action.yml

name: Notify Slack
author: Freckle
description: |
  Minimal inputs action to notify Slack of Job status

inputs:
  slack-webhook-url:
    description: |
      Slack webhook url, typically a repository secret.
    required: true

  slack-channel:
    description: |
      Explicit channel for this notification. If omitted (the default), the
      channel configured in the webhook is used.
    required: false
    default: ""

  event-name:
    description: |
      A name for the event being notified about. If not given, the
      workflow and job id is used.
    required: false
    default: ""

  message:
    description: |
      Additional content to add to the message. Details about the commit that
      triggered the Job in which this step is run are always included.
    required: false
    default: ""

  commit-sha:
    description: |
      Commit SHA to fetch details for. Default is the PR head sha or github.sha
      if not in the context of a PR.
    required: false
    default: "${{ github.event.pull_request.head.sha || github.sha }}"

  slack-users:
    description: |
      A JSON object (as a string in the Yaml) mapping GitHub usernames to Slack
      User Ids (e.g. UXXXXXX). If present, the commit author is looked up in the
      map and the Slack user, if found, is at-mentioned in the notification
      details. If a Slack user is not found, an error is generated as a build
      annotation.
    required: false
    default: ""

  slack-users-file:
    description: |
      Relative path within the repository to read the slack-users JSON from a
      file. The file is read from the default branch via the API.
    required: false
    default: ""

  job-name:
    description: |
      An explicit job-name, in cases where github.job (the job.id) won't work
      such as matrix jobs.
    required: false
    default: ""

  job-status:
    description: |
      An explicit job-status, in cases where the status of the current job is not
      the desired status to notify about.
    required: false
    default: ""

  github-token:
    description: ""
    required: false
    default: "${{ github.token }}"

  dry-run:
    description: "Don't actually notify (useful for testing)"
    required: false
    default: false

runs:
  using: composite
  steps:
    - shell: bash
      run: |
        # Set global ENV
        cat >>"$GITHUB_ENV" <<'EOM'
        COMMIT_JSON=/tmp/commit.json
        SLACK_USERS_JSON=/tmp/slack-users.json
        EOM

    - shell: bash
      run: |
        # Fetch commit.json
        gh api "/repos/${{ github.repository }}/commits/$COMMIT_SHA" >"$COMMIT_JSON"
      env:
        GH_TOKEN: ${{ inputs.github-token }}
        COMMIT_SHA: ${{ inputs.commit-sha }}

    - if: ${{ inputs.slack-users }}
      shell: bash
      name: Write slack-users.json from input
      run: echo "$USERS" >"$SLACK_USERS_JSON"
      env:
        USERS: ${{ inputs.slack-users }}

    - if: ${{ inputs.slack-users-file }}
      shell: bash
      run: |
        # Write slack-users.json from repository file
        gh api "/repos/${{ github.repository }}/contents/$USERS_FILE" --jq '.content' |
          base64 -d >"$SLACK_USERS_JSON"
      env:
        GH_TOKEN: ${{ inputs.github-token }}
        USERS_FILE: ${{ inputs.slack-users-file }}

    - shell: bash
      run: |
        # Set SLACK_TITLE
        event_name=$EVENT_NAME
        event_name=${event_name:-${{ github.workflow }} ${{ github.job }}}

        {
          case "${{ inputs.job-status || job.status }}" in
            success)
              echo "SLACK_TITLE=$event_name succeeded"
              echo "SLACK_COLOR=success"
              ;;
            failure)
              echo "SLACK_TITLE=$event_name failed"
              echo "SLACK_COLOR=danger"
              ;;
            cancelled)
              echo "SLACK_TITLE=$event_name was cancelled"
              echo "SLACK_COLOR=grey"
              ;;
          esac
        } >> "$GITHUB_ENV"
      env:
        EVENT_NAME: ${{ inputs.event-name }}

    - shell: bash
      run: |
        # Set SLACK_MESSAGE
        # https://unix.stackexchange.com/a/451250
        relative_date() {
          awk -v date="$(date +%s -d "$1")" -v now="$(date +%s)" '
            BEGIN {  diff = now - date;
               if (diff > (24*60*60)) printf "%.0f days ago", diff/(24*60*60);
               else if (diff > (60*60)) printf "%.0f hours ago", diff/(60*60);
               else if (diff > 60) printf "%.0f minutes ago", diff/60;
               else printf "%s seconds ago", diff;
            }'
        }

        commit_author=$(jq -r '.author.login' "$COMMIT_JSON")
        commit_timestamp=$(jq -r '.commit.committer.date' "$COMMIT_JSON")
        commit_timestamp_r=$(relative_date "$commit_timestamp")
        commit_sha_short=$(jq -r '.sha' "$COMMIT_JSON" | head -c 7)
        commit_url=$(jq -r '.html_url' "$COMMIT_JSON")

        if [[ -f "$SLACK_USERS_JSON" ]]; then
          author=$(jq -r ".\"$commit_author\" // \"unknown\" | \"<@\" + . + \">\"" "$SLACK_USERS_JSON")
        else
          author="$commit_author"
        fi

        if [[ "$author" == '<@unknown>' ]]; then
          cat "$GITHUB_ACTION_PATH/unknown.txt" >&2
          author="$author ($commit_author)"
        fi

        {
          echo "SLACK_MESSAGE<<EOM"
          printf '%s committed <%s|%s> %s (%s)\n' \
            "$author" \
            "$commit_url" \
            "$commit_sha_short" \
            "$commit_timestamp_r" \
            "$commit_timestamp"
          echo "$MESSAGE"
          echo "EOM"
        } >>"$GITHUB_ENV"
      env:
        MESSAGE: ${{ inputs.message }}

    - shell: bash
      run: |
        # Set SLACK_FOOTER
        url=$(
          gh --repo '${{ github.repository }}' run view '${{ github.run_id }}' \
            --json jobs \
            --jq ".jobs[] | select(.name == \"$JOB_NAME\") | .url"
        )

        if [[ -z "$url" ]]; then
          echo "No Job with name $JOB_NAME found in Workflow Runs:" >&2
          gh --repo '${{ github.repository }}' run view '${{ github.run_id }}' \
            --json jobs --jq '.jobs[] | .name' >&2
          exit 1
        fi

        echo "SLACK_FOOTER=$url" >>"$GITHUB_ENV"
      env:
        GH_TOKEN: ${{ inputs.github-token }}
        JOB_NAME: ${{ inputs.job-name || github.job }}

    - if: ${{ inputs.dry-run != 'true' }}
      name: Notify
      uses: rtCamp/action-slack-notify@v2
      env:
        MSG_MINIMAL: "true" # SLACK_MESSAGE will include all details
        SLACK_ICON: https://github.com/freckle-automation.png?size=48
        SLACK_USERNAME: GitHub Actions
        SLACK_WEBHOOK: ${{ inputs.slack-webhook-url }}
        SLACK_CHANNEL: ${{ inputs.slack-channel }}