name: On PR merge

# PROCESS
#
# 1. Fetch PR details previously saved from untrusted location
# 2. Parse details for safety
# 3. Add `pending-release` label for related issue
# 4. Make a comment in PR if related issue is invalid or can't be labeled

# USAGE
#
# NOTE: meant to be used with ./.github/workflows/record_pr.yml
#
# Security Note:
#
#   This workflow depends on "Record PR" workflow that runs in an untrusted location (forks) instead of `pull_request_target`.
#   This enforces zero trust where "Record PR" workflow always runs on fork with zero permissions on GH_TOKEN.
#   When "Record PR" completes, this workflow runs in our repository with the appropriate permissions and sanitize inputs.
#
#   Coupled with "Approve GitHub Action to run on forks", we have confidence no privilege can be escalated,
#   since any malicious change would need to be approved, and upon social engineering, it'll have zero permissions.

on:
  workflow_run:
    workflows: ["Record PR details"]
    types:
      - completed

permissions:
  contents: read

jobs:
  get_pr_details:
    permissions:
      actions: read  # download PR artifact
      contents: read # checkout code
    if: github.event.workflow_run.event == 'pull_request' && github.event.workflow_run.conclusion == 'success'
    uses: ./.github/workflows/reusable_export_pr_details.yml
    with:
      record_pr_workflow_id: ${{ github.event.workflow_run.id }}
      workflow_origin: ${{ github.event.repository.full_name }}
    secrets:
      token: ${{ secrets.GITHUB_TOKEN }}
  release_label_on_merge:
    needs: get_pr_details
    runs-on: ubuntu-latest
    permissions:
      pull-requests: write  # make a comment in PR if unable to find related issue
      issues: write         # label issue with pending-release
    if: needs.get_pr_details.outputs.prIsMerged == 'true'
    steps:
      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683  # v4.2.2
      - name: "Label PR related issue for release"
        uses: actions/github-script@60a0d83039c74a4aee543508d2ffcb1c3799cdea # v7.0.1
        env:
          PR_NUMBER: ${{ needs.get_pr_details.outputs.prNumber }}
          PR_BODY: ${{ needs.get_pr_details.outputs.prBody }}
          PR_IS_MERGED: ${{ needs.get_pr_details.outputs.prIsMerged }}
          PR_AUTHOR: ${{ needs.get_pr_details.outputs.prAuthor }}
        with:
          github-token: ${{ secrets.GITHUB_TOKEN }}
          script: |
            const script = require('.github/scripts/label_related_issue.js')
            await script({github, context, core})