name: Build docker image

permissions:
  contents: read

on:
  # Backstop for a manually-created release: releases created by the Release
  # workflow itself never emit this event (see the workflow_call comment
  # below), so in the normal flow the push happens via workflow_call instead.
  release:
    types:
      - published
  push:
    branches:
      - master
  # Allow maintainers to build/validate the multi-arch image on demand
  # (e.g. from a feature branch) without pushing anything to the registry.
  workflow_dispatch:
  # Called directly by the Release workflow, since a GitHub Release created
  # with that workflow's own GITHUB_TOKEN does not emit a `release:
  # published` event (GitHub recursion prevention), so the trigger above
  # never fires for it.
  workflow_call:
    inputs:
      push_image:
        description: "Push the built image to ghcr.io (used by the Release workflow)"
        type: boolean
        default: false

env:
  REGISTRY: ghcr.io
  IMAGE_NAME: ${{ github.repository }}

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

    steps:
      - name: Checkout repository
        uses: actions/checkout@v5

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

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

      - name: Docker meta
        id: meta
        uses: docker/metadata-action@v5
        with:
          images: |
            ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
          # generate Docker tags based on the following events/attributes
          tags: |
            type=ref,event=branch
            type=ref,event=pr
            type=semver,pattern={{version}}
            type=semver,pattern={{major}}.{{minor}}

      - name: Log in to the Container registry
        # Only authenticate when we will actually push: a published release
        # event, or the Release workflow calling this with push_image: true
        # (see the workflow_call comment above). The master push and
        # workflow_dispatch runs build for validation only and must never
        # touch the registry, so they skip the login entirely.
        if: github.event_name == 'release' || inputs.push_image == true
        uses: docker/login-action@v3
        with:
          registry: ${{ env.REGISTRY }}
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}

      - name: Build and push Docker image
        uses: docker/build-push-action@v6
        with:
          context: .
          platforms: linux/amd64,linux/arm64
          # Push on a published release event, or when the Release workflow
          # calls this with push_image: true. Every other trigger (push to
          # master, workflow_dispatch) builds both architectures for
          # validation but never pushes.
          push: ${{ github.event_name == 'release' || inputs.push_image == true }}
          tags: ${{ steps.meta.outputs.tags }}
          labels: ${{ steps.meta.outputs.labels }}