name: Docker publish

# Builds the image and pushes it to a Gitea Container Registry.
#
# Configure the repository by adding these secrets / variables:
#   Secrets:
#     REGISTRY_TOKEN  - Gitea PAT with `write:package` (and `read:repository`) scope.
#   Optional variables (Settings -> Actions); defaults come from the repository:
#     REGISTRY_HOST    - the Gitea registry host (default: host of this Gitea instance)
#     REGISTRY_OWNER   - owner/namespace of the image (default: repository owner)
#     REGISTRY_REPO    - image name (default: repository name)
#     REGISTRY_USER    - the username owning the token (default: user who pushed the tag)
#
# NOTE: variable/secret names must NOT start with GITEA_ or GITHUB_.

on:
  push:
    tags:
      - "v*.*.*"
      - "v*"

env:
  REGISTRY_HOST: ${{ vars.REGISTRY_HOST }}
  REGISTRY_OWNER: ${{ vars.REGISTRY_OWNER || github.repository_owner }}
  REGISTRY_REPO: ${{ vars.REGISTRY_REPO || github.event.repository.name }}
  REGISTRY_USER: ${{ vars.REGISTRY_USER || github.actor }}

jobs:
  publish:
    name: Build and push image
    runs-on: ubuntu-latest
    permissions:
      packages: write
      contents: read
    steps:
      - name: Checkout
        uses: actions/checkout@v4

      - name: Compute tags
        id: meta
        env:
          VERSION: ${{ github.ref_name }}
          SERVER_URL: ${{ github.server_url }}
        run: |
          # Keep only semver body so "v1.2.3" -> "1.2.3".
          tag="${VERSION#v}"
          echo "version_tagname=$tag" >> "$GITHUB_OUTPUT"
          # The Gitea registry lives on the same host as the instance itself.
          host="${REGISTRY_HOST:-${SERVER_URL#*://}}"
          host="${host%%/*}"
          echo "host=$host" >> "$GITHUB_OUTPUT"
          # Image references must be lowercase ("BalanceServer" -> "balanceserver").
          image="$host/${REGISTRY_OWNER,,}/${REGISTRY_REPO,,}"
          echo "image=$image" >> "$GITHUB_OUTPUT"
          echo "Publishing $image:$tag as $REGISTRY_USER"

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

      - name: Log in to Gitea Container Registry
        uses: docker/login-action@v3
        with:
          registry: ${{ steps.meta.outputs.host }}
          username: ${{ env.REGISTRY_USER }}
          password: ${{ secrets.REGISTRY_TOKEN }}

      - name: Build and push
        uses: docker/build-push-action@v6
        with:
          context: .
          push: true
          tags: |
            ${{ steps.meta.outputs.image }}:${{ steps.meta.outputs.version_tagname }}
            ${{ steps.meta.outputs.image }}:latest
          cache-from: type=gha
          cache-to: type=gha,mode=max,ignore-error=true