notify-release.yml

name: Notify Release

on:
  workflow_call:
    inputs:
      repo_name:
        required: false
        type: string
        description: 'Repository name to display in the Slack message. Defaults to the calling repository name.'
        default: ''
      tag:
        required: true
        type: string
        description: 'Release tag being published (e.g., 3.0.0, v1.2.3)'
      previous_sha:
        required: false
        type: string
        description: 'Previous release short SHA for compare link. Auto-discovered from latest release if not provided.'
    secrets:
      slack_webhook:
        required: true
        description: 'Slack incoming webhook URL for posting release notifications'

jobs:
  notify:
    runs-on: ubuntu-latest
    steps:
      - name: Resolve repository name
        id: repo
        run: |
          if [ -n "${{ inputs.repo_name }}" ]; then
            echo "name=${{ inputs.repo_name }}" >> "$GITHUB_OUTPUT"
          else
            echo "name=${{ github.event.repository.name }}" >> "$GITHUB_OUTPUT"
          fi

      - name: Get current SHA
        id: current
        run: echo "sha=${GITHUB_SHA::7}" >> "$GITHUB_OUTPUT"

      - name: Get previous release SHA
        id: previous
        uses: actions/github-script@v8
        with:
          script: |
            try {
              const { data: previousRelease } = await github.rest.repos.getLatestRelease({
                owner: context.repo.owner,
                repo: context.repo.repo,
              });
              // getLatestRelease returns target_commitish which is often the branch name,
              // not the commit SHA. Resolve the tag to its actual commit via getCommit.
              const { data: commit } = await github.rest.repos.getCommit({
                owner: context.repo.owner,
                repo: context.repo.repo,
                ref: previousRelease.tag_name,
              });
              core.setOutput('sha', commit.sha.substring(0, 7));
            } catch (error) {
              core.setOutput('sha', '');
            }

      - name: Select previous SHA
        id: selected
        run: |
          if [ -n "${{ inputs.previous_sha }}" ]; then
            echo "sha=${{ inputs.previous_sha }}" >> "$GITHUB_OUTPUT"
          else
            echo "sha=${{ steps.previous.outputs.sha }}" >> "$GITHUB_OUTPUT"
          fi

      - name: Build compare URL
        id: compare
        run: |
          PREV="${{ steps.selected.outputs.sha }}"
          CURR="${{ steps.current.outputs.sha }}"
          OWNER="${{ github.repository_owner }}"
          REPO="${{ github.event.repository.name }}"
          if [ -n "$PREV" ]; then
            echo "url=https://github.com/${OWNER}/${REPO}/compare/${PREV}...${CURR}" >> "$GITHUB_OUTPUT"
          else
            echo "url=https://github.com/${OWNER}/${REPO}/releases/tag/${{ inputs.tag }}" >> "$GITHUB_OUTPUT"
          fi

      - name: Post to Slack
        uses: slackapi/slack-github-action@v3.0.1
        with:
          webhook: ${{ secrets.slack_webhook }}
          webhook-type: incoming-webhook
          payload: |
            {
              "text": "<!here> releasing ${{ steps.repo.outputs.name }} ${{ inputs.tag }} ${{ steps.compare.outputs.url }}",
              "username": "${{ github.actor }}",
              "icon_url": "https://github.com/${{ github.actor }}.png?size=32"
            }