name: Eval

on:
  pull_request_target:
  push:
    # Keep this synced with ci/request-reviews/dev-branches.txt
    branches:
      - master
      - staging
      - release-*
      - staging-*
      - haskell-updates
      - python-updates

permissions:
  contents: read

jobs:
  attrs:
    name: Attributes
    runs-on: ubuntu-latest
    outputs:
      mergedSha: ${{ steps.merged.outputs.mergedSha }}
      baseSha: ${{ steps.baseSha.outputs.baseSha }}
      systems: ${{ steps.systems.outputs.systems }}
    steps:
      # Important: Because of `pull_request_target`, this doesn't check out the PR,
      # but rather the base branch of the PR, which is needed so we don't run untrusted code
      - name: Check out the ci directory of the base branch
        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
        with:
          path: base
          sparse-checkout: ci
      - name: Check if the PR can be merged and get the test merge commit
        id: merged
        env:
          GH_TOKEN: ${{ github.token }}
          GH_EVENT: ${{ github.event_name }}
        run: |
          case "$GH_EVENT" in
            push)
              echo "mergedSha=${{ github.sha }}" >> "$GITHUB_OUTPUT"
              ;;
            pull_request_target)
              if mergedSha=$(base/ci/get-merge-commit.sh ${{ github.repository }} ${{ github.event.number }}); then
                echo "Checking the merge commit $mergedSha"
                echo "mergedSha=$mergedSha" >> "$GITHUB_OUTPUT"
              else
                # Skipping so that no notifications are sent
                echo "Skipping the rest..."
              fi
              ;;
          esac
          rm -rf base
      - name: Check out the PR at the test merge commit
        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
        # Add this to _all_ subsequent steps to skip them
        if: steps.merged.outputs.mergedSha
        with:
          ref: ${{ steps.merged.outputs.mergedSha }}
          fetch-depth: 2
          path: nixpkgs

      - name: Determine base commit
        if: github.event_name == 'pull_request_target' && steps.merged.outputs.mergedSha
        id: baseSha
        run: |
          baseSha=$(git -C nixpkgs rev-parse HEAD^1)
          echo "baseSha=$baseSha" >> "$GITHUB_OUTPUT"

      - name: Install Nix
        uses: cachix/install-nix-action@08dcb3a5e62fa31e2da3d490afc4176ef55ecd72 # v30
        if: steps.merged.outputs.mergedSha

      - name: Evaluate the list of all attributes and get the systems matrix
        id: systems
        if: steps.merged.outputs.mergedSha
        run: |
          nix-build nixpkgs/ci -A eval.attrpathsSuperset
          echo "systems=$(<result/systems.json)" >> "$GITHUB_OUTPUT"

      - name: Upload the list of all attributes
        uses: actions/upload-artifact@b4b15b8c7c6ac21ea08fcf65892d2ee8f75cf882 # v4.4.3
        if: steps.merged.outputs.mergedSha
        with:
          name: paths
          path: result/*

  outpaths:
    name: Outpaths
    runs-on: ubuntu-latest
    needs: attrs
    # Skip this and future steps if the PR can't be merged
    if: needs.attrs.outputs.mergedSha
    strategy:
      matrix:
        system: ${{ fromJSON(needs.attrs.outputs.systems) }}
    steps:
      - name: Download the list of all attributes
        uses: actions/download-artifact@fa0a91b85d4f404e444e00e005971372dc801d16 # v4.1.8
        with:
          name: paths
          path: paths

      - name: Check out the PR at the test merge commit
        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
        with:
          ref: ${{ needs.attrs.outputs.mergedSha }}
          path: nixpkgs

      - name: Install Nix
        uses: cachix/install-nix-action@08dcb3a5e62fa31e2da3d490afc4176ef55ecd72 # v30

      - name: Evaluate the ${{ matrix.system }} output paths for all derivation attributes
        env:
          MATRIX_SYSTEM: ${{ matrix.system }}
        run: |
          nix-build nixpkgs/ci -A eval.singleSystem \
            --argstr evalSystem "$MATRIX_SYSTEM" \
            --arg attrpathFile ./paths/paths.json \
            --arg chunkSize 10000
          # If it uses too much memory, slightly decrease chunkSize

      - name: Upload the output paths and eval stats
        uses: actions/upload-artifact@b4b15b8c7c6ac21ea08fcf65892d2ee8f75cf882 # v4.4.3
        if: needs.attrs.outputs.mergedSha
        with:
          name: intermediate-${{ matrix.system }}
          path: result/*

  process:
    name: Process
    runs-on: ubuntu-latest
    needs: [ outpaths, attrs ]
    outputs:
      baseRunId: ${{ steps.baseRunId.outputs.baseRunId }}
    steps:
      - name: Download output paths and eval stats for all systems
        uses: actions/download-artifact@fa0a91b85d4f404e444e00e005971372dc801d16 # v4.1.8
        with:
          pattern: intermediate-*
          path: intermediate

      - name: Check out the PR at the test merge commit
        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
        with:
          ref: ${{ needs.attrs.outputs.mergedSha }}
          path: nixpkgs

      - name: Install Nix
        uses: cachix/install-nix-action@08dcb3a5e62fa31e2da3d490afc4176ef55ecd72 # v30

      - name: Combine all output paths and eval stats
        run: |
          nix-build nixpkgs/ci -A eval.combine \
            --arg resultsDir ./intermediate \
            -o prResult

      - name: Upload the combined results
        uses: actions/upload-artifact@b4b15b8c7c6ac21ea08fcf65892d2ee8f75cf882 # v4.4.3
        with:
          name: result
          path: prResult/*

      - name: Get base run id
        if: needs.attrs.outputs.baseSha
        id: baseRunId
        run: |
          # Get the latest eval.yml workflow run for the PR's base commit
          if ! run=$(gh api --method GET /repos/"$REPOSITORY"/actions/workflows/eval.yml/runs \
            -f head_sha="$BASE_SHA" \
            --jq '.workflow_runs | sort_by(.run_started_at) | .[-1]') \
            || [[ -z "$run" ]]; then
            echo "Could not find an eval.yml workflow run for $BASE_SHA, cannot make comparison"
            exit 0
          fi
          echo "Comparing against $(jq .html_url <<< "$run")"
          runId=$(jq .id <<< "$run")
          conclusion=$(jq -r .conclusion <<< "$run")

          while [[ "$conclusion" == null ]]; do
            echo "Workflow not done, waiting 10 seconds before checking again"
            sleep 10
            conclusion=$(gh api /repos/"$REPOSITORY"/actions/runs/"$runId" --jq '.conclusion')
          done

          if [[ "$conclusion" != "success" ]]; then
            echo "Workflow was not successful, cannot make comparison"
            exit 0
          fi

          echo "baseRunId=$runId" >> "$GITHUB_OUTPUT"
        env:
          REPOSITORY: ${{ github.repository }}
          BASE_SHA: ${{ needs.attrs.outputs.baseSha }}
          GH_TOKEN: ${{ github.token }}

      - uses: actions/download-artifact@v4
        if: steps.baseRunId.outputs.baseRunId
        with:
          name: result
          path: baseResult
          github-token: ${{ github.token }}
          run-id: ${{ steps.baseRunId.outputs.baseRunId }}

      - name: Compare against the base branch
        if: steps.baseRunId.outputs.baseRunId
        run: |
          nix-build nixpkgs/ci -A eval.compare \
            --arg beforeResultDir ./baseResult \
            --arg afterResultDir ./prResult \
            -o comparison

          # TODO: Request reviews from maintainers for packages whose files are modified in the PR

      - name: Upload the combined results
        if: steps.baseRunId.outputs.baseRunId
        uses: actions/upload-artifact@b4b15b8c7c6ac21ea08fcf65892d2ee8f75cf882 # v4.4.3
        with:
          name: comparison
          path: comparison/*

  # Separate job to have a very tightly scoped PR write token
  tag:
    name: Tag
    runs-on: ubuntu-latest
    needs: process
    if: needs.process.outputs.baseRunId
    permissions:
      pull-requests: write
    steps:
      - name: Download process result
        uses: actions/download-artifact@fa0a91b85d4f404e444e00e005971372dc801d16 # v4.1.8
        with:
          name: comparison
          path: comparison

      - name: Tagging pull request
        run: |
          gh api \
            --method POST \
            /repos/${{ github.repository }}/issues/${{ github.event.number }}/labels \
            --input <(jq -c '{ labels: .labels }' comparison/changed-paths.json)
        env:
          GH_TOKEN: ${{ github.token }}