name: PR Merged

on:
  pull_request_target:
    types: [closed]

permissions:
  contents: read

jobs:
  merged:
    name: Show info
    if: github.event.pull_request.merged == true
    runs-on: ubuntu-24.04-arm
    steps:
      # github.event.pull_request.base may not refer to the _actual_ parent commit of the PR,
      # instead it is the commit that the PR was merged/rebased onto.
      #
      # Since we want to diff the PR's commits, query the first commit's first parent.
      #
      # Alternatively, we could compare
      # github.event.pull_request.merge_commit_sha to github.event.pull_request.base.sha,
      # however I'm unsure how that'll interact with grouped Merge Queue 🤔
      - name: Get base commit
        id: base
        env:
          GH_TOKEN: ${{ github.token }}
          owner: ${{ github.repository_owner }}
          repo: ${{ github.event.repository.name }}
          pr: ${{ github.event.pull_request.number }}
        run: |
          out=$(mktemp)
          gh api graphql -F owner="$owner" -F repo="$repo" -F pr="$pr" -f query='
              query($owner: String!, $repo: String!, $pr: Int!) {
                repository(owner: $owner, name: $repo) {
                  pullRequest(number: $pr) {
                    commits(first: 1) {
                      edges {
                        node {
                          commit {
                            parents(first: 1) {
                              edges {
                                node {
                                  oid
                                }
                              }
                            }
                          }
                        }
                      }
                    }
                  }
                }
              }
              ' --jq '
                .data
                .repository
                .pullRequest
                .commits
                .edges[0]
                .node
                .commit
                .parents
                .edges[0]
                .node
                .oid
              ' > "$out"
          echo "sha=$(cat "$out")" >> "$GITHUB_OUTPUT"

      # Checkout CI scripts from the latest commit from the base branch.
      # This ensures we get the latest scripts, even if the PR's base was outdated.
      - name: Checkout base branch
        id: checkout
        uses: actions/checkout@v5
        with:
          sparse-checkout: |
            flake/dev/diff-plugins.py
            flake.lock
          sparse-checkout-cone-mode: false

      - name: Get nixpkgs
        id: nixpkgs
        run: |
          jq --raw-output --exit-status '
            .nodes[.nodes[.root].inputs.nixpkgs].locked
            | "https://github.com/\(.owner)/\(.repo)/archive/\(.rev).tar.gz"
            | "url=\(.)"
          ' flake.lock >> "$GITHUB_OUTPUT"

      - name: Install Nix
        uses: cachix/install-nix-action@v31
        with:
          nix_path: nixpkgs=${{ steps.nixpkgs.outputs.url }}
          extra_nix_config: |
            accept-flake-config = true

      # NOTE: This is here for debugging and gathering data
      # TODO: Remove
      - name: Print metadata
        env:
          checked_out: ${{ steps.checkout.outputs.commit }}
          workflow_base: ${{ github.base_ref }}
          workflow_head: ${{ github.head_ref }}
          parent: ${{ steps.base.outputs.sha }}
          base: ${{ github.event.pull_request.base.sha }}
          head: ${{ github.event.pull_request.head.sha }}
          merge: ${{ github.event.pull_request.merge_commit_sha }}
          pull_request: ${{ toJSON(github.event.pull_request) }}
        run: |
          {
            echo '## Commits'
            echo
            echo "Checked out: $checked_out"
            echo "Workflow base: $workflow_base"
            echo "Workflow head: $workflow_head"
            echo "PR parent: $parent"
            echo "Base: $base"
            echo "Head: $head"
            echo "Merge: $merge"
            echo
            echo '<details><summary><code>pull_request</code> details</summary>'
            echo
            echo '```json'
            echo "$pull_request" | jq .
            echo '```'
            echo
            echo '</details>'
            echo
          } >> "$GITHUB_STEP_SUMMARY"

      - name: Compare parent -> head
        id: diff1
        env:
          base: ${{ steps.base.outputs.sha }}
          head: ${{ github.event.pull_request.head.sha }}
        run: |
          out=$(mktemp)
          ./flake/dev/diff-plugins.py --compact "$base" "$head" > "$out"
          {
            echo -n 'json='
            jq -c . < "$out"
          } >> "$GITHUB_OUTPUT"
          jq . < "$out"

      - name: Compare base -> merge
        id: diff2
        env:
          base: ${{ github.event.pull_request.base.sha }}
          head: ${{ github.event.pull_request.merge_commit_sha }}
        run: |
          out=$(mktemp)
          ./flake/dev/diff-plugins.py --compact "$base" "$head" > "$out"
          {
            echo -n 'json='
            jq -c . < "$out"
          } >> "$GITHUB_OUTPUT"
          jq . < "$out"

      - name: Print summary
        env:
          json1: ${{ steps.diff1.outputs.json }}
          json2: ${{ steps.diff2.outputs.json }}
        run: |
          {
            echo '## JSON plugin diff: parent -> head'
            echo
            echo '```json'
            echo "$json1" | jq .
            echo '```'
            echo
            echo '## JSON plugin diff: base -> merge'
            echo
            echo '```json'
            echo "$json2" | jq .
            echo '```'
            echo
          } >> "$GITHUB_STEP_SUMMARY"