name: Build kernel module

on:
  # Release flow: triggered when a version tag is pushed (tag a commit on master).
  # Builds every target and publishes the modules to a Gitea release.
  push:
    tags:
      - 'v*'
  # Compile-check flow: every PR that targets master. Builds only, no release.
  pull_request:
    branches:
      - master

jobs:
  # Build (and thereby compile-check) the module for each pinned kernel version.
  # Runs on both triggers — on a PR this is the whole story; on a tag the
  # `release` job below consumes the artifacts.
  #
  # HEADERS_PKG is fixed to linux-headers-rpi-v8 (64-bit, Pi Zero 2 W): the -v6/-v7
  # headers are 32-bit (armhf) and aren't carried by the arm64 raspberrypi archive
  # this arm64 builder uses.
  build:
    runs-on: ubuntu-latest
    env:
      HEADERS_PKG: linux-headers-rpi-v8
    strategy:
      # Don't cancel the other versions if one fails to build.
      fail-fast: false
      matrix:
        kernel_version:
          - "1:6.12.93-1+rpt1"
    steps:
      - name: Checkout
        uses: actions/checkout@v4

      - name: Build module (${{ matrix.kernel_version }})
        working-directory: kernel
        env:
          HEADERS_PKG: ${{ env.HEADERS_PKG }}
          KERNEL_VERSION: ${{ matrix.kernel_version }}
        run: |
          set -eux
          # arm64 emulation for the builder image (no-op if already registered).
          if [ ! -e /proc/sys/fs/binfmt_misc/qemu-aarch64 ]; then
            docker run --privileged --rm tonistiigi/binfmt --install arm64
          fi
          # Builder image: toolchain + matching raspberrypi kernel headers.
          docker build --platform linux/arm64 \
            --build-arg HEADERS_PKG="$HEADERS_PKG" \
            --build-arg KERNEL_VERSION="$KERNEL_VERSION" \
            -t iec-kbuild .
          # Compile inside the container. We use `docker cp` instead of the bind
          # mount that build-in-docker.sh uses for local builds: under the runner's
          # docker-in-docker, /workspace is a volume the host daemon can't see, so
          # `-v "$PWD:/build"` mounts an empty dir and make finds no Makefile.
          cid=$(docker create --platform linux/arm64 --entrypoint sleep iec-kbuild infinity)
          docker start "$cid"
          docker cp ./. "$cid:/build"
          docker exec "$cid" /usr/local/bin/docker-entrypoint.sh clean
          docker exec "$cid" /usr/local/bin/docker-entrypoint.sh
          docker cp "$cid:/build/iec_listener.ko" ./iec_listener.ko
          docker rm -f "$cid"

      - name: Stage build output (modules/iec_listener_<kernel_version>.ko)
        working-directory: kernel
        run: |
          ver="${{ matrix.kernel_version }}"
          safe="${ver//[:\/]/-}"        # path-friendly: 1:6.12.93-1+rpt1 -> 1-6.12.93-1+rpt1
          echo "kernel version $ver -> file modules/iec_listener_${safe}.ko"
          mkdir -p out/modules
          mv iec_listener.ko "out/modules/iec_listener_${safe}.ko"

      - name: Upload build output
        uses: https://github.com/christopherHX/gitea-upload-artifact@v4
        with:
          # Name by the path-friendly version so artifact names stay unique; all
          # of them merge back into the single modules/ folder at download time.
          name: ${{ matrix.kernel_version }}
          path: kernel/out
          if-no-files-found: error

  # Release flow only: merges all built modules into one modules/ folder, wraps it
  # in a single repo-named top folder alongside selftest.sh, zips it and attaches
  # it to the Gitea release for the pushed tag. Skipped entirely on pull requests.
  release:
    needs: build
    if: startsWith(github.ref, 'refs/tags/')
    runs-on: ubuntu-latest
    steps:
      - name: Checkout
        uses: actions/checkout@v4

      - name: Download all build output
        uses: actions/download-artifact@v4
        with:
          path: dist
          # Merge every artifact back into the shared modules/ folder.
          merge-multiple: true

      - name: Assemble release package
        run: |
          repo="${{ github.event.repository.name }}"
          root="package/$repo"
          mkdir -p "$root"
          cp -r dist/modules "$root"/       # modules/iec_listener_<kernel_version>.ko
          cp kernel/selftest.sh "$root"/    # selftest.sh only at the package root
          (cd package && zip -r "../${repo}-${{ github.ref_name }}.zip" "$repo")

      - name: Publish to Gitea release
        uses: actions/gitea-release-action@v1.3.6
        with:
          api_key: ${{ secrets.GITEA_TOKEN }}
          files: |-
            *.zip