REAgraph/.github/actions/reagraph-diff/action.yml

name: "REAgraph byte-agnostic diff"
description: >-
  Diff two build graphs with REAgraph's structural, byte-agnostic diff and
  surface the real delta -- not the thousands of per-build-id phantom changes.
  Writes a Markdown summary and (on pull requests) posts/updates a PR comment.
author: "Graphify Labs"
branding:
  icon: git-commit
  color: green

inputs:
  base:
    description: "Path to the base build graph (reagraph / REA node-link JSON)."
    required: true
  head:
    description: "Path to the head build graph (reagraph / REA node-link JSON)."
    required: true
  by:
    description: >-
      Node-identity regime for matching: 'auto' (detect REA graphs and match by
      build-stable signature, else by id), 'id', or 'signature'.
    required: false
    default: "auto"
  comment:
    description: >-
      When 'true' and the event is a pull_request, post or update a PR comment
      with the diff. A stable marker makes re-runs update rather than duplicate.
    required: false
    default: "true"
  reagraph-version:
    description: >-
      How to install reagraph. Default installs from the public repo (reagraph
      is not yet on PyPI). Once published, set this to a pinned spec such as
      'reagraph==0.1.0'.
    required: false
    default: "reagraph @ git+https://github.com/Graphify-Labs/REAgraph@main"

outputs:
  changed:
    description: "Count of real changes (added + removed + rewired nodes)."
    value: ${{ steps.diff.outputs.changed }}
  added:
    description: "Added node count."
    value: ${{ steps.diff.outputs.added }}
  removed:
    description: "Removed node count."
    value: ${{ steps.diff.outputs.removed }}
  rewired:
    description: "Rewired node count."
    value: ${{ steps.diff.outputs.rewired }}

runs:
  using: "composite"
  steps:
    - name: Set up Python
      uses: actions/setup-python@v5
      with:
        python-version: "3.12"

    - name: Install reagraph
      shell: bash
      run: |
        python -m pip install --upgrade pip
        # reagraph is not yet on PyPI, so the default installs from the repo.
        # Pin to a released version once it is published (see reagraph-version).
        python -m pip install "${{ inputs.reagraph-version }}"
        reagraph --help >/dev/null

    - name: Run byte-agnostic diff
      id: diff
      shell: bash
      env:
        REAGRAPH_BASE: ${{ inputs.base }}
        REAGRAPH_HEAD: ${{ inputs.head }}
        REAGRAPH_BY: ${{ inputs.by }}
      run: |
        set -euo pipefail

        # Fail early with a clear message if either graph is missing.
        for var in REAGRAPH_BASE REAGRAPH_HEAD; do
          path="${!var}"
          if [ -z "$path" ]; then
            echo "::error::$var is empty -- pass a path to a reagraph/REA graph JSON file."
            exit 1
          fi
          if [ ! -f "$path" ]; then
            echo "::error::graph file not found: $path (set the '$( [ "$var" = REAGRAPH_BASE ] && echo base || echo head )' input to a reagraph/REA node-link JSON file)."
            exit 1
          fi
        done

        # Run the exact diff command and capture its full output (banner + report).
        set +e
        out="$(reagraph diff "$REAGRAPH_BASE" "$REAGRAPH_HEAD" --by "$REAGRAPH_BY" 2>&1)"
        rc=$?
        set -e
        echo "$out"
        if [ $rc -ne 0 ]; then
          echo "::error::reagraph diff exited with status $rc"
          # Still surface what we captured, then fail.
          printf '%s\n' "$out" >&2
          exit $rc
        fi

        # Parse the counts out of the text report. Lines look like:
        #   added nodes     : 4
        #   removed nodes   : 0
        #   rewired nodes   : 2
        added="$(printf '%s\n'   "$out" | sed -n 's/^[[:space:]]*added nodes[[:space:]]*:[[:space:]]*\([0-9][0-9]*\).*/\1/p'   | head -n1)"
        removed="$(printf '%s\n' "$out" | sed -n 's/^[[:space:]]*removed nodes[[:space:]]*:[[:space:]]*\([0-9][0-9]*\).*/\1/p' | head -n1)"
        rewired="$(printf '%s\n' "$out" | sed -n 's/^[[:space:]]*rewired nodes[[:space:]]*:[[:space:]]*\([0-9][0-9]*\).*/\1/p' | head -n1)"
        added="${added:-0}"; removed="${removed:-0}"; rewired="${rewired:-0}"
        changed=$(( added + removed + rewired ))

        echo "added=$added"     >> "$GITHUB_OUTPUT"
        echo "removed=$removed" >> "$GITHUB_OUTPUT"
        echo "rewired=$rewired" >> "$GITHUB_OUTPUT"
        echo "changed=$changed" >> "$GITHUB_OUTPUT"

        # Build the shared Markdown block (summary + PR comment use the same text).
        marker="<!-- reagraph-diff -->"
        {
          echo "$marker"
          echo "## REAgraph build diff (byte-agnostic)"
          echo ""
          echo '```text'
          printf '%s\n' "$out"
          echo '```'
          echo ""
          echo "**${changed} real change(s)** (byte-agnostic): ${added} added, ${removed} removed, ${rewired} rewired. The real delta, not the thousands of phantom per-build-id ones."
        } > "$RUNNER_TEMP/reagraph-diff.md"

        # Step summary.
        cat "$RUNNER_TEMP/reagraph-diff.md" >> "$GITHUB_STEP_SUMMARY"
        echo "body_path=$RUNNER_TEMP/reagraph-diff.md" >> "$GITHUB_OUTPUT"
        echo "marker=$marker" >> "$GITHUB_OUTPUT"

    - name: Post or update PR comment
      if: ${{ inputs.comment == 'true' && github.event_name == 'pull_request' }}
      uses: actions/github-script@v7
      with:
        script: |
          const fs = require('fs');
          const marker = '<!-- reagraph-diff -->';
          const body = fs.readFileSync(process.env.REAGRAPH_BODY_PATH, 'utf8');
          const { owner, repo } = context.repo;
          const issue_number = context.issue.number;
          if (!issue_number) {
            core.info('No PR number in context; skipping comment.');
            return;
          }
          const existing = await github.paginate(
            github.rest.issues.listComments,
            { owner, repo, issue_number, per_page: 100 }
          );
          const mine = existing.find(c => c.body && c.body.includes(marker));
          if (mine) {
            await github.rest.issues.updateComment({ owner, repo, comment_id: mine.id, body });
            core.info(`Updated existing comment ${mine.id}.`);
          } else {
            await github.rest.issues.createComment({ owner, repo, issue_number, body });
            core.info('Created new comment.');
          }
      env:
        REAGRAPH_BODY_PATH: ${{ steps.diff.outputs.body_path }}