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 header package. Runs on
  # both triggers — on a PR this is the whole story; on a tag the `release` job
  # below consumes the artifacts. All packages build against the latest archive
  # kernel; the exact version is auto-resolved from the image at build time.
  build:
    runs-on: ubuntu-latest
    strategy:
      # Don't cancel the other targets if one package fails to build.
      fail-fast: false
      matrix:
        headers_pkg:
          - linux-headers-rpi-v8   # 64-bit (Pi Zero 2 W)
          - linux-headers-rpi-v7   # 32-bit
          - linux-headers-rpi-v6   # 32-bit (older Pis)
    steps:
      - name: Checkout
        uses: actions/checkout@v4

      - name: Build module (${{ matrix.headers_pkg }})
        working-directory: kernel
        env:
          HEADERS_PKG: ${{ matrix.headers_pkg }}
        run: ./build-in-docker.sh

      - name: Stage build output (<kernel_version>/<headers_pkg>.ko)
        working-directory: kernel
        run: |
          # Ask the just-built image which kernel tree it installed, then drop the
          # -rpi-vN arch suffix so every package shares one version folder.
          kver=$(docker run --rm --platform linux/arm64 --entrypoint sh \
                   "${IMAGE:-iec-kbuild}" -c 'ls -1 /lib/modules | sort -V | tail -n1')
          ver="${kver%-rpi-*}"
          echo "resolved kernel: $kver -> version folder: $ver"
          mkdir -p "out/$ver"
          mv iec_listener.ko "out/$ver/${{ matrix.headers_pkg }}.ko"

      - name: Upload build output
        uses: actions/upload-artifact@v4
        with:
          # Name by headers_pkg so artifact names stay unique; the shared
          # <kernel_version>/ folder is reassembled at download via merge-multiple.
          name: ${{ matrix.headers_pkg }}
          path: kernel/out
          if-no-files-found: error

  # Release flow only: reassembles the <kernel_version>/ folders, wraps them 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: modules
          # Merge every artifact back into the shared <kernel_version>/ tree.
          merge-multiple: true

      - name: Assemble release package
        run: |
          repo="${{ github.event.repository.name }}"
          root="package/$repo"
          mkdir -p "$root"
          cp -r modules/. "$root"/          # <kernel_version>/<headers_pkg>.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