gen_tweet.yaml

name: twitter bot

# runs on issues that have been created
on:
  issue_comment:
    types: [created]

# setup environment variables
env:
  TWEET_KEYWORD: '__[tweet]__'
  UNTWEET_EDIT_COMMENT_KEYWORD: '__[tweet withdrawn]__'
  TWEET_MAX_CHAR: 280
  TWITTER_HANDLE: fortranlang
  TWITTER_URL: https://twitter.com/fortranlang

jobs:
  # withdraws the tweet CI comment
  untweet:
    runs-on: ubuntu-latest
    if: github.event.issue.pull_request && startsWith(github.event.comment.body,'#untweet')
    steps:
    - name: find the tweet comment matching the keyword env.TWEET_KEYWORD
      uses: peter-evans/find-comment@v1
      id: fc
      with:
        issue-number: ${{github.event.issue.number}}
        comment-author: github-actions[bot]
        body-includes: ${{env.TWEET_KEYWORD}}
#   - run: echo ${{steps.fc.outputs.comment-id}}
    - name: if tweet CI comment is found, replace CI comment to undo it
      if: ${{steps.fc.outputs.comment-id != null}}
      uses: peter-evans/create-or-update-comment@v1
      with:
        comment-id: ${{steps.fc.outputs.comment-id}}
        edit-mode: replace
        body: |
          ${{env.UNTWEET_EDIT_COMMENT_KEYWORD}}
    - name: fetch comment url
      if: ${{steps.fc.outputs.comment-id != null}}
      id: get-comment-url
      run: |
        echo ::set-output name=comment-url::$(echo "${{github.event.issue.pull_request.url}}\#issuecomment-${{steps.fc.outputs.comment-id}}" | sed 's/api\.//; s/repos\///; s/pulls/pull/')
    - name: if tweet CI comment found, report it in a new comment
      if: ${{steps.fc.outputs.comment-id != null}}
      uses: peter-evans/create-or-update-comment@v1
      with:
        issue-number: ${{github.event.issue.number}}
        body: |
          ${{env.UNTWEET_KEYWORD}} removed previous tweet [above](${{steps.get-comment-url.outputs.comment-url}}).
  # writes a tweet CI comment
  tweet:
    runs-on: ubuntu-latest
    if: github.event.issue.pull_request && startsWith(github.event.comment.body,'#tweet')
    steps:
    - name: search for a previous tweet CI comment matching the keyword env.TWEET_KEYWORD
      uses: peter-evans/find-comment@v1
      id: fc
      with:
        issue-number: ${{github.event.issue.number}}
        comment-author: github-actions[bot]
        body-includes: ${{env.TWEET_KEYWORD}}
#   - run: echo ${{steps.fc.outputs.comment-id}}
    - name: if tweet CI comment is found, replace CI comment to undo it
      if: ${{steps.fc.outputs.comment-id != null}}
      uses: peter-evans/create-or-update-comment@v1
      with:
        comment-id: ${{steps.fc.outputs.comment-id}}
        edit-mode: replace
        body: |
          ${{env.UNTWEET_EDIT_COMMENT_KEYWORD}}
#   - name: fetch comment url
#     if: ${{steps.fc.outputs.comment-id != null}}
#     id: get-comment-url
#     run: |
#       echo ::set-output name=comment-url::$(echo "${{github.event.issue.pull_request.url}}\#issuecomment-${{steps.fc.outputs.comment-id}}" | sed 's/api\.//; s/repos\///')
#   - name: if tweet CI comment is found, report it in a new comment
#     if: ${{steps.fc.outputs.comment-id != null}}
#     uses: peter-evans/create-or-update-comment@v1
#     with:
#       issue-number: ${{github.event.issue.number}}
#       body: |
#         ${{env.UNTWEET_KEYWORD}} removed previous tweet [above](${{steps.get-comment-url.outputs.comment-url}}).
    - name: extract the new tweet message
      id: get-comment-body
      env: 
        COMMENT_BODY: ${{github.event.comment.body}}
      run: |
        body=$(echo "$COMMENT_BODY" | sed '1 s/#tweet//' | sed '1 s/ //')
        echo ::set-output name=tweet_length::$(echo $body | tr -d '\n\r%' | wc -c)
        body_quote=$(echo $body | sed 's/^/> /')
        # escape string content to preserve new lines
        # (see example in https://github.com/peter-evans/create-or-update-comment)
        body="${body//'%'/'%25'}"
        body="${body//$'\n'/'%0A'}"
        body="${body//$'\r'/'%0D'}"
        body_quote="${body_quote//'%'/'%25'}"
        body_quote="${body_quote//$'\n'/'%0A'}"
        body_quote="${body_quote//$'\r'/'%0D'}"
        echo ::set-output name=body::$body
        echo ::set-output name=body_quote::$body_quote
    - name: print new tweet CI message in a new comment
      uses: peter-evans/create-or-update-comment@v1
      with:
        issue-number: ${{github.event.issue.number}}
        body: |
          ${{env.TWEET_KEYWORD}} the following message will be tweeted in [@${{env.TWITTER_HANDLE}}](${{env.TWITTER_URL}}) after this PR is merged (character count: ${{steps.get-comment-body.outputs.tweet_length}}/${{env.TWEET_MAX_CHAR}}):
          ${{steps.get-comment-body.outputs.body_quote}}