name: Generate Release Changelog PR

on:
  push:
    tags:
      - 'v*.*.*'
  workflow_dispatch:

jobs:
  generate-release-changelog-pr:
    permissions:
      contents: write    # Needed for pushing commits and creating branches.
      pull-requests: write
    runs-on: ubuntu-latest
    steps:
      # 1. Checkout the repository (with full history).
      - name: Checkout Repository
        uses: actions/checkout@v4
        with:
          fetch-depth: 0

      # 2. Generate the release changelog using our custom configuration.
      - name: Generate Release Changelog
        id: generate_release
        uses: mikepenz/release-changelog-builder-action@v5.1.0
        env:
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
        with:
          configuration: ".github/configuration-release.json"
          owner: ${{ github.repository_owner }}
          repo: ${{ github.event.repository.name }}
          outputFile: CHANGELOG-release.md

      # 3. Update the main CHANGELOG.md:
      #    - If it doesn't exist, create it with a basic header.
      #    - Remove the "Unreleased" section (if present).
      #    - Prepend the new release changelog above previous releases.
      #    - Remove all temporary files before committing.
      - name: Update CHANGELOG.md
        run: |
          # Determine the release tag, e.g. "v1.2.3"
          TAG=${GITHUB_REF##*/}
          echo "Using release tag: $TAG"
          
          # Ensure CHANGELOG.md exists; if not, create a basic header.
          if [ ! -f CHANGELOG.md ]; then
            echo "# Changelog" > CHANGELOG.md
            echo "" >> CHANGELOG.md
            echo "All notable changes to this project will be documented in this file." >> CHANGELOG.md
            echo "" >> CHANGELOG.md
          fi

          echo "Updating CHANGELOG.md…"
          
          # Remove the "Unreleased" section (from "## [Unreleased]" until the first occurrence of '---') if it exists.
          if grep -q "^## \[Unreleased\]" CHANGELOG.md; then
            awk '/^## \[Unreleased\]/{flag=1} flag && /^---/{flag=0; next} !flag' CHANGELOG.md > CHANGELOG.cleaned
          else
            cp CHANGELOG.md CHANGELOG.cleaned
          fi

          # Split the cleaned file into:
          #   - header.md: content before the first release header ("## [v...").
          #   - tail.md: content from the first release header onward.
          awk '/^## \[v/{exit} {print}' CHANGELOG.cleaned > header.md
          awk 'f{print} /^## \[v/{f=1; print}' CHANGELOG.cleaned > tail.md

          # Combine header, the new release changelog, and the tail.
          echo "Combining updated changelog parts..."
          cat header.md CHANGELOG-release.md > CHANGELOG.md.new
          echo "" >> CHANGELOG.md.new
          cat tail.md >> CHANGELOG.md.new

          mv CHANGELOG.md.new CHANGELOG.md

          # Remove temporary files.
          rm -f CHANGELOG.cleaned header.md tail.md CHANGELOG-release.md

          echo "Final CHANGELOG.md content:"
          cat CHANGELOG.md

      # 4. Create (or update) the Pull Request with the updated CHANGELOG.md.
      - name: Create Pull Request
        uses: peter-evans/create-pull-request@v7
        with:
          token: ${{ secrets.GITHUB_TOKEN }}
          sign-commits: true
          commit-message: "chore: update CHANGELOG for release ${{ github.ref_name }}"
          base: main
          branch: "changelog/${{ github.ref_name }}"
          reviewers: danny-avila
          title: "📜 docs: Changelog for release ${{ github.ref_name }}"
          body: |
            **Description**:
            - This PR updates the CHANGELOG.md by removing the "Unreleased" section and adding new release notes for release ${{ github.ref_name }} above previous releases.