernel32.WaitForSingleObject(qevt, timeout) != Kernel32.WAIT_STATUS.WAIT_OBJECT_0)
			{
				Assert.That(DnsServiceResolveCancel(cancel), ResultIs.Successful);
				Assert.Fail("Resolve callback not called.");
			}
			Kernel32.SetEvent(pQueryContext);
		}

		void ResolveCallback(Win32Error Status, IntPtr pQueryContext, IntPtr pInstance)
		{
			using var inst = new SafePDNS_SERVICE_INSTANCE(pInstance);
			System.Diagnostics.Debug.WriteLine($"Stat:{(Win32Error)Status}; Name:{inst.pszInstanceName}");
			Kernel32.SetEvent(pQueryContext);
		}
	}

	[Test]
	public void DnsServiceRegisterTest()
	{
		SafePDNS_SERVICE_INSTANCE si;
		Assert.That(si = DnsServiceConstructInstance("initial._windns-example._udp.local", "example.com", IntPtr.Zero, IntPtr.Zero, 1, 0, 0, 0, null, null), ResultIs.ValidHandle);

		var callbackCalled = false;
		var sr = new DNS_SERVICE_REGISTER_REQUEST
		{
			Version = DNS_QUERY_REQUEST_VERSION1,
			pRegisterCompletionCallback = Callback,
			pServiceInstance = si,
		};
		Assert.That(DnsServiceRegister(sr, out var cancel), ResultIs.Value(Win32Error.DNS_REQUEST_PENDING));
		Thread.Sleep(500);
		if (!callbackCalled)
			Assert.That(DnsServiceRegisterCancel(cancel), ResultIs.Successful);
		Assert.That(DnsServiceDeRegister(sr, cancel), ResultIs.Value(Win32Error.DNS_REQUEST_PENDING));

		void Callback(Win32Error Status, IntPtr pQueryContext, IntPtr pInstance) => callbackCalled = true;
	}

	[Test]
	public void DnsValidateNameTest()
	{
		Assert.That(DnsValidateName(dnsSvr, DNS_NAME_FORMAT.DnsNameHostnameFull), ResultIs.Successful);
	}

	[Test]
	public void DnsValidateServerStatusTest()
	{
		Assert.That(DnsValidateServerStatus(new Ws2_32.SOCKADDR(IPAddress.Parse(dnsSvrIp)), null, out var stat), ResultIs.Successful);
		Assert.That(stat, Is.EqualTo(DnsServerStatus.ERROR_SUCCESS));
	}

	[Test]
	public void DnsWriteQuestionToBufferTest()
	{
		var sz = 64U;
		using var mem = new SafeHGlobalHandle(sz);
		Assert.That(DnsWriteQuestionToBuffer(mem, ref sz, "microsoft", DNS_TYPE.DNS_TYPE_A, 1, true), ResultIs.Successful);
		var buf = mem.ToStructure<DNS_MESSAGE_BUFFER>();
		DNS_BYTE_FLIP_HEADER_COUNTS(ref buf);
		buf.WriteValues();
		if (sz <= mem.Size)
			TestContext.Write(string.Join(":", mem.ToArray<byte>((int)sz - 12, 12)));
	}

	[Test]
	public void DnsCacheDataTable()
	{
		// Ensure RAW_DNS_RECORD is the same size as defined in WinAPI
		Assert.That(Marshal.SizeOf<RAW_DNS_RECORD>(), Is.EqualTo(Environment.Is64BitProcess ? 48 : 40));
		
		DnsGetCacheDataTable(out var dnsCacheDataTable);

		foreach (DNS_CACHE_ENTRY dnsCacheEntry in dnsCacheDataTable)
		{
			DnsQuery(
				dnsCacheEntry.pszName!,
				dnsCacheEntry.wType,
				DNS_QUERY_OPTIONS.DNS_QUERY_NO_WIRE_QUERY | DNS_QUERY_OPTIONS.DNS_QUERY_LOCAL,
				IntPtr.Zero,
				out var dnsRecords,
				IntPtr.Zero);

			// Iterate using DNS_RECORD structure
			var cacheUsingStruct = DnsIterateDnsCache(dnsRecords).ToList();

			// Iterate using pointer
			var cacheUsingPointer = DnsIterateDnsCache(
				dnsRecords.GetRecordPointers().Select(dnsRecordPtr => dnsRecordPtr.ToStructure<DNS_RECORD>())).ToList();

			// Iterate using raw DNS_RECORD structure
			var cacheUsingRawStruct = DnsIterateDnsCache(DnsIterateRecords(dnsRecords)).ToList();

			Assert.That(cacheUsingStruct, Is.EquivalentTo(cacheUsingPointer));
			Assert.That(cacheUsingPointer, Is.EquivalentTo(cacheUsingRawStruct));
		}
	}

	private static IEnumerable<IPAddress> DnsIterateDnsCache(IEnumerable<DNS_RECORD> dnsRecords)
	{
		foreach (var dnsRecord in dnsRecords)
		{
			switch (dnsRecord.wType)
			{
				case DNS_TYPE.DNS_TYPE_A:
					yield return new IPAddress(((DNS_A_DATA)dnsRecord.Data!).IpAddress.S_un_b);
					break;
				case DNS_TYPE.DNS_TYPE_AAAA:
					yield return new IPAddress(((DNS_AAAA_DATA)dnsRecord.Data!).Ip6Address.bytes);
					break;
			}
		}
	}

	private static unsafe List<DNS_RECORD> DnsIterateRecords(SafeDnsRecordList dnsRecords)
	{
		var ret = new List<DNS_RECORD>();

		for (var dnsRecordPtr = (RAW_DNS_RECORD*) dnsRecords.DangerousGetHandle().ToPointer();
			dnsRecordPtr != null;
			dnsRecordPtr = (RAW_DNS_RECORD*) dnsRecordPtr->pNext)
		{
			ret.Add(new DNS_RECORD
			{
				pNext = dnsRecordPtr->pNext,
				pName = Marshal.PtrToStringUni(dnsRecordPtr->pName)!,
				wType = dnsRecordPtr->wType,
				wDataLength = dnsRecordPtr->wDataLength,
				Flags = dnsRecordPtr->Flags,
				dwTtl = dnsRecordPtr->dwTtl,
				dwReserved = dnsRecordPtr->dwReserved,
				Data = dnsRecordPtr->Address
			});
		}

		return ret;
	}

	[StructLayout(LayoutKind.Sequential)]
	private struct RAW_DNS_RECORD
	{
		public IntPtr pNext;
		public IntPtr pName;
		public DNS_TYPE wType;
		public ushort wDataLength;
		public DNS_RECORD_FLAGS Flags;
		public uint dwTtl;
		public uint dwReserved;
		public AddressData Address;

		[StructLayout(LayoutKind.Sequential, Pack = 1)]
		public struct AddressData
		{
			public uint Part1;
			public uint Part2;
			public ulong Part3;
		}
	}
}