name: Check PR with clang-format

on: [pull_request_target]

jobs:
  build:
    # We need at least 20.04 to install clang-format-11.
    runs-on: ubuntu-20.04

    steps:
    - uses: actions/checkout@v2
      with:
        ref: ${{ github.event.pull_request.head.sha }}
        persist-credentials: false
        # We need the history of the dev branch all the way back to where the PR
        # diverged. We're fetching everything here, as we don't know how many
        # commits back that point is.
        fetch-depth: 0

    - name: Install prerequisites
      env:
        DEBIAN_FRONTEND: noninteractive
      run: |
        sudo apt update -y
        sudo apt install -y clang-format-11
        sudo update-alternatives --install /usr/bin/clang-format clang-format /usr/bin/clang-format-11 100
        sudo update-alternatives --install /usr/bin/git-clang-format git-clang-format /usr/bin/git-clang-format-11 100

    - name: Run clang format
      id: clang_format
      env:
        ALIBUILD_GITHUB_TOKEN: ${{secrets.ALIBUILD_GITHUB_TOKEN}}
      run: |
        set -x
        # We need to fetch the other commit.
        git fetch origin ${{ github.event.pull_request.base.ref }} \
                         pull/${{ github.event.pull_request.number }}/head:${{ github.event.pull_request.head.ref }}

        # We create a new branch which we will use for the eventual PR.
        git config --global user.email "alibuild@cern.ch"
        git config --global user.name "ALICE Action Bot"
        git checkout -b alibot-cleanup-${{ github.event.pull_request.number }} ${{ github.event.pull_request.head.sha }}

        # github.event.pull_request.base.sha is the latest commit on the branch
        # the PR will be merged into, NOT the commit this PR derives from! For
        # that, we need to find the latest common ancestor between the PR and
        # the branch we are merging into.
        BASE_COMMIT=$(git merge-base HEAD ${{ github.event.pull_request.base.sha }})
        echo "Running clang-format against branch ${{ github.event.pull_request.base.ref }}, with hash ${{ github.event.pull_request.base.sha }}"
        COMMIT_FILES=$(git diff --diff-filter d --name-only $BASE_COMMIT | grep -ivE 'LinkDef|Utilities/PCG/')
        [ "X$COMMIT_FILES" = X ] && { echo "No files to check" ; exit 0; }
        RESULT_OUTPUT="$(git-clang-format --commit $BASE_COMMIT --diff --style file $COMMIT_FILES)"

        for x in $COMMIT_FILES; do
          case $x in
            *.hxx|*.cc|*.hpp) echo "$x uses non-allowed extension." && exit 1 ;;
            *) ;;
          esac
        done

        if [ "$RESULT_OUTPUT" == 'no modified files to format' ] ||
           [ "$RESULT_OUTPUT" == 'clang-format did not modify any files' ]
        then
          echo "clang-format passed."
          git push --set-upstream https://alibuild:$ALIBUILD_GITHUB_TOKEN@github.com/alibuild/AliceO2.git :alibot-cleanup-${{ github.event.pull_request.number }} -f || true
          echo ::set-output name=clean::true
        else
          git-clang-format --diff --commit $BASE_COMMIT --style file $COMMIT_FILES |
            patch -p1
          echo "clang-format failed."
          echo "To reproduce it locally please run"
          echo -e "\tgit checkout ${{ github.event.pull_request.head.ref }}"
          echo -e "\tgit-clang-format --commit $BASE_COMMIT --diff --style file"
          echo "Note: using clang-format version $(clang-format --version)"
          echo "Opening a PR to your branch with the fixes"
          git commit -m "Please consider the following formatting changes" -a
          git show | cat
          git fetch https://github.com/AliceO2Group/AliceO2.git pull/${{ github.event.pull_request.number }}/head
          git push --set-upstream https://alibuild:$ALIBUILD_GITHUB_TOKEN@github.com/alibuild/AliceO2.git HEAD:refs/heads/alibot-cleanup-${{ github.event.pull_request.number }} -f
          echo ::set-output name=clean::false
        fi

    - name: pull-request
      uses: alisw/pull-request@master
      with:
        source_branch: 'alibuild:alibot-cleanup-${{ github.event.pull_request.number }}'
        destination_branch: '${{ github.event.pull_request.head.label }}'
        github_token: ${{ secrets.ALIBUILD_GITHUB_TOKEN }}
        pr_title: "Please consider the following formatting changes to #${{ github.event.pull_request.number }}"
        pr_body: | 
          This PR cannot be merged as is. You should either run clang-format yourself and update the pull request, or merge this PR in yours.
          You can find AliceO2 coding conventions at http://github.com/AliceO2Group/CodingGuidelines. 
      continue-on-error: true # We do not create PRs if the branch is not there.

    - name: Exit with error if the PR is not clean
      run: |
        case ${{ steps.clang_format.outputs.clean }} in
          true) echo "PR clean" ; exit 0 ;;
          false) echo "PR not clean" ; exit 1 ;;
        esac