parameters:
  - name: Paths
    type: object
    default: []
  - name: Repositories
    type: object
    default:
      - Name: $(Build.Repository.Name)
        Commitish: $(Build.SourceVersion)
        WorkingDirectory: $(System.DefaultWorkingDirectory)
  - name: SkipDefaultCheckout
    type: boolean
    default: false

steps:
  - ${{ if not(parameters.SkipDefaultCheckout) }}:
    - checkout: none

  - task: PowerShell@2
    displayName: 'Sparse checkout repositories'
    inputs:
      targetType: inline
      # Define this inline, because of the chicken/egg problem with loading a script when nothing
      # has been checked out yet.
      script: |
        function SparseCheckout([Array]$paths, [Hashtable]$repository)
        {
            $dir = $repository.WorkingDirectory
            if (!$dir) {
              $dir = "./$($repository.Name)"
            }
            New-Item $dir -ItemType Directory -Force
            Push-Location $dir

            if (Test-Path .git/info/sparse-checkout) {
              $hasInitialized = $true
              Write-Host "Repository $($repository.Name) has already been initialized. Skipping this step."
            } else {
              Write-Host "Repository $($repository.Name) is being initialized."

              Write-Host "git clone --no-checkout --filter=tree:0 https://github.com/$($repository.Name) ."
              git clone --no-checkout --filter=tree:0 https://github.com/$($repository.Name) .

              Write-Host "git sparse-checkout init"
              git sparse-checkout init

              Write-Host "git sparse-checkout set '/*' '!/*/' '/eng'"
              git sparse-checkout set '/*' '!/*/' '/eng'
            }

            # Prevent wildcard expansion in Invoke-Expression (e.g. for checkout path '/*')
            $quotedPaths = $paths | ForEach-Object { "'$_'" }
            $gitsparsecmd = "git sparse-checkout add $quotedPaths"
            Write-Host $gitsparsecmd
            Invoke-Expression -Command $gitsparsecmd

            Write-Host "Set sparse checkout paths to:"
            Get-Content .git/info/sparse-checkout

            # sparse-checkout commands after initial checkout will auto-checkout again
            if (!$hasInitialized) {
              Write-Host "git checkout $($repository.Commitish)"
              git checkout $($repository.Commitish)  # this will use the default branch if repo.Commitish is empty
            } else {
              Write-Host "Skipping checkout as repo has already been initialized"
            }

            Pop-Location
        }

        # Paths may be sourced as a yaml object literal OR a dynamically generated variable json string.
        # If the latter, convertToJson will wrap the 'string' in quotes, so remove them.
        $paths = '${{ convertToJson(parameters.Paths) }}'.Trim('"') | ConvertFrom-Json
        # Replace windows backslash paths, as Azure Pipelines default directories are sometimes formatted like 'D:\a\1\s'
        $repositories = '${{ convertToJson(parameters.Repositories) }}' -replace '\\', '/' | ConvertFrom-Json -AsHashtable
        foreach ($repo in $Repositories) {
          SparseCheckout $paths $repo
        }
      pwsh: true
      workingDirectory: $(System.DefaultWorkingDirectory)