name: Build & Push Server Image

on:
  workflow_dispatch:
  push:
    tags:
      - "v*"
    paths:
      - "server-deploy/**"
      - ".github/workflows/build-server-image.yml"

env:
  REGISTRY: ghcr.io
  # Image published as ghcr.io/<owner>/<repo> (metadata-action lowercases it).
  IMAGE_NAME: ${{ github.repository }}

concurrency:
  group: ${{ github.workflow }}-${{ github.ref }}
  cancel-in-progress: true

jobs:
  build:
    runs-on: ubuntu-latest
    permissions:
      contents: read
      packages: write
    steps:
      - name: Checkout
        uses: actions/checkout@v4

      # The Dockerfile reads MC/loader versions from pack.toml itself; here we only
      # need the MC version to derive the image tag.
      - name: Extract MC version
        id: pack
        run: |
          mc=$(grep '^minecraft' server-deploy/pack/pack.toml | head -n1 | cut -d'"' -f2)
          if [ -z "$mc" ]; then echo "::error::could not read minecraft version from pack.toml"; exit 1; fi
          echo "mc=$mc" >> "$GITHUB_OUTPUT"
          echo "Minecraft=$mc"

      - name: Log in to GHCR
        uses: docker/login-action@v3
        with:
          registry: ${{ env.REGISTRY }}
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}

      - name: Docker metadata
        id: meta
        uses: docker/metadata-action@v5
        with:
          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
          tags: |
            type=raw,value=latest,enable={{is_default_branch}}
            type=raw,value=mc-${{ steps.pack.outputs.mc }}
            type=ref,event=branch
            type=ref,event=tag
            type=sha,format=short

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

      - name: Build and push
        uses: docker/build-push-action@v6
        with:
          context: server-deploy
          file: server-deploy/Dockerfile
          # mc-server-runner is downloaded as linux_amd64 in the Dockerfile.
          platforms: linux/amd64
          push: true
          tags: ${{ steps.meta.outputs.tags }}
          labels: ${{ steps.meta.outputs.labels }}
          cache-from: type=gha
          cache-to: type=gha,mode=max