name: Build changed packages

# Build every package directory a PR touches, one job per package per arch, on
# the self-hosted droplet pool. Artifacts are unsigned; publish.yml signs and
# publishes them on merge.
#
# Tooling runs from the base branch; a PR supplies only pkgbuilds/. The
# vouch gate limits who may spend compute; this limits what their PR can run.

# No paths filter: `result` is the required status check, so it has to be
# reported on every PR. A PR that touches no package directory gets an empty
# matrix and a passing result in seconds.
on:
  pull_request:
    types: [opened, synchronize, reopened, labeled]
  workflow_dispatch:
    inputs:
      packages:
        description: "Space-separated package directories to build"
        required: true

concurrency:
  group: build-${{ github.event.pull_request.number || github.run_id }}
  cancel-in-progress: true

jobs:
  # Builds cost real machines, so they run only for trusted authors:
  # collaborators, anyone in .github/VOUCHED.td (read from the default
  # branch, so a PR cannot vouch for itself), or a PR a maintainer has
  # labelled "build-approved". Everyone else gets this job's plan output
  # and a failing `result` until a maintainer approves the build.
  changes:
    runs-on: ubuntu-latest
    outputs:
      matrix: ${{ steps.list.outputs.matrix }}
      count: ${{ steps.gate.outputs.count }}
      trusted: ${{ steps.gate.outputs.trusted }}
      empty: ${{ steps.list.outputs.empty }}
    steps:
      # Same rule as the build job: bin/build-matrix comes from base, the
      # package directories from the PR head.
      - uses: actions/checkout@v4
        with:
          ref: ${{ github.event.pull_request.base.sha || github.sha }}
          fetch-depth: 0
          persist-credentials: false
      - if: github.event_name == 'pull_request'
        run: |
          git fetch --no-tags --depth=1 origin "${{ github.event.pull_request.head.sha }}"
          git checkout "${{ github.event.pull_request.head.sha }}" -- pkgbuilds/
          # Bootstrap: the PR that introduces this tooling has a base without
          # it. Take the plan helper from the PR head in that one case; it
          # runs on a hosted runner and only prints a plan.
          if [[ ! -x bin/build-matrix ]]; then
            git checkout "${{ github.event.pull_request.head.sha }}" -- bin/build-matrix helpers/
            echo "::notice::base branch has no bin/build-matrix; using the PR's copy for planning"
          fi
      - id: vouch
        if: github.event_name == 'pull_request'
        uses: mitchellh/vouch/action/check-user@f23dbb5e745334f97414ec70463ce7301071a661 # v1
        with:
          user: ${{ github.event.pull_request.user.login }}
          allow-fail: true
        env:
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
      - id: approval
        if: github.event_name == 'pull_request'
        uses: actions/github-script@v7
        with:
          script: |
            const { data: pr } = await github.rest.pulls.get({
              ...context.repo, pull_number: context.payload.pull_request.number,
            });
            // Approving or rerunning a held run keeps its original event,
            // which may predate the label. Read the current approval instead.
            core.setOutput('approved', pr.state === 'open' &&
              pr.head.sha === context.payload.pull_request.head.sha &&
              pr.labels.some(label => label.name === 'build-approved'));
      # One matrix entry per package per architecture. Every package builds
      # once, against edge; the channels it ships to on merge are carried
      # along for information. A filename means one set of bytes.
      - id: list
        run: |
          if [[ -n "${{ github.event.inputs.packages }}" ]]; then
            names="${{ github.event.inputs.packages }}"
          else
            names=$(git diff --name-only "${{ github.event.pull_request.base.sha }}" "${{ github.event.pull_request.head.sha }}" -- pkgbuilds \
              | awk -F/ '$1=="pkgbuilds" && NF>2 {print $2}' | sort -u)
          fi
          matrix=$(printf '%s\n' $names | bin/build-matrix)
          echo "matrix=$matrix" >> "$GITHUB_OUTPUT"
          echo "planned=$(jq '.include | length' <<<"$matrix")" >> "$GITHUB_OUTPUT"
          jq -r '.include[] | "\(.package) \(.arch) -> \(.channels)"' <<<"$matrix"
          # A PR whose diff against its base is empty changes nothing: its
          # content already landed some other way (a sync PR beat it, or a
          # merge from master swallowed it). Merging it would record a change
          # that isn't one. Flag it so `result` fails rather than passes.
          if [[ "${{ github.event_name }}" == pull_request ]]; then
            total=$(git diff --name-only "${{ github.event.pull_request.base.sha }}" "${{ github.event.pull_request.head.sha }}" | wc -l)
            echo "empty=$([[ $total -eq 0 ]] && echo true || echo false)" >> "$GITHUB_OUTPUT"
            echo "files changed vs base: $total"
          else
            echo "empty=false" >> "$GITHUB_OUTPUT"
          fi
      - id: gate
        env:
          STATUS: ${{ github.event_name == 'workflow_dispatch' && 'dispatch' || steps.vouch.outputs.status }}
          AUTHOR: ${{ github.event.pull_request.user.login }}
          APPROVED: ${{ steps.approval.outputs.approved || 'false' }}
          PLANNED: ${{ steps.list.outputs.planned }}
        run: |
          case "$STATUS" in
            bot|collaborator|vouched|dispatch) trusted=true ;;
            # A denouncement is absolute: the label cannot override it.
            denounced) trusted=false ;;
            unknown) trusted=$APPROVED ;;
            *) trusted=false ;;
          esac
          echo "trusted=$trusted" >> "$GITHUB_OUTPUT"
          if [[ $trusted == true ]]; then
            echo "count=$PLANNED" >> "$GITHUB_OUTPUT"
            echo "Author $AUTHOR is trusted ($STATUS); building $PLANNED package(s)."
          else
            echo "count=0" >> "$GITHUB_OUTPUT"
            echo "::warning::Author $AUTHOR is not trusted ($STATUS). $PLANNED package build(s) planned but not run."
            if [[ $STATUS == denounced ]]; then
              echo "::warning::The author is denounced in .github/VOUCHED.td; the build-approved label does not apply."
            else
              echo "::warning::A maintainer can add the author to .github/VOUCHED.td, or apply the 'build-approved' label to build this PR."
            fi
          fi

  build:
    needs: changes
    if: needs.changes.outputs.count != '0'
    runs-on: [self-hosted, omarchy-builder]
    timeout-minutes: 180
    strategy:
      fail-fast: false
      matrix: ${{ fromJson(needs.changes.outputs.matrix) }}
    steps:
      # Tooling from base: everything that executes on this droplet's host
      # (bin/, helpers/, build/) comes from the base branch. Only the PR's
      # package directories are overlaid. A PR can therefore change what
      # gets built, never how the runner builds it. A PR that changes both
      # tooling and a package builds the package with the OLD tooling; land
      # the tooling first. workflow_dispatch has no PR and runs as checked out.
      - uses: actions/checkout@v4
        with:
          ref: ${{ github.event.pull_request.base.sha || github.sha }}
          persist-credentials: false
      - name: Overlay the PR's package directories onto base tooling
        if: github.event_name == 'pull_request'
        run: |
          set -euo pipefail
          git fetch --no-tags --depth=1 origin "${{ github.event.pull_request.head.sha }}"
          git checkout "${{ github.event.pull_request.head.sha }}" -- pkgbuilds/
          echo "tooling: $(git rev-parse --short HEAD) (base)  packages: ${{ github.event.pull_request.head.sha }} (PR head)"
          git status --short | head
      - name: Build ${{ matrix.package }} (${{ matrix.arch }}, ships to ${{ matrix.channels }})
        env:
          CONTAINER_ENGINE: docker
        run: bin/build --mirror edge --arch ${{ matrix.arch }} --package ${{ matrix.package }}
      # The artifact label carries the package directory's git tree hash so
      # the publish step can find the build for exactly the tree that merged.
      # The package file inside keeps makepkg's standard name untouched.
      # The artifact label uses the PR head's tree for this package: that is
      # the tree that merges, and what publish looks up.
      - name: Tree hash
        id: tree
        run: echo "hash=$(git rev-parse "${{ github.event.pull_request.head.sha || github.sha }}:pkgbuilds/${{ matrix.package }}")" >> "$GITHUB_OUTPUT"
      - name: Upload artifact
        if: always()
        uses: actions/upload-artifact@v4
        with:
          name: ${{ matrix.package }}-${{ matrix.arch }}-${{ steps.tree.outputs.hash }}
          path: build-output/edge/${{ matrix.arch }}/*.pkg.tar.zst
          if-no-files-found: error
          retention-days: 7

  # The one required status check. Matrix job names carry the package name, so
  # they cannot be listed in branch protection; this job's name is stable and
  # it fails if any package failed. It also runs (and passes) when no package
  # changed, so tooling-only PRs are not stuck waiting for a status.
  result:
    needs: [changes, build]
    if: always()
    runs-on: ubuntu-latest
    steps:
      - run: |
          echo "trusted=${{ needs.changes.outputs.trusted }} build=${{ needs.build.result }}"
          # An untrusted author's PR fails until a maintainer vouches or labels it.
          if [[ "${{ needs.changes.outputs.trusted }}" != "true" ]]; then
            echo "::error::Builds were not run: author is not vouched. Add to .github/VOUCHED.td or apply the 'build-approved' label."
            exit 1
          fi
          # Nothing to merge: the PR's diff against its base is empty. Its
          # change already landed elsewhere. Close it rather than merge it.
          if [[ "${{ needs.changes.outputs.empty }}" == "true" ]]; then
            echo "::error::This PR changes no files relative to its base. Its content is already on the target branch; close it instead of merging."
            exit 1
          fi
          [[ "${{ needs.build.result }}" == "success" || "${{ needs.build.result }}" == "skipped" ]]