name: Check for IANA special-purpose address registry updates

on:
  schedule:
    - cron: "20 16 * * *"
  workflow_dispatch:

jobs:
  check-iana-registries:
    runs-on: ubuntu-latest

    permissions:
      contents: write
      pull-requests: write

    steps:
      - name: Checkout iana/data from main branch
        uses: actions/checkout@v4
        with:
          sparse-checkout: iana/data

      # If the branch already exists, this will fail, which will remind us about
      # the outstanding PR.
      - name: Create an iana-registries-gha branch
        run: |
            git checkout --track origin/main -b iana-registries-gha

      - name: Retrieve the IANA special-purpose address registries
        run: |
            IANA_IPV4="https://www.iana.org/assignments/iana-ipv4-special-registry/iana-ipv4-special-registry-1.csv"
            IANA_IPV6="https://www.iana.org/assignments/iana-ipv6-special-registry/iana-ipv6-special-registry-1.csv"

            REPO_IPV4="iana/data/iana-ipv4-special-registry-1.csv"
            REPO_IPV6="iana/data/iana-ipv6-special-registry-1.csv"

            curl --fail --location --show-error --silent --output "${REPO_IPV4}" "${IANA_IPV4}"
            curl --fail --location --show-error --silent --output "${REPO_IPV6}" "${IANA_IPV6}"

      - name: Create a commit and pull request
        env:
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
        shell:
          bash
        # `git diff --exit-code` returns an error code if there are any changes.
        run: |
            if ! git diff --exit-code; then
                git add iana/data/
                git config user.name "Irwin the IANA Bot"
                git commit \
                    --message "Update IANA special-purpose address registries"
                git push origin HEAD
                gh pr create --fill
            fi