name: check-bot-scope

# Required on dev. bot-nix-hashes.yml pushes bot/nix-hashes and auto-merges its pull request without review, so this
# fails that branch unless it changes nothing but a valid nix/hashes.json. Every other branch passes. The bot's own
# pushes start no workflows, so bot-nix-hashes.yml dispatches this; pull_request covers anyone else pushing the branch.

on:
  pull_request:
    types: [opened, synchronize, reopened, ready_for_review]
  workflow_dispatch:

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

permissions:
  contents: read

jobs:
  bot-scope:
    name: bot-scope
    runs-on: ubuntu-24.04
    timeout-minutes: 10
    steps:
      - name: Check branch
        id: branch
        env:
          HEAD_REF: ${{ github.event_name == 'pull_request' && github.head_ref || github.ref_name }}
        run: |
          if [ "$HEAD_REF" = bot/nix-hashes ]; then
            echo "bot=true" >> "$GITHUB_OUTPUT"
          else
            echo "$HEAD_REF is not a bot branch; nothing to check"
          fi

      - name: Checkout repository
        if: steps.branch.outputs.bot == 'true'
        uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
        with:
          ref: ${{ github.event.pull_request.head.sha || github.sha }}
          fetch-depth: 0
          filter: blob:none
          persist-credentials: false

      - name: Check changed files
        if: steps.branch.outputs.bot == 'true'
        env:
          BASE: ${{ github.base_ref || 'dev' }}
        run: |
          set -euo pipefail
          git fetch --no-tags --filter=blob:none origin "+refs/heads/$BASE:refs/remotes/origin/$BASE"
          changed=$(git diff --name-only "origin/$BASE...HEAD")
          echo "Changed files:"
          echo "$changed"
          if [ "$changed" != nix/hashes.json ]; then
            echo "::error::bot/nix-hashes may change only nix/hashes.json"
            exit 1
          fi

      # Runs dev's validator: the step above proved this branch leaves .github/ unchanged.
      - name: Validate nix/hashes.json
        if: steps.branch.outputs.bot == 'true'
        run: bash .github/nix-hashes/validate.sh nix/hashes.json