From 72efadd0a25ca7dcfdd49f7c6ff9689ef36e1562 Mon Sep 17 00:00:00 2001
From: neuecc <ils@neue.cc>
Date: Tue, 12 May 2020 03:01:05 +0900
Subject: [PATCH] DistinctUntilChanged

---
 .../Linq/DistinctUntilChanged.cs              | 297 ++++++++++++++++++
 src/UniTask.NetCoreTests/Linq/Sets.cs         |  38 +++
 .../UniTask.NetCoreTests.csproj               |   4 +-
 3 files changed, 338 insertions(+), 1 deletion(-)
 create mode 100644 src/UniTask.NetCore/Linq/DistinctUntilChanged.cs

diff --git a/src/UniTask.NetCore/Linq/DistinctUntilChanged.cs b/src/UniTask.NetCore/Linq/DistinctUntilChanged.cs
new file mode 100644
index 0000000..4f25336
--- /dev/null
+++ b/src/UniTask.NetCore/Linq/DistinctUntilChanged.cs
@@ -0,0 +1,297 @@
+using Cysharp.Threading.Tasks.Internal;
+using System;
+using System.Collections.Generic;
+using System.Threading;
+
+namespace Cysharp.Threading.Tasks.Linq
+{
+    public static partial class UniTaskAsyncEnumerable
+    {
+        public static IUniTaskAsyncEnumerable<TSource> DistinctUntilChanged<TSource>(this IUniTaskAsyncEnumerable<TSource> source)
+        {
+            return DistinctUntilChanged(source, EqualityComparer<TSource>.Default);
+        }
+
+        public static IUniTaskAsyncEnumerable<TSource> DistinctUntilChanged<TSource>(this IUniTaskAsyncEnumerable<TSource> source, IEqualityComparer<TSource> comparer)
+        {
+            Error.ThrowArgumentNullException(source, nameof(source));
+            Error.ThrowArgumentNullException(comparer, nameof(comparer));
+
+            return new DistinctUntilChanged<TSource>(source, comparer);
+        }
+
+        public static IUniTaskAsyncEnumerable<TSource> DistinctUntilChanged<TSource, TKey>(this IUniTaskAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector)
+        {
+            return DistinctUntilChanged(source, keySelector, EqualityComparer<TKey>.Default);
+        }
+
+        public static IUniTaskAsyncEnumerable<TSource> DistinctUntilChanged<TSource, TKey>(this IUniTaskAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer)
+        {
+            Error.ThrowArgumentNullException(source, nameof(source));
+            Error.ThrowArgumentNullException(keySelector, nameof(keySelector));
+            Error.ThrowArgumentNullException(comparer, nameof(comparer));
+
+            return new DistinctUntilChanged<TSource, TKey>(source, keySelector, comparer);
+        }
+
+        public static IUniTaskAsyncEnumerable<TSource> DistinctUntilChangedAwait<TSource, TKey>(this IUniTaskAsyncEnumerable<TSource> source, Func<TSource, UniTask<TKey>> keySelector)
+        {
+            return DistinctUntilChangedAwait(source, keySelector, EqualityComparer<TKey>.Default);
+        }
+
+        public static IUniTaskAsyncEnumerable<TSource> DistinctUntilChangedAwait<TSource, TKey>(this IUniTaskAsyncEnumerable<TSource> source, Func<TSource, UniTask<TKey>> keySelector, IEqualityComparer<TKey> comparer)
+        {
+            Error.ThrowArgumentNullException(source, nameof(source));
+            Error.ThrowArgumentNullException(keySelector, nameof(keySelector));
+            Error.ThrowArgumentNullException(comparer, nameof(comparer));
+
+            return new DistinctUntilChangedAwait<TSource, TKey>(source, keySelector, comparer);
+        }
+
+        public static IUniTaskAsyncEnumerable<TSource> DistinctUntilChangedAwaitWithCancellation<TSource, TKey>(this IUniTaskAsyncEnumerable<TSource> source, Func<TSource, CancellationToken, UniTask<TKey>> keySelector)
+        {
+            return DistinctUntilChangedAwaitWithCancellation(source, keySelector, EqualityComparer<TKey>.Default);
+        }
+
+        public static IUniTaskAsyncEnumerable<TSource> DistinctUntilChangedAwaitWithCancellation<TSource, TKey>(this IUniTaskAsyncEnumerable<TSource> source, Func<TSource, CancellationToken, UniTask<TKey>> keySelector, IEqualityComparer<TKey> comparer)
+        {
+            Error.ThrowArgumentNullException(source, nameof(source));
+            Error.ThrowArgumentNullException(keySelector, nameof(keySelector));
+            Error.ThrowArgumentNullException(comparer, nameof(comparer));
+
+            return new DistinctUntilChangedAwaitCancellation<TSource, TKey>(source, keySelector, comparer);
+        }
+    }
+
+    internal sealed class DistinctUntilChanged<TSource> : IUniTaskAsyncEnumerable<TSource>
+    {
+        readonly IUniTaskAsyncEnumerable<TSource> source;
+        readonly IEqualityComparer<TSource> comparer;
+
+        public DistinctUntilChanged(IUniTaskAsyncEnumerable<TSource> source, IEqualityComparer<TSource> comparer)
+        {
+            this.source = source;
+            this.comparer = comparer;
+        }
+
+        public IUniTaskAsyncEnumerator<TSource> GetAsyncEnumerator(CancellationToken cancellationToken = default)
+        {
+            return new Enumerator(source, comparer, cancellationToken);
+        }
+
+        class Enumerator : AsyncEnumeratorBase<TSource, TSource>
+        {
+            readonly IEqualityComparer<TSource> comparer;
+            TSource prev;
+            bool first;
+
+            public Enumerator(IUniTaskAsyncEnumerable<TSource> source, IEqualityComparer<TSource> comparer, CancellationToken cancellationToken)
+
+                : base(source, cancellationToken)
+            {
+                this.comparer = comparer;
+                this.first = true;
+            }
+
+            protected override bool TryMoveNextCore(bool sourceHasCurrent, out bool result)
+            {
+                if (sourceHasCurrent)
+                {
+                    var v = SourceCurrent;
+                    if (first || !comparer.Equals(prev, v))
+                    {
+                        first = false;
+                        Current = prev = v;
+                        result = true;
+                        return true;
+                    }
+                    else
+                    {
+                        result = default;
+                        return false;
+                    }
+                }
+
+                result = false;
+                return true;
+            }
+        }
+    }
+
+    internal sealed class DistinctUntilChanged<TSource, TKey> : IUniTaskAsyncEnumerable<TSource>
+    {
+        readonly IUniTaskAsyncEnumerable<TSource> source;
+        readonly Func<TSource, TKey> keySelector;
+        readonly IEqualityComparer<TKey> comparer;
+
+        public DistinctUntilChanged(IUniTaskAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer)
+        {
+            this.source = source;
+            this.keySelector = keySelector;
+            this.comparer = comparer;
+        }
+
+        public IUniTaskAsyncEnumerator<TSource> GetAsyncEnumerator(CancellationToken cancellationToken = default)
+        {
+            return new Enumerator(source, keySelector, comparer, cancellationToken);
+        }
+
+        class Enumerator : AsyncEnumeratorBase<TSource, TSource>
+        {
+            readonly IEqualityComparer<TKey> comparer;
+            readonly Func<TSource, TKey> keySelector;
+            TKey prev;
+            bool first;
+
+            public Enumerator(IUniTaskAsyncEnumerable<TSource> source, Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer, CancellationToken cancellationToken)
+
+                : base(source, cancellationToken)
+            {
+                this.comparer = comparer;
+                this.keySelector = keySelector;
+                this.first = true;
+            }
+
+            protected override bool TryMoveNextCore(bool sourceHasCurrent, out bool result)
+            {
+                if (sourceHasCurrent)
+                {
+                    var v = SourceCurrent;
+                    var key = keySelector(v);
+                    if (first || !comparer.Equals(prev, key))
+                    {
+                        first = false;
+                        prev = key;
+                        Current = v;
+                        result = true;
+                        return true;
+                    }
+                    else
+                    {
+                        result = default;
+                        return false;
+                    }
+                }
+
+                result = false;
+                return true;
+            }
+        }
+    }
+
+    internal sealed class DistinctUntilChangedAwait<TSource, TKey> : IUniTaskAsyncEnumerable<TSource>
+    {
+        readonly IUniTaskAsyncEnumerable<TSource> source;
+        readonly Func<TSource, UniTask<TKey>> keySelector;
+        readonly IEqualityComparer<TKey> comparer;
+
+        public DistinctUntilChangedAwait(IUniTaskAsyncEnumerable<TSource> source, Func<TSource, UniTask<TKey>> keySelector, IEqualityComparer<TKey> comparer)
+        {
+            this.source = source;
+            this.keySelector = keySelector;
+            this.comparer = comparer;
+        }
+
+        public IUniTaskAsyncEnumerator<TSource> GetAsyncEnumerator(CancellationToken cancellationToken = default)
+        {
+            return new Enumerator(source, keySelector, comparer, cancellationToken);
+        }
+
+        class Enumerator : AsyncEnumeratorAwaitSelectorBase<TSource, TSource, TKey>
+        {
+            readonly IEqualityComparer<TKey> comparer;
+            readonly Func<TSource, UniTask<TKey>> keySelector;
+            TKey prev;
+            bool first;
+
+            public Enumerator(IUniTaskAsyncEnumerable<TSource> source, Func<TSource, UniTask<TKey>> keySelector, IEqualityComparer<TKey> comparer, CancellationToken cancellationToken)
+
+                : base(source, cancellationToken)
+            {
+                this.comparer = comparer;
+                this.keySelector = keySelector;
+                this.first = true;
+            }
+
+            protected override UniTask<TKey> TransformAsync(TSource sourceCurrent)
+            {
+                return keySelector(sourceCurrent);
+            }
+
+            protected override bool TrySetCurrentCore(TKey key, out bool terminateIteration)
+            {
+                if (first || !comparer.Equals(prev, key))
+                {
+                    first = false;
+                    prev = key;
+                    Current = SourceCurrent;
+                    terminateIteration = false;
+                    return true;
+                }
+                else
+                {
+                    terminateIteration = false;
+                    return false;
+                }
+            }
+        }
+    }
+
+    internal sealed class DistinctUntilChangedAwaitCancellation<TSource, TKey> : IUniTaskAsyncEnumerable<TSource>
+    {
+        readonly IUniTaskAsyncEnumerable<TSource> source;
+        readonly Func<TSource, CancellationToken, UniTask<TKey>> keySelector;
+        readonly IEqualityComparer<TKey> comparer;
+
+        public DistinctUntilChangedAwaitCancellation(IUniTaskAsyncEnumerable<TSource> source, Func<TSource, CancellationToken, UniTask<TKey>> keySelector, IEqualityComparer<TKey> comparer)
+        {
+            this.source = source;
+            this.keySelector = keySelector;
+            this.comparer = comparer;
+        }
+
+        public IUniTaskAsyncEnumerator<TSource> GetAsyncEnumerator(CancellationToken cancellationToken = default)
+        {
+            return new Enumerator(source, keySelector, comparer, cancellationToken);
+        }
+
+        class Enumerator : AsyncEnumeratorAwaitSelectorBase<TSource, TSource, TKey>
+        {
+            readonly IEqualityComparer<TKey> comparer;
+            readonly Func<TSource, CancellationToken, UniTask<TKey>> keySelector;
+            TKey prev;
+            bool first;
+
+            public Enumerator(IUniTaskAsyncEnumerable<TSource> source, Func<TSource, CancellationToken, UniTask<TKey>> keySelector, IEqualityComparer<TKey> comparer, CancellationToken cancellationToken)
+
+                : base(source, cancellationToken)
+            {
+                this.comparer = comparer;
+                this.keySelector = keySelector;
+                this.first = true;
+            }
+
+            protected override UniTask<TKey> TransformAsync(TSource sourceCurrent)
+            {
+                return keySelector(sourceCurrent, cancellationToken);
+            }
+
+            protected override bool TrySetCurrentCore(TKey key, out bool terminateIteration)
+            {
+                if (first || !comparer.Equals(prev, key))
+                {
+                    first = false;
+                    prev = key;
+                    Current = SourceCurrent;
+                    terminateIteration = false;
+                    return true;
+                }
+                else
+                {
+                    terminateIteration = false;
+                    return false;
+                }
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/UniTask.NetCoreTests/Linq/Sets.cs b/src/UniTask.NetCoreTests/Linq/Sets.cs
index e730f61..6d3c45c 100644
--- a/src/UniTask.NetCoreTests/Linq/Sets.cs
+++ b/src/UniTask.NetCoreTests/Linq/Sets.cs
@@ -65,6 +65,44 @@ namespace NetCoreTests.Linq
             }
         }
 
+        [Theory]
+        [MemberData(nameof(array1))]
+        public async Task DistinctUntilChanged(int[] array)
+        {
+            var ys = await array.ToAsyncEnumerable().DistinctUntilChanged().ToArrayAsync();
+            {
+                (await array.ToUniTaskAsyncEnumerable().DistinctUntilChanged().ToArrayAsync()).Should().BeEquivalentTo(ys);
+                (await array.ToUniTaskAsyncEnumerable().DistinctUntilChanged(x => x).ToArrayAsync()).Should().BeEquivalentTo(ys);
+                (await array.ToUniTaskAsyncEnumerable().DistinctUntilChangedAwait(x => UniTask.Run(() => x)).ToArrayAsync()).Should().BeEquivalentTo(ys);
+                (await array.ToUniTaskAsyncEnumerable().DistinctUntilChangedAwaitWithCancellation((x, _) => UniTask.Run(() => x)).ToArrayAsync()).Should().BeEquivalentTo(ys);
+            }
+        }
+
+        [Fact]
+        public async Task DistinctUntilChangedThrow()
+        {
+            foreach (var item in UniTaskTestException.Throws())
+            {
+                {
+                    var xs = item.DistinctUntilChanged().ToArrayAsync();
+                    await Assert.ThrowsAsync<UniTaskTestException>(async () => await xs);
+                }
+                {
+                    var xs = item.DistinctUntilChanged(x => x).ToArrayAsync();
+                    await Assert.ThrowsAsync<UniTaskTestException>(async () => await xs);
+                }
+                {
+                    var xs = item.DistinctUntilChangedAwait(x => UniTask.Run(() => x)).ToArrayAsync();
+                    await Assert.ThrowsAsync<UniTaskTestException>(async () => await xs);
+                }
+                {
+                    var xs = item.DistinctUntilChangedAwaitWithCancellation((x, _) => UniTask.Run(() => x)).ToArrayAsync();
+                    await Assert.ThrowsAsync<UniTaskTestException>(async () => await xs);
+                }
+            }
+        }
+
+
         [Fact]
         public async Task Except()
         {
diff --git a/src/UniTask.NetCoreTests/UniTask.NetCoreTests.csproj b/src/UniTask.NetCoreTests/UniTask.NetCoreTests.csproj
index 240d795..aa0765b 100644
--- a/src/UniTask.NetCoreTests/UniTask.NetCoreTests.csproj
+++ b/src/UniTask.NetCoreTests/UniTask.NetCoreTests.csproj
@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
     <TargetFramework>netcoreapp3.1</TargetFramework>
@@ -11,6 +11,8 @@
   <ItemGroup>
     <PackageReference Include="FluentAssertions" Version="5.10.3" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.6.1" />
+    <PackageReference Include="System.Interactive.Async" Version="4.1.1" />
+    <PackageReference Include="System.Linq.Async" Version="4.1.1" />
     <PackageReference Include="System.Reactive" Version="4.4.1" />
     <PackageReference Include="xunit" Version="2.4.1" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.1">