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 *
 * OPC Foundation MIT License 1.00
 * 
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using System.IO;
using System.Text;
using NUnit.Framework;
using System.Linq;
using System;
using Opc.Ua.Tests;
using System.Reflection;

namespace Opc.Ua.Fuzzing
{

    [TestFixture]
    [Category("Fuzzing")]
    public class EncoderTests
    {
        #region DataPointSources
        public static readonly TestcaseAsset[] GoodTestcases = new AssetCollection<TestcaseAsset>(TestUtils.EnumerateTestAssets("Testcases", "*.*")).ToArray();
        public static readonly TestcaseAsset[] CrashAssets = new AssetCollection<TestcaseAsset>(TestUtils.EnumerateTestAssets("Assets", "crash*.*")).ToArray();
        public static readonly TestcaseAsset[] TimeoutAssets = new AssetCollection<TestcaseAsset>(TestUtils.EnumerateTestAssets("Assets", "timeout*.*")).ToArray();
        public static readonly TestcaseAsset[] SlowAssets = new AssetCollection<TestcaseAsset>(TestUtils.EnumerateTestAssets("Assets", "slow*.*")).ToArray();

        [DatapointSource]
        public static readonly string[] TestcaseEncoderSuffixes = new string[] { ".Binary", ".Json", ".Xml" };

        [DatapointSource]
        public static readonly FuzzTargetFunction[] FuzzableFunctions = typeof(FuzzableCode).GetMethods(BindingFlags.Static | BindingFlags.Public)
            .Where(f => f.GetParameters().Length == 1)
            .Select(f => new FuzzTargetFunction(f)).ToArray();
        #endregion

        [Theory]
        public void FuzzGoodTestcases(
            FuzzTargetFunction fuzzableCode,
            [ValueSource(nameof(GoodTestcases))] TestcaseAsset messageEncoder)
        {
            FuzzTarget(fuzzableCode, messageEncoder.Testcase);
        }

        [Theory]
        public void FuzzEmptyByteArray(FuzzTargetFunction fuzzableCode)
        {
            FuzzTarget(fuzzableCode, Array.Empty<byte>());
        }

        [Theory]
        public void FuzzCrashAssets(FuzzTargetFunction fuzzableCode)
        {
            // note: too many crash files can take forever to create
            // all permutations with nunit, so just run all in one batch
            foreach (var messageEncoder in CrashAssets)
            {
                FuzzTarget(fuzzableCode, messageEncoder.Testcase);
            }
        }

        [Theory]
        [CancelAfter(1000)]
        public void FuzzTimeoutAssets(
            FuzzTargetFunction fuzzableCode,
            [ValueSource(nameof(TimeoutAssets))] TestcaseAsset messageEncoder)
        {
            FuzzTarget(fuzzableCode, messageEncoder.Testcase);
        }

        [Theory]
        [CancelAfter(1000)]
        public void FuzzSlowAssets(
            FuzzTargetFunction fuzzableCode,
            [ValueSource(nameof(SlowAssets))] TestcaseAsset messageEncoder)
        {
            FuzzTarget(fuzzableCode, messageEncoder.Testcase);
        }

        delegate void LibFuzzTemplate(ReadOnlySpan<byte> span);

        private void FuzzTarget(FuzzTargetFunction fuzzableCode, byte[] blob)
        {
            var parameters = fuzzableCode.MethodInfo.GetParameters();
            if (parameters.Length != 1)
            {
                throw new InvalidOperationException("Fuzzable function must have exactly one parameter.");
            }
            if (parameters[0].ParameterType == typeof(string))
            {
                string text = Encoding.UTF8.GetString(blob);
                _ = fuzzableCode.MethodInfo.Invoke(null, new object[] { text });
            }
            else if (typeof(Stream).IsAssignableFrom(parameters[0].ParameterType))
            {
                using (var stream = new MemoryStream(blob))
                {
                    _ = fuzzableCode.MethodInfo.Invoke(null, new object[] { stream });
                }
            }
            else if (parameters[0].ParameterType == typeof(ReadOnlySpan<byte>))
            {
                var span = new ReadOnlySpan<byte>(blob);
                LibFuzzTemplate fuzzFunction = (LibFuzzTemplate)fuzzableCode.MethodInfo.CreateDelegate(typeof(LibFuzzTemplate));
                fuzzFunction(span);
            }
        }
    }

    /// <summary>
    /// A Testcase as test asset.
    /// </summary>
    public class TestcaseAsset : IAsset, IFormattable
    {
        public TestcaseAsset() { }

        public string Path { get; private set; }
        public byte[] Testcase { get; private set; }

        public void Initialize(byte[] blob, string path)
        {
            Path = path;
            Testcase = blob;
        }

        public string ToString(string format, IFormatProvider formatProvider)
        {
            var file = System.IO.Path.GetFileName(Path);
            return $"{file}";
        }
    }

    /// <summary>
    /// A Testcase as test asset.
    /// </summary>
    public class FuzzTargetFunction : IFormattable
    {
        public FuzzTargetFunction(MethodInfo methodInfo)
        {
            MethodInfo = methodInfo;
        }

        public MethodInfo MethodInfo { get; private set; }

        public string ToString(string format, IFormatProvider formatProvider)
        {
            var name = MethodInfo.Name;
            return $"{name}";
        }
    }
}