name: Build Docker Image

on:
  push:
    branches: [main]
    paths:
      - docker-compose.yaml
  workflow_dispatch:

jobs:
  docker:
    name: Build & Push Docker Image
    runs-on: linux-amd64

    steps:
      - name: Checkout code
        uses: actions/checkout@v4
        with:
          fetch-depth: 0

      - name: Detect image version change
        id: image
        shell: bash
        run: |
          extract_image() {
            grep -E '^[[:space:]]*image:[[:space:]]+' "$1" \
              | head -n1 \
              | awk '{ print $2 }' \
              | sed 's/^["'\'']//; s/["'\'']$//'
          }

          CURRENT_IMAGE="$(extract_image docker-compose.yaml)"
          if [ -z "$CURRENT_IMAGE" ]; then
            echo "::error::No image found in docker-compose.yaml"
            exit 1
          fi

          OLD_IMAGE=""
          if [ "${{ github.event_name }}" = "push" ] && [ -n "${{ github.event.before }}" ]; then
            if git cat-file -e "${{ github.event.before }}:docker-compose.yaml" 2>/dev/null; then
              git show "${{ github.event.before }}:docker-compose.yaml" > /tmp/docker-compose.previous.yaml
              OLD_IMAGE="$(extract_image /tmp/docker-compose.previous.yaml || true)"
            fi
          fi

          IMAGE_BASE="${CURRENT_IMAGE%:*}"
          IMAGE_TAG="${CURRENT_IMAGE##*:}"
          REGISTRY="${CURRENT_IMAGE%%/*}"

          if [ "$IMAGE_TAG" = "$CURRENT_IMAGE" ] || [ -z "$IMAGE_TAG" ]; then
            echo "::error::Image must include an explicit tag, e.g. git.techniverse.net/scriptos/sinusbot:1.1"
            exit 1
          fi

          CHANGED="false"
          if [ "${{ github.event_name }}" = "workflow_dispatch" ] || [ "$CURRENT_IMAGE" != "$OLD_IMAGE" ]; then
            CHANGED="true"
          fi

          echo "current_image=$CURRENT_IMAGE"
          echo "old_image=${OLD_IMAGE:-<none>}"
          echo "changed=$CHANGED"

          echo "changed=$CHANGED" >> "$GITHUB_OUTPUT"
          echo "image=$CURRENT_IMAGE" >> "$GITHUB_OUTPUT"
          echo "image_base=$IMAGE_BASE" >> "$GITHUB_OUTPUT"
          echo "tag=$IMAGE_TAG" >> "$GITHUB_OUTPUT"
          echo "registry=$REGISTRY" >> "$GITHUB_OUTPUT"

      - name: Stop when image version did not change
        if: steps.image.outputs.changed != 'true'
        run: echo "Image version unchanged. Skipping Docker build."

      - name: Login to Gitea Container Registry
        if: steps.image.outputs.changed == 'true'
        uses: docker/login-action@v3
        with:
          registry: ${{ steps.image.outputs.registry }}
          username: ${{ secrets.REGISTRY_USER }}
          password: ${{ secrets.REGISTRY_TOKEN }}

      - name: Set up Docker Buildx
        if: steps.image.outputs.changed == 'true'
        uses: docker/setup-buildx-action@v3

      - name: Build and push Docker image
        if: steps.image.outputs.changed == 'true'
        uses: docker/build-push-action@v6
        with:
          context: .
          platforms: linux/amd64
          push: true
          provenance: false
          tags: |
            ${{ steps.image.outputs.image }}
            ${{ steps.image.outputs.image_base }}:latest
          labels: |
            org.opencontainers.image.title=Sinusbot
            org.opencontainers.image.version=${{ steps.image.outputs.tag }}
            org.opencontainers.image.source=${{ github.server_url }}/${{ github.repository }}
            org.opencontainers.image.licenses=MIT