name: Preview

on:
  # pull_request_target gives write access to GHCR even for PRs from forks.
  # This is safe because:
  # 1. We explicitly checkout the PR's head commit (no base branch code execution)
  # 2. We ONLY build a Docker image (isolated container, no workflow scripts from PR)
  # 3. No actions that execute PR code in the workflow context (no github-script, etc)
  # 4. Build happens in isolated Docker container with well-defined Dockerfile
  pull_request_target:

jobs:
  docker:
    runs-on: ubuntu-latest
    permissions:
      packages: write
      contents: read
    steps:
      - name: Free Disk Space
        uses: jlumbroso/free-disk-space@54081f138730dfa15788a46383842cd2f914a1be # v1.3.1
        with:
          large-packages: false
          docker-images: false
          swap-storage: false
      - name: Checkout
        uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6
        with:
          # For pull_request_target, we need to explicitly fetch the PR ref from forks
          # since the PR's commit SHA is not reachable in the base repository.
          # This is safe because no PR code is executed in workflow context.
          # Only Docker build uses the PR code (isolated in container).
          ref: refs/pull/${{ github.event.pull_request.number }}/head
      - name: Git describe
        id: ghd
        uses: proudust/gh-describe@v2
      - name: Login to GHCR
        uses: docker/login-action@5e57cd118135c172c3672efd75eb46360885c0ef # v3
        with:
          registry: ghcr.io
          username: ${{ github.repository_owner }}
          password: ${{ secrets.GITHUB_TOKEN }}
      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@8d2750c68a42422c14e847fe6c8ac0403b4cbd6f # v3
        with:
          version: latest
      - name: Docker meta
        id: meta
        uses: docker/metadata-action@c299e40c65443455700f0fdfc63efafe5b349051 # v5
        with:
          images: ghcr.io/${{ github.repository_owner }}/${{ github.event.repository.name }}
          tags: |
            type=ref,event=pr
            type=sha,format=long
      - name: Build and push PR image
        uses: docker/build-push-action@263435318d21b8e681c14492fe198d362a7d2c83 # v6
        with:
          context: .
          platforms: linux/amd64
          push: true
          tags: ${{ steps.meta.outputs.tags }}
          labels: ${{ steps.meta.outputs.labels }}
          cache-from: type=gha
          cache-to: type=gha,mode=max
          build-args: |
            RELEASE_VERSION=${{ steps.ghd.outputs.describe }}