name: Version Bump

on:
  pull_request:
    branches: [master]
    types: [opened, synchronize, reopened, labeled, unlabeled, closed]

permissions:
  contents: write

jobs:
  # Register this job's name as a required status check on master's branch
  # protection - that's what actually blocks the merge button.
  check-bump-label:
    if: github.event.action != 'closed'
    runs-on: ubuntu-latest
    steps:
      - name: Require a bump:major/minor/patch label
        env:
          LABELS: ${{ toJson(github.event.pull_request.labels.*.name) }}
        run: |
          echo "$LABELS" | grep -qE '"bump:(major|minor|patch)"' || {
            echo "::error::PR into master must carry one of bump:major, bump:minor, bump:patch"
            exit 1
          }

  # Runs once, after the merge has already happened, to commit the actual
  # version bump onto master.
  apply-version-bump:
    if: github.event.pull_request.merged == true
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          ref: master
          fetch-depth: 0

      - name: Determine bump level from PR labels
        id: level
        env:
          LABELS: ${{ toJson(github.event.pull_request.labels.*.name) }}
        run: |
          for lvl in major minor patch; do
            if echo "$LABELS" | grep -q "\"bump:$lvl\""; then
              echo "level=$lvl" >> "$GITHUB_OUTPUT"
              exit 0
            fi
          done
          echo "::error::merged PR into master has no bump:major/minor/patch label"
          exit 1

      - name: Bump CMakeLists.txt and flake.nix
        env:
          LEVEL: ${{ steps.level.outputs.level }}
        run: |
          set -euo pipefail

          CURRENT=$(grep -oP '(?<=VERSION )[0-9]+(\.[0-9]+){1,2}' CMakeLists.txt | head -1)

          # Pad to 3 components so a pre-existing 2-component version (e.g.
          # "0.1") still splits into MAJOR/MINOR/PATCH correctly.
          IFS='.' read -r MAJOR MINOR PATCH <<< "${CURRENT}.0.0"

          case "$LEVEL" in
            major) MAJOR=$((MAJOR + 1)); MINOR=0; PATCH=0 ;;
            minor) MINOR=$((MINOR + 1)); PATCH=0 ;;
            patch) PATCH=$((PATCH + 1)) ;;
          esac

          NEW="$MAJOR.$MINOR.$PATCH"

          sed -i "s/VERSION ${CURRENT}/VERSION ${NEW}/" CMakeLists.txt
          sed -i "s/version = \"${CURRENT}\"/version = \"${NEW}\"/" flake.nix

          echo "CURRENT_VERSION=${CURRENT}" >> "$GITHUB_ENV"
          echo "NEW_VERSION=${NEW}" >> "$GITHUB_ENV"

      - name: Commit and push
        run: |
          set -euo pipefail
          if [ "$CURRENT_VERSION" = "$NEW_VERSION" ]; then
            echo "::error::version did not change (${CURRENT_VERSION} -> ${NEW_VERSION})"
            exit 1
          fi
          git config user.name "gitea-actions"
          git config user.email "actions@noreply.localhost"
          git add CMakeLists.txt flake.nix
          git commit -m "Bump version to ${NEW_VERSION}"
          git push origin HEAD:master