name: Container image

# Builds the multi-arch container image. On tag push (v*) it logs in
# to the Gitea registry on this host and publishes the image as
# git.cer.sh/<owner>/<repo>:<version> plus :latest. On pull requests
# it builds without pushing — purely a smoke test that the Dockerfile
# still works.
on:
  push:
    tags:
      - 'v*'
  pull_request:

permissions:
  contents: read
  packages: write

jobs:
  image:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout
        uses: actions/checkout@v4

      - name: Set up QEMU
        uses: docker/setup-qemu-action@v3

      - name: Set up Buildx
        uses: docker/setup-buildx-action@v3

      # github.repository is owner/name with the repo's original casing;
      # registries require lowercase, so normalise once here and reuse
      # the result in metadata-action below.
      - name: Resolve image name
        id: img
        run: |
          repo='${{ github.repository }}'
          echo "ref=git.cer.sh/${repo,,}" >> "$GITHUB_OUTPUT"

      - name: Login to Gitea registry
        if: github.event_name == 'push'
        uses: docker/login-action@v3
        with:
          registry: git.cer.sh
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}

      - name: Docker metadata
        id: meta
        uses: docker/metadata-action@v5
        with:
          images: ${{ steps.img.outputs.ref }}
          tags: |
            type=semver,pattern={{version}}
            type=semver,pattern={{major}}.{{minor}}
            type=raw,value=latest,enable=${{ startsWith(github.ref, 'refs/tags/v') }}

      - name: Build (and push on tag)
        uses: docker/build-push-action@v6
        with:
          context: .
          file: ./Dockerfile
          platforms: linux/amd64,linux/arm64
          push: ${{ github.event_name == 'push' }}
          tags: ${{ steps.meta.outputs.tags }}
          labels: ${{ steps.meta.outputs.labels }}
          build-args: |
            VERSION=${{ github.ref_name }}
          # Inline cache embeds layer metadata into the pushed image
          # itself — no external cache server needed, which keeps the
          # workflow self-contained on the Gitea runner.
          cache-from: type=inline
          cache-to: type=inline