name: Step 2, Add a Dockerfile

# This step triggers after we push changes to `Dockerfile` on branch `cd`.
# This workflow updates from step 2 to step 3.

# This will run every time we push changes to `Dockerfile` on branch `cd`.
# Reference: https://docs.github.com/en/actions/learn-github-actions/events-that-trigger-workflows
on:
  workflow_dispatch:
  push:
    branches:
      - cd
    paths:
      - Dockerfile

# Reference: https://docs.github.com/en/actions/security-guides/automatic-token-authentication
permissions:
  # Need `contents: read` to checkout the repository.
  # Need `contents: write` to update the step metadata.
  contents: write

jobs:
  # Get the current step to only run the main job when the learner is on the same step.
  get_current_step:
    name: Check current step number
    runs-on: ubuntu-latest
    steps:
      - name: Checkout
        uses: actions/checkout@v4
      - id: get_step
        run: |
          echo "current_step=$(cat ./.github/steps/-step.txt)" >> $GITHUB_OUTPUT
    outputs:
      current_step: ${{ steps.get_step.outputs.current_step }}

  on_push_dockerfile:
    name: On push Dockerfile
    needs: get_current_step

    # We will only run this action when:
    # 1. This repository isn't the template repository.
    # 2. The step is currently 2.
    # Reference: https://docs.github.com/en/actions/learn-github-actions/contexts
    # Reference: https://docs.github.com/en/actions/learn-github-actions/expressions
    if: >-
      ${{ !github.event.repository.is_template
          && needs.get_current_step.outputs.current_step == 2 }}

    # We'll run Ubuntu for performance instead of Mac or Windows.
    runs-on: ubuntu-latest

    steps:
      # We'll need to check out the repository so that we can edit the README.
      - name: Checkout
        uses: actions/checkout@v4
        with:
          fetch-depth: 0 # Let's get all the branches.

      # Check the learner added intended contents to the file.
      - name: Verify Dockerfile contents
        uses: skills/action-check-file@v1
        with:
          file: "Dockerfile"
          search: "FROM nginx:1.24-alpine"

      # In README.md, switch step 2 for step 3.
      - name: Update to step 3
        uses: skills/action-update-step@v2
        with:
          token: ${{ secrets.GITHUB_TOKEN }}
          from_step: 2
          to_step: 3
          branch_name: cd