. $PSScriptRoot\..\..\Load-PesterModules.ps1
$here = Split-Path -Parent $MyInvocation.MyCommand.Path
$sut = (Split-Path -Leaf $MyInvocation.MyCommand.Path) -replace '\.tests\.', '.'
$functionPath = Join-Path -Path $here -ChildPath $sut
Write-Host "Overriding SUT: $functionPath"
Import-Module $functionPath -Force
$moduleForMock = ""

Describe 'Invoke-Parallel' {
        Context 'Ensure Correctness - Batched Parallelism' {
        It 'Returns Correct Results' {
            $numbers = 1..50

            $results = Invoke-Parallel -objects $numbers -returnObjects -script {
                param($number)
                return $number;
            };

            # Make sure it has the right number of results.
            $results.Count | Should -Be 50

            # Make sure it returned all of the right results.
            # The sum of 1-50 is 1275
            $sum = 0;
            foreach($result in $results) {
                $sum += $result;
            }
            $sum | Should -Be 1275
        }

        It 'Handles Zero Items' {
            $numbers = $null;

            $results = Invoke-Parallel -objects $numbers -returnObjects -script {
                param($number)
                return $number;
            };

            $results | Should -Be $null;
        }

        It 'Handles One Item' {
            $numbers = @(1);

            $results = Invoke-Parallel -objects $numbers -returnObjects -script {
                param($number)
                return $number;
            };

            $results | Should -Be 1;
        }

        It 'Handles ThreadCount -gt NumObjects' {
            $numbers = 1..8;
            $numThreads = 400;
            $results = Invoke-Parallel -objects $numbers -returnObjects -numThreads $numThreads -script {
                param($number)
                return $number;
            };

            $results.Count | Should -Be 8;
        }

        It 'Handles Odd Thread Division' {
            $numbers = 1..8;
            $numThreads = 3;
            $results = Invoke-Parallel -objects $numbers -returnObjects -numThreads $numThreads -script {
                param($number)
                return $number;
            };

            $results.Count | Should -Be 8;
        }

        It 'Handles Jobless Last Thread' {
            # This is an edge case where Ceil(21 items / 8 threads) is rounded up to 3 items per thread.
            # 7*3 == 21, which means the last thread at 8 threads doesn't have any work to do.
            # There isn't a more fair way to divy up the work between the threads.
            # Arbitrarily giving the 8th thread work from the 7th thread won't help in theory.
            $numbers = @(1..21)
            $numThreads = 8;
            $results = Invoke-Parallel -objects $numbers -returnObjects -numThreads $numThreads -script {
                param($number)
                return $number;
            }

            $results.Count | Should -Be 21;
        }
    }

    Context 'Ensure Correctness - Thread Per Object Parallelism' {
        It 'Returns Correct Results' {
            $numbers = 1..6

            $results = Invoke-Parallel -objects $numbers -returnObjects -threadPerObject -script {
                param($number)
                return $number;
            };

            # Make sure it has the right number of results.
            $results.Count | Should -Be 6

            # Make sure it returned all of the right results.
            # The sum of 1-6 is 21
            $sum = 0;
            foreach($result in $results) {
                $sum += $result;
            }
            $sum | Should -Be 21
        }

        It 'Handles Zero Items' {
            $numbers = $null;

            $results = Invoke-Parallel -objects $numbers -returnObjects -threadPerObject -script {
                param($number)
                return $number;
            };

            $results | Should -Be $null;
        }

        It 'Handles One Item' {
            $numbers = @(1);

            $results = Invoke-Parallel -objects $numbers -returnObjects -threadPerObject -script {
                param($number)
                return $number;
            };

            $results | Should -Be 1;
        }

        It 'Handles ThreadCount -gt NumObjects' {
            $numbers = 1..8;
            $numThreads = 400;
            $results = Invoke-Parallel -objects $numbers -returnObjects -numThreads $numThreads -threadPerObject -script {
                param($number)
                return $number;
            };

            $results.Count | Should -Be 8;
        }
    }
}