#region Copyright notice and license

// Copyright 2019 The gRPC Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#endregion

using System;
using Grpc.Core;
using Grpc.Core.Internal;
using Grpc.Core.Utils;
using NUnit.Framework;

namespace Grpc.Core.Internal.Tests
{
    public class DefaultSerializationContextTest
    {
        [TestCase]
        public void CompleteAllowedOnlyOnce()
        {
            using (var scope = NewDefaultSerializationContextScope())
            {
                var context = scope.Context;
                var buffer = GetTestBuffer(10);

                context.Complete(buffer);
                Assert.Throws(typeof(InvalidOperationException), () => context.Complete(buffer));
                Assert.Throws(typeof(InvalidOperationException), () => context.Complete());
            }
        }

        [TestCase]
        public void CompleteAllowedOnlyOnce2()
        {
            using (var scope = NewDefaultSerializationContextScope())
            {
                var context = scope.Context;

                context.Complete();
                Assert.Throws(typeof(InvalidOperationException), () => context.Complete(GetTestBuffer(10)));
                Assert.Throws(typeof(InvalidOperationException), () => context.Complete());
            }
        }

        [TestCase(0)]
        [TestCase(1)]
        [TestCase(10)]
        [TestCase(100)]
        [TestCase(1000)]
        public void ByteArrayPayload(int payloadSize)
        {
            using (var scope = NewDefaultSerializationContextScope())
            {
                var context = scope.Context;
                var origPayload = GetTestBuffer(payloadSize);

                context.Complete(origPayload);

                var nativePayload = context.GetPayload().ToByteArray();
                CollectionAssert.AreEqual(origPayload, nativePayload);
            }
        }

        [TestCase(0)]
        [TestCase(1)]
        [TestCase(10)]
        [TestCase(100)]
        [TestCase(1000)]
        public void BufferWriter_OneSegment(int payloadSize)
        {
            using (var scope = NewDefaultSerializationContextScope())
            {
                var context = scope.Context;
                var origPayload = GetTestBuffer(payloadSize);

                var bufferWriter = context.GetBufferWriter();
                origPayload.AsSpan().CopyTo(bufferWriter.GetSpan(payloadSize));
                bufferWriter.Advance(payloadSize);
                context.Complete();

                var nativePayload = context.GetPayload().ToByteArray();
                CollectionAssert.AreEqual(origPayload, nativePayload);
            }
        }

        [TestCase(0)]
        [TestCase(1)]
        [TestCase(10)]
        [TestCase(100)]
        [TestCase(1000)]
        public void BufferWriter_OneSegment_GetMemory(int payloadSize)
        {
            using (var scope = NewDefaultSerializationContextScope())
            {
                var context = scope.Context;
                var origPayload = GetTestBuffer(payloadSize);

                var bufferWriter = context.GetBufferWriter();
                origPayload.AsSpan().CopyTo(bufferWriter.GetMemory(payloadSize).Span);
                bufferWriter.Advance(payloadSize);
                context.Complete();

                var nativePayload = context.GetPayload().ToByteArray();
                CollectionAssert.AreEqual(origPayload, nativePayload);
            }
        }

        [TestCase(1, 4)]  // small slice size tests grpc_slice with inline data
        [TestCase(10, 4)]
        [TestCase(100, 4)]
        [TestCase(1000, 4)]
        [TestCase(1, 64)]  // larger slice size tests allocated grpc_slices
        [TestCase(10, 64)]
        [TestCase(1000, 50)]
        [TestCase(1000, 64)]
        public void BufferWriter_MultipleSegments(int payloadSize, int maxSliceSize)
        {
            using (var scope = NewDefaultSerializationContextScope())
            {
                var context = scope.Context;
                var origPayload = GetTestBuffer(payloadSize);

                var bufferWriter = context.GetBufferWriter();
                for (int offset = 0; offset < payloadSize; offset += maxSliceSize)
                {
                    var sliceSize = Math.Min(maxSliceSize, payloadSize - offset);
                    // we allocate last slice as too big intentionally to test that shrinking works
                    var dest = bufferWriter.GetSpan(maxSliceSize);
                    
                    origPayload.AsSpan(offset, sliceSize).CopyTo(dest);
                    bufferWriter.Advance(sliceSize);
                }
                context.Complete();
                
                var nativePayload = context.GetPayload().ToByteArray();
                CollectionAssert.AreEqual(origPayload, nativePayload);
            }
        }

        [TestCase]
        public void ContextIsReusable()
        {
            using (var scope = NewDefaultSerializationContextScope())
            {
                var context = scope.Context;

                Assert.Throws(typeof(NullReferenceException), () => context.GetPayload());

                var origPayload1 = GetTestBuffer(10);
                context.Complete(origPayload1);
                CollectionAssert.AreEqual(origPayload1, context.GetPayload().ToByteArray());

                context.Reset();

                var origPayload2 = GetTestBuffer(20);
    
                var bufferWriter = context.GetBufferWriter();
                origPayload2.AsSpan().CopyTo(bufferWriter.GetMemory(origPayload2.Length).Span);
                bufferWriter.Advance(origPayload2.Length);
                context.Complete();
                CollectionAssert.AreEqual(origPayload2, context.GetPayload().ToByteArray());

                context.Reset();

                Assert.Throws(typeof(NullReferenceException), () => context.GetPayload());
            }
        }

        [TestCase]
        public void GetBufferWriterThrowsForCompletedContext()
        {
            using (var scope = NewDefaultSerializationContextScope())
            {
                var context = scope.Context;
                context.Complete(GetTestBuffer(10));

                Assert.Throws(typeof(InvalidOperationException), () => context.GetBufferWriter());
            }
        }

        private DefaultSerializationContext.UsageScope NewDefaultSerializationContextScope()
        {
            return new DefaultSerializationContext.UsageScope(new DefaultSerializationContext());
        }

        private byte[] GetTestBuffer(int length)
        {
            var testBuffer = new byte[length];
            for (int i = 0; i < testBuffer.Length; i++)
            {
                testBuffer[i] = (byte) i;
            }
            return testBuffer;
        }
    }
}