parameters:
- name: VariableName
  displayName: Variable Name
- name: VariableValue
  displayName: Variable Value

steps:
- task: PowerShell@2
  displayName: Update Pipeline Variable - ${{parameters.VariableName}}
  env:
    SYSTEM_ACCESSTOKEN: $(System.AccessToken)
  inputs:
    targetType: inline
    script: |
      [string]$repositoryUrl = $env:SYSTEM_COLLECTIONURI
      [string]$repositoryName = $env:SYSTEM_TEAMPROJECT
      [string]$definitionId = $env:SYSTEM_DEFINITIONID
      [string]$variableName = ${{parameters.VariableName}}
      [string]$variableValue = ${{parameters.VariableValue}}
      [string]$accessToken = $env:SYSTEM_ACCESSTOKEN
      [string]$debugMode = $env.SYSTEM_DEBUG

      if ($debugMode -eq 'true') {
          Write-Host '##[section]Starting: DEBUG INFORMATION'

          Write-Host "##[debug]repositoryUrl = $repositoryUrl"
          Write-Host "##[debug]repositoryName = $repositoryName"
          Write-Host "##[debug]definitionId = $definitionId"
          Write-Host "##[debug]variableName = $variableName"
          Write-Host "##[debug]variableValue = $variableValue"

          Write-Host '##[section]Finishing: DEBUG INFORMATION'
          Write-Host ''
      }

      if($repositoryUrl.EndsWith('/')) {
          $repositoryUrl = $repositoryUrl.TrimEnd('/')
      }

      $headers = @{ 
          'Authorization' = "Bearer $accessToken"
      }

      # Get an overview of the build definition
      $definitionUrl = "$repositoryUrl/$repositoryName/_apis/build/Definitions/$($definitionId)?api-version=5.0"
      $definitionResponse = Invoke-RestMethod -Method Get -Uri $definitionUrl -Headers $headers -UseBasicParsing

      # If the build has the variable, update it.
      if ($definitionResponse.variables.$variableName) {
          $oldValue = $definitionResponse.variables.$variableName.value
          $definitionResponse.variables.$variableName.value = $variableValue

          Write-Output -InputObject "Updating $variableName from $($oldValue) to $($variableValue)..."

          $body = ConvertTo-Json -InputObject $definitionResponse -Depth 100 -Compress
          $response = Invoke-RestMethod -Method Put -Uri $definitionsUrl -Headers $headers -ContentType 'application/json' -Body $body -UseBasicParsing
      }
    pwsh: true