action.yml

---
# https://docs.github.com/en/actions/creating-actions/metadata-syntax-for-github-actions
name: Kubernetes port-forward
author: '@vbem'
description: Forward local ports to a workload in Kubernetes
branding:
  icon: truck
  color: green

inputs:
  workload:
    description: 'Kubernetes workload `type/name` such as `deploy/mydeploy`, `svc/mysvc` or `po/mypod`'
    required: true
  mappings:
    description: 'Ports mappings `[LOCAL_PORT:]REMOTE_PORT [...[LOCAL_PORT_N:]REMOTE_PORT_N]` (default as `8080:80`)'
    required: false
    default: '8080:80'
  options:
    description: 'Other command-line options, such as `--namespace=myns`'
    required: false
    default: ''
  sleep:
    description: 'Seconds to wait before action finished (default as `3`)'
    required: false
    default: '3'

# https://docs.github.com/en/actions/creating-actions/metadata-syntax-for-github-actions#outputs-for-composite-actions
outputs:
  pid:
    description: 'Process ID of port-forward daemon'
    value: ${{ steps.main.outputs.pid }}
  log:
    description: 'Path to port-forward log file'
    value: ${{ steps.main.outputs.log }}

# https://docs.github.com/en/actions/creating-actions/metadata-syntax-for-github-actions#runs-for-composite-actions
runs:
  using: composite
  steps:
    - id: main
      shell: bash
      run: |
        # implementation details

        # Group stdin to stderr with title
        # https://docs.github.com/en/actions/using-workflows/workflow-commands-for-github-actions#grouping-log-lines
        #   $1: group title
        #   stdin: logs
        #   stderr: grouped logs
        #   $?: 0 if successful and non-zero otherwise
        function kit::wf::group {
            echo "::group::$1"      >&2
            echo "$(< /dev/stdin)"  >&2
            echo '::endgroup::'     >&2
        }

        # Set stdin as value to output of current step with given name
        # https://docs.github.com/en/actions/using-workflows/workflow-commands-for-github-actions#setting-an-output-parameter
        # https://renehernandez.io/snippets/multiline-strings-as-a-job-output-in-github-actions/
        #   $1: output name
        #   $2: masked value in logs
        #   stdin: output value
        #   stderr: grouped logs
        #   $?: 0 if successful and non-zero otherwise
        function kit::wf::output {
            local val
            val="$(< /dev/stdin)"
            { # https://www.gnu.org/software/bash/manual/bash.html#Command-Grouping
                echo "$1<<__GITHUB_OUTPUT__"
                echo "$val"
                echo '__GITHUB_OUTPUT__'
            } >> "$GITHUB_OUTPUT"
            kit::wf::group "🖨️ step output '$1' has been set" <<< "${2:-$val}"
        }

        PORT_FORWARD_LOG="${{ runner.temp }}/k8s-pod-forward.$RANDOM.log"
        kit::wf::group '🚢 Run backgroup port-forward daemon' \
          <<<"kubectl port-forward '${{ inputs.workload }}' ${{ inputs.mappings }} ${{ inputs.options }}"
        nohup kubectl port-forward '${{ inputs.workload }}' ${{ inputs.mappings }} ${{ inputs.options }} \
          < /dev/null &> "$PORT_FORWARD_LOG" &
        kit::wf::output 'pid' <<< "$!"
        kit::wf::output 'log' <<< "$PORT_FORWARD_LOG"
        sleep '${{ inputs.sleep }}'
        kit::wf::group '🚢 Current port-forward log' < "$PORT_FORWARD_LOG"
...