name: Open / Update Version Bump PR

# Triggered when any PR merges to main touching src/ or debian/.
# Accumulates changes on chore/version-bump branch by appending to CHANGES.md.
# Opens the bump PR if it doesn't exist, updates body if it does.
# Label is never changed on update — preserving manual bump:minor / bump:major.
# Bot guard prevents firing on the changelog commit from version-bump.yml.

on:
  push:
    branches:
      - main
    paths:
      - 'src/**'
      - 'debian/**'

permissions:
  contents: write
  pull-requests: write

jobs:
  pr:
    runs-on: ubuntu-latest
    if: github.actor != 'github-actions[bot]'

    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0
          token: ${{ secrets.GITHUB_TOKEN }}

      - name: Collect src/ commits from this merge
        id: commits
        run: |
          LOG=$(git log "HEAD~1..HEAD" --oneline -- src/ | head -50)
          EOF=$(openssl rand -hex 16)
          echo "log<<$EOF" >> "$GITHUB_OUTPUT"
          echo "$LOG"      >> "$GITHUB_OUTPUT"
          echo "$EOF"      >> "$GITHUB_OUTPUT"

      - name: Update chore/version-bump branch
        env:
          COMMITS: ${{ steps.commits.outputs.log }}
        run: |
          git config user.name  "github-actions[bot]"
          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"

          # Always rebase the bump branch on the latest main so the PR
          git fetch origin main
          if git fetch origin chore/version-bump 2>/dev/null; then
            git checkout chore/version-bump
            git rebase origin/main
          else
            git checkout -b chore/version-bump origin/main
          fi

          # Append this merge's changes to the top of CHANGES.md
          mkdir -p .github/version-bump
          PREV=$(cat .github/version-bump/CHANGES.md 2>/dev/null || true)
          {
            echo "${COMMITS:-No src/ changes detected.}"
            echo ""
            echo "$PREV"
          } > .github/version-bump/CHANGES.md

          git add .github/version-bump/CHANGES.md
          MAIN_SHA=$(git rev-parse --short origin/main)
          git commit -m "chore: accumulate changes from ${MAIN_SHA}"

          # Rebase rewrites history, so the push must be a force (lease-guarded).
          git push --force-with-lease origin chore/version-bump

      - name: Build PR body from accumulated changes
        run: |
          VERSION=$(grep -m1 '(' debian/changelog | sed 's/.*(\(.*\)).*/\1/')
          {
            echo "## Pending changes for next release (current: v${VERSION})"
            echo ""
            cat .github/version-bump/CHANGES.md
            echo ""
            echo "---"
            echo "*Change label to \`bump:minor\` or \`bump:major\` before merging if needed.*"
            echo "*Default is \`bump:patch\`.*"
            echo "*Merge this PR when ready to release.*"
          } > /tmp/pr-body.md

      - name: Create or update version bump PR
        env:
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
        run: |
          BUMP_BRANCH="chore/version-bump"
          TITLE="chore: release next version"

          EXISTING=$(gh pr list \
            --head "$BUMP_BRANCH" \
            --base main \
            --json number --jq '.[0].number' 2>/dev/null || true)

          if [[ -n "$EXISTING" ]]; then
            gh pr edit "$EXISTING" \
              --title "$TITLE" \
              --body-file /tmp/pr-body.md
            echo "Updated PR #${EXISTING} (label unchanged)"
          else
            gh pr create \
              --title "$TITLE" \
              --body-file /tmp/pr-body.md \
              --base main \
              --head "$BUMP_BRANCH" \
              --label "bump:patch"
            echo "Opened new version bump PR with label bump:patch"
          fi