Homework7

Homework7/Homework7.sln

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+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 17
+VisualStudioVersion = 17.0.31903.59
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{F2A71F9B-5D33-465A-A702-920D77279786}") = "MiniCrawler", "MiniCrawler\MiniCrawler.fsproj", "{7A2FFF58-1A54-4E4A-A5A7-C0C06E345050}"
+EndProject
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+EndProject
+Project("{F2A71F9B-5D33-465A-A702-920D77279786}") = "Lazy", "Lazy\Lazy.fsproj", "{5310B6BA-3D02-4A8D-A067-A9452C046FC9}"
+EndProject
+Project("{F2A71F9B-5D33-465A-A702-920D77279786}") = "Lazy.Tests", "Lazy.Tests\Lazy.Tests.fsproj", "{C21915B1-5326-48A3-B3B1-7C5E98736BCD}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
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+		{7A2FFF58-1A54-4E4A-A5A7-C0C06E345050}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{7A2FFF58-1A54-4E4A-A5A7-C0C06E345050}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{7A2FFF58-1A54-4E4A-A5A7-C0C06E345050}.Release|Any CPU.Build.0 = Release|Any CPU
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+		{541551EE-AF15-4DCC-848D-36EDF6A07DD1}.Debug|Any CPU.Build.0 = Debug|Any CPU
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+		{541551EE-AF15-4DCC-848D-36EDF6A07DD1}.Release|Any CPU.Build.0 = Release|Any CPU
+		{5310B6BA-3D02-4A8D-A067-A9452C046FC9}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{5310B6BA-3D02-4A8D-A067-A9452C046FC9}.Debug|Any CPU.Build.0 = Debug|Any CPU
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+		{C21915B1-5326-48A3-B3B1-7C5E98736BCD}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+EndGlobal

Homework7/Lazy.Tests/Lazy.Tests.fsproj

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+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <IsPackable>false</IsPackable>
+    <GenerateProgramFile>false</GenerateProgramFile>
+    <IsTestProject>true</IsTestProject>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="Tests.fs" />
+    <Compile Include="Program.fs" />
+  </ItemGroup>
+  <ItemGroup>
+    <PackageReference Include="FsUnit" Version="6.0.0" />
+    <PackageReference Include="FsCheck" Version="2.16.6" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.6.0" />
+    <PackageReference Include="NUnit" Version="4.1.0" />
+    <PackageReference Include="NUnit3TestAdapter" Version="4.5.0" />
+    <PackageReference Include="NUnit.Analyzers" Version="4.0.1" />
+    <PackageReference Include="coverlet.collector" Version="6.0.0" />
+  </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\Lazy\Lazy.fsproj" />
+  </ItemGroup>
+</Project>

Homework7/Lazy.Tests/Program.fs

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+module Program =
+
+    [<EntryPoint>]
+    let main _ = 0

Homework7/Lazy.Tests/Tests.fs

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+module Lazy.Tests
+
+open Lazy
+open NUnit.Framework
+open FsUnit
+
+let mutable counter = 0
+
+let lazyConstructors =
+    [ (fun f -> SingleThreadedLazy f :> ILazy<obj>)
+      (fun f -> ThreadSafeLazy f :> ILazy<obj>)
+      (fun f -> LockFreeLazy f :> ILazy<obj>) ]
+    |> List.map (fun f -> TestCaseData(f))
+
+let multiThreadLazyConstructors =
+    [ (fun f -> ThreadSafeLazy f :> ILazy<obj>)
+      (fun f -> LockFreeLazy f :> ILazy<obj>) ]
+    |> List.map (fun f -> TestCaseData(f))
+
+[<TestCaseSource(nameof lazyConstructors)>]
+let ``Value should compute only once`` (lazyConstructor: (unit -> obj) -> ILazy<obj>) =
+    let supplier () =
+        counter <- counter + 1
+        obj ()
+
+    counter <- 0
+
+    let lazyObject = lazyConstructor supplier
+    let firstCallValue = lazyObject.Get()
+    let secondCallValue = lazyObject.Get()
+
+    Assert.That(counter, Is.EqualTo(1))
+
+
+[<TestCaseSource(nameof lazyConstructors)>]
+let ``Computed value should be same for several Gets`` (lazyConstructor: (unit -> obj) -> ILazy<obj>) =
+    let supplier () = obj ()
+
+    let lazyObject = lazyConstructor supplier
+    let firstCallValue = lazyObject.Get()
+    let secondCallValue = lazyObject.Get()
+
+    Assert.That(firstCallValue, Is.EqualTo(secondCallValue))
+
+
+[<TestCaseSource(nameof lazyConstructors)>]
+let ``Exception in supplier should be thrown`` (lazyConstructor: (unit -> obj) -> ILazy<obj>) =
+    let lazyObject = lazyConstructor (fun () -> raise (System.Exception()))
+    Assert.Throws<System.Exception>(fun () -> lazyObject.Get() |> ignore) |> ignore
+
+
+[<TestCaseSource(nameof multiThreadLazyConstructors)>]
+let ``Multithread lazies test`` (lazyConstructor: (unit -> obj) -> ILazy<obj>) =
+    let supplier () = obj ()
+
+    let lazyObject = lazyConstructor supplier
+    let amountOfThreads = 8
+
+    let tasksArray =
+        Seq.init amountOfThreads (fun _ -> async { return lazyObject.Get() })
+
+    tasksArray
+    |> Async.Parallel
+    |> Async.RunSynchronously
+    |> Seq.distinct
+    |> Seq.length
+    |> should equal 1

Homework7/Lazy/Lazy.fsproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Library</OutputType>
+    <TargetFramework>net8.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="Library.fs" />
+  </ItemGroup>
+
+</Project>

Homework7/Lazy/Library.fs

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+module Lazy
+
+type ILazy<'a> =
+    abstract member Get: unit -> 'a
+
+type SingleThreadedLazy<'a>(supplier: unit -> 'a) =
+    let mutable value: Result<'a, exn> option = None
+
+    interface ILazy<'a> with
+        member this.Get() =
+            match value with
+            | Some(Ok v) -> v
+            | Some(Error ex) -> raise ex
+            | None ->
+                try
+                    let v = supplier ()
+                    value <- Some(Ok v)
+                    v
+                with ex ->
+                    value <- Some(Error ex)
+                    raise ex
+
+type ThreadSafeLazy<'a>(supplier: unit -> 'a) =
+    let mutable value: Result<'a, exn> option = None
+    let syncObj = obj ()
+
+    interface ILazy<'a> with
+        member this.Get() =
+            match value with
+            | Some(Ok v) -> v
+            | Some(Error ex) -> raise ex
+            | None ->
+                lock syncObj (fun () ->
+                    match value with
+                    | Some(Ok v) -> v
+                    | Some(Error ex) -> raise ex
+                    | None ->
+                        try
+                            let v = supplier ()
+                            value <- Some(Ok v)
+                            v
+                        with ex ->
+                            value <- Some(Error ex)
+                            raise ex)
+
+type LockFreeLazy<'a>(supplier: unit -> 'a) =
+    let mutable value: Result<'a, exn> option = None
+
+    interface ILazy<'a> with
+        member this.Get() =
+            match value with
+            | Some(Ok v) -> v
+            | Some(Error ex) -> raise ex
+            | None ->
+                try
+                    let result = supplier ()
+
+                    match System.Threading.Interlocked.CompareExchange(&value, Some(Ok result), None) with
+                    | Some(Ok v) -> v
+                    | Some(Error ex) -> raise ex
+                    | None -> result
+                with ex ->
+                    System.Threading.Interlocked.CompareExchange(&value, Some(Error ex), None)
+                    |> ignore
+
+                    raise ex

Homework7/MiniCrawler.Tests/MiniCrawler.Tests.fsproj

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+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <IsPackable>false</IsPackable>
+    <GenerateProgramFile>false</GenerateProgramFile>
+    <IsTestProject>true</IsTestProject>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="Tests.fs" />
+    <Compile Include="Program.fs" />
+  </ItemGroup>
+  <ItemGroup>
+    <PackageReference Include="FsUnit" Version="6.0.0" />
+    <PackageReference Include="FsCheck" Version="2.16.6" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.6.0" />
+    <PackageReference Include="NUnit" Version="4.1.0" />
+    <PackageReference Include="NUnit3TestAdapter" Version="4.5.0" />
+    <PackageReference Include="NUnit.Analyzers" Version="4.0.1" />
+    <PackageReference Include="coverlet.collector" Version="6.0.0" />
+  </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\MiniCrawler\MiniCrawler.fsproj" />
+  </ItemGroup>
+</Project>

Homework7/MiniCrawler.Tests/Program.fs

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+module Program =
+
+    [<EntryPoint>]
+    let main _ = 0

Homework7/MiniCrawler.Tests/Tests.fs

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+module MiniCrawler.Tests
+
+open MiniCrawler
+open FsUnit
+open NUnit.Framework
+
+[<Test>]
+let ``extractLinks test`` () =
+    let url = "https://example.com"
+
+    async {
+        let! htmlPage = downloadPageAsync url
+        let actualLinks = extractLinks htmlPage
+        let expectedLinks = [ "https://www.iana.org/domains/example" ]
+        Assert.AreEqual(expectedLinks, actualLinks)
+    }

Homework7/MiniCrawler/Library.fs

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+module MiniCrawler
+
+open System.Net.Http
+open System.Text.RegularExpressions
+
+let downloadPageAsync (url: string) =
+    async {
+        try
+            use client = new HttpClient()
+            let! html = client.GetStringAsync(url) |> Async.AwaitTask
+            return html
+        with ex ->
+            printfn "Failed to download %s: %s" url ex.Message
+            return ""
+    }
+
+let extractLinks (html: string) =
+    let pattern = @"<a\s+(?:[^>]*?\s+)?href=([""'])(http[^""']+)\1"
+    let matches = Regex.Matches(html, pattern)
+    [ for m in matches -> m.Groups.[2].Value ]
+
+let downloadPages (url: string) =
+    async {
+        let! mainPageHtml = downloadPageAsync url
+        let linksFromMainPage = extractLinks mainPageHtml
+
+        let downloadTasks =
+            linksFromMainPage
+            |> List.map (fun link ->
+                async {
+                    let! html = downloadPageAsync link
+                    return (link, html.Length)
+                })
+
+        let! results = Async.Parallel downloadTasks
+        return results |> List.ofArray
+    }
+
+let printSizes (results: (string * int) list) =
+    results |> List.iter (fun (link, size) -> printfn "%s — %d" link size)
+
+let downloadAndPrintSizes (url: string) =
+    async {
+        let! results = downloadPages url
+        printSizes results
+    }

Homework7/MiniCrawler/MiniCrawler.fsproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Library</OutputType>
+    <TargetFramework>net8.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="Library.fs" />
+  </ItemGroup>
+
+</Project>