name: Docker

# Gitea Actions workflow: builds the Docker image and publishes it to the
# Gitea Container Registry hosted on this Gitea instance.

on:
  push:
    branches:
      - main
      - develop
    tags:
      - "v*.*.*"
  pull_request:
    branches:
      - main
      - develop

jobs:
  build:
    runs-on: ubuntu-latest
    permissions:
      contents: read
      packages: write

    steps:
      # Derive the registry host from the Gitea instance URL (e.g.
      # https://gitea.example.com -> gitea.example.com). The Gitea Container
      # Registry is served from the instance root, so this works on any host.
      - name: Resolve registry host
        run: echo "REGISTRY=${GITHUB_SERVER_URL#*://}" >> "$GITHUB_ENV"

      - name: Checkout repository
        uses: actions/checkout@v4

      # Set up BuildKit Docker container builder to be able to build
      # multi-platform images and export cache.
      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v3

      # Log into the Gitea Container Registry except on PR.
      #
      # NOTE: Gitea's automatic Actions token (secrets.GITHUB_TOKEN) is NOT
      # granted package scope, so it cannot push to the container registry.
      # Create a Gitea personal access token with the "write:package" scope
      # (Settings -> Applications -> Access Tokens) and add it as a repo/org
      # Actions secret named PACKAGES_TOKEN. Set PACKAGES_USER to the token
      # owner's username (defaults to the triggering actor).
      - name: Log into registry ${{ env.REGISTRY }}
        if: github.event_name != 'pull_request'
        uses: docker/login-action@v3
        with:
          registry: ${{ env.REGISTRY }}
          username: ${{ vars.PACKAGES_USER || github.actor }}
          password: ${{ secrets.PACKAGES_TOKEN }}

      # Extract metadata (tags, labels) for Docker.
      - name: Extract Docker metadata
        id: meta
        uses: docker/metadata-action@v5
        with:
          images: ${{ env.REGISTRY }}/${{ github.repository }}

      # Build and push the Docker image with Buildx (don't push on PR).
      - name: Build and push Docker image
        id: build-and-push
        uses: docker/build-push-action@v5
        with:
          context: .
          push: ${{ github.event_name != 'pull_request' }}
          tags: ${{ steps.meta.outputs.tags }}
          labels: ${{ steps.meta.outputs.labels }}
          cache-from: type=gha
          cache-to: type=gha,mode=max
          platforms: linux/amd64