action.yml

name: autotag
description: 'Automatically create tags in yyyy.mm.dd.n format'

inputs:
  dry-run:
    description: "Don't create the tag"
    default: 'false'
    required: false

  github-token:
    description: "GitHub access token. Use a personal access token to trigger workflow runs from created tags."
    default: ${{ github.token }}
    required: false

outputs:
  tag:
    description: "Generated tag name"
    value: ${{ fromJson(steps.tag.outputs.result).tag }}
  ref:
    description: "Generated tag ref"
    value: ${{ fromJson(steps.tag.outputs.result).ref }}
  sha:
    description: "Tagged commit sha"
    value: ${{ fromJson(steps.tag.outputs.result).sha }}
  json:
    description: "All outputs in JSON"
    value: ${{ steps.tag.outputs.result }}

runs:
  using: composite
  steps:
    - id: tag
      uses: actions/github-script@v7
      with:
        debug: true
        github-token: ${{ inputs.github-token }}
        script: |
          const today = new Date();

          const prefix = [
            today.getUTCFullYear().toString(),
            (today.getUTCMonth() + 1).toString().padStart(2, '0'),
            today.getUTCDate().toString().padStart(2, '0'),
          ].join('.') + '.';

          core.info(`Tag prefix: ${prefix}`);

          let lastComponent = 0;

          for await (const response of github.paginate.iterator(github.rest.repos.listTags, context.repo)) {
            for (const tag of response.data) {
              if (!tag.name.startsWith(prefix))
                continue;

              core.debug(`Found matching tag: ${tag.name}`);

              try {
                const components = tag.name.split('.', 4);
                const n = parseInt(components[3], 10);

                if (n >= lastComponent)
                  lastComponent = n + 1;

              } catch (err) {
                core.warning(`Can't parse tag ${tag}: ${err}`);
              }
            }
          }

          const tag = `${prefix}${lastComponent}`;
          const ref = `refs/tags/${tag}`;
          const sha = context.sha;
          const dryRun = ${{ inputs.dry-run }};

          if (dryRun) {
            core.info(`Generated tag: ${tag}`);
            return { tag, ref, sha };
          }

          core.info(`Tagging ${sha} as ${ref}`);

          await github.rest.git.createRef({
            ...context.repo,
            ref,
            sha,
          });

          return { tag, ref, sha };