namespace TypeChecks

module TyparNameTests =

    open FSharp.Compiler.Symbols
    open Xunit
    open FSharp.Test
    open FSharp.Test.Compiler

    let private getGenericParametersNamesFor
        (cUnit: CompilationUnit)
        (entityDisplayName: string)
        (valueDisplayName: string)
        (additionalFile: SourceCodeFileKind)
        : string array =
        let typeCheckResult =
            cUnit |> withAdditionalSourceFile additionalFile |> typecheckProject false

        assert (Array.isEmpty typeCheckResult.Diagnostics)

        typeCheckResult.AssemblySignature.Entities
        |> Seq.tryPick (fun (entity: FSharpEntity) ->
            if entity.DisplayName <> entityDisplayName then
                None
            else
                entity.MembersFunctionsAndValues
                |> Seq.tryFind (fun mfv -> mfv.DisplayName = valueDisplayName)
                |> Option.map (fun (mfv: FSharpMemberOrFunctionOrValue) ->
                    mfv.GenericParameters |> Seq.map (fun gp -> gp.DisplayName) |> Seq.toArray))
        |> Option.defaultValue Array.empty

    [<Fact>]
    let ``The call site of a generic function should have no influence on the name of the type parameters`` () =
        let definitionFile =
            Fs """
module A

let someGenericFunction _ = ()
"""
            |> withFileName "A.fs"

        let usageFile =
            ("""
module B

let otherGenericFunction _ _ _ =
    A.someGenericFunction 1
"""
             |> FsSource)
                .WithFileName("B.fs")

        let namesForB =
            getGenericParametersNamesFor definitionFile "A" "someGenericFunction" usageFile

        let alternativeUsageFile =
            ("""
module C

let alternateGenericFunction _ =
    A.someGenericFunction 1
"""
             |> FsSource)
                .WithFileName("C.fs")

        let namesForC =
            getGenericParametersNamesFor definitionFile "A" "someGenericFunction" alternativeUsageFile

        Assert.Equal<string array>(namesForB, namesForC)

    [<Fact>]
    let ``Fixed typar name in signature file is still respected`` () =
        let signatureFile =
            Fsi
                """
module A

val someGenericFunction: 'x -> unit
"""
            |> withFileName "A.fsi"

        let implementationFile =
            ("""
module A

let someGenericFunction _ = ()
"""
             |> FsSource)
                .WithFileName("A.fs")

        let names =
            getGenericParametersNamesFor signatureFile "A" "someGenericFunction" implementationFile

        Assert.Equal<string array>([| "x" |], names)

    [<Fact>]
    let ``Hash constraint typar in signature file gets pretty name`` () =
        let signatureFile =
            Fsi
                """
module A

val someGenericFunction: #exn list -> unit
"""
            |> withFileName "A.fsi"

        let implementationFile =
            ("""
module A

let someGenericFunction (_ : #exn list) = ()
"""
             |> FsSource)
                .WithFileName("A.fs")

        let names =
            getGenericParametersNamesFor signatureFile "A" "someGenericFunction" implementationFile

        Assert.Equal<string array>([| "a" |], names)

    [<Fact>]
    let ``Hash constraint with generic type parameter should have pretty name`` () =
        let signatureFile =
            Fsi
                """
module A

val array2D: rows: seq<#seq<'T>> -> 'T[,]
"""
            |> withFileName "A.fsi"

        let implementationFile =
            ("""
module A

let array2D (rows: seq<#seq<'T>>) : 'T[,] = failwith "todo"
"""
             |> FsSource)
                .WithFileName("A.fs")

        let names =
            getGenericParametersNamesFor signatureFile "A" "array2D" implementationFile

        Assert.Equal<string array>([| "a"; "T" |], names)
