name: Autoformat code
on: pull_request

#
# The autoformat action is a 2-parter:
# Part 1 (this file):
#     * This is done in a safe context with no secrets (target: pull_request)
#     * We clone the repo and check out the pull request
#     * We run 'dotnet format' to format incorrectly formatted code (this is the potentially unsafe action, since who knows what kind of attach vector 'dotnet format' is)
#     * We see if any code was formatted, and create a commit with those changes.
#     * We preare a patch for the commit, and store it as an artifact.
# Part 2 (autoformat2.yml):
#     * This is done in a context with more powers (most importantly it can push to forks)
#     * We get the πatch artifact from part 1
#     * We push the commit, and add a label to the PR.
#
# Ref:
#     https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#workflow_run
#     https://securitylab.github.com/research/github-actions-preventing-pwn-requests/
#     https://github.com/actions/checkout/issues/455
#     https://stackoverflow.com/a/65081720/183422
#

jobs:
  autoformat-code:
    name: Autoformat code
    runs-on: ubuntu-latest
    if: contains(github.event.pull_request.labels.*.name, 'actions-disable-autoformat') == false

    steps:
    - name: 'Checkout repo'
      uses: actions/checkout@v3
      with:
        fetch-depth: 0
        repository: ${{ github.event.pull_request.head.repo.full_name }}
        ref: ${{ github.event.pull_request.head.sha }}

    - name: 'Autoformat'
      id: autoformat
      run: |
        set -exo pipefail

        ./tools/autoformat.sh

        mkdir -p autoformat
        echo ${{ github.event.number }} > ./autoformat/PR

        if git diff --exit-code >/dev/null; then
          echo "No code formatting occurred"
        else
          git add -- .
          git reset -- autoformat/PR # Don't add this file to the diff
          git config --global user.email "github-actions-autoformatter@xamarin.com"
          git config --global user.name "GitHub Actions Autoformatter"
          git checkout "$GITHUB_HEAD_REF"
          git commit -m "Auto-format source code"

          git format-patch HEAD^..HEAD --stdout > ./autoformat/autoformat.patch
        fi

    - name: 'Upload patch'
      uses: actions/upload-artifact@v3
      with:
        name: autoformat
        path: autoformat/